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Notes: Tentative Synthesis of ‘Bis(triasterane)’ and Synthesis of the Heterocyclic (Tricyclo[4.4.1.01,6]undeca-3,8-diene-11,11-dimethyl)sulfiteThe synthesis of the bis(triasterane) (1) has been tried; the reaction of ‘isotetraline’ (1,4,5,8-Tetrahydronaphthalene; 2) with diazomalonate yielded the tricyclic systems 5 and 6, and not 4. Hydrolysis of 5 gave the monocarboxylic acid 7, and not the dicarboxylic acid 9. The latter could be obtained from the dibromoderivative 8, but 9 couldn't be converted to the acyl chloride 10. The reduction of 9 with LiAlH4 yielded the crystalline diol 11, which was cyclized with SOCl2 to the heterocycle 12. The spectral data of the new compounds 5, 6, 7, 11 and 12 are reported and discussed.

Notes: A detailed study of the biodegradation of one of the fish toxic chlorinated resin acids, 12,14-dichlorodehydroabietic acidThe correct IUPAC-name is 12,14-dichloro-8,9,11,12-tetradehydro-7,8-dihydroabietic acid. (3) is presented. When exposed to the fungus Mortierella isabellina, 3 is converted into a number of hydroxylated and keto derivatives which show low levels of toxicity to fish. These metabolites were isolated and characterized.

Notes: Zero-current Ion-transport Studies and Potentiometric Measurements on Membranes Containing Chromoionophores for Li+ and UO22+Non-macrocyclic ionophores for Li+ and UO22+ have been substituted with a diphenylmaleimide unit. In membranes the obtained chromoionophores induce the same ion-selectivity and ion-transport behavior as the unsubstituted ligands.

Notes: Reactivity-structure correlations for anisole and eleven of its substituted derivatives established from bromination rate constants in liquid SO2, unlike observations in water, show the reaction to be highly sensitive to substituent effects, (ρH2O+ = -7.1; ρSO2+ = -10.51). This result is ascribed to the solvation of the methoxy group which decreases the conjugation of para-substituted (ρO+ = -9.70) compared to that of ortho-substituted derivatives (ρP+ = -8.86). The highly solvated transition state lies far from reactants on the reaction coordinate and the positive charge developed in this state is nearly unity.

Notes: Peptidic model conjugates carrying a single 2-carboxy-4,6-dinitrophenyl haptenic group, and as carbohydrate moieties D-gluconoyl, β-D-mannopyranosyl, 2-deoxy-β-D-glucopyranos-2-yl, or lactobionoyl residues, including the pseudocarbohydrate residue 1,3,4,5-tetrahydroxycyclohexane-1-carbonyl, were synthesized. Conjugates carrying the lactobionoyl of the bis(2-deoxy-β-D-glucopyranos-2-yl) moiety were anaphylactogenic in the guinea pig, passively sensitized against 2-carboxy-4,6-dinitrophenyl antigen.

Notes: The stereochemical aspects of the intramolecular Ramberg-Bäcklund reaction, i.e. the 1,3-elimination of hydrogen halide followed by sulfur dioxide extrusion, have been studied on the α-bromosulfones of the 1-thiadecalinThroughout this paper ‘1-thiadecalin’ will be used in place of ‘decahydro-1-thianaphthalene’. series. Whereas the cis,exo-bromosulfone 23a containing the ideal W-type arrangement of the reacting atoms undergoes a clean Ramberg-Bäcklund reaction, the trans,exo- and trans,endo-bromosulfones, 24a and 24b, respectively, lead to an α,β-unsaturated sulfone by simple 1,2-elimination of HBr. Application of the Ramberg-Bäcklund reaction to 9-bromo-8-thiabicyclo[5.2.1]decane-8,8-dioxide (17) permits a short synthesis of the Bredt olefin bicyclo[5.1.1]non-1(8)-ene (5), which can be isolated but shows the typical high reactivity of other methylene-bridged (E)-cyclooctenes.

Notes: Conversion of 2-bromomethylstyrene 22 and benzocyclobutenyl carbamate 28 to the benzophenanthridine alkaloids (±)-chelidonine (1, five steps, 25% from 28) and to (±)-norchelidonine (2, six steps, 24% from 28) are described. The key step 29 → 31 involves a highly regio- and stereocontrolled intramolecular Diels-Alder reaction of the (E)-quinodimethane 30.

Notes: Dehydrogenation of hydroaromatic compounds with quinones was reinvestigated in the light of recent criticism of the reaction mechanism. Kinetic and spectroscopic evidence shows that disappearance of substrate proceeds at the same rate as the product-forming step. A mechanism consisting in fast formation followed by slow decomposition of an intermediate can be ruled out. The order of reactivities of 1,4-cyclohexadiene (1), 1,4-dihydronaphthalene (8) and 9,10-dihydroanthracene (11) changes in going from benzoquinone to chloranil or 2,3-dichloro-5,6-dicyanobenzoquinone. It is suggested that this behaviour could be due to contribution of CT-complexes or HOMO-LUMO interactions for determining the reactivity of the substrates.

Notes: Dependence of the Stereoselectivity on the Leaving Group, the Temperature and the Solvent in the Favorskii-Reaction of Enolisable CyclobutanonesThe base-induced contraction of enolisable 2-halocyclobutanones is often not stereoselectiv. The cis/trans-isomer ratio in the cyclopropanecarboxylic acid 9 derived from 2,4-cis-substituted cyclobutanones 7 depends on the nature of the leaving group. In addition, the choice of the base, the temperature and the solvent can profoundly affect the stereoselectivity of the Favorskii-reaction. The use of the p-bromophenylsulphonyloxy group as leaving group and an inhomogenous reaction medium leads exclusively to cis-carboxylic acid 9.

Notes: Synthesis of Glyceryletherphosphatides, 2nd Communication. Preparation of 2-O-Acetyl-1-O-[(Z)-9-octadecenyl]-sn -glyceryl-3-phosphorylcholin (‘Oleyl-PAF’), of its Enantiomer and Some Analogous, Unsaturated CompoundsSyntheses of the unsaturated glyceroletherphospholipid 1a as an olefin-analog of ‘Platelet Activating Factor’ (PAF) are described together with the methods for the preparation of the enantiomer 1′a, the corresponding ‘lyso compounds’ 1b and 1′b and their positional isomers 21a, 21′a, 26, 26′, 25, 25′ obtained on formally exchanging the attachment site of the functional groups at the glycerol moiety. Structural assignments and optical purity of the compounds are confirmed.

Notes: Three macrocyclic polyamines [24]ane-N6 1, [32]ane-N8 2 and [27]ane-N6O3 3 of ring size 24, 32 and 27, respectively, have been synthesized. They contain either trimethylenediamine of ethylenediamine units. The acyclic analog 4, as the reference compound, was also prepared. Compounds 1-3 are macrocyclic analogs of natural polyamines and are potential ligands for metal cations as well as, when protonated, for anions. The protonation constants of compounds 1-4 have been determined. They are high enough for compounds 1-4 to be fully protonated in a pH-range close to neutrality, as required for binding of anions of weak acids. The effect of structural features on the protonation constants are briefly discussed in relation to the design of macrocyclic polyamine ligands.

Notes: Irradiation (λ〉280 nm) of 3-hydroxypyrroles 1 in acetonitrile leads to the formation of 3,3′-bi-3H-pyrroles 2 in reasonable to good yields.

Notes: On the Course of the Intramolecular Diels-Alder-Reaction of Cyclopentadienes with Olefinic SubstituentsThe 1:3 mixture of 4-bromobicyclo [3.2.0]hept-2-en-6-one and -7-one (1/2), available by N-bromosuccinimide bromination of bicyclo [3.2.0]hept-2-en-6-one, reacted rapidly with the organo-magnesium and -zinc reagents 3, 10a, 10b and 10d by cyclobutanone ring opening and bromide ion expulsion to give the 5-substituted cyclopentadienes 5, 12a, 12b/12c, and 12d as non-isolated intermediates. Further transformation occured in situ either by a direct intramolecular Diels-Alder reaction (path a) or by a [1,5]-H-migration prior to the intramolecular Diels-Alder reaction (path b). The intermediate 5 followed only path a to give the bridged norbornene derivative 7, the intermediates 12a, 12b and 12c followed only path b to give the annellated norbornene derivatives 15a, 15b and 15c, respectively, and the intermediate 12d followed both paths to give the bridged 14d and the annellated norbornene derivative 15d (in the ration of about 1.4:1). These observations are discussed in terms of the relative velocities of [1,5]-H-migrations and intramolecular Diels-Alder reactions. The major conclusions are: (1) bridged norbornene derivatives with a six-membered ring C (such as 14d) can be prepared by an intramolecular Diels-Alder reaction from 5-alkenyl-cyclopentadienes 12, as long as the dienophilic double bond is activated by an appropriate substituent (as in 12d); (2) such 5-alkenyl-cyclopentadienes 12 are available from the reaction of the bromo-bicyclo-heptenones 1/2 with suitable C-nucleophiles 10.

Notes: Spiro 3-Oxazolines from the 1,3-Dipolar Cycloaddition of Benzonitrilio-2-propanide and 1,4-QuinonesOn irradiation with light of wavelength 290-350 nm, 2,2-dimethyl-3-phenyl-2H-azirine (1b) reacts with 1,4-naphthoquinone to give the 1H-benzo [f]isoindol-4,9-dione (11) (Scheme 3) via cycloaddition of the benzonitrilio-2-propanide (2b) onto the quinone C, C-double bond. With 2-methyl- and 2,3-dimethyl-1,4-naphthoquinone, the nitrile ylide 2b undergoes cycloaddition preferentially onto the C, O-double bond of the quinone, leading to spiro-oxazolines 12 and 14 (Scheme 4). Steric as well as electronic effects can be discussed to explain the observed site selectivity of the cycloaddition.With the 1,4-benzoquinones 15a, 15b, 15d and 15f, nitrile ylide 2b undergoes the 1,3-dipolar cycloaddition exclusively onto the C, O-double bond. The corresponding spiro-oxazolines have been isolated in 17-32% yield. This contrasts with the previously reported results with benzonitrilipo-phenylmethanide (2a), which undergoes cycloaddition to the C, C-double bond of 1,4-benzoquinones (cf. [1]). This difference in the site selectivity of the 1,3-dipolar cycloaddition can be explained with Houk's concept of LUMO-polarization, that is, the stronger nucleophilic dipol 2b polarizes the LUMO of a α,β-unsaturated carbonyl compound more efficient than the less nucleophilic 2a. This leads to a preference of the cycloaddition to the C, O-double bond in the case of 2b.With 2,3-dimethyl- (15c) and 2,3,5,6-tetramethyl-1,4-benzoquinone (15e), nitrile ylide 2b undergoes C, O- as well as C, C-cycloaddition (Schemes 7 and 8).

Notes: About the Availability of 13C-NMR Substituent Increments in 1,4-Benzo- and 1,4-NaphthoquinonesThe 13C-NMR spectra of a number of substituted 1,4-benzo- and 1,4-naphthoquinones have been obtained and assigned. Effects of CH3-, O-alkyl-, Cl-, NH2- and N3- substituents have been deduced for the quinoid part of the molecules and used for the calculation of 13C-chemical shifts.

Notes: Flow thermolysis of 2-propynyl propiolate (5) at 580° afforded butatriene (6) (ca. 50%) and, as by-products, 4-methylene-2-cyclobuten-1-one (7), 2-ethynylpropenal (8), 1-penten-4-yn-3-one (9), 4-penten-2-ynal (10) (total ca. 10%), along with some propynal, acetylene, CO2 and CO. In the same way, propiolic acid (1,1-D2)-2-propynyl propiolate (11) led to (1,1-D2)-butatriene (12) and a little 4-((D2)methylene)-2-cyclobuten-1-one (13). A mechanism is proposed for the transformation of 5 into 6 and of 11 into 12, which also accounts for the formation of 7,8,9 and 10, as well as 13. The position of one of the published 13C-NMR signals of butatriene (6) must be revised. Thermolysis of methyl-(1) and ethyl propiolate (2) resulted in small yields of 2-buten-4-olide (3) and 2-penten-4-olide (4).

Notes: 13C-NMR. Substituent Increments of the Azido-group in 1,4-BenzoquinonesThe empirical substituent increments of the azido-group in 1,4-benzoquinones have been derived from the 13C-NMR. chemical shifts of 2-azido-5-chloro-1,4-benzoquinone. The validity of the obtained values was tested by comparison of the empirical and computed 13C-NMR. chemical shifts of other azido-chloro-1,4-benzoquinones.

Notes: The synthesis of a large variety of enantiomerically pure substituted reactive cyclopentenes 16, 23, 24 and 28 have been synthesized from the readily available (-)-quinic acid 1. The straightforward strategy involves a high-yielding intramolecular aldolization-dehydration of acyclic 1,6-dialdehydes 13, 18, 19 and 27 obtained by oxidative cleavage of cyclohexanediols 5, 7, 11 and 12, using either lead tetraacetate or triphenylbismuth carbonate. Neither sulfoxide formation nor racemization of the intermediate dialdehydes at the oxygenated chiral centre was observed. Transformation of the thioacetal 25 to the corresponding ketone 26 using phenylselenic anhydride is also described.

Notes: Photochromism of spiropyrans. Photodegradation of aza-, oxaza-, and thiaza-cyclopentane- and -cyclohexanespiropyransStudy of the photodegradation of saturated azaheterocyclic spiropyrans showed that electron-donor substituents improve, as in the benzoheterocyclic series, the fatigue properties towards. UV. light. The introduction of oxygen or sulfur in the 5- or 6-membered saturated azacycles or the substitution with an orthofused aromatic nucleus have practically no influence on the results of photodegradation. The indolinospiropyrans allow the greatest number of photochromic cycles before falling to half the initial absorbance on photolysis under accurate conditions.

Notes: Low-Temperature 13C-NMR. Spectroscopy of Organolithium Derivatives. - 13C, 6Li-Coupling, a Powerful Structural InformationThe 13C-NMR. spectra of thirteen lithiated hydrocarbons (1c-13c. Table 2) and of eighteen a-halo-lithium carbenoids (14c-31c, Table 3) have been recorded in donor solvent (R2O, R3N) mixtures at temperatures down to -150°. The organolithium species were generated from singly or doubly 13C-labelled precursors by H/6Li- or Br/6-exchange. - 13C, 6Li-Coupling was observed of all species but those which supposedly contain contact ion pair C,Li-bonds (benzylic and acetylenic derivatives). The multiplicities of the signals are correlated with the degree of aggregation in solution: the triplets of the halocarbenoids must arise from monomers or heteroatom-bridged oligomers, the quintuplets of butyl-, cyclopropyl-, bycyclo[1.1.0]butyl-, vinyl-, and phenyllithium from dimers with planar arrangement of two Li- and two C-atoms, as known from crystal structures (Scheme 3). All 13C, 6Li-couplings are temperature-dependent, dynamic processes cause them to disappear above ca. -70° (Fig. 1-4). - Types of organolithium compounds are categorized according to the change of chemical shift δΔ (H, Li) upon H/Li-substitution, according to the 13C, 6Li-coupling constants ranging from 0 to 17 Hz, and according to the multiplicities which indicate the aggregation: type A are Li-derivatives of alkanes and cycloalkanes, type B are s̰-bonded vinyl, aryl, and alinyl derivatives, type C are a-heterosubstituted (RS, hetero=halogen) organolithium compounds, and type D are π-bonded allylic and benzylic systems (Table 5). The C,Li-distances in the crystal structures of representatives of all four classes are within the small range of 2.18-2.28 Å (cf. Scheme 3). - Some surprising observations and their interpretations and consequences are: (a) butyllithium solutions in THF, THF/TMEDA, and dimethyl ether contain increasing amounts of dimer upon cooling, the equilibrium (tetramer · 4 THF)+4 THF ⇌ 2 (dimer · 4 THF) being shifted to the right (Fig. 1 and Scheme 4); thus, more of a different species is present at low temperatures, with the accompanying changes in reactivity; (b) mixed higher aggregates are formed upon addition of butyllithium to bicyclobutyllithium; these are broken up to dimers upon addition of TMEDA (Tetramethylethylene-diamine) (Fig. 2 and Scheme 5); (c) the solid state, the calculated gas-phase and the solution species of phenyllithium all have dimeric structures, and so do vinyl and cyclopropyl lithium derivatives; the 13C-deshielding observed upon replacement of H by Li on sp2- and sp-C-atoms is related to a polarization of the π-electrons (Table 3, Fig. 3 and Scheme 6); (d) the spectra of halo-lithium carbenoids show three striking features as compared to the C,H-compound: deshielding of up to 280 ppm (Table 3), strong decrease of the coupling constant with 1H- and 13C-nuclei attached to the carbenoid C-atom (Table 4), and a structure-independant, almost constant, large 13C, 6Li-coupling constant of 17 Hz (Table 3); as shown in Scheme 7, these effects might be the consequence of a reduced degree of hybridization of the carbenoid C-atom. - The preparation of the labelled compounds and the generation of solutions of the organolithium compounds for NMR. measurements are described in full detail.

Notes: From treatment of D-labelled 1, 2exo-, 1, 2endo- and 2endo, 6endo-trimethylene-norbornane (1, 2 and 3, resp.) with aluminum bromide in carbon disulfide, the evidence is gained that a degenerate rearrangement is involved in the admantane rearrangement of both 1 and 2 to 3.

Notes: The 1,3-dipolar cycloaddition of the C-t-butyloxycarbonyl-N-mannosyl-nitrone 5, formed in situ from the partially protected D-mannose-oxime 3 and the glyoxylate 4, to ethylene gave preferentially the (3S)-N-glycosyl-isoxazolidine 6 which was transformed into the 3-isoxazolidine-carboxylate (L-5-oxaproline ester) 12 and into some derivatives thereof. The (S)-configuration of 12 was proved by chemical correlation with a derivative of L-asparagine. The D-5-oxaproline ester was obtained from the corresponding N-ribosyl-nitrone 24. Two protected dipeptides containing either C-terminal- (28) or N-terminal-5-oxaproline (= Opro) (30) were synthesized. Starting from 12, the analogue 1 of captopril® (2) was prepared and its activity as an inhibitor of the angiotensin-converting-enzyme (ACE) was examined.

Notes: (3S, 8E)-1,3-Dihydroxy-8-decen-5-one, a Metabolite of Streptomyces fimbriatus (MILLARD and BURR 1926)From the cultures of Streptomyces fimbriatus, strain Tü 2335, the title compound 1 was isolated by solvent extraction, chromatography, and distillation. Its constitution was determined by spectroscopic investigations of 1 and some of its derivatives, and the chirality by transformation to (R)-1,3-isopropylidenedioxy-decane (12); a reference sample of the latter was prepared from (R)-methyl 3-hydroxydecanoate (10). In the equilibrium mixture the keto form 1 predominates the two hemiacetals 2a and 2b. Compound 1 is inactive against bacteria, yeasts and fungi.

Notes: (Phenacetin)4·2I4·2H2O is triclinic, a = 13.641 (7), b = 12.807 (6), c = 7.201 (3) Å, α = 99.8 (4), b̃ = 86.5 (4), γ = 104.0 (5)°, P1, Z = 1. The ordered crystal structure has been refined to RF = 0.050, using 4173 independent reflections measured on a four-circle diffractometer with MoKa (graphite monochromator) radiation. The crystals are composed of alternating positively and negatively charged slices; each positive slice contains a double layer of stacks of hemi-protonated phenacetin molecules which are H-bonded through their carbonyl groups (d(O - - - O) = 2.432 (4) Å) while each negative slice contains a single layer of I2-4-ions linked in chains along [100] through H-bonds to pairs of water molecules. The axes of the phenacetin stacks are parallel to the planes of the (I2-4·2H2O)-layers. The I2-4-ion is centro-symmetric and can be approximately represented as I-- - - I-I- - - I- (d(I- - - - I) = 3.404 (1) Å; d(I-I) = 2.774 (1) Å). The compound is a pseudo-type A basic salt.

Notes: The influence of steric compression on electronic structure in polycyclic olefinic alcohols and amines is studied by PE. spectroscopy.The unsubstituted alcohol 2 and amine 7 show PE.-spectroscopic properties that can be reconciled by postulating a predominance of intramolecularly H-bonded species in the gas phase.For the alkylated derivatives 5 and 9, in which H-bonding is precluded, distinct, but only moderate lone-pair double-bond interactions are observed.

Notes: The [2.2.2]hericene (6), a bicyclo[2.2.2]octane bearing three exocyclic s-cis-butadiene units has been prepared in eight steps from coumalic acid and maleic anhydride. The hexaene 6 adds successively three mol-equiv. of strong dienophiles such as ethylenetetracarbonitrile (TCE) and dimethyl acetylenedicarboxylate (DMAD) giving the corresponding monoadducts 17 and 20 (k1), bis-adducts 18 and 21 (k2) and tris-adducts 19 and 22 (k3), respectively. The rate constant ratio k1/k2 is small as in the case of the cycloadditions of 2,3,5,6-tetramethylidene-bicyclo [2.2.2]octane (3) giving the corresponding monoadducts 23 and 27 (k1) and bis-adducts 25 and 29 (k2) with TCE and DMAD, respectively. Constrastingly, the rate constant ratio k2/k3 is relatively large as the rate constant ratio k1/k2 of the Diels-Alder additions for 5,6,7,8-tetramethylidenebicyclo [2.2.2]oct-2-ene (4) giving the corresponding monoadducts 24 and 28 (k1) and bis-adducts 26 and 30 (k2). The following second-order rate constants (toluene, 25°) and activation parameters were obtained for the TCE additions: 3+TCE→23: k1 = 0.591±0.012 mol-1·l·s-1, ΔH≠=10.6±0.4 kcal/mol, and ΔS≠ = -24.0±1.4 cal/mol·K (e.u.); 23+TCE→25: k2=0.034±0.0010 mol-1·l·s-1, ΔH≠ = 10.6±0.6 kcal/mol, and ΔS≠ = -29.7±2.0 e.u.; 4+TCE→26: k1 = 0.172±0.035 mol-1·l·s-1, ΔH≠ 11.3±0.8 kcal/mol, and ΔS≠ = -24.0±2.8 e.u.; 24+TCE→26: k2 = (6.1±0.2)·10-4 mol-1·l·s-1, ΔH≠ = 13.0±0.3 kcal/mol, and ΔS≠ = -29.5±0.8 e.u.; 6+TCE→17: k1 = 0.136±0.002 mol-1·l·s-1, ΔH≠ = 11.3±0.2 kcal/mol, and ΔS≠ = -24.5±0.8 e.u.; 17+TCE→18: k2 = 0.0156±0.0003 mol-1·l·s-1, ΔH≠ = 10.9±0.5 kcal/mol, and ΔS≠ = -30.1 ± 1.5 e.u.; 18+TCE→19: k3=(5±0.2) · 10-5 mol-1 mol-1 ·l·s-1, ΔH≠ = 15±3 kcal/mol, and ΔS≠ = -28 ± 8 e.u. The following rate constants were evaluated for the DMAD additions (CD2Cl2, 30°): 6+DMAD→20: k1 = (10±1)·10-4 mol-1 · l·s-1; 20+DMAD→21: k2 = (6.5±0.1) · 10-4 mol-1 ·l·-1; 21+DMAD→22: k3 = (1.0±0.1) · 10-4 mol-1 ·l·s-1.The reactions giving the barrelene derivatives 19, 22, 26 and 30 are slower than those leading to adducts that are not barrelenes. The former are estimated less exothermic than the latter. It is proposed that the Diels-Alder reactivity of exocyclic s-cis-butadienes grafted onto bicycle [2.2.1]heptanes and bicyclo [2.2.2]octanes that are modified by remote substitution of the bicyclic skeletons can be affected by changes inthe exothermicity of the cycloadditions, in agreement with the Dimroth and Bell-Evans-Polanyi principle.Force-field calculations (MMPI 1) of 3, 4, 6 and related exocyclic s-cis-butadienes as a moiety of bicyclo [2.2.2]octane suggested single minimum energy hypersurfaces for these systems (eclipsed conformations, planar dienes). Their flexibility decreases with the degree of unsaturation of the bicyclic skeleton. The effect of an endocyclic double bond is larger than that of an exocyclic diene moiety.

Notes: Attempted Synthesis of Push-Pull DiacetylenesTwo alternative synthesis of push-pull diacetylenes of type 1 (5-amino-2,4-alkadiynals) are investigated. A bromination-dehydrobromination sequence starting with 5-dimethylamino-2,4-pentadienal (2) as well as the application of the well-known Cadiot-Chodkiewicz coupling reaction give new intermediates 3-5, and 7 and 8, respectively, but fail to give the target molecules 1.

Notes: Ring Transformations of 3-Substituted 5-Trifluoromethyl-1,3,4-thiadiazol-2(3H)-one with NucleophilesThe 3-chlormethyl-5-trifluoromethyl-1,3,4-thiadiazolone 3 undergoes a ring transformation to 3-acylated 2,3-dihydro-1,3,4-thiadiazoles 4 with many nucleophiles. Upon formal replacement of the chloromethyl group in the 3-position of 3 by an extended bromoalkyl chain (→9a-c), the reaction with nucleophiles yields 4-acylated 5,6-dihydro-4H-1,3,4-thiadiazines 10 (from 9a), 4,5,6,7-tetrahydrothiadiazepines 13 (from 9b) and 5,6,7,8-tetrahydro-4H-1,3,4-thiadiazocines 14 (from 9c) by ring enlargement. The 3-propargyl-thiadiazolone 17 rearranges with nucleophiles to 4-acylated 6-methylidene-5,6-dihydro-4H-1,3,4-thiadiazines 18. The structures of the new compounds were elucidated by 1H- and 13C-NMR spectroscopy.

Notes: On the Mechanism of the α-Alkynone Cyclization: Synthesis and Thermolysis of 1-(1-Methylcyclopentyl)[3-13C]prop-2-ynoneThe relative migratory aptitude of two acetylenic substituents in the α-alkynone cyclization, a thermal conversion of α-acetylenic ketones A to 2-cyclopentenones C, was investigated by isotope-labeling experiments. The α-alkynone [β-13C]-1, specifically labeled with 13C at the β-acetylenic C-atom C(3), was synthesized by an intramolecular Witting reaction (230-300°) of the diacylmethylidenephosphorane [13C]-7. The latter resulted from acylation of methylidenetriphenylphosphorane with the acid chloride 4 to yield the acylmethylidenephosphorane 5, which in turn was formylated with acetic [13C]formic anhydride ([13C]-6.) Upon thermolysis of [β-13C]-1, its label at C(β) was transferred almost exclusively to C(β) of the 2-cyclopentenone moiety in the resulting cyclization product [13C]-2. We conclude that there is a distinct preference for hydrogen migration in the acetylene → alkylidene carbene isomerization (A → B) which precedes the cyclization step (B → C). No evidence was found for a fast reversibility of this isomerization (A ⇄ B) involving both acetylenic substituents.

Notes: The Synthesis of 2,3,4,5-1H-Tetrahydroimidazo[2,1-b]quinazolin-2,5-diones and analogous 2,3,4,5-1H-Tetrahydroimidazo[1,2-a]thieno[2,3-d] (or [3,2-d])-pyrimidin-2,5-dionesThe syntheses of various imidazo [2, 1-b]quinazolinediones and their thiophene analogs are described.

Notes: A conformational study was carried out on Boc-(L-Val-D-Val)6-OMe in the crystalline state by X-ray and IR. and by 1H-NMR. in chloroform. The dodecapeptide crystallizes from CHCl3/EtOAc with a left-handed helical structure of the type ↑↓ β5.6, and from CHCl3/MeOH (or MeOH) with a different structure. In chloroform it forms three slowly interconverting species: one is a ↑↓ β5.6 left-handed helical species, and the other two are most likely single-stranded β4.4 helical species of opposite handedness. The double-stranded helical species is predominant in fresh solutions of samples obtained from CHCl3/EtOAc. Because of the slow conversion or formation of this species some hours are needed to reach the conformational equilibrium in chloroform at 25°.

Notes: Reaction of cobaltocene with cyclopentadiene and air results in the formation of the title compound; its structure has been elucidated by spectroscopic and X-ray methods.

Notes: Synthesis of ‘Push-Pull’ DiacetylenesThe first synthesis of push-pull diacetylenes of type 1 is described. Reaction of perchlorobutenyne (8) with two equivalents of dialkylamine, followed by dechlorination using two equivalents of butyllithium gives lithio-dialkylamino-diynes 7. Final acylation of these intermediates leads to push-pull diacetylenes 1b-1e in good yields. The method allows the introduction of both push and pull substituents in a simple one-pot-procedure. In addition, 1a is prepared by hydroxymethylation of lithio-morpholino-diyne 7c, followed by oxidation with manganese dioxide in acetone.

Notes: The 31P{1H}-NMR characteristics of the complexes [HgX2(1)] and [HgX2-(PPh2Bz)2] (X = NO3, Cl, Br, I, SCN, CN) and the solid state structures of the complexes [HgCl2(1)] and [HgI2(1)] (1 = 2,11-bis (diphenylphosphinomethyl)benzo-[c]phenanthrene) have been determined.The 1J(199Hg, 31P) values increase in the order CN 〈 I 〈 SCN 〈 Br 〈 Cl 〈 NO3. The two molecular structures show a distorted tetrahedral geometry about mercury. Pertinent bond lengths and bond angles from the X-ray analysis are as follows: Hg—P = 2.485(7) Å and 2.509 (8) Å, Hg—Cl = 2.525 (8) Å and 2.505 (10) Å, P—Hg—P = 125.6(3)°, Cl—Hg—Cl = 97.0(3)° for [HgCl2(1)] and Hg—P = 2.491 (10) Å and 2.500(11) Å, Hg—I = 2.858(5) Å and 2.832(3) Å, P—Hg—P = 146.0(4)°, I—Hg—I = 116.9(1)° for [HgI2(1)]. The equation, derived previously, relating 1J(199Hg, 31P) and the angles P—Hg—P and X—Hg—X is shown to be valid for 1.

Notes: Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL2], trans-[PtR(4-PADA)L2][BF4], trans-[PtRX() and trans-[PtR(4-PADA)()][BF4] R=H, Me; X=Cl-, I-; L=PEt3, bis(3-trifluoromethyl-phenyl)benzylphosphine (4), =the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene (3); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10-2 M ionic strength (LiClO4 as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed.The expected steric effects of the bulky ligands, especially of 3, on the rates and mechanisms of all the reactions studied are small. All reactions take place by the usual two-term rate law. Noteworthy, for the complexes with the bulky ligands 3 and 4, the direct reaction path with the entering nucleophile is predominant. There is no preference for a solvent or dissociative path. The reactivity order for the hydride complexes is trans-[PtHX (PEt3)2]〈trans-[PtHX(4)2]〈trans-[PtHX (3)]. However, for the corresponding methyl complexes, there is some retardation by ligand 3, probably due to an interaction between the methyl group and the hydrocarbon moiety of 3, which inhibits the fluxional behavior of this ligand. The results have some relevance for the understanding of olefin-insertion reactions of hydride complexes containing these phosphine ligands.

Notes: 5-Substituted 1,3,4-thiadiazol-2(3H)-ones were shown to exist almost exclusively in the oxo tautomeric form with the aid of proton-coupled 15N-NMR spectra using the corresponding 3-methyl-1,3,4-thiadiazol-2(3H)-ones and 5-substituted-2-methoxy-1,3,4-thiadiazoles as reference compounds.

Notes: Reactions of 2,4,6-trimethylbenzenediazonium (1), 2,6-diethylbenzenediazonium (2) and 2,6-diisopropylbenzenediazonium (3) tetrafluoroborates were studied in magic acid, SbF5/SO2ClF, acetonitrile and acetone by 1H-NMR and by analysis of the dediazoniation products. The Nα-Nβ rearrangement of β-N15-labelled tetrafluoroborates 1-3 was followed by 15N-NMR of the corresponding arylazonaphthols, as well as by MS analysis of the anilines obtained by reduction of the azo compounds. Diazonium salts 2 and 3 were synthesized for the first time and the steric effect of substituents at C(2) and C(6) on the reactions under study is discussed. All the results obtained can be rationalized by heterolytic dediazoniation of diazonium salts 1-3 and product formation from the corresponding aryl cations.

Notes: The evaluation of the dediazoniation kinetics of various m- and p-substituted benzenediazonium tetrafluoroborates in 1,2-dichloroethane at 50° in the presence of 18-crown-6, 21-crown-7 and dicyclohexano-24-crown-8 demonstrates that the rate constant for the dediazoniation within the complex (k2) is smallest, and the equilibrium constant for complex formation (K) is largest for the complexes with 21-crown-7 (cf. Scheme 1). The logarithms of the equilibrium constants (K) for complex formation with each of the crown ethers studied correlate well with Hammett's substituent constants, σ, to give reaction constants ρ = 1.18-1.38.A linear correlation between the logarithms of the rate constants for the dediazoniation within the complex with those of the dediazoniation rate constants of uncomplexed diazonium ions (log k2 vs. log.k1), found for most substituted diazonium salts, indicates that the dediazoniation mechanism of the complexed diazonium ions is not significantly different from that of the free ions. For very electrophilic diazonium ions (p-Cl, m-CN), k2 was much larger than expected on the basis of the linear log k2 vs. log k1 relationship. Analysis of the dediazoniation products showed that this was due to a change in mechanism from heterolytic to homolytic dediazoniation.The complexation rate of diazonium salts by crown ethers (kc) is practically diffusion controlled and does not change much with the size of the crown ether. The decomplexation rate (kd), however, is significantly lower for complexes with 21-crown-7, than for those with 18-crown-6 and dicyclohexano-24-crown-8, and is therefore the reason for the variations in the equilibrium constant (K) and thus for the fact that complexes of arenediazonium salts with 21-crown-7 are the most stable.The amounts of the Nα-Nβ rearrangement, as well as those of the exchange of the 15N-labelled diazonio group with external nitrogen during dediazoniation of p-toluenediazonium salt were independent of the addition of crown ethers.A dediazoniation mechanism involving a charge transfer, as well as an insertion-type diazonium ion-crown ether complex is proposed. In this mechanism, dediazoniation of the insertion complex does not take place directly, but through the charge-transfer complex.

Notes: Oxidation of sulfides with PhIO/RuCl2 (PPh3)3 leads to sulfones. Electronwithdrawing substituents in the aromatic ring of PhIO reduce the reactivity and improves selectivity of the system. Thus, with m-iodosylbenzoic acid sulfides are converted to sulfoxide. Under the same conditions aliphatic primary alcohols are transformed to aldehydes with m-iodosylbenzoic acid, while PhIO affords carboxylic acids.

Notes: The thujone-derived enone 1 is converted via enol lactone intermediates 4 and 5 to the optically active steroidal analogue 13 and the corresponding 19-norsteroid analogue 14. The structure of 13 was determined by X-ray diffraction analysis. The acid-catalyzed cyclopropane-ring opening of 13 and ozonolysis of the resulting olefin provided the 16-keto-steroid analogue 18.

Notes: Conduction band electrons produced by band gap excitation of TiO2-particles reduce efficiently thiosulfate to sulfide and sulfite. \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm 2e}_{{\rm cb}}^ - ({\rm TiO}_{\rm 2}) + {\rm S}_{\rm 2} {\rm O}_3^{2 - } \longrightarrow {\rm S}^{2 - } + {\rm SO}_3^{2 - } $\end{document}This reaction is confirmed by electrochemical investigations with polycrystalline TiO2-electrodes. The valence band process in alkaline TiO2-dispersions involves oxidation of S2O32- to tetrathionate which quantitatively dismutates into sulfite and thiosulfate, the net reaction being: \documentclass{article}\pagestyle{empty}\begin{document}$ 2{\rm h}^{\rm + } ({\rm TiO}_{\rm 2}) + 0.5{\rm S}_{\rm 2} {\rm O}_{\rm 3}^{{\rm 2} - } + 1.5{\rm H}_{\rm 2} {\rm O} \longrightarrow {\rm SO}_3^{2 - } + 3{\rm H}^{\rm + } $\end{document}This photodriven disproportionation of thiosulfate into sulfide and sulfite: \documentclass{article}\pagestyle{empty}\begin{document}$ 1.5{\rm H}_{\rm 2} {\rm O } + 1.5{\rm S}_{\rm 2} {\rm O}_{\rm 3}^{{\rm 2} - } \mathop \to \limits^{h\nu} 2{\rm SO}_3^{2 - } + {\rm S}^{{\rm 2} - } + 3{\rm H}^{\rm + } $\end{document} should be of great interest for systems that photochemically split hydrogen sulfide into hydrogen and sulfur.

Notes: A general scheme for the synthesis of the tetrahydroisoindolinone moiety of naturally occurring cytochalasans and unnatural analogs was developed. The key-step consists of the intermolecular [2+4]cycloaddition of 4-methylsorbinol (7) to an alkylidene malonic ester derivative such as 6, 9 or 10, obtained from the corresponding amino acids. The products obtained, 4a, 17, and 18 were converted to the desired lactams 5, 21, and 22.Cycloaddition of the diene alcohol 7 to the optically active alkylidene malonic ester derivative 9b (s. Footnote 5) prepared from L-leucine gave compound 17b with 98% enantiomeric excess. The optical activity was retained during the conversion of 17b to the lactam 21b. The latter is a subunit for the synthesis of the aspochalasins.

Notes: (-)-1-Camphanoyloxyacrylonitrile (=(-)-1-cyanovinyl camphanate; 1) obtained from the commercially available (-)-camphanoyl chloride and 2-oxo-propiononitrile added to furan at 20° in the presence of Cu (BF4)2 · 6H2O or ZnI2 and gave a mixture of 2-cyano-7-oxabicyclo [2.2.1]hept-5-en-2-yl camphanates (2-5) from which isomer 5 could be obtained pure by crystallization. The latter was transformed into (+)-(1R)-7-oxabicyclo[2.2.1]hept-5-en-2-one (6) in high yield and optical purity. Adducts 2-4 were recycled into 1+furan by heating in toluene, and (-)-camphanic acid was recovered after saponification of 5. The absolute configuration of 6 was deduced from its CD spectrum which showed two 1200-cm-1 Franck-Condon series for its n→πCO* transition.

Notes: The absolute configurations of the two algal pheromones multifidene 1 and viridiene 2 were determined as (+)-(3S, 4S)-3-[(Z)-1-butenyl]-4-vinylcyclopentene and (+)-(3R, 4S)-3-[(1Z)-1, 3-butadienyl]-4-vinylcyclopentene, respectively. The strategy involves enzyme-initiated asymmetric synthesis of the ring-saturated pheromone analogues (+)-8a and (-)-8b and their subsequent catalytic hydrogenation to the chiral cycloalkanes 9a and 9b, only the letter of which is also obtained from the two natural messengers (+)-1 or (+)-2. Biological activity assays proved these enantiomers of 1 or 2 to be the characteristic pheromones for male gametes of the seaweeds Syringoderma, Cutleria multifida and Chorda tomentosa.

Notes: A method is proposed for correcting experimental fluorescence readings for inner filter effects, i.e. the absorption of the exciting light and/or the absorption of the emitted radiation, which cause the non-linearity between fluorescence intensity and fluorophor concentration. Basically the method consists of measuring the fluorescence intensity at two different points along the diagonal in the cell. Unlike similar methods proposed in the literature, the two points are corrected simultaneously for both absorption of excitation and of emission radiation without the necessity of reading the optical density of the solution, and with a very simple data elaboration.

Notes: The synthesis of uridine-5′-diphosphate analogs, spin-labeled either at C(4) or C(5) is reported as well as their enzymatic incorporation into ribonucleic acids, some of which had previously been shown to be potent interferon inducers upon annealing with poly (inosinic acid). Also, the synthesis of spin-labeled poly (cytidylic acid) obtained by chemical acylation is presented.

Notes: Conversion of Bicyclo [3.2.0]hept-2-en-6-one into Cyclopentadienylacetic Acid DerivativesThe reaction of a mixture of 4exo-bromobicyclo [3.2.0]hept-2-en-6-one (2) and -7-one (3) with O- or N-nucleophiles yielded cyclopentadien-5′-yl-acetates 4a-f or-acetamides 4g-h. Due to their rapid isomerization, the products 4 were not isolated, but some of them were demonstrated spectroscopically or captured in situ with maleimide as 10′-substituted norbornene derivatives 7. The formation of 4 from 2/3 involves a fragmentation of the bond between the carbonyl and the bridge-head C-atom, induced by the attacking nucleophile and the leaving Br-ion and aided by the relief of the four-membered ring strain. Some of the isomerization products of 4, i.e. the cyclopentadiene-1′-yl- and 2′-yl-acetyl derivatives were captured with maleimide as the 1′- and 8′-substituted norbornene-derivatives 8 and 9. Two C-nucleophiles did not induce the fragmentation: sodium acetylacetonate substituted the Br-atom and sodium (diethoxyphosphoryl)ethoxycarbonylmethide condensed with the carbonyl group of 2/3, yielding 11/12 and 13/14, respectively.

Notes: The first total synthesis of racemic neplanocin A (1)After submitting our paper we learned that Arita et al. [J. Am. Chem. Soc.105, 4049(1983)] synthesized the natural enantioner of Neplanocin A. from cyclopentadiene and acylnitroso-3,5-dinitrobenzoic acid is described. The synthesis is suitable for specific isotopic labelling of the hydroxymethyl group of neplanocin A.

Notes: Urinary metabolites 5-methyl-5-[2-(2,6,6-trimethyl -3-oxo-1-cyclohexen-1-yl)-vinyl]-2-tetrahydrofuranone (1) and 5-[2-(6-hydroxymethyl-2, 6-dimethyl-3-oxo-1- cyclohexen-1-yl)vinyl]-5-methyl-2-tetrahydrofuranone (2) of retinoic acid have been synthesized from 4-[2,2,6-trimethyl-3-(tetrahydro-2 H -pyran-2-yl)oxy-1-cyclohexen-1-yl]-3-buten-2-one (4) and methyl 2-(3,3-ethylenedioxy-1-butenyl)-1, 3-dimethyl-4-oxo-2-cyclohexene-1-carboxylate (5).

Notes: Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. X. Synthesis of (3R,3′S,5′R)-Capsanthin, (3S,5R,3′S,5′R)-Capsorubin, (3′S,5′R)-Cryptocapsin, and Some Related Compounds. A New Approach to Optically Active, Five-Membered-Ring Carotenoid Building Units by HydroboratonThe synthesis of (3R,3′S,5′R)-capsanthin (1), (3S,5R,3′S,5′R)-capsorubin (2), and (3′S,5′R)-cryptocapsin (3), found in the red paprika Capsicum annuum, is described using (+)-camphor (7) as a readily available starting material. As the key reaction, the unsaturated acetal 16 is hydroborated with (+)-diisopinocampheylborane to give the hydroxy ketone 12a in very high chemical and optical yield. A subsequent aldol condensation with 13 in THF/toluene gives 2 in high yield. The C40-compounds 1 and 3 are synthesized using the same type of condensation. The pigments 1-3 are transformed by an Oppenauer oxidation to (3R,5′R)-capsanthone (5), (5R,5′R)-capsorubone (4) and (5′R)-cryptocapsone (6), respectively.

Notes: The Synthesis of 7-anti-Substituted 2-exo- and 2-endo-NorbornanolsThe title compounds and the corresponding p-toluenesulfonates were prepared in connection with a mechanistic study of C-participation in carbocations.

Notes: Indolizino [6,5,4,3-aij]quinoline (1) and its 3,9-dimethyl- (2), di-tert-butyl- (3) and diphenyl-(4) derivatives yield persistent radical cations which have been studied by ESR and ENDOR spectroscopy. The corresponding radical anions have also been prepared, but only that of 3 was amenable to a complete characterization by hyperfine data. The π-spin populations in the radical anions are essentially localized on the 13-membered C-perimeter, and thus both the HOMO and LUMO of 1 exhibit an ‘annulenyl character’. The radical anions of 1 and 2 have gradually been converted into those of the corresponding 3,4-dihydro derivatives (1-H2 and 2-H2) which have been unambiguously identified by a combination of preparative and spectroscopic methods.

Notes: Enantioselective synthesis of phenylalanine was performed by reacting phenylpyruvic acid with pyridoxamine followed by ketimine-aldimine isomerization of the Schiff base formed catalyzed by an optically active copper (II)-complex. By UV and CD measurements it was shown that the enantiomeric excess strongly depends on the reaction conditions and on the reaction time. In favorable cases it reached values up to 80%. The selectivity of the reaction is discussed on the basis of possible structures of the intermediate mixed ligand complex.

Notes: Ortho Esters with 2,4,10-Trioxaadamantane Structure as Carboxyl Protecting Group; Applications in the Synthesis of Substituted Carboxylic Acids by Means of Grignard ReagentsThe surprising stability of 2,4,10-trioxa-3-adamantyl derivatives 1 against nucleophilic substitution by organomagnesium compounds is discussed and shown to be caused by unfavourable stereoelectronic and steric factors governing the substitution of these cage compounds (Scheme 2). As a consequence, a number of Grignard reagents 2 containing the carboxyl group masked as 2,4,10-trioxa-3-adamantyl group could be prepared and have been reacted in a second step with various electrophiles (cf. Scheme 4). In the products 7-13 and 15b the carboxyl masking group is removed by mild acid hydrolysis and saponification (cf. Scheme 3) to yield the corresponding acids 16a-21a, 22, and 23a. Acids 21a and 23a have been further transformed to give the macrocyclic lactones 24 and 26, isolated from Galbanum oleo-gum-resin, and acid 22 to give 12-methyl-13-tridecanolide (25), isolated from Angelica root oil. In addition 1-bromo-ω-(2,4, 10-trioxa-3-adamantyl)alkanes 1c and 1b have been used to synthesize (±)-methyl recifeiolate (29b) and pure cis-ambrettolic acid ((Z)-32a).

Notes: Selected [2+2]-cycloadditions of three alkylvinylketenes 2 to one mono- and seven dialkyl-olefins 3 yielded eleven 2-alkyl-2-vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl-elimination from α,β-unsaturated acid chlorides 1; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]-cycloadditions were fully regio- and stereoselective with respect to the olefin 3, but less so with respect to the ketene 2, so that - where possible - two stereoisomers of 4 resulted, namely A and B, whose configurations were determined from their 1H-NMR, spectra, mechanistic considerations and, in one case, 4f, by chemical correlation with a previously known cycloadduct 8.

Notes: Syntheses and Chemical Properties of New Bridged Quinone Derivatives. Coupling Reactions of Aryldiazonium Salts with 2-Methoxy-1,6-methano[10]annuleneCoupling of 2-methoxy-1,6-methano[10]annulene (3) with the aryldiazonium salts 4a-4i yields the quinone hydrazones 5a-5i. The spectroscopic properties of these products are described. The reaction of 3 with 4-nitrophenyldiazonium tetrafluoroborate buffered with sodium acetate in dry methanol yielded after chromatographic separation the azo derivative 7 on the one hand and a mixture of the valence tautomers 8a and 8b on the other.

Notes: The influence of remote substituents on the stereochemical outcome of electrocyclization in the silicon-directed Nazarov reaction has been examined. While the degree of stereocontrol was modest (ca. 3:1) the substituent in the major isomer (4,5 or 7-substituted cis-hexahydroind-2-en-1-ones) is always cis to the protons on the ring fusion. Thorough spectroscopic and conformational analysis revealed that divergent senses of electrocyclization are responsible for the observed products. Additional experiments suggest that steric, rather than stereoelectronic forces control the sense of cyclization. A qualitative description of the nature of reactive intermediates in the silicon-directed Nazarov reaction is proposed as well as an explanation for the remarkable efficacy of FeCl3 for inducing the reaction.

Notes: Differences in the distribution of deuterium at individual atomic sites in vanillin samples are revealed by 2H-NMR measurements, and can be used to determine whether the sample is of natural or synthetic origin.

Notes: Starting from (+)-camphor-10-sulfonic acid (1) the chiral crystalline alcohols 3 and 11 were prepared in two steps. Lewis-acid-mediated [4+2]-additions of their acrylates to 1,3-dienes were studied. Notably, the crystalline acrylate 4 underwent TiCl2 (OiPr)2-promoted Diels-Alder addition to cyclopentadiene giving after recrystallization efficiently the pure (2R)-adduct 5.

Notes: Isolation and Identification of 8-C-Galactosylapigenin from Leaves of Carlina acanthifolia8-C-galactosylapigenin was isolated from the leaves of Carlina acanthifolia (Compositae). This identification represents only the third report of a mono C-galactosylapigenin in plants and the first report in the Compositae.

Notes: Wolff-Kishner reduction of the optically active ketomorphinan 5 afforded the optically active morphinan 6 differing chromatographically and spectroscopically from the material obtained in a Grewe-cyclization of the isoquinoline 1. A single crystal X-ray analysis of a hydrobromide salt of a phenolic amine obtained from 1 and 2 with refluxing hydrobromic acid showed this compound to be the N-methylapomorphinan 4.

Notes: In view of the significance of steric compression in the base-catalyzed intramolecular cyclization of polycyclic olefinic alcohols, the standard enthalpies of formation of anti9,10-10 endo-hydroxytricyclo [4.2.1.12,5]deca-3,7-dien-9-one (1) and 9-oxatetracyclo [5.4.0.03,10.04,8]undec-5-en-2-one (2) as well as the kinetics of the ether formation 1 → 2 were determined.

Notes: The solvolysis rates and products of the tertiary 2-methyl-2-exo- and -2-endo-norbornyl 2,4-dinitrophenyl ethers 1 and 2, (X = 2,4-(NO2)22C6H3O) have been determined. The different sensitivities of the rates of these ethers to the inductive effect of substituents at C(6) indicate that graded bridging of C(2) by C(6) occurs in the ionization of the exo-ethers 1, not, however, in the ionization of the endo-ethers 2. In both cases hydrolysis leads to 2-methyl-2-exo-norbornanols only. Consequently, substitution takes place with retention at C(2) in the exo-series 1 and with inversion at C(2) in the endo-series 2. It is concluded that stereoelectronic and polar effects, rather than steric bulk effects, determine the high exo/endo rate ratios of the parent norbornyl derivatives 1a and 2a.

Notes: The structures of voafrine A and voafrine B, two novel dimeric indole alkaloids isolated from Voacanga africana Stapf cell suspension cultures, were established and the medium-dependent formation of both alkaloids was investigated.

Notes: The base-catalyzed reaction of 4-nitro-3-oxobutyrate (6) with acetylacetone (8 Scheme 3), formylacetone (13, Scheme 4), formylcyclohexanone (31, Scheme 5), 2,4-dioxopentanoates 39 and 40 (Scheme 6), and 2,4,6-heptanetrione (2, Scheme 7) affords substituted 3-nitrosalicylates, products of a double aldol condensation. With unsymmetrical dicarbonyl compounds both regioisomers are formed. High selectivity was found in the case of β-keto-aldehydes 13 and 31 with preferred addition of the NO2-substituted carbon to the aldehyde carbonyl. The major products of these cyclocon-densations, which are isolated in yields ranging from 20% to 80%, are all new compounds. Less successful are the conversions with β-alkoxy- and β-chloro-vinyl ketones (23, 25, and 26), and with alkinone 24, where the condensation products are formed in very low yield (Scheme 4).

Notes: The complex [IrCl3(CO)(1)](4,1=2,11-bis (diphenylphosphinomethyl)benzo[c]phenanthrene) has been prepared by CuCl2-oxidation of [IrCl(CO)(1)](2a). It is shown that the chlorine oxidation of 2a gives a mixture of products whose composition depends on the reaction conditions. The X-ray crystal structures of 2a and 4 have been determined. The small conformational differences observed for the trans-spanning ligand 1 in the two complexes are likely to be caused by the difference in Ir-P bond lengths in square planar 2a and octahedral 4 (2.310(4) and 2.411(3) Å, respectively).

Notes: The reported wavelength-dependence of the photoreactivity of 1-piperidinoanthra-quinone (1-PAQ) in hydrogen-donor solvents is ascribed to a chemical sensitization by trace amounts of 1-chloroanthraquinone, as the action spectrum for photoreactivity of the former matches the absorption spectrum of the latter. The photochemistry and photophysics of 1-PAQ seem therefore not to violate the Kasha-Vavilov rule, i.e. its photoreactivity does not involve an upper n  -  π* triplet state.

Notes: A method has been developed to analyzed the bond and current correlation structures of a molecular many-electron wave function. It is shown that the second order density matrix contains information about the bond and current correlations in its off-diagonal components with respect to the indices of orbital basis functions. We break down the off-diagonal correlation functions into five kinds: charge, spin scalar, spin quadrupole, charge spin, and spin polar correlation functions. For a real wave function, the four correlation functions, except for the spin polar one, have only symmetric-symmetric and antisymmetric-antisymmetric components. The former components give site-bond and bond-bond correlations of charges and spins, while the latter components give current-current correlations of charges and spins. The spin polar correlation function has only symmetric-antisymmetric components that give site-current and bond-current correlations of spins. The five off-diagonal correlation functions are expressed in terms of the off-diagonal components of the second order density matrix. The linked off-diagonal correlation functions are defined in that they give dynamical bond and current correlations. The method is applied to the analyses of the bond and current correlations in the low lying exact eigenstates of the PPP Hamiltonian of benzene.

Notes: This work amalgamates some basic elements defined in the first paper of this series and in related papers with the theory of coupling coefficients for an arbitrary group with the view of generating the Clebsch-Gordan coefficients and V symbols for point symmetry groups. The connection between Clebsch-Gordan coefficients and V symbols is established for an arbitrary group in a form that reduces to the one known for the chain SU(2) ⊃ U(1). The Clebsch-Gordan coefficients and V symbols of any point symmetry group G are shown to be obtainable from Clebsch-Gordan coefficients and \documentclass{article}\pagestyle{empty}\begin{document}$ {\bar f} $\end{document} symbols of the chain SU(2) ⊃ G through the resolving of a system of nonlinear equations.

Notes: The nature of the correlation function G(1,2) appearing in the definition of the reduced first order density operator γ′(1,2) = ρ(1)1/2ρ(2)1/2G(1,2) is analyzed. It is shown that when G(1,2) is expanded in terms of plane waves in the context of a single-determinant approximation to the wave function, the correction to the Weizsacker term in the kinetic energy density expression is the Thomas-Fermi term.

Notes: In the framework of our theoretical approach of the structure and reactivity of chemical intermediates we have been led to reexamine the concept of stability which is widely used by the experimentalists often without specifying its true meaning. In this work we propose a more general definition of the concept of stabilization energy, namely, \documentclass{article}\pagestyle{empty}\begin{document}$$ SE = \Delta H_a - \Sigma N_{AB} E_{AB} $$\end{document} where ΔHa is the heat of atomization of the species under consideration and the EAB's are standard bond energy terms derived from the heats of atomization of reference compounds. Using experimental heats of formation or semiempirical ones deduced from theoretical heats of reaction of appropriate isodesmic processes, we have calculated the stabilization energies of various types of chemical species: saturated, unsaturated and conjugated molecules, free radicals, carbocations, and carbanions. The results obtained can be rationalized in terms of steric hindrance, angular strain, polar interactions, electron delocalization, and substituent effects. Moreover, we have shown that heats of hydrogenation and bond dissociation energies do not provide accurate information on the thermodynamic stabilization of unsaturated compounds and free radicals, respectively. Among other applications the concept of stabilization energy allowed us to propose a detailed classification of free radicals and to rationalize their reactivity. Considering the particular case of radical recombination reactions we have been able to deduce interesting equations showing the relations between the concept of stabilization energy and other quantities commonly used in chemical physics, namely, the bond cleavage enthalpy [BDE(C—C) if one considers alkane thermolysis], the thermodynamic stability measured by the free enthalpy change of a given reaction, and the kinetic stabilization related to the activation energy of a chosen chemical process \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm BDE}(R - R) = E(R - R) - 2{\rm SE(R}^ \cdot {\rm)} + {\rm SE(R} - R{\rm),}} \\ {\Delta G^0_r 2{\rm SE(}R^ \cdot {\rm)} - {\rm SE(R} - R{\rm)} - E(R - R) - T\Delta S^0,} \\ {E_a (r) = \alpha [ - {\rm BDE(}R - R{\rm)}] + \beta ({\hbox{Evans - Polanyi relation}}),}\\ {E_a (r) = a[2{\rm SE(R}^ \cdot )} - {\rm SE(}R - R{\rm)] + }b{\rm .} \end{array} $$\end{document} This analysis allowed us to give a new interpretation of the adjectives transient, persistent, and stable introduced by Griller and Ingold and to show that the persistence of a radical may be due to other factors than steric ones. In conclusion, the concept of stabilization energy appears to be a good tool for rationalizing the static and dynamic properties of chemical species.

Notes: Two-dimensional fully numerical solutions of the Hartree-Fock problem are reported for the singlet ground states of H-, He, H2, and HeH+. The H2 energy at R = 1.4 a.u. is -1.13362957 a.u.

Notes: In this paper, some operator endomorphisms which give rise to conditions for N representability of pth order density matrices are presented.

Notes: A simple analysis of the bonding between the d orbitals in binuclear complexes of chromium indicate that the usual multiple bond picture used to describe these systems is incomplete. This analysis is fairly general and depends only on the symmetry of these complexes and the rather weak coupling between the 3d orbitals on the two metal centers. A series of INDO calculations on Cr2Cl8-4 and Cr2(CH3)8-4 are reported, and suggest that the dominant description of the bonding is one of two Cr atoms antiferromagnetically coupled. Although this description properly accounts for the eclipsed versus staggered conformations found for these systems, the calculated bond length is too long. An analysis of the components of the wave function suggests that the role of multiple bonded structures (configurations) may be small but is important in its influence in shifting the very flat potential energy surfaces to shorter Cr—Cr distances.

Notes: The interaction energies of proton with ethylene and substituted ethylenes in a positive bridged ion have been calculated by ab initio MO method with STO-3G basis set, and the energies were further decomposed according to decomposition scheme proposed by Kitaura and Morokuma [Int. J. Quantum Chem. 10, 325 (1976)].

Notes: Correlation corrections to coupled Hartree-Fock (CHF) static dipole polarizabilities and dipole moment of the HF molecule are calculated using third-order Rayleigh-Schrödinger perturbation theory with Møller-Plesset partitioning (RSMP) in a finite-field procedure. Computations are also made for the dipole moment and polarizability derivatives at the equilibrium internuclear separation. Three different basis sets using contracted Gaussian orbitals augmented by field-induced diffuse polarization functions have been employed to investigate the nature of variation of the properties under study, and the importance of field-induced diffuse polarization functions is discussed. [2/1] Padé approximants are used to accelerate the convergence of the properties. The correlated dipole moment and polarizability values are in excellent agreement with the existing theoretical and experimental values. The dipole moment derivative is in perfect agreement with the existing correlated value. However, the polarizability derivatives at SCF and correlated levels differ appreciably from the existing SCF values and represent as improvement.

Notes: The observed proton hyperfine coupling constants of radicals from resorcinol and 2-carboxylic, 5-carboxylic, and 5-methyl resorcinols in acidic and alkaline solution were reproduced by means of the INDO (intermediate neglect of differential overlap) with molecular geometry adjusting method. The bond lengths of C—O were longer in acidic solution than in alkaline solution and the total energies were lower in acidic solution than in alkaline solution. The assignments of the coupling constants of the radicals from resorcinols were |A2| 〉 |A5| in alkaline oxidation and |A2| 〈 |A5| in acidic oxidation.

Notes: In the present work, the problem of the determination of the potential energy surface for nonrigid molecules is examined in the case of the double rotation of the methyl groups in acetone. From the symmetry adapted functional form for the potential, the minimum number of configurations to be calculated is deduced in order to have a reliable surface. With this consideration in mind, the potential energy surface of acetone is determined in some Hartree-Fock semiempirical (CNDO/2) and ab initio procedures with different standard basis sets. In addition, ab initio calculations are performed using different sets of floating Gaussian functions in order to introduce some polarization effects in the wave function. Finally, the influence of the electronic correlation effects in the barrier height, and the role of the possible relaxation of the structure during the rotation is discussed.

Notes: Cross sections for energy transfer into many-body systems can be expressed in terms of time-correlation functions (TCFS) of transition operators. A semiclassical version is presented by treating internal motions as quantized and relative motions as classical. The time evolution of internal motions can be calculated in the Heisenberg picture and avoids expansions in target states. The decoupling of fast and slow internal motions is treated and applied to vibrational-rotational decoupling in polyatomic molecules. Results are presented for Li+-CO2 collisions.

Notes: Water chain intervention in the hydrolysis of methyl fluoride and in some tautomeric 1,3 proton transfer reactions has been studied. The results show that in solution the process are neither unimolecular nor bimolecular as in the gas phase, but are multimolecular, where the geometric parameters of the solvent intervene in the reaction coordinate.

Notes: The computational considerations involved in calculating ordinary and rotatory intensities and electronic excitation energies in the random phase approximation (RPA) are examined. We employ a localized orbital formulation in order to analyze the results in terms of local and charge-transfer excitations. Occupied orbitals are localized by the Foster-Boys procedure. The virtual space is transformed into a localized “valence” set that maximizes dipole strengths with the occupied counterparts, and a delocalized remainder. The two-electron integral transformation is performed with an efficient algorithm, based on Diercksen's, that generates only the particle-hole-type integrals required in the RPA. The lowest solutions of the RPA equations are obtained iteratively using a modification of the Davidson-Liu simultaneous vector expansion method. This allows the inclusion of the entire set of particle-hole states supported by a basis set of up to 102 orbitals. Calculations at this level give better excitation energies and intensities than SDCI methods, at substantial savings in computational effort. Comparative timings, computed results and analysis in terms of localized orbitals are given for planar and distorted ethylene using extended atomic orbital bases including diffuse functions. The results for planar ethylene are in excellent agreement with experiment.

Notes: Nonlinear equations are important for the description of dissipative processes and soliton-related phenomena. One of the principal aims of the theory of symmetry breaking in quantum mechanics is to provide a systematic method for introducing interactions which reduce the symmetry of a system. Such a method is applied here to compute the general form of the symmetry-breaking interaction F(x,t, Ψ, Ψ*) for the time-dependent Schrödinger equation in one spatial dimension \documentclass{article}\pagestyle{empty}\begin{document}$$ \left[{\partial _{xx} + 2i\partial_t - 2g_2(t)x^2 - 2g_1(t)x - 2g_0 (t)} \right]\psi (x,t) = F(x,t,\psi,\psi *). $$\end{document} For F = 0, it has been shown that the Lie algebra of space-time invariances of this equation is S1 = s1 (2,IR)□w1, the Schrödinger algebra. Following the method of Boyer, Sharp, and Winternitz, all conjugacy classes of subalgebras of S1 are given. For each subalgebra, the most general form of the interaction term F(x,t, Ψ, ψ*) is constructed. The potential F then reduces the symmetry from S1 to the considered subalgebra. Furthermore, the one-dimensional subalgebras of S1 obtained above partition S1 into orbits of operators. To each orbit there corresponds a coordinate system in which the above equation separates variables. A partial resolution of the solutions of the above equation has been obtained by exploiting this relation. The algebraic approach to symmetry breaking yields a rich variety of interaction terms F, which appear to generalize the nonlinear Schrödinger-Langevin-Kostin equation for nonconservative systems and the so-called nonlinear Schrödinger equation. A criterion in terms of the existence or nonexistence of Bäcklund transformations is conjectured in order to distinguish between dissipative and soliton equations.

Notes: Calculating the electrostatic potential around the Ser-His-Asp catalytic triad in serine proteinases the very important substituent effect of the buried aspartate is revealed. It is found that the strong Coulomb field of this distant but charged side chain considerably enhances the nucleophilicity of the active serine hydroxyl group. The interpretation of the vital importance of aspartate may replace the “charge-relay” hypothesis which seems to be disproved in the light of recent experiments.

Notes: Effective solutions for two difficulties which may be present in MCSCF calculation are discussed: (i) We show how the large configuration state function state expansion case may be handled simply and effectively without the introduction of extraneous projection operators or Lagrange multipliers; (ii) we present a simplified two-electron integral transformation procedure which significantly reduces the operation count (and hence computational efficiency is increased) for second order and particularly for third order MCSCF procedures. The procedures we introduce use some freedom available in the orthogonal complement Cl space and the virtual orbital space to simplify MCSCF calculations.

Notes: A modified scheme for SCF interaction energy decomposition has been proposed where the nonphysical basis set superposition error (BSSE) has been corrected by means of the counterpoise method. A new procedure to separate the exchange and induction energy terms free of nonphysical BSSE has been tested in the case of the H2O dimer. The first order BSSE appears to be non-negligible for strong hydrogen bonded complexes. In addition the scheme allows separation of the long-controversial charge-transfer contribution within the induction term, which has been considerably overestimated in previous studies.

Notes: The carbene reaction 1CH2 + C2H6 was studied with the semiempirical method SINDO 1. The pertinent transition states and products were obtained by geometry optimization on a CI surface. We find the insertion reaction forming C3H8 greatly favored compared to the double insertion leading to CH4 + C2H4. The result is qualitatively the same for the reaction of the two possible intermediate radicals CH3 and C2H5. The geometries and energies of all transition states are presented.

Notes: Exact computer-generated formulas can be produced for each term of an infinite series that gives the value of three-center Coulomb integrals over Slater-type orbitals of the s-type with equal screening constants. As a specific example, the Coulomb energy of an equilateral triangular arrangement of all 1s orbitals is calculated using seven terms of an infinite expansion to obtain an answer comparable to earlier work in elliptic coordinates. Generalization to all three-center cases of this implementation of the Löwdin α-function method is straightforward.

Notes: Hartree-Bogoliubov-Valatin (HBV) theory may be implemented with Lipkin Hamiltonians to obtain self-consistent BCS wave functions which describe bond formation and dissociation. These wave functions are in turn vacuua for Nambu's representation of Feynman-Dyson-Goldstone diagrammatic perturbation theory, and hence provide suitable references for the many-body treatment of correlation. Exact SCF solutions of the HBV equations are equivalent to special even-replacement MC-SCF solutions. The latter are similar to generalized valence bond theory, and require one Fock operator for each one-particle shell. The commutative coupling case of HBV theory is realized when the number-conserving renormalized one-body and number-nonconserving pairing operators commute. In this case, a set of orbital equations which involves a single Fock operator may be solved. Since this could prove to be a significant simplification for large systems, the commutative coupling and exact solutions are compared here for the fragmentation of H2 and F2. Results suggest that commutative coupling orbitals will be useful for the aforementioned many-body theory.

Notes: A MNDO study of molecular geometries, enthalpies, formation, atomization, bond separation, and hydrogenation of a series of unsaturated boron-nitrogen compounds, linear with two and three members and cyclic with three, four, five, and six members are presented. For all these molecules, MNDO calculations are in excellent agreement with available ab initio calculations or experimental data. The high rotational barrier in aminoborane H2BNH2, 30.6 kcal/mol, and the length of bond in iminoborane HBNH, 1.183 Å, imply strong double and triple BN bond character in these two molecules. In the odd membered heterocycles, examination of the molecular geometries and energies of equilibrium states shows that in all cases, the stability of the compounds grows with the number of boron atoms and decreases with that of the nitrogen atoms. Moreover, compared study of the two BN-fulvenes with their homologous hydrocarbon shows that only BN (BB)-fulvene has a polyenic structure similar to that of fulvene.

Notes: The linear, quadratic, and cubic response of a multiconfigurational Hartree-Fock state to a time independent one-electron perturbation has been derived. A comparison between the exact response functions as obtained from Rayleigh-Schrödinger perturbation theory and the multiconfigurational Hartree-Fock response functions allows a identification of matrix elements of the perturbation operator between the ground and excited states and between excited states. We discuss some ambiguities which result from such an identification.