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  • 1
    Electronic Resource
    Electronic Resource
    Electrochemistry of Mono- through Hexakis-adducts of C60 (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1334-1344 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first systematic electrochemical study by cyclic voltammetry (CV) and rotating-disk electrode (RDE) of the changes in redox properties of covalent fullerene derivatives (2-11) as a function of increasing number of addends is reported. Dialkynylmethanofullerenes 2-4 undergo multiple, fullerene-centered reduction steps at slightly more negative potentials than C60 (1; see Table and Fig. 1). The two C-spheres in the dumbbell-shaped dimeric fullerene derivative 4 show independent, identical redox characteristics. This highlights the insulating character of the sp3-C-atoms in methanofullerenes which prevent through-bond communication of substituent effects from the methano bridge to the fullerene sphere. In the series of mono- through hexakis-adducts 5-11, formed by tether-directed remote functionalization, reductions become increasingly difficult and more irreversible with increasing number of addends (see Table and Fig. 2). Whereas, in 0.1M Bu4NPF6/CH2Cl2, the first reduction of mono-adduct 5 occurs reversibly at -1.06 V vs. the ferrocene/ferricinium couple (Fc/Fc+), hexakis-adduct 11 is reduced irreversibly only at - 1.87 V. Hence, with incremental functionalization of the fullerene, the LUMO of the remaining conjugated framework is raised in energy. Reduction potentials are also dependent on the relative spatial disposition of the addends on the surface of the fullerene sphere. Observed UV/VIS spectral changes and changes in the chemical reactivity along the series 5-11 are in accord with the results of electrochemical measurements. Further, with increasing number of addends, the oxidation of derivatives 5-11 becomes more reversible. Whereas oxidations are increasingly facilitated upon going from mono-adduct 5 (+1.22 V) to tris-adduct 7 (+0.90 V), they occur at nearly the same potential (+0.95 to +0.99 V) in the higher adducts 8-11. This indicates that the oxidations occur in these compounds at a common sub-structural element, for which a ‘cubic’ cyclophane is proposed (see Fig. 3). This sub-structure is fully developed in hexakis-adduct 11.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780523
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of Covalently Linked Viologen-Metallocenes (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 2603-2605 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and physical data of the covalently linked viologen-ferrocenes 3 a and 5 a and of the corresponding ruthenocene 3 b are described.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650832
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  • 3
    Electronic Resource
    Electronic Resource
    Eindeutige Synthese des 4,7-Dihydro-4-oxo-1 H-pyrazolo[3,4-b]pyridins - Bemerkungen zur „(N—C)-Umlagerung“ von (2-Alkoxycarbonyl-vinyl-amino)pyrazolenHerrn Prof. Dr. Dr. h. c. mult. Alfred Rieche zum 80. Geburtstag gewidmet (1982)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 557-562 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unambiguous Synthesis of 4,7-Dihydro-4-oxo-1H-pyrazolo[3,4-b]pyridine  -  Further Comments on the “(N—C)-Rearrangement” of (2-Alkoxycarbonyl-vinyl-amino)pyrazols4,7-Dihydro-4-oxo-1H-pyrazolo[3,4-b]pyridine 1a is synthesized by decarboxylation of 1-benzyl-5-carboxy-4-hydroxy-pyrazolo[3,4-b]pyridine 4b and debenzylation of 1-benzyl-4,7-dihydro-4-oxo-pyrazolo[3,4-b]pyridine 1b with sodium in liquid ammonia. The product from 3-amino-pyrazol and methyl propiolate, formerly described as 1a, obviously is the 6-oxo isomer 2a.Use of the parameter δ13(C=O) for the structural assignment of pyrazolo[3,4-b]pyridones is only permitted, if in the corresponding media mainly the oxo-tautomer is existing. It is again demonstrated that DMSO is often an insufficient medium.Debenzylation of 1b and similar compounds with SeO2 is only possible, if the α-position of C=O is blocked by a substituent. Otherwise diselenids of type 6 are formed. This obviously is a general reaction of cyclic lactames.The cyclisation of (2-alkoxycarbonyl-vinyl-amino)pyrazols 7 in acidic media, and with catalytical amounts of the corresponding amino-pyrazols gives 6,7-dihydro-6-oxo-pyrazolo[3,4-b]pyridines 2 via amino 4-(2-alkoxycarbonyl-vinyl)pyrazols 8, i.e. via products of an “(N—C)-rearrangement”, while by thermal cyclisation of 7 4,7-dihydro-4-oxo-pyrazolo[3,4-b]pyridines 1 are formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19823240409
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of the difunctional primary products in the Oxidates of Medium n-Paraffins (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 545-551 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proportion of difunctional and monofunctional products with the original carbon skeleton was determined in the oxidates of n-decane, n-tridecane, n-pentadecane, and n-octadecane to about 0.32. This proportion does not significantly depend on the conversion of the starting paraffin. As well as mono- and difunctional products with the original carbon skeleton already at very low conversions of n-tridecane, about 45% of lower oxygen-containing compounds, for example aldehydes, alkan-2-ones, carboxylic acids and γ-lactones, are also obtained. Obviously, a part of the difunctional primary products reacts very fast with scission of the carbon chain, forming lower oxygen-containing compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290402
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  • 5
    Electronic Resource
    Electronic Resource
    Phosphinites of carbohydrates as chiral ligands for asymmetric synthesis catalysed by complexes. IV. Influence of the solvent and the structure of cationic 4,6-0-benzylidene-2,3-0-bis(diphenylphosphino)-D-hexopyranoside-rhodium(I) chelates on enantioselectivity in Hydrogenation of Dehydroamino Acid DerivativesDedicated to Prof. Dr. habil Horst Pracejus (†) on the oceassion of his 60th birthday (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 717-724 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic rhodium(I)-chelates of 4,6-benzylidene-2,3-0-bis(diphenylphosphino)-D-hexopyranosides bearing axial 0-functions, as for instance manno- 5 and galactopyranosides 4c, 4d or α-D-glycopyranosides, show lower enantioselectivity in the hydrogenation of dehydroamino acid derivatives than chelates of the all-equatorial phenyl 4,6-0-(R)-benzylidene-2,3-0-bis(diphenylphosphino)-β-D-glucopyranoside 3d (abbreviated Ph-β-glup). Complexes of the galactopyranosides 4c and 4d give an abnormal decrease of enantiomeric excess with the prochiral dehydroamino acid 1c in contrast to the analogous substrate ester 1d. In hydrogenations with [Rh(Ph-β-glup)(COD)] A as precatalyst various weak coordinating anions A⊖ do not produce differences in % ee, and the solvent effect remains low. However, an analogous chelate of the methyl α-anomer bisphosphinite Me-α-glup 3a gives rise to inversion of the optical induction using benzene as solvent.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290422
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  • 6
    Electronic Resource
    Electronic Resource
    Die Reaktion von α,β-Dihalogen-propionitrilen mit monosubstituierten Hydrazinen - einfache Synthese 1-substituierter 3- bzw. 5-Amino-pyrazole (1979)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 321 (1979), S. 93-101 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Reaction of α,β-Dihalogeno-propionitriles with Monosubstituted Hydrazines  -  A Simple Synthesis of 1-Substituted 3- or 5-Amino-pyrazolesIn methanol hydrazines 3, and α,β-dihalogeno-propionitriles 1, 2 even at 0°C irreversibly yield 3 · HX, and α-halogenoacrylonitriles 4, 5 (A1). Fast addition of alkyl- and aralkyl- hydrazines 3 to 4, 5 (C) gives 1-substituted 1-(2′-halogeno-2′-cyan-ethyl)-hydrazines 6, the addition of arylhydrazines 3 to 4, 5 (D) 1-aryl-2-(2′-halogeno-2′-cyan-ethyl)-hydrazines 8. In methanol 6 spontaneously cyclise (E) to hydrogen halides 7 · HX of 1-alkyl- and 1-aralkyl-3-amino-pyrazoles, 8 with 2 moles of acids (F) to salts 10 · 2HY of 1-aryl-4-halogeno-5-imino-pyrazolidines, and the free 10 spontaneously (G) to hydrogen halides 9 · HX of 1-aryl-5-amino-pyrazoles. Mechanisms (A1), (C), (D), (E), (F), and (G) are proved by t.l.c., 1H-n.m.r., and isolation of intermediates, the structures of 7 resp. 9, using the significant 1H-n.m.r.-parameter ΔHMPTCDCl3. Simple general syntheses are described for 3-amino-pyrazoles 7 (R = H, alkyl, aralkyl) or 5-amino-pyrazoles 9 (R = aryl) starting with α,β-dihalogeno-propionitriles 1, 2, and for α-bromo-acrylonitrile 5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19793210112
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  • 7
    Electronic Resource
    Electronic Resource
    Allgemeine Synthesen und rationelle Strukturparameter isomerer Derivate von [3,4]-kondensierten Pyrazolen (1979)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 321 (1979), S. 881-898 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: General Syntheses and Rational Parameters for Structural Assignment of Isomeric Derivatives of [3,4]-fused Pyrazoles4 isomeric 1- or 2-methyl-, and 1- or 2-benzyl-pyrazolo[3,4-b]pyridones, i.e. the 4-oxo-types 17a, b or 11a, b and the 6-oxo-types 16a, b or 10a, b, are synthesized unambiguously. Cyclisation of 1-substituted 3- or 5-(1-methyl-2-ethoxycarbonyl-vinylamino)-pyrazoles 9a, b or. 15a, b, which were synthesized from 1-substituted 3- or 5-amino-pyrazoles and ethyl acetoacetate yields 11a, b or 17a, b in downtherm, but 10a, b or 16a, b in presence of acidic catalysts. The acidic cyclisation is preceded by a new rearrangement of 9 or 15 into 1- substituted 3- 27 or 5-amino-4-(1-methyl-2-ethoxycarbonyl-vinyl)-pyrazoles 30; mechanism and concurring reactions are explained. Because of their higher electron densities at C-4 it is easier to cyclise derivatives of 5-amino-pyrazoles compared to 3-amino-pyrazoles. All isomeric 1- or 2-substituted 4(6)-chloro-6(4)-methyl-pyrazolo-[3,4-b]pyridines are formed with POCl3 from the corresponding oxo-compounds.The position of a substituent at N-1 or N-2 of [3,4]-fused pyrazoles can be assigned using the significant 1H-n.m.r.-parameter ΔHMPTCDCL3 = δCDCl3  -  - δHMPT (conc. HC - 3). If solvent influences are considered, δ(C = O) is a useful 13C-n.m.r.-parameter to distinguish the 4-oxo-types (11a, b; 17a, b) from the 6-oxo-types (10a, b; 16a, b) of pyrazolo[3,4-b]pyridones. Further own and lit. dates conc. structural assignment (n.m.r., i.r., u.v.) are discussed critically.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19793210602
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  • 8
    Electronic Resource
    Electronic Resource
    Stereoselective inhibition of thromboxane-induced coronary vasoconstriction by 1,4-dihydropyridine calcium channel antagonists (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 233-240 
    Details
    ISSN: 0899-0042
    Keywords: 1,4-dihydropypyridine enantiomers ; stereoselectivity ; thromboxane A2 (TxA2) ; coronary vasoconstriction ; calcium channel binding ; blood pressure ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The biological activity of the (+)-S- and (-)-R-enantiomers of niguldipine, of the (-)-S- and (+)-R-enantiomers of felodipine and nitrendipine, and of rac-nisoldipine and rac-nimodipine was investigated in vitro and in vivo. Inhibition of coronary vasoconstriction due to the thromboxane A2 (TxA2)-mimetic U-46619 in guinea pig Langendorff hearts, displacement of (+)-[3H]isradipine from calcium channel binding sites of guinea pig skeletal muscle T-tubule membranes, and blood pressure reduction in spontaneously hypertensive rats were determined. The enantiomers were obtained by stereoselective synthesis. Cross-contamination was 〈0.5% for both S- and R-enantiomers of niguldipine and nitrendipine and 〈1% for those of felodipine. From the doses necessary for a 50% inhibition of coronary vasoconstriction, stereoselectivity ratios for (+)-(S)-/(-)-(R)-niguldipine, (-)-(S)-/(+)-(R)-felodipine, and (-)-(S)-/(+)-(R)-nitrendipine of 28, 13, and 7, respectively, were calculated. The potency ratio racnisoldipine/rac-nimodipine was 3.5. Ratios obtained from binding experiments and antihypertensive activity were (+)-(S)-/(-)-(R)-niguldipine = 45 and 35, (-)-(S)-/(+)-(R)-felodipine = 12 and 13, (-)-(S)-/(+)-(R)-nitrendipine = 8 and 8, and rac-nisoldipine/rac-nimodipine = 8 and 7, respectively. Highly significant correlations were found between the in vitro potency of the substances to prevent U-46619-induced coronary vasoconstriction and their affinity for calcium channel binding sites as well as their antihypertensive activity. The mechanism of TxA2-induced coronary vasoconstriction in guinea pig Langendorff hearts can be readily explained by a transmembrane influx of extracellular Ca2+ susceptible to stereoselective blockade by 1,4-dihydropyridine calcium channel antagonists.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530020408
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  • 9
    Electronic Resource
    Electronic Resource
    Geminal Benzotriazolyl Ethoxy Derivatives - Efficient Auxiliaries in the synthesis of unsaturated carbonyl compounds (1997)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 98-100 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19973390119
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  • 10
    Electronic Resource
    Electronic Resource
    Orthoamide. LI. Push-Pull-Butadiene und Heterocyclen aus CH2-aciden Verbindungen und Orthoamiden von AlkincarbonsäurenTeil eines Vortrages zur 3. Fachtagung über Iminiumsalze, Stimpfach-Rechenberg, 17.-19. September 1997 (s.a. Heft 4/98).Herrn Professor Dr. Horst Hartmann zum 60. Geburtstag gewidmet. (1998)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 408-423 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Orthoamides. LI. Push-Pull-Butadienes and Heterocycles from Alkyne Carboxylic Acid Orthoamides and CH2-acidic CompoundsThe acetylides 4b, 4f react with N,N,N′,N′,N″,N″-hexamethylguanidiniumchloride (5) to give the orthoamides 6b, 6f, resp. From CH2-acidic compounds and the orthoamides 6a, c, e can be obtained the push-pull-substituted butadienes 8a-8aj. The 2,3,5-trimethyl-thiadiazolium salt 9 does not condense with 6e, as other CH2-acidic compounds do, instead the vinylogous guanidinium salt 10a is produced. On heating, the ketenaminals 8d, aa cyclize to give the pyridone-carbonitriles 11a, b, resp. From 4-amino-coumarins 12 and the orthocarboxylic acid amideacetals 13a, b and the ketenaminal 16 resp., the amidines 14a-c and the heterocyclic compounds 15a-c resp., are formed. The enamines 17a-c, 19a, b react with the orthoamides 6a-f to give the pyridine derivatives 18a-1, 20a-h and 21a, b, resp. Analogously, from 6-aminouracil 22 and 6a, b, e, f are formed the pure 7-dimethylaminopyrido[2,3-d] pyrimidines 23a, b or mixtures of compounds 23c, d and the isomeric 4-dimethylamino-pyrido[2,3-d]pyrimidines 24a, b resp., which can be separated via their salts 25a,b/26a,b. The heterocyclic compounds 30a-d, 32a,b can be prepared from the pyrazole derivatives 28, 31 resp. and the orthoamides 6a-f.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19983400503
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