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  • 2020-2022
  • 1990-1994  (8)
  • 1960-1964  (4)
  • 1890-1899
  • Heterocycles
  • 1
    ISSN: 1434-4475
    Schlagwort(e): Cycloalkanes ; Heterocycles ; Friedel-Crafts acylation ; Isomerization ; Methyloctahydro-anthracen-9-ones ; Reduction ; LAH/AlCl3
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Reaktion voncis-2-(4-methylbenzoyl)-cyclopropan-(1) und-cyclobutancarbonsäuren (2), der stereoisomeren cyclohexyl-Homologen (3 und4) und von di-endo-3-(4-methylbenzoyl)-bicyclo[2.2.1]heptan-2-carbonsäure (5) mit Hydrazinen ergibt die cycloalkankondensierten 3(2H)-Pyridazinone6–9 und das methylenüberbrückte di-endo-Derivat10. Die Verbindungen1 und3–5 wurden mit Hydroxylamin zu den cycloalkan- und norbornankondensierten 1,2-Oxazin-6-onen11–14 umgesetzt.3–6 reagierten zumtrans-Hexahydroanthron17a und seinem methylenüberbrückten Analogen24. Die teilweise gesättigten Anthrone wurden auch aus den stereoisomeren Hexahydro-1(3H)-isobenzofuranonen20 und21 hergestellt (16b und17b), wobei der Methylsubstituent jedoch in Position 6 lokalisiert ist. Reduktion von16b ergab das 2-Methyloctahydroanthracen22. Die Strukturen der Verbindungen wurden durch NMR-Spektroskopie abgesichert (1H,13C, DEPT, CH-COSY, NOE).
    Notizen: Summary Reactions ofcis-2-(4-methylbenzoyl)-cyclopropane- (1) and-cyclobutanecarboxylic acids (2), the stereoisomeric cyclohexyl homologues (3 and4), and di-endo-3-(4-methylbenzoyl)-bi-cyclo-[2.2.1]heptane-2-carboxylic acid (5) with hydrazines yield the cycloalkane-condensed (3(2H)-pyridazinones6–9 and the norbornane di-endo-fused derivatives10. With hydroxylamine, compounds1 and3–5 were transformed to the cycloalkane- and norbornane-condensed 1,2-oxazin-6-ones11–14. Transformation of3–5 led to thetrans-hexahydroanthrone17a and its methylene-bridged analogue24. From the stereoisomeric hexahydro-1(3H)-isobenzofuranones20 and21, the partly saturated anthrones were also prepared; the products (16b and17b) contain the methyl substituent in position 6. On reduction,16b yield the 2-methyloctahydroanthracene22. The structures of the compounds were proved by1H and13C NMR spectroscopy, making use of NOE, DEPT, and CH-COSY techniques.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 908-913 
    ISSN: 0044-2313
    Schlagwort(e): Methylene-bridged Phosphines ; Phosphaalkenes ; Heterocycles ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Synthesis and Molecular Structure of new Ring Systems from 1,1,3,3-Tetrachloro-1,3-diphosphapropane1,1,3,3-Tetrachloro-1,3-diphosphapropane 1 reacts in two different ways to form new heterocycles. Partial oxidation of 1 with tetrachloroorthobenzoquinone furnishes the methylene-bridged λ3P, λ5P species 3. Subsequent reactions with di- and triethylamine lead to the condensed ring system 6 with the P=C bonds connected to a central four-membered ring. Compound 6 displays crystallographic inversion symmetry, a short transannular P—P distance and an extremely distorted tetrahedral coordination geometry at the four-membered ring phosphorus atoms. 1 reacts with 7 to give the heterocycle 8 with a central eight-membered ring involving four phosphorus atoms. The eight - membered ring shows a „bent“ crown conformation, the condensed five - membered rings display envelope conformation.
    Notizen: Aus 1,1,3,3-Tetrachlor-1,3-diphosphapropan 1 lassen sich auf zwei verschiedenen Reaktionswegen neue Heterocyclen gewinnen. Die Oxidation von 1 mit einem Äquivalent Tetrachlororthobenzochinon führt zu der methylenverbrückten λ3P, λ5P Spezies 3. Bei der anschließenden Umsetzung mit Di- und Triethylamin entsteht das kondensierte Ring-system 6 mit am zentralen Vierring exocyclisch angeordneten P=C Bindungen. 6 zeigt kristallographische Inversionssymmetrie, einen kurzen P—P Transannularabstand und eine extrem verzerrte tetraedrische Koordinationsgeometrie an den λ5-Phosphoratomen. 1 und 7 reagieren unter Bildung eines Heterocyclus mit einem zentralen Achtring mit vier alternierend angeordneten Phosphoratomen. Der Achtring liegt in einer „geknickten“ Kronenform vor, die ankondensierten Fünfringe besitzen Briefumschlagkonformation.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 614-616 
    ISSN: 0749-1581
    Schlagwort(e): 13C NMR ; 4,5-Dihydroisoxazoles ; Substituent effects ; Heterocycles ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evaluation by empirically derived equations for the substituent effect (α, β, γ, δ) on the 13C NMR chemical shifts for C-3, C-4, C-5 and halomethyl-substituent carbon (C-6) in 5-halomethyl-5-hydroxy-4,5-dihydroisoxazoles (where C-3 substituent=H), alkyl or phenyl, C-4 substituent=H, alkyl or heteroalkyl and C-5 substituent (=dior trihalomethyl), taking as reference 5-trichloromethyl-5-hydroxy-4,5-dihydroisoxazole, is reported. From the calculated values for the α, β, γ and δ effects for each substituent it was possible to estimate the chemical shift of each carbon of the compounds.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1434-4475
    Schlagwort(e): Spiro compounds ; Heterocycles ; Rearrangement ; 17O-NMR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Im Verlauf einer versuchten Eliminierungstreaktion wurde ausgehend von einem Aminoalkoholderivat eines Isothiochromansystems unerwarteterweise ein Benzo[c]thiophen-derivat isolert. Die Konstitution des Umlagerungsproduktes wurde eindeutig durch17O-NMR-Spektroskopie bestätigt.
    Notizen: Summary In the course of an attempted elimination reaction starting from an isothiochromane derivative substituted with an amino-alcohol moiety, a benzo[c]thiophene derivative formed via a rearrangement reaction was isolated unexpectedly. Its constitution was confirmed unambiguously via17O-NMR-spectroscopy.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 960-962 
    ISSN: 0749-1581
    Schlagwort(e): E/Z 2-hydroxyindolenines ; 1H-NMR ; 13C-NMR ; Heterocycles ; Substituent effects ; Conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H NMR spectra of E/Z 2-hydroxyindolenines are reported in both CDCl3 and DMSO-d6 solvents. The data suggest a preferred conformation of the heterocyclic ring, which is slightly distorted from planarity, in agreement with the x-ray crystallographic data of one of the isomers. The 13C NMR spectra for the Z-hydroxyindolenines are also described. Substituent effects on E/Z isomerism about the exocyclic C=C bond are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 122 (1991), S. 323-325 
    ISSN: 1434-4475
    Schlagwort(e): Bis-(trifluoroacetoxy)pentafluoroiodobenzene ; Iodosylbenzene ; Oxidation ; Heterocycles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Acridine3,5 und6 sowie das Dibenzo[b,f]azepin4 wurden mit Hilfe der beiden hypervalenten Jod-Verbindungen Jodosobenzol (1) und Bis-trifluoroacetoxyiodbenzol (2) zu den entsprechenden 3-Acridinonen7,9 und10 sowie zum Dibenzoazepin-3-on8 oxidiert.
    Notizen: Summary The acridines3,5, and6, as well as the dibenzo[b,f]-azepine4 were converted into the 3-oxo-derivatives7–10 using hypervalent iodine compounds (iodosylbenzene and bis-(trifluoroacetoxy)iodopentafluorobenzene).
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 30 (1991), S. 217-237 
    ISSN: 0570-0833
    Schlagwort(e): Coordination number ; Phosphorus-nitrogen compounds ; Bond theory ; Heterocycles ; Imino phosphanes ; Phosphanes ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The large number of known stable compounds in which phosphorus has a low coordination number makes it clear that such compounds can no longer be regarded as “exotic” in main group chemistry. While the rich chemistry of P—C multiply bonded systems makes clear their affinity to their organic congeners, iminophosphanes in particular are also of increasing importance. The linkage of a phosphinidine fragment with an imine fragment via a multiple bond gives rise to a class of compounds with an unusually wide range of structural types. This in turn leads to a broad spectrum of chemical behavior which makes iminophosphanes extremely useful synthetic building blocks in organoelement chemistry.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 30 (1991), S. 238-264 
    ISSN: 0570-0833
    Schlagwort(e): 3-Amino-2H-azirines ; Azirines ; Amino acids ; Peptides ; Heterocycles ; Synthetic methods ; 2-Aminoisobutyric acid ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The recent upswing in peptide chemistry has been accompanied by an increasing interest in nonproteinogenic amino acids. These include the α,α-disubstituted glycines, the best known of which is Aib (2-aminoisobutyric acid, 2-methylalanine). These α-amino acids occur in natural oligopeptides such as the peptaibols, a class of membrane-active ionophores that has been isolated from fungal cultures. The twofold substitution at the α-C atom of the amino acids severely restricts the conformational freedom of the peptides and causes particular secondary structures to be favored; thus, α, α-disubstituted α-amino acids induce the formation of β turns or helices. 3-Amino-2H-azirines are ideal synthons for the construction of oligopeptides, cyclic peptides and depsipeptides (peptolides) containing such α,α-disubstituted α-amino acids. The presence of the ring strain in these molecules means that they can be used in peptide coupling without the need for additional activating reagents. Using 3-amino-2H-azirines a large array of heterocycles containing α, α-disubstituted α-amino acids as structural elements within their skeleton can be synthesized. The driving force in these reactions is the release of the strain on the three-membered ring, which usually takes place in a ring-expansion reaction. The mechanistic elucidation of these reactions, which can be quite complex, contains some surprises.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 333-341 
    ISSN: 0570-0833
    Schlagwort(e): Strained molecules ; Heterocycles ; Diaziridines ; Diazirines ; Oxaziranes ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Since their discovery five years ago, the diaziridines have become an extensive and easily accessible class of compounds. Hydrolysis of these compounds effects a simple synthesis of hydrazine, alkylhydrazines, and N,N′-dialkylhydrazines. They are also powerful oxidizing agents. The rigidity of the three-membered ring gives rise to a few stereoelectronic peculiarities. Investigations on the mechanism of formation of the three-membered rings led to a new synthesis of oxaziranes and to discovery of the isomeric oximes with a three-membered ring structure. The latter decompose readily to form diimide. Diazirines are cyclic isomers of the aliphatic diazo compounds and are surprisingly easy to obtain by dehydrogenation of suitable diaziridines; they are chemically much more stable than the linear isomers. Grignard reagents add onto the N=N double bond without destruction of the three-membered ring. Thermal decomposition yields carbenes.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 10
    ISSN: 0570-0833
    Schlagwort(e): Kinetics ; Dipolar cycloaddition ; Cycloaddition ; Heterocycles ; Reaction mechanisms ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Criteria for the mechanism of 1,3-dipolar cycloadditions which lead to 5-membered rings are provided by the stereoselectivity observed with cis-trans isomeric dipolarophiles, by the effect of solvent and substituents on the rate constants, by the activation parameters, and by orientation phenomena. A concerted addition, which can also be described in terms of molecular orbitals and in which the two new σ-bonds are formed simultaneously, although not necessarily at equal rates, offers the best explanation of the experimental facts.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 459-476 
    ISSN: 0570-0833
    Schlagwort(e): Aminoguanidine ; Heterocycles ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Due to its unique structure, aminoguanidine is capable of reacting as a derivative of hydrazine, guanidine or formamidine. Addition and condensation reactions yield products which can be cyclized to heterocyclic compounds. Frequently, heterocyclics are directly accessible from aminoguanidine in one stage.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 565-598 
    ISSN: 0570-0833
    Schlagwort(e): Dipolar cycloaddition ; Cycloaddition ; Heterocycles ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In contrast to the very large number of special methods applicable to syntheses in the heterocyclic series, relatively few general methods are available. The 1,3-dipolar addition offers a remarkably wide range of utility in the synthesis of five-membered heterocycles. Here the “1,3-dipole”, which can only be represented by zwitterionic octet resonance structures, combines in a cycloaddition with a multiple bond system - the “dipolarophile” - to form an uncharged five-membered ring. Although numerous individual examples of this reaction were known, some even back in the nineteenth century, fruitful development of this synthetic principle has been achieved only in recent years.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
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