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  • 1990-1994  (8)
  • 1965-1969  (10)
  • 1960-1964  (4)
  • 1935-1939
  • 1890-1899
  • 1860-1869
  • Heterocycles
  • 1
    ISSN: 1434-4475
    Keywords: Cycloalkanes ; Heterocycles ; Friedel-Crafts acylation ; Isomerization ; Methyloctahydro-anthracen-9-ones ; Reduction ; LAH/AlCl3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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).
    Notes: 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.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 908-913 
    ISSN: 0044-2313
    Keywords: Methylene-bridged Phosphines ; Phosphaalkenes ; Heterocycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 614-616 
    ISSN: 0749-1581
    Keywords: 13C NMR ; 4,5-Dihydroisoxazoles ; Substituent effects ; Heterocycles ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 2 Tab.
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  • 4
    ISSN: 1434-4475
    Keywords: Spiro compounds ; Heterocycles ; Rearrangement ; 17O-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 960-962 
    ISSN: 0749-1581
    Keywords: E/Z 2-hydroxyindolenines ; 1H-NMR ; 13C-NMR ; Heterocycles ; Substituent effects ; Conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 2 Ill.
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  • 6
    ISSN: 1434-4475
    Keywords: Bis-(trifluoroacetoxy)pentafluoroiodobenzene ; Iodosylbenzene ; Oxidation ; Heterocycles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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).
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 30 (1991), S. 217-237 
    ISSN: 0570-0833
    Keywords: Coordination number ; Phosphorus-nitrogen compounds ; Bond theory ; Heterocycles ; Imino phosphanes ; Phosphanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 30 (1991), S. 238-264 
    ISSN: 0570-0833
    Keywords: 3-Amino-2H-azirines ; Azirines ; Amino acids ; Peptides ; Heterocycles ; Synthetic methods ; 2-Aminoisobutyric acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 478-482 
    ISSN: 0570-0833
    Keywords: Sesquifulvalenes ; Fulvalene ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterosesquifulvalenes containing sulfur or oxygen as hetero atom may be prepared, e.g., by condensation of cyclopentadienes with thiopyrones or pyrones in acetic anhydride. Heterosesquifulvalenes containing nitrogen can be obtained from the oxygen compounds by O,N-exchange. The ground state of all these compounds is determined mainly by the nonpolar resonance formula.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 962-974 
    ISSN: 0570-0833
    Keywords: Heterocycles ; Aziridinium salts ; Azetidinium salts ; Cycloaddition ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and important reactions of stable aziridinium salts are described in this article. The more stable azetidinium salts, which undergo similar reactions, have also been studied. Polar and dipolar cycloadditions produce heterocycles by ring expansions that can be represented as .
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  • 11
    ISSN: 0570-0833
    Keywords: Sulfonyl hydrazones ; Amides ; Azo sulfones ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sulfonyl hydrazones of cyclic amides undergo oxidative coupling with phenols and reactive methylene components. The reaction proceeds via the azo sulfones, which may be used as such, and which, as ambident cations, enter into many reactions with nucleophiles and extend the scope of oxidative coupling. The reaction with phenols is a two-step process, in which the limiting cases k1 ≪ k2, k1 ≈ k2, and k1 ≫ k2 can be realized by slight variation of the reactants.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 6 (1967), S. 919-928 
    ISSN: 0570-0833
    Keywords: Heteroaromatic compounds ; Hydration ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Many aromatic N-heterocycles add water across the C=N double bond. Methods are described for recognizing this phenomenon and for diagnosis of the site of attack. These methods are extended to the determination of (a) the ionization constants of unstable states (whether hydrated or anhydrous), (b) the ratio of hydrated to anhydrous forms at equilibrium, and (c) the rate constants of hydration. The features that stabilize hydration in a molecule are discussed. The literature through 1965 and 1966 is reviewed with special reference to the emergence of new principles, such as di-hydration and the shifting of hydration within a molecule.
    Additional Material: 5 Ill.
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  • 13
    ISSN: 0570-0833
    Keywords: Ketones ; Sulfur ; Amines ; Heterocycles ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A large number of preparatively interesting compounds have become readily available by the simultaneous action of sulfur and ammonia or amines on ketones. Direct syntheses of Δ3-thiazolines, Δ3-imidazoline-5-thiones, 5,6-dihydro-4H-1,4-thiazines, and the 1,2,3,4,5,6-hexathiocane system from ketones, sulfur, and ammonia or amines, and further possibilities for the synthesis of these heterocyclic systems have been proposed. Other heterocycles containing N or N and S (thiazoles, thiophenes, thiazolidines, tetrahydrothiazolo[2,3-c]-1,4-thiazines, thiomorpholines, 4-amino-2H-imidazoles, etc.) are readily obtainable by further reactions of these compounds. Hydrolysis of the Δ3-thiazolines yields α-mercapto ketones, which are the starting materials for other syntheses. Most of the syntheses described proceed at room temperature and at normal pressure.
    Additional Material: 10 Tab.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 5 (1966), S. 35-39 
    ISSN: 0570-0833
    Keywords: Heterocycles ; Pyrimidines ; Quinazolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some syntheses of heretofore unknown pyrimidines, tetrahydroquinazolines, and quinazolines are described. These methods are uniquely simple one- or two-step reactions, general and versatile in scope, and give high yields. Some interesting chemistry associated with these heterocyclic systems is discussed.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 5 (1966), S. 760-776 
    ISSN: 0570-0833
    Keywords: Silicon-nitrogen heterocycles ; Heterocycles ; Cyclosilazanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Great progress has recently been made in the chemistry of the silicon-nitrogen bondC. Eaborn: Organosilicon Compounds. Butterworths, London 1960, p. 339.R. Fessenden and J. S. Fessenden, Chem. Reviews 61, 361 (1961).K. A. Andrianov, I. Haiduc, and L. M. Khananashvili, Uspekhi Khim. 32, 563 (1963); Chem. Abstr. 59, 8782 (1963).U. Wannagat, Advances inorg. Chem. Radiochem. 6, 265 (1964).I. Haiduc: Westep do Chemii Nieorganicznych Zwiazkow Pierscieniowyrh. WPN, Warsaw 1964, Chap. 10 (in Polish).. Whereas attention was formerly concentrated on open-chain silazanes and silylamines, growing interest is now being shown in the cyclic SiN compounds. A major factor which has contributed to the rapid development in this field is the need for better polymers and liquids for use above 350 °CCf. E. G. Rochow, Chim. et Ind. 85, 897 (1961).. The present article deals with monomeric cyclic compounds containing at least one silicon-nitrogen bond in the ring, as well as the polycyclic compounds derived from these.
    Additional Material: 8 Tab.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 543-557 
    ISSN: 0570-0833
    Keywords: Hetarynes ; Heterocycles ; Alkynes ; Arynes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigations carried out during the last six years have shown that, as in the case of benzene, an extra bond can be introduced into heteroaromatic rings. Since this possibility does not appear to be confined to exceptional cases, the heterocyclic arynes (hetarynes) promise a much wider variety than the carbocyclic arynes. Hetarynes occur mainly as intermediates in nucleophilic substitutions on halogenated heterocyclic compounds. Since the replacement of a CH group in dehydrobenzene by a nitrogen atom and the condensation of benzene rings have stabilizing effects, the stability of hetarynes is expected to increase with the number of N atoms and with the number of condensed aromatic rings.
    Additional Material: 1 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 292-300 
    ISSN: 0570-0833
    Keywords: Pyridazones ; Heterocycles ; Mucochloric acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthesis of mucochloric acid by chlorination of butynediol has facilitated the preparation of a series of 4,5-dichoropyridazones. The high reactivity of these compounds has been investigated and applied in several ways. New classes of compounds, some with biological activity, were obtained by displacement of the chlorine atoms. New heterocyclic systems were prepared by condensation and rearrangement reactions.
    Additional Material: 2 Tab.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 1023-1038 
    ISSN: 0570-0833
    Keywords: Heterocycles ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of heterocycles containing phosphorus is described. The chemical behavior of ring systems containing trivalent phosphorus is mainly determined by their phosphine character; heterocyclic behavior in the ordinary sense is shown by rings containing functional groups. Syntheses and reactions of cyclic compounds of pentavalent and hexavalent phosphorus are particularly interesting.
    Additional Material: 3 Tab.
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 333-341 
    ISSN: 0570-0833
    Keywords: Strained molecules ; Heterocycles ; Diaziridines ; Diazirines ; Oxaziranes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 1 Ill.
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  • 20
    ISSN: 0570-0833
    Keywords: Kinetics ; Dipolar cycloaddition ; Cycloaddition ; Heterocycles ; Reaction mechanisms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 2 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 459-476 
    ISSN: 0570-0833
    Keywords: Aminoguanidine ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 565-598 
    ISSN: 0570-0833
    Keywords: Dipolar cycloaddition ; Cycloaddition ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 4 Tab.
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