Showing papers by "Alan R. Katritzky published in 1984"
115 citations
TL;DR: In this article, the conformational analysis of six-membered rings is discussed, and a treatment of individual ring systems is provided, in which the discussion centers on conformational preferences of substituents on tertiary nitrogen and on ring carbon atoms, and phenomena arising from the presence of two or more heteroatoms in one ring.
Abstract: Publisher Summary This chapter deals with conformational equilibria: (1) in piperidines, (2) in piperidine derivatives, in which ring methylenes are replaced by nitrogen, oxygen, and sulfur atoms, and (3) in systems incorporating these rings in fused ring structures, in which the additional rings are also six-membered. Fused-ring structures with other sizes of rings are generally not included, except for tropane. The chapter illustrates the principal methods available for the investigation of heterocyclic conformational analysis. Then follows a treatment of individual ring systems, in which the discussion centers on the conformational preferences of substituents on tertiary nitrogen and on ring carbon atoms, the energetics of nitrogen inversion, and phenomena arising from the presence of two or more heteroatoms in one ring. Emphasis is placed on simply the substituted free bases. The chapter deals with ring reversal equilibria and kinetics in the conformational analysis of six-membered rings. The problems of conformational equilibria in N-alkylpiperidinium salts and N-quaternization reactions, and the relationships of these to conformational equilibria in the free bases are not covered since this area is a large one requiring separate treatment.
52 citations
49 citations
TL;DR: The 2-(2- or 4-Pyridyl)ethyl group is readily introduced by pyridylethylation and easily removed after activation by quaternisation with methyl iodide.
42 citations
TL;DR: A new general synthesis of 1H-pyrrole-2-carboxylic acid derivatives is described in this paper, where reaction between appropriately substituted 2H-azirines and enamines gives a mixture of 2,3- and 3,4-dihydropyrroles, which on acid treatment yields the title compounds in moderate to high yields.
Abstract: A new general synthesis of 1H-pyrrole-2-carboxylic acid derivatives is described. Reaction between appropriately substituted 2H-azirines and enamines gives a mixture of 2,3- and 3,4-dihydropyrroles, which on acid treatment yields the title compounds in moderate to high yields. Attempts to extend the reaction to the preparation of 2H- and 3N-pyrroles were unsuccessful; reasons are discussed. The crystal and molecular structure of ethyl 3-phenyl-4,5,6,7-tetrahydroindole-2-carboxylate has been determined. The molecules pack in highly coplanar, centrosymmetric, hydrogen-bonded pairs.
24 citations
01 Jan 1984
TL;DR: In this article, the authors focus on five-membered heterocyclic compounds with two or more heteroatoms and discuss their possible structures, nomenclature, properties, and tautomerism.
Abstract: This chapter focuses on five-membered heterocyclic compounds with two or more heteroatoms and discusses their possible structures, nomenclature, properties, and tautomerism. Systematic replacement of CH by N leads to nine additional monocyclic heteroaromatic nitrogen systems, which are known collectively as azoles. Reduction of one or two double bonds in the azole ring gives nonaromatic systems, which have been described as azolines and azolidines. Each of the aromatic azolium cations can be converted into a neutral system by substitution of an anionic O, S, or NR group on to a ring carbon atom. Examples of oxygen and sulfur rings with exocyclic conjugation systems are the 1,2-dithiole-3-thione and the type A mesoionic 1,3-thiazolium-4-olate. Isoxazole, thiazole, and their derivatives are examples of five-membered heterocyclics when ring atoms can be chosen from oxygen, sulfur, and nitrogen. The chapter presents the findings of research studies on the intermolecular forces between five-membered heterocyclic molecules and their influence on melting and boiling points, solubilities, and chromatographic properties, their thermochemistry, conformations of saturated ring systems, and aromaticity. Overall, the aromaticity of azoles is intermediate between that of five-membered heterocycles with one heteroatom and six-membered heterocycles (azines). Furthermore, types of tautomerism in five-membered heterocyclic compounds with two or more heteroatoms, including prototropic tautomerism, ring-chain tautomerism, and valence tautomerism are discussed.
20 citations
TL;DR: The synthesis of 1-(2-propynyl)pyridinium salts was described in this paper, where a second pyridine molecule was added to the first to form products of type 4.
Abstract: The synthesis of 1-(2-propynyl)pyridinium salts 3 described. Compounds 3 react with a second pyridine molecule, in the presence of the corresponding hydrochloride, to form products of type 4, Certain bases cause the 1-(2-propynyl)pyridinium salts 3 to rearrange into 1-propadienylpyridinium salts. 5. Diethylamine converts compounds 3 into 1-acetonylpyridinium salts 8. Moreover, treatment of 3 or 5 with sodium methoxide gives enol ether sof type 9, which can be hydrolyzed to teh ketones 8. Addition of bromine to some of teh unsaturated compounds is also reported.
20 citations
TL;DR: The synthesis of fluorescent and coloured pyrylium and pyridinium salts, including water-soluble derivatives, designed to serve as marker reagents for primary amines was described in this paper.
19 citations
TL;DR: In this paper, the Pyryliumsalz wurde isoliert vor etwa 80 years and was used as a Zwischenstufen for nucleophilen Substitution.
Abstract: Das erste Pyryliumsalz wurde vor etwa 80 Jahren isoliert. In den letzten dreisig Jahren ist die Zahl der Veroffentlichungen erstaunlich stark gestiegen: Man hatte die Bedeutung der Pyryliumsalze als Zwischenstufen erkannt. Sie lassen sich nach vielen Methoden herstellen und sind gegenuber Nucleophilen sehr reaktiv. Wir haben hochsubstituierte Pyryliumsalze fur den zweistufigen Austausch der Aminogruppe in Alkylaminen RNH2 gegen zahlreiche andere Gruppen verwendet. Im ersten Schritt werden die Pyryliumsalze mit den Aminen zu N-substituierten Pyridiniumsalzen umgesetzt, die im zweiten Schritt mit Nu⊖ die gewunschten Produkte RNu bilden. In einigen Fallen wird auch der Rest R verandert, z. B. durch Eliminierung. Die Reaktionen haben zu interessanten Einblicken in den Mechanismus der nucleophilen Substitution gefuhrt und Alkylamine zu wichtigen Zwischenstufen fur Synthesen werden lassen. Die Methode erganzt somit die Diazotierung von Arylaminen.
18 citations
13 citations
TL;DR: The title pyrylium cation reacts with amines in aqueous solution to give mixtures of divinylogous amide and pseudobase, and the two products are formed by kinetic control in quantities which then slowly come to equilibrium.
Abstract: The title pyrylium cation reacts with amines in aqueous solution to give mixtures of divinylogous amide and pseudobase. The two products are formed by kinetic control in quantities which then slowly come to equilibrium. Further pyridinium ion is formed slowly from pseudobase. The divinylogous amide cyclises to pyridinium ion. Kinetic rate constants are described for reactions with lysine and other typical primary amines. With s-butylamine appreciable quantities of the 2H-pyran are formed.
TL;DR: A series of water-soluble pyrylium salts and zwitterions have been prepared containing two or three carboxylic or sulphonic acid groups, usually as betaines as mentioned in this paper.
Abstract: A series of water-soluble pyrylium salts and zwitterions has been prepared containing two or three carboxylic or sulphonic acid groups. These pyrylium salts react in aqueous solution with ammonia to give the corresponding pyridines and with n-butylamine, benzylamine, and the ω-amino groups of lysine to give the corresponding pyridinium systems, usually as betaines. The pyridinium betaines (m.p. > 300 °C) show characteristic 13C n.m.r. spectra which have been nearly fully assigned.
TL;DR: The kinetic and equilibrium interrelationships of these species and the corresponding 2H-pyran and oxodienol over a wide pH range have been studied and elucidated as mentioned in this paper.
Abstract: The title pyrylium cation (7) coexists in water with the enedione pseudobase (12) and the anion [cf.(13)]. The kinetic and equilibrium interrelationships of these species and the corresponding 2H-pyran and oxodienol over a wide pH range have been studied and elucidated.
TL;DR: Depending on the conditions, and the basicity of the amine, arylamines react with chelidonic acid to yield five different types of product: salts, N-arylchelidamic acids, N.aryl-4-pyridone-2-carboxylic acids,N-aryl- 4-p Pyridones, or chelIDamic acid itself.
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TL;DR: The most important synthetic routes for the synthesis of 2H-imidazoles have been from ketones by cyclization, by the transformation of imidazolone derivatives, and by the reaction between 1H-IMIDazoles and electrophiles as discussed by the authors.
Abstract: Publisher Summary This chapter seeks to cover all known 2H-imidazoles. The most important synthetic routes for the synthesis of 2H-imidazoles have been from ketones by cyclization, by the transformation of imidazolone derivatives, and by the reaction between 1H-imidazoles and electrophiles. The chapter also describes a few miscellaneous methods, methods for N-Oxides and N,N’-dioxides, and N-Ylides for the synthesis of 2H-imidazoles. This chapter accounts for structural (X-ray crystallography and tautomerism) and physical (ultraviolet spectra, infrared spectra, 1 H-NMR spectra, 13 C-NMR spectra, and mass spectra) properties of 2H-imidazoles. Reactions such as thermal and photochemical reactions formally involving no other species, reactions of ring atoms with electrophiles, reactions of ring atoms with nucleophiles, reactions with cyclic transition states, and reactions of ring substituents, outline the chemical properties of the 2H-imidazoles.
TL;DR: This paper determined des vitesses de solvolyse des composes du titre for lesquels alkyl equivaut a methyl, ethyl, propyl, pentyl, octyl, isobutyl, neopentyl, phenethyl and methoxyethyl dans le methanol.
Abstract: Determination des vitesses de solvolyse des composes du titre pour lesquels alkyl equivaut a methyl, ethyl, propyl, pentyl, octyl, isobutyl, neopentyl, phenethyl et methoxyethyl dans le methanol, l'ethanol, le pentanol, l'acide acetique et son derive trifluore
TL;DR: On etudie les reactions du perchlorate de methoxy-4' benzyl-1 triphenyl-2,4,6 pyridinium and du tetrafluoroborate de benzyl 14 tetrahydro-5,6,8,9 phenyl-7 dibenzo [a, h] acridinium avec la piperidine dans le chlorobenzene as mentioned in this paper.
Abstract: On etudie les reactions du perchlorate de methoxy-4' benzyl-1 triphenyl-2,4,6 pyridinium et du tetrafluoroborate de benzyl-14 tetrahydro-5,6,8,9 phenyl-7 dibenzo [a, h] acridinium avec la piperidine dans le chlorobenzene
TL;DR: The title pyrylium salt reacts with lysine residues in gelatin and chymotrypsin in aqueous buffer to form rapidly the corresponding divinylogous amide and pseudobase in a ratio depending on the protein concentration.
Abstract: The title pyrylium salt reacts with lysine residues in gelatin and chymotrypsin in aqueous buffer to form rapidly the corresponding divinylogous amide and pseudobase in a ratio depending on the protein concentration. First-order ring closure of the divinylogous amide proceeds at rates comparable to those observed with the analogous intermediate from free lysine.
TL;DR: Cyclic 2-(acylmethyl)-1,3-diketones are converted into 1-acyl-1H-Pyrroles in high yields by ammonium acetate in acetic acid, via rearrangement of a hydroxypyrroline intermediate.
Abstract: Cyclic 2-(acylmethyl)-1,3-diketones are converted into 1-acyl-1H-Pyrroles in high yields by ammonium acetate in acetic acid, via rearrangement of a hydroxypyrroline intermediate.
TL;DR: In this paper, the N-substituents are transferred from the title cations to the C-atom of nitroalkane anions in high yield at 25-80°C in DMSO solution.
TL;DR: In this article, conditions for maximising yields of pyridinium cations from pyrylium salts and amines in aqueous media have been deduced.
Abstract: Pyrylium cation equilibria and kinetics in aqueous solution have been measured and compared with existing data. Competing reactions of pyrylium cations with amines, water molecules, and hydroxide ions have been elucidated and rationalised. Conditions for maximising yields of pyridinium cations from pyrylium salts and amines in aqueous media have been deduced.
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TL;DR: In this article, the 4H-imidazoles have a tetrahedral carbon atom in the ring and thus are nonaromatic and can be synthesized from transformation of imidazolone derivatives.
Abstract: Publisher Summary This chapter discusses the 4H-imidazoles that have a tetrahedral carbon atom in the ring and thus are nonaromatic. The synthesis of 4H-imidazoles can be done from transformation of imidazolone derivatives, ketones and amidines, imines and amidines, reaction between 1H-imidazoles and electrophiles, azirines, and methods for N-oxides. The structure (X-ray crystallography, MINDO/3 calculations, tautomerism, and dipole moments) and spectroscopic properties (ultraviolet spectra, infrared spectra, 1H-nuclear magnetic resonance spectra, 13C-nuclear magnetic resonance spectra, and mass spectra) of 4H-imidazoles are described in the chapter. Reactions such as thermal reactions formally involving no other species, reactions of ring atoms with electrophiles, reactions of ring atoms with nucleophiles, andreactions of ring substituents, outline the chemical properties of 4H-imidazoles.
TL;DR: In this article, a series of 1-(s-alkyl) pyridinium cations in 2,2,2-trifluoroethanol or 1,1, 1, 3,3,3-hexafluoropropan-2-ol were reported for solvolysis in the absence of nucleophiles.
Abstract: ρ* Values are reported for solvolyses of a series of 1-(s-alkyl) pyridinium cations in 2,2,2-trifluoroethanol or 1,1,1,3,3,3-hexafluoropropan-2-ol as solvents in the absence of nucleophiles. The corresponding reactions with pyridine, piperidine, or morpholine as nucleophile in chloroform, acetonitrile, 2,2,2-trifluoroethanol, or 1,1,1,3,3,3-hexafluoropropan-2-ol are kinetically first-order (independent of nucleophile concentration); these allow ρ* to be calculated. ρ* Values correlate with solvent ET Values except for pentanol and acetic acid, in which cases they are smaller than expected.Product analysis discloses rearrangement products (derived by hydride shifts) only for solvolysis in non-nucleophilic solvents (trifluoroacetic acid and 1,1,1,3,3,3-hexafluoropropan-2-ol) in the absence of added nucleophilic solvents. The results are interpreted in terms of (a) solvent-assisted solvolysis in nucleophilic solvents, (b)SN1 cleavage of the C–N bond in the rate-determining step both for the unimolecular reactions in the presence of external nucleophiles, and for solvolysis in 2,2,2-trifluoroethanol, and (c) rate-determining ion-molecule pair dissociation for solvolysis in trifluoroacetic acid or 1,1,1,3,3,3-hexafluoropropan-2-ol.
TL;DR: In two-step sequences, lysine has been converted into the thio-substituted derivatives RS[CH2]4CH(NH2)CO2H (R = Ph or PhCH2), and glycylglycine into PhSCH2CONHCH2CO2 H (R + Ph) to provide models for the selective conversion of proteins at the ω-amino groups of lysines side chains and at the terminal amino groups.
Abstract: In two-step sequences, lysine has been converted into the thio-substituted derivatives RS[CH2]4CH(NH2)CO2H (R = Ph or PhCH2), and glycylglycine into PhSCH2CONHCH2CO2H. All reactions proceeded in aqueous solution at ⩽75 °C; they thus provide models for the selective conversion of proteins at the ω-amino groups of lysine side chains and at the terminal amino groups, respectively.
TL;DR: In this paper, the N-alkylhexahydroacridines undergo thermolysis at ca. 160 °C and the n-aryl analogues at > 250 °C to give alkanes and arenes.
Abstract: 5,6,8,9-Tetrahydrodibenzo[c,h]xanthylium salts (13) react with amines to yield the corresponding tetrahydroacridinium salts (14) which are reduced by NaBH4 to hexahydroacridines (15). The N-alkylhexahydroacridines undergo thermolysis at ca. 160 °C and the N-aryl analogues at > 250 °C to give alkanes and arenes. The N-alkyltetrahydroacridinium salts (14) and their 7-phenyl analogues (12) react at ca. 130 °C with 1,5-diazabicyclo[4.3.0]non-5-ene to give the corresponding alkanes in good yield.
TL;DR: In this paper, 1-Methyl and 1-allyl-2,4,6-triphenylpyridinium cations react with aromatic aldehydes at the α-CH2 to give aldol products (7) and (8).
Abstract: 1-Methyl and 1-allyl-2,4,6-triphenylpyridinium cations react with aromatic aldehydes at the α-CH2 to give aldol products (7) and (8). The allyl adducts (8) were thermally converted into aldehydes and ketones, whereas thermolysis of (7) took a variety of courses. Zwitterions from 1-methylpyridinium cations were also added Michael-fashion to activated carbon–carbon double bonds.
TL;DR: Aus den Halogenethylpyridiniumsalzen (Ia) und (Ic), deren Herstellung aus den Pyridinen (III) beschrieben ist, werden mit Alkali die Vinyl-pyrideinium-salze (VI) erhalten as discussed by the authors.
Abstract: Aus den Halogenethyl-pyridiniumsalzen (Ia) und (Ic), deren Herstellung aus den Pyridinen (III) beschrieben ist, werden mit Alkali die Vinyl-pyridiniumsalze (VI) erhalten.
TL;DR: In this article, 1,2-diaryl-and 1,6-triarylpyridinium salts, containing various five-and six-membered heteroaromatic substituents in the 1, 2, and 6-positions of the pyrinium ring, were synthesized.
Abstract: New 1,2-diaryl- and 1,2,6-triarylpyridinium salts, containing various five- and six-membered heteroaromatic substituents in the 1, 2, and 6-positions of the pyridinium ring, were synthesized. New tetra- and hexacyclic compounds were prepared by photocyclization of the cations of these salts. Photocyclization proceeds through a singlet excited state with nonadiabatic formation of a dihydro intermediate, followed by its oxidative dehydrogenation. The structure and quantum yield of the formation of photoproducts are determined by steric and electronic effects of the substituents, and in bichromophore compounds by the presence of S-S intramolecular interfragment energy transfer.