Reactions of 1,4-dihydropyridines (review)

The literature published over the period 1986–1990 on the chemical properties (oxidation, addition, substitution, reactions of the functional groups, etc.) of 1,4-dihydropyridines is correlated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, No. 5, pp. 579–612, May, 1993.     

Molecular crystal structure and chemical properties of 4-phenyl-3,5-diethoxycarbonyl-1,2,6-trimethyl-1,2-dihydropyridine

The molecular crystal structure of 4-phenyl-3,5-diethoxycarbonyl-1,2,6-trimethyl-1,2-dihydropyridine has been investigated by x-ray structural analysis. The three-dimensional structural properties of the molecule have been compared against the large observed reactivity of the 3-ethoxycarbonyl group with respect to nucleophilic substitution reactions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1236–1239, September, 1991.     

Reduction of 2,3,4-substituted quinolines with sodium borohydride

1,2-Dihydroquinolines were obtained by the reduction of 3-substituted 2-methyl-4-phenylquinolines with sodium borohydride in aliphatic carboxylic acids; N-alkyl derivatives are also formed. The corresponding 1,4-dihydroquinoline was obtained in the reaction of 2-methyl-3-nitroquinolinium perchlorate with sodium borohydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1680–1686, December, 1991.     

Synthesis of 3-cyano-4, 6-diaryl-3, 4-dihydropyridine-2-thionks

3-Cyano-4, 6-diaryl-3, 4-dihydropyridine-2-thiones have been synthesized for the first time by the condensation of arylideneacetophenones or 1-piperidino-1-phenyl-2-benzoylethane with cyanothioacetamide and the 1, 1-dicyano-2-aryl-3-benzoylpropane with hydrogen sulfide in the presence of bases. It has been established by PMR spectroscopy that 3-cyano-3,4-dihydropyridine-2-thiones exist in solutions in the form of mixture of cis and trans isomers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1515–1520, November, 1983.     

Voltamperometry of 1,4-dihydropyridine derivatives

Thirty-nine -substituted 1,4-dihydropyridine derivatives were subjected to electrochemical oxidation on a rotating platinum microelectrode in acetonitrile, and the E_p (E_1/2) values were measured. A satisfactory linear correlation between the E_p and Taft. ^* constants of the substituents in the position was observed. A linear correlation of the E_p values with the ⁰, - and ^– constants also exists.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1525–1529, November. 1975.     

Free radicals in electrochemical reduction of 3,5-dicarbethoxy-1,4-dihydropyridines with nitrophenyl groups in positions 2, 4, and 6

In the electrochemical reduction of 2,6-bis- and 2,4,6-tris(nitrophenyl) derivatives of 3,5-dicarbethoxy-1,4-dihydropyridine, in the first stage, one of the para-nitrophenyl groups in position 2 or 6 of the heterocycle is reduced. Free radicals have been obtained and identified, the primary species being ion radicals of the nitrophenyl type. The presence of the heterocycle in the molecule of the 1,4-dihydropyridine derivative stabilizes secondary free radicals of the nitrosophenyl type. In the process of electrochemical reduction, no evidence has been found of any intramolecular transfer of electrons or protons from the dihydropyridine part of the molecule to the nitrophenyl groups. Derivatives of 2,6-bis(p-nitrophenyl)-3,5-dicarbethoxy-1,4-dihydropyridine have been synthesized, and the oxidation and methylation of these derivatives have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 481–487, April, 1991.     

Synthesis and oxidation of 2,6-dimethyl-3, 5-di(phenoxycarbonyl)-1,4-dihydropyridines

A number of new aryl esters of acetoacetic acid were obtained in the reaction of phenols with diketene in the presence of triethylamine. Reaction of the esters thus obtained with hexamethylenetetramine gave, for the first time, aryl esters of 1,4-dihydropyridine-3,5-dicarboxylic acid, the oxidation of which with chloranil gave the corresponding pyridines.     

Synthesis of 3-(N-R)carbamoyl-5-(pyrid-4′-yl)pyridine-2(1H)-thiones and their derivatives

The condensation of salts of amidinium vinylogs with N-R-thiocarbamoylacetamides gave 3-(N-R)carbamoyl-5-(pyrid-4-yl)pyridine-2(1H)-thiones, which undergo oxidative cyclization in concentrated sulfuric acid with the formation of 3-oxo-5-(pyrid-4-yl)isothiazolo[5,4-b]pyridines. The oxidation and alkylation of the compounds referred to were investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–79, January, 1992.     

Structure and properties of 2,4a-dimethyl-4-phenyl-3-ethoxycarbonyl-5-oxo-4a,5-dihydro-4H-indeno[1,2-b]pyridine

The molecular and crystal structure of 2,3a-dimethyl-4-phenyl-3-ethoxycarbony-5-oxo-4a,5-dihydro-4H-indeno[1,2-b]pyridine has been determined, and its reduction and alkaline and acid hydrolysis reactions have been studied.Translated from Khimiya Geterotsiklicheskikh Soedineii, No. 10, pp. 1388–1392, October, 1984.