Ya. Ya. Ozols

1,4-Dihydropyridines containing sulfur (review)

The literature on the synthesis and reactions of monocyclic and polycyclic 1, 4-dihydropyridines containing sulfur in substituents or in the ring is reviewed.

2-Aryl-3,5-dinitro-1,2-dihydropyridines

The reaction of α-nitroacetaldehyde with paraformaldehyde or aromatic aldehydes and ammonium acetate in acetic acid yielded 2-aryl-3,5-dinitro-1,2-dihydropyridines. Aromatic aldehydes, in an ethanol and acetic acid mixture, gave isomeric 3,5-dinitro-1,4-dihydropyridines in addition to 1,2-dihydropyridines. Physicochemical properties and reactivities of the compounds have been studied.

Equilibrium NH-acidity of 1,4-dihydropyridines and 4,5-dihydroindeno[1,2-b]pyridines

The patterns governing the dependence of NH-acidity on the presence of α-, Β- and γ-substituents in the 1,4-dihydropyridine ring and on their nature have been established by comparison of the pKa values of monocyclic 1,4-dihydropyridines and 4,5-dihydroindenopyridines. Additional data were obtained on the influence of the the electronic effects of sulfur-containing substitutents on the reaction center in the dihydropyridine molecules.

Ethyl 1,4-dihydropyridinecarbodithioates and the electronic effects of sulfur-containing ester substituents

Methods have been developed for the synthesis of the ethyl esters of 2,6-dimethyl-1,4-dihydropyridine-3,5-bis(carbodithioic) and 4-ary1-2-methyl-5-oxo-4,5-dihydro-1H-indeno[1,2-b]pyridine-3-carbodithioic acids. From the physicochemical properties (acid dissociation constants and electrochemical oxidation potentials of the 1,4-dihydropyridines with sulfur-containing substituents in the β-positions, the electronic effects of these groups in the 1,4-dihydropyridine system have been determined. The inductive and resonance constants of these substituents in aromatic compounds have been found by 13C and 19F NMR spectroscopy.

1,4-Dihydrobenzothieno[3,2-b]pyridine-5,5-dioxides

A series of polycyclic 1,4-dihydropyridines has been synthesized, viz., 1,4-dihydrobenzothieno[3,2-b]pyridine-5,5-dioxides with electron-acceptor substituents at position 3. Their alkylation, chemical oxidation, and reactivity in electrochemical oxidation have been studied. The effect of a sulfonyl group in the indene segment on properties (pK, electrochemical oxidation potential) of the dihydrobenzothienopyridine system is considered.

SYNTHESIS OF PHENYL-SUBSTITUTED DERIVATIVES OF DECAHYDROPHENANTHRIDINE-1,7-DIONE AND HEXAHYDRO-8-ISOQUINOLONE

Abstract2-Bromo-2-aroylcydohexan-1-ones were prepared by bromination of 2-aroylcyclohexan-1-ones with Nbromosucccinimide and were isomerized into 6-bromo-2-aroylcyclohexan-1-ones in attempted dehydrobromination by heating in organic solvents. The reaction of 2-benzoyldimedone with oxalyl chloride was investigated. The 2-benzoyl-3-chloro-5,5-dimethyl-2-cyclohexen-1-one obtained formed 2-benzoyl-5,5-dimethyl-2-cyclohexen-1-one in reduction with zinc activated with silver acetate. The cyclohexenone was reacted with some enaminocarbonyl compounds, yielding derivatives of decahydrophenanthridine-1,7-dione and hexahydro-8-isoquinolone.

HEXAHYDRO-8-ISOQUINOLONES WITH ELECTRON-ACCEPTOR SUBSTITUENTS IN POSITION 4

By the interaction of 2-acetyl-5,5-dimethyl-2-cyclohexen-1-one with certain nitroenamines, a number of hexahydro-8-isoquinolones with a nitro group in position 4 have been obtained; potentials of their electrochemical oxidation have been determined, and a possible mechanism and manifestation of structural effects in this process have been suggested and discussed. The structure of 1,3,6,6-tetramethyl-4-nitro-2, 4a-5,6,7,8-hexahydro-8-isoquinolone has been established by means of x-ray diffraction analysis.

Reduction of 3-substituted 2-methylquinolines with sodium tetrahydroborate

Reduction of esters of 2-metylquinoline-3-carboxylic acids and their perchlorates gave esters of 1,4-dihydro-2-methylquinoline-3-carboxylates, while derivatives of 1,2-dihydroquinoline were formed in the case of 1,2-dimethyl-3-ethoxycarbonyl-7-methoxyquinolinium perchlorate. Reduction of esters of 2-methylquinoline-3-carboxylic acid, 1,2-dimethyl-3-ethoxycarbonyl-1-methoxyquinolinium perchlorate and 3-acetyl-2-methyl-quinoline with sodium tetrahydroborate in acetic acid gave esters of 1,2-dimethyl- and 2-methyl-1,2,3,4-tetrahydroquinoline-3-carboxylic acid and 3-acetyl-2-methyl-1,2,3,4-tetrahydroquinoline.

1,4-Dihydropyridine-3,5-dicarbothionic acid S-esters

Procedures have been developed for the synthesis of 1,4-dihydropyridine-3,5-dicarbothionic acid S-esters via the direct thiolysis of 1,4-dihydropyridine-3,5-dicarboxylic acids and their ester derivatives. The use of different acid activating agents and thiolysis agents is discussed.

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

Abstract1,2-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.