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.     

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.Latvian Institute of Organic Synthesis, Riga, LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1383–1390, October, 1996. Original article submitted October 11, 1995.