NATURE OF THE REDUCING AGENT AND MECHANISM OF THE REDUCTIVE CONDENSATION OF TRICHLOROMETHYLARENES WITH HYDROXYLAMINE AND HYDRAZINES IN PYRIDINE

Article abstract of DOI:10.1007/BF01169070

It was shown that during the reductive condensation of trichloromethylarenes with hydroxylamine or hydrazines in pyridine the event of reduction with replacement of one chlorine atom by a hydrogen atom occurs without the participation of hydroxylamine or hydrazine.The first step of the reaction is the formation of N-(α,α-dichloroarylmethyl)pyridinium chlorides, which are converted by the action of the chloride anion or a second pyridine molecule to the corresponding 4-substituted 1,4-dihydropyridines.The latter undergo further aromatization with transfer of hydrogen from the 4-position of the dihydropyridine ring to the benzyl dichloromethylene group and the formation of N-(α-chloroarylmethyl)-4-chloropyridinium chlorides or N-(α-chloroarylmethyl)-4-(pyridino)pyridinium dichlorides, which give the corresponding aldehydes in hydrolysis or products of reductive condensation under the action of hydroxylamine or hydrazines.