Reductive deamination of alkyl and aryl primary amines via 1,4-dihydropyridines and a note on the mechanism of reductive deamination of benzylamine via a 1,2-dihydropyridine

Abstract

Alkyl- and aryl-amines react with 2,3,5,6-tetraphenylpyrylium cations to yield pyridinium salts which are reduced regiospecifically by NaBH₄ to the 1,4-dihydropyridines which thermolyse at 180–200°C (for the alkyl derivatives) to give the corresponding alkanes in synthetically useful overall yields (some aryl derivatives thermolyse at 300°C to give the corresponding arenes); ²H n.m.r. spectroscopy is used to demonstrate the radical nature of the thermolysis of 1-benzyl-2,4,6-triphenyl-1,2-dihydropyridine.