Hydrogenolysis of enamines—I : Reaction with aluminium hydride

Abstract

Enamines react with AlH 3, AlH 2Cl and AlHCl 2 to give saturated amines and olefins, products of hydrogenation and hydrogenolysis, respectively. The proportion of the latter is lower with the chlorinated reducing agents. Good yields of olefins are obtained by reaction of AlH 3 with pyrrolidine enamines of acyclic and cyclic ketones. Enamines of α-substituted cyclohexanones are converted to 3-alkylcyclohexenes. Those derived from disubstituted acetaldehydes are only poorly hydrogenolysed as is the dienamine derived from Δ 1,9-octalone. 1-N-Pyrrolidinocyclo-octene is unique in giving cyclo-octane in the hydrogenolysis reaction; trans-cyclo-octene is the likely intermediate.