The stability of allylic and vinylic deuterium atoms during the lithium/ammonia reduction of some styrenoid systems

Abstract

Reduction of 2-(p-methoxyphenyl)cyclohexan-1-one (8) with lithium aluminium deuteride followed by acetylation gave trans-l-acetoxy-2-(p-methoxyphenyl)(1-²H₁)cycohexane (10b). Base-catalysed deuteration of 2-(p-methoxypheny1)cyclohexan-1-one (8) afforded the corresponding trideuterated ketone (11a) which upon hydride reduction and acetylation yielded trans-1-acetoxy-2-(p-methoxy- phenyl)(2,6,6-²H₃)cyclohexane (15b). Pyrolysis of the acetate (10b) at 600º/1.0 mm gave 1-(p-methoxyphenyl)(2-²H₁)cyclohex-1-ene (16) which was separated from the unconjugated isomer (13) by preparative g.l.c. 1-(p-Methoxyphenyl)(3,3-²H₂)cyclohex-1-ene (18) was similarly obtained by pyrolysis of the trideutero acetate (15b).

Lithium/ammonia reduction of the deuterated styrenoid compounds (16) and (18) proceeded in each case without any detectable loss or redistribution of the deuterium atoms.