Unexpected influence of mono-phenyl substitution on the photochemistry of β,γ-unsaturated oxime acetates

Abstract

On irradiation the oxime acetate of trans-2,2-dimethyl-4-phenylbut-3-enal (5) undergoes stereospecific aza-di-π-methane rearrangement to the oxime acetate of trans-2,2-dimethyl-3-phenylcyclopropanecarbaldehyde (7), while surprisingly the irradiation of the oxime acetate of 2,2-dimethyl-3-phenylbut-3-enal (10) follows a different reaction path and affords the oxime acetate of 4-methyl-3-phenylpent-3-enal (13) by a novel 1,3-migration pathway.