α-Carboalkoxymethylation of Conjugated Enones via Cyclobutane Intermediates

Abstract

Recently, a number of processes^1-3 have been developed for the introduction, specifically to the α-position of an α,β-unsaturated ketone, of a single 2-oxoalkyl chain (→) using enone photoannulation as a general entry. By the use of these methods, conjugated enones are cleanly transformed into 1,4-dicarbonyl compounds (type ) of broad synthetic interest⁴ and, in contrast to normal alkylation methods⁶, an enolizable γ-hydrogen atom in the starting ketone is not required for such a transformation⁷. We now describe a new photochemical route which facilitates the α-monocarboalk-oxymethylation of both the enolizable and the non-enolizable (towards the γ-position) α,β-unsaturated ketones and which promises to have wide synthetic utility.