Photochemical deconjugation of α,β-unsaturated ketones

Abstract

It is shown that ‘photochemically inert’α,β-unsaturated ketones can undergo synthetically useful u.v. light induced deconjugation via photoenolization in the presence of a mild base, and the mechanism of this reaction has been examined by measurement of the relative quantum yield of deconjugation as a function of base and solvent; the results indicate two competing mechanism for the reketonization of the intermediate dienols, one involving a thermal 1,5-sigmatropic hydrogen shift, and the other base-catalysed proton trabnsfer.