Intermediates in the photocyclisation of 1-(o-alkylphenyl)propane-1,2-diones

Abstract

An intermediate in the photocyclisation of 1-(o-alkylphenyl)propane-1,2-diones may, in several cases, be efficiently trapped by sulphur dioxide but not by maleic anhydride. Reaction of 1-(o-bromoalkylphenyl)propane-1,2-diones with zinc leads to products expected from the photoenols of the parent diketones but there are significant differences between this reaction and the photocyctisation. It is argued that there is no evidence to implicate such enols as intermediates in the photoreaction.