A triphenylphosphine mediated photo-rearrangement and methanol addition of aryl chalcones to 1-propanones.

Aryl chalcones rearrange and add methanol to give substituted propane-1-ones upon UV-A irradiation in the presence of PPh3. We propose two possible mechanisms for this photo-rearrangement. The reaction involves either the formation of a phosphine-carbonyl intermediate, nucleophilic addition of MeOH and 1,2-aryl migration or the formation of ylide and carbene intermediates. The intermediates trapped from the reaction mixture support the first mechanistic hypothesis.