Photolysis of alpha-azidoacetophenones: trapping of triplet alkyl nitrenes in solution

reaction: see text] Selective excitation of the ketone chromophore in alpha-azidoacetophenones, 1, leads to intramolecular triplet energy transfer to the azido group, which forms the corresponding triplet alkyl nitrene, 2. Azides 1 also undergo alpha-cleavage to form benzoyl and methyl azido radicals in competition with nitrene formation. Thus the major photoproduct, 2-benzoylamino-1-phenylethanone, 3, comes from trapping of 2 with a benzoyl radical. This appears to be the first observation of bimolecular trapping of triplet alkyl nitrenes in solution.