Photoreactivity of the conjugate bases of two aromatic ketones: photochemistry of the enolates of .alpha.,.alpha.-diphenylacetophenone and deoxybenzoin

Photoexcitation of the enolate anion of deoxybenzoin induces geometric isomerization, as evidenced by ground state bleaching and formation of a metastable isomer. In aerated THF, the enolate of α,α-diphenylacetophenone 5 reacts by electron transfer to the excited triplet state of its thermal autoxidation product benzophenone. The calculated geometries of 4 and 5 (AM-1) correlate well with those found by solution and solid-state NMR spectroscopy, with enolate 4 existing as the more stable Z-isomer and enolate 5 in a twisted, locked geometry