The temperature dependence of product distributions in the photolysis of α-diazobenzylphosphonates in alcohols

Abstract

The product distributions from the photolysis of α-diazobenzylphosphonates (1) in alcohols change dramatically with the temperature used. Thus the direct photolysis of (1) in alcohols at 27 °C gives the O–H insertion product, whereas in frozen alcohol matrices at –196 °C it resulted in the C–H insertion products in high yield. Photolysis of (1) in alcohol at 27 °C, sensitized by Michler's ketone, leads to a significant increase in the yield of double hydrogen-abstraction product as well as the C–H insertion products. The C–H insertion products in the matrix experiments are explained in terms of hydrogen abstraction of triplet phosphorylcarbene, followed by efficient recombination of the resulting radical pairs within the matrix.