TEMPERATURE-DEPENDENCE OF PRODUCT DISTRIBUTIONS IN THE PHOTOLYSIS OF ALPHA-DIAZOBENZYLPHOSPHONATES IN ALCOHOLS

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.