Imine-forming radical elimination reactions of O-(1-naphthoyl)-N,N- bis(p-substituted benzyl)hydroxylamines activated by triplet benzophenone

Article abstract of DOI:10.1246/bcsj.72.2537

It was shown that despite the occurrence of a diffusion-limited triplet energy transfer between the title hydroxylamine 1 and benzophenone, triplet 1 decomposed inefficiently giving p-substituted N-(p-substituted benzylidene)benzylamine 2 and 1-naphthoic acid (3) as unimolecular radical elimination products. The logarithm of the k(r)/k(d) ratio (where k(r) is the rate constant for homolytic cleavage of the N-O bond in triplet 1 and k(d) is that for its deactivation) used as a measure of the triplet-state reactivities of 1, showed a negligible dependence on the substituent constant. This finding was explained in terms of a very small contribution of the ionic structure to the transition state for the N-O bond homolysis.