THE MECHANISM OF THE BETA-ACYLOXYALKYL RADICAL REARRANGEMENT - KINETIC AND O-18-LABELING STUDIES

Experiments with O-18-enriched substrates indicate that the rearrangement of 2-butanoyloxy-2,2-dimethyl radical 1 (R = Pr) by migration of the acyloxy group involves complete transposition of the ether and carbonyl oxygen atoms, whereas the similar but much faster rearrangement of the substituted cholestanyl radical 11 proceeds with only 24% transposition. The rearrangement of 1 is considered to involve a five-membered cyclic transition state 2, while that of 11 probably proceeds via a tight anion-radical-cation pair 21.