beta-(phosphatoxy)alkyl and beta-(acyloxy)alkyl radical migrations studiedby laser flash photolysis

A number of beta-(phosphatoxy)alkyl and beta-(acyloxy)alkyl radicals have b een generated by laser flash photolysis of the corresponding Barton PTOC es ters. Time resolved studies permitted the determination of late constants a nd kinetic parameters for their rearrangement in benzene, THF, and acetonit rile. Migrations are accelerated by electron-donating groups on the alkyl m oiety, electron-withdrawing groups on the migrating group, and more polar s olvents. All reactions showed strictly first order kinetics. The results ar e interpreted in terms of concerted mechanisms occurring through three elec tron, three center and five electron, five center mechanisms. (C) 1999 Else vier Science Ltd. All rights reserved.