Kinetic studies on the cyclizations of alkyl radicals to benzyl oxime ethers

Abstract

Kinetic studies were carried out to determine the rate constants for the cyclizations of alkyl radicals to O-benzyl oxime ethers. The kinetic data were obtained by the relative ratios of the cyclized products and the reduced products in the presence of a large excess of tributyltin hydride. The relative ratios of two products were analyzed by HPLC and from the ratios, the rate constants were determined. The rate constant for the 5-exo addition to O-benzyl oxime ether was $3.9\times10^{7}s^{-1}$ and the rate constant for the corresponding 6-exo addition was $2.3\times10^{6}s^{-1}$, respectively. Those rate constants were confirmed by competitive reactions using a benzyl oxime ether and an olef in as a radical acceptor.