LEWIS-ACID ACTIVATION AND CATALYSIS OF DIALKYLAMINYL RADICAL REACTIONS

Lewis acid activation and catalysis of dialkylaminyl radical reactions is demonstrated both qualitatively and quantitatively. Cyclization of the N-butyl-4-pentenaminyl radical (1) in the presence of a wide rang e of Lewis acids was shown to be efficient with good to excellent yiel ds of cyclic products obtained in reactions conducted even at -78 degr ees C. Rate constants for fragmentation of the N-ethyl-2,2-diphenyleth ylaminyl radical (6), 6-exo cyclization of the N-methyl-6,6-diphenyl-5 -hexenaminyl radical (7), and 5-exo cyclization of the N-methyl-5,5-di phenyl-4-pentenaminyl radical (8) in the presence of the Lewis acids L iBF4, MgBr2, and BF3 were measured by laser flash photolysis (LFP) met hods. The LFP studies demonstrated saturation kinetic behavior with re spect to the Lewis acids. Equilibrium binding constants for the Lewis acids with the dialkylaminyl radicals and rate constants for reactions of the Lewis acid complexed dialkylaminyl radicals were obtained from nonlinear regression analysis of the observed rate constants.