Quantitating the effect of an ortho substituent on cyclization and intramolecular hydrogen-transfer reactions of aryl radicals

Reduction of allyl 2-iodobenzyl malonates with triphenyltin hydrides generates aryl radicals that partition between 6-exo cyclization, 7-endo cyclization, and 1,5-hydrogen atom transfer. Rate constants for all of these processes are high (> 10(8) M-1 s(-1)), and the rates are only marginally reduced (< 33%) by the introduction of methyl group ortho to the reacting radical.