Kinetic and thermodynamic factors in the regioselectivity of α-carboallyloxymethyl radical cyclizations. A computational study

Abstract

Ab initio transition-state modeling of α-carboallyloxymethyl radical (1) demonstrates not only that 6-endo cyclization is kinetically disfavored by an overwhelming margin, but that the 5-exo educt radical (2) is also thermodynamically favored over the 6-endo educt radical (3). This may account for the absence of any examples of 6-endo cyclization of any N-allylic α-carbamoylalkyl or O-allylic α-carbalkoxyalkyl radical congeners of 1 in the literature.