Regioselectivity of methyl chlorobenzoate analogues with trimethylstannyl anions by radical nucleophilic substitution: theoretical and experimental study

Abstract

Reactions of methyl 2,5-dichlorobenzoate, methyl 4-chlorobenzoate, methyl 2-chlorobenzoate and methyl 3-chlorobenzoate with Me₃Sn⁻ ions gave the corresponding substitution products by an S_RN1 mechanism. Competition experiments showed that the relative reactivity of chlorine as the leaving group with respect to the ester group in methyl chlorobenzoate is para ≥ ortho ≫ meta toward Me₃Sn⁻ ions. Theoretical studies were able to explain the observed reactivity on the basis of the energetic properties of the transition states of the radical anions formed in these reactions.