Bimolecular nucleophilic substitution (SN2) reactions of neopentyl arenesulfonates with anilines and benzylamines in methanol

Abstract

Bimolecular nucleophilic substitution (S_N2) reactions of neopentyl arenesulfonates with anilines and benzylamines in methanol at 55.0 °C are reported. The tightness of the transition state (TS) is similar to that for other typical S_N2 processes at a primary alkyl carbon centre based on the magnitude of the cross-interaction constant ρ_xz(0.30) between the substituents in the nucleophile (X) and leaving group (Z). The TS variation is in accord with that predicted by the potential energy surface diagram, which in turn is consistent with the positive sign of ρ_xz; a later TS is obtained with a weaker nucleophile and nucleofuge. Taft's polar substituent constant, σ*, for the trimethylsilyl group is estimated to be –0.48 by using a factor of 1.875 for the fall-off of σ* from the tert-butyl to the neopentyl group and extrapolating from the experimental Taft plot.