BIMOLECULAR NUCLEOPHILIC-SUBSTITUTION (S-N(2)) REACTIONS OF NEOPENTYLARENESULFONATES WITH ANILINES AND BENZYLAMINES IN METHANOL

Bimolecular nucleophilic substitution (S(N)2) reactions of neopentyl a renesulfonates with anilines and benzylamines in methanol at 55.0 degr ees C are reported. The tightness of the transition state (TS) is simi lar to that for other typical S(N)2 processes at a primary alkyl carbo n centre based on the magnitude of the cross-interaction constant p(xz ) (0.30) between the substituents in the nucleophile (X) and leaving g roup (Z). The TS variation is in accord with that predicted by the pot ential energy surface diagram, which in turn is consistent with the po sitive sign of p(xz); a later TS is obtained with a weaker nucleophile and nucleofuge. Taft's polar substituent constant, sigma. for the tr imethylsilyl group is estimated to be -0.48 by using a factor of 1.875 for the fall-off of sigma from the tert-butyl to the neopentyl group and extrapolating from the experimental Taft plot.