Kinetics and mechanism of the addition of benzylamines to beta-nitrostyrenes in acetonitrile

The kinetics and mechanism of the addition of benzylamines to beta-nitrosty renes in acetonitrile at 25.0 degrees C have been investigated. The additio n reaction proceeds by two pathways, uncatalyzed (k(2)) and catalyzed (k(3) ) paths. The kinetic isotope effects (k(H)/k(D)) involving deuterated benzy lamine nucleophiles support the proposal that proton transfer from the amin e to the beta-carbon occurs concurrently with addition of the amine to the alpha-carbon. The transition state is predicted to have four- (I) and six-m embered (II) cyclic structures for the k(2) and k(3) paths, respectively, w ith a tighter and more rigid structure for the uncatalyzed process. The cro ss-interaction constants, rho(XY), are negative (-0.90 and -0.54 when the f all-off factor is taken into account) and the magnitude is larger for the u ncatalyzed path than for the normal backside attack S(N)2 reaction of benzy l derivatives with anilines (-0.6 to -0.8).