Kinetics and Mechanism of the Addition of Benzylamines to Benzylidenedimethylmalonates in Acetonitrile

the addition of benzylamine (BA) to benz-ylidenedimethylmalonate (BMM) take place in a single step in which the C_α-N bond formation and proton transfer to C_β of BMM occur concurrently with a four-membered cyclic TS structure. The reaction center carbon, C_α , becomes more negative (ρ_Y > 0) on going from the reactant to TS, but the negative charge development is stronger than that for the reactions of BID. The sign and magnitude of the cross-interaction constant, ρ_XY, is comparable to those for the normal bond formation processes in the S_N2 and addition reactions. The normal kinetic isotope effects, k_H/k_D (>1), involving deuterated benzylamine nucleophiles (XC₆H₄CH₂ND₂), are somewhat smaller than those corresponding values for the reaction of CNS due to the smaller extent of bond formation in the TS. The relatively low ΔΗ^≠ and large negative ΔS^≠ values are also consistent with the mechanism proposed