Kinetics and mechanism of the addition of benzylamines to benzylidenediethylmalonates in acetonitrile.
Kinetic studies of the benzylamine additions to benzylidenediethylmalonates (BDM: YC(6)H(4)CH[double bond]C(COOEt)(2)) in acetonitrile at 20.0 degrees C are reported. The rates in acetonitrile are consistent with that expected from the through-conjugative electron-accepting power of the activating groups, (COOEt)(2). The sign and magnitude of the cross-interaction constant, rho(XY) = -0.45, are in general agreement with those for the single-step amine additions to activated olefins. The kinetic isotope effects (k(H)/k(D) > 1.0) measured with deuterated benzylamines (XC(6)H(4)CH(2)ND(2)) increase with a stronger electron-acceptor substituent in benzylamines (partial differential sigma(X) > 0) and a stronger electron donor in the substrate (partial differential sigma(Y) < 0). These trends are the same as those found for benzylidene-1,3-indandiones but are exactly opposite to those for other activated olefin series, e.g., beta-nitrostyrene. It has been shown that the former series are thermodynamically controlled, whereas the latter are intrinsically controlled with a relatively strong transition state imbalance. The activation parameters, Delta H(++) and Delta S(++), also support our proposed transition state involving concurrent C(alpha)-N and C(beta)-H bond formation with a four-membered cyclic structure.
Oh
Hyuck Keun
HK
Department of Chemistry, Chonbuk National University, Chonju 560-756, Korea.
Kim
In Kon
IK
Lee
Hai Whang
HW
Lee
Ikchoon
I