Kinetics and Mechanism of the Addition of Benzylamines to Ethyl- ￥á-cyanocinnamates in Acetonitrile

摘要

Nucleophilic addition reactions of benzylamines (BA; XC₆H₄CH₂NH₂) to ethyl-メ-cyanocinnamates (ECC;YC₆H₄CH=C(CN)COOEt) have been investigated in acetonitrile at 30.0∩. The rate is first order with respect to BA and ECC. The rate is slower than that expected from the additive effect of ヲ- or R- for the activating groups (CN and COOEt). Natural. bond . orbital ヰ*_c=c calculations show that the contribution of COOEt group may not be fully effective despite the coplanar molecular structure. The selectivity parameters including the cross-interaction constant ( ヱ_XY = -0.22) indicate that the addition occurs in a single step. The kinetic isotope effects (k_H/k_D=.2.5-2.8) involving deuterated BA (XC₆H₄CH₂ND₂) nucleophiles and activation parameters (ツH×=4~6 kcal mol-1 ; ツS×=-45~ -52 e.u.) suggest a cyclic transition state in which N-C_メ and H-C_モ bonds are formed concurrently.