Kinetics and mechanism of the aminolysis of phenyl cyclopropanecarboxylates in acetonitrile

Abstract

Kinetic studies of the reaction of Z-phenyl cyclopropanecarboxylates with X-benzylamines in acetonitrile at 55.0 °C have been carried out. The reaction proceeds by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, T^±, with a hydrogen-bonded four-center type transition state (TS). These mechanistic conclusions are drawn based on (i) the large magnitude of ρ_X and ρ_Z, (ii) the normal kinetic isotope effects (k_H/k_D > 1.0) involving deuterated benzylamine nucleophiles, (iii) the positive sign of ρ_XZ and the larger magnitude of ρ_XZ than that for normal S_N2 processes, and lastly (iv) adherence to the reactivity–selectivity principle (RSP) in all cases.