Abstract
It is known that the phenonium ion which has specific bridged structure is formed in the solvolysis of ester having aryl group at β position of reaction center. In our laboratory, we introduce electron-withdrawing groups (CF3 etc.) at α or β position of reaction center and investigate the effect of them to reaction mechanism, reaction rate, and stability of phenonium ion. The acetolysis of triflate which has electron-withdrawing group, CF3, at α or β position was observed great retardation effect. The retardation effect of β-CN group is equal to β-CF3 group, that is, the electron withdrawing ability is equal. However α-CN-OTf didn't show the retardation equal to α-CF3-OTf. It is considered that the causes are stabilization of phenonium ion type transition state by the inverse electron releasing resonance of CN and destabilization of the ground state by geminal interaction of CN. In this paper, we examined the effect of -COOMe group which has π electron system analogous to CN and is important in organic synthesis. As a result of measurement, large acceleration was observed in α-COOMe as well as α-CN group.
