摘要:
The effect of the carboxylate used in a concerted metalation-deprotonation reaction is probed, and shows a direct correlation of pK(a) to observed rate up to a pK(a) of 4.3, Where the rate drops off at higher pK(a). The rate of the C-H antivation of 2-(4-methoxyphenyl)pyridine with [Cp*RhCl2](2) and carboxylate follows first-order kinetics hi the active metal species, Cp*RhCl(kappa(2)-OAc), and zero-Order kinetics in substrate when in a 1:1 ratio. There is a first-order dependence on substrate observed when excess substrate is present. The evaluation of the mechanism using kinetic studies allowed for a mechanistic proposal in which a second Ph'Py coordinates prior to the rate-determining C-H activation.