Mechanistic investigation of substrate oxidation by Ce(IV) reagents in acetonitrile.

Rates and activation parameters for the Ce(4+)-mediated oxidation of a beta-keto ester, a beta-diketone, and a beta-keto silyl enol ether were determined in acetonitrile. In the case of the dicarbonyls, the enol content of the substrate impacts the rate of oxidation by Ce(4+), predominantly through contributions from DeltaH(). For the silyl enol ether, the transition state for oxidation by Ce(4+) is substantially more ordered than it is for the beta-keto ester or the beta-diketone.