Regioselective C3 alkenylation of 4 H-pyrido[1,2-a]pyrimidin-4-ones via palladium-catalyzed C-H activation.

A general and efficient palladium-catalyzed direct C3 alkenylation of 4H-pyrido[1,2-a]pyrimidin-4-ones using AgOAc/O2 as the oxidant has been developed. A variety of 4H-pyrido[1,2-a]pyrimidin-4-ones were successfully coupled with acrylate esters, styrenes, methylvinylketone, and acrylamide in moderate to excellent yields. The reaction exhibited complete regio- and stereoselectivity. This transformation provides an attractive new approach to functionalize 4H-pyrido[1,2-a]pyrimidin-4-ones.