Tandem C–O and C–H Activation at Palladium Enables Catalytic Direct C–H Alkenylation with Enol Pivalates

The use of oxygen-based electrophiles in cross-coupling remains challenging for substrates with strong C–O bonds, with few examples that can combine C–O activation with an-other strong-bond activation in tandem. We report the first example of a direct, tandem C–O/C–H activation approach to C–C bond formation using palladium catalysis. This reaction combines C–O oxidative addition at enol pivalates with con-certed metallation deprotonation of functionalized heterocycles to achieve base-free direct C–H alkenylation, with pivalic acid as the only byproduct. Mechanistic studies reveal that the Pd(II) C–O oxidative addition product is the major catalyst resting state, indicating that C–H activation is the turnover-limiting step.