Insight into the palladium catalyzed oxidative arylation of benzofuran: Heteropoly acid oxidants evoke a Pd(II)/Pd(IV) mechanism.

The effects of oxidant and organic acid additives on the oxidative cross-coupling reactions of electron rich heterocycles such as benzofuran with benzene were studied. Both regioselectivity and reaction rate could be controlled by varying the condition parameters. Furthermore, mechanistic insight was achieved via kinetic studies which indicate that reactions that are oxidized by the heteropoly acid H ₄ PMo ₁₁ VO ₄₀ operate via a Pd(II)/Pd(IV) mechanisms, while reactions oxidized by either AgOAc or Cu(OAc) ₂ operate by a Pd(II)/Pd(0) mechanism.