Catalytic Transformations Involving the Activation of sp2 Carbon–Oxygen Bonds

Abstract

This review describes transition metal-catalyzed transformations of con- ventionally unemployed C(sp2)–O bonds, specifically those of aryl and alkenyl ethers, carboxylates, and carbamates. Nickel-based catalysts are among the most intensively studied in this context, allowing for direct coupling using phenol- and enol-derived electrophiles. Reactions using other metals (Ru, Fe, and Rh) are also presented. The synthetic utility of these C–O bond activation reactions is illustrated in the synthesis of several elaborated molecules, especially through the orthogonal cross-couplings and oxygen-directed functionalization/C–O activation tandem.