Palladium-Catalyzed Heck Cross-Coupling Reactions in Water: A Comprehensive Review

Palladium-catalyzed cross-coupling reactions have emerged as one of the most versatile tools in organic chemistry. Extensive efforts were made to adapt these reactions to aqueous media, not only for the purpose of environmental conservation but also to expand the scope, increase the efficiency and implement bio-compatible protocols. Among different palladium cross-coupling reactions, the Heck reaction turned out to be the most challenging in an aqueous environment. This led to various original developments in catalyst design. This review summarizes the different approaches pursued to perform Heck reactions in neat water as well as aqueous mixtures. Both, homogeneous and immobilized catalysts, including nanoparticles are presented herein.