High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

Abstract This review discusses the problems associated with developing high‐turnover catalysts for the cross‐coupling and Heck reactions. New developments in the area, principally constituted by palladacycles and coordinatively unsaturated Pd catalysts featuring bulky phosphanes of high donicity, are reviewed from a mechanistic and synthetic standpoint, and compared with more traditional catalysts obtained from conventional mono‐ and polydentate N‐ and P‐based ligands, as well as Pd catalysts without strong ligands, such as Pd colloids or heterogeneous catalysts. Carbene ligands are also briefly presented. Whereas a single, most promising approach to high‐turnover Pd catalysis cannot presently be defined, it…