2.1.1 General Principles of Metal/Organocatalyst Dual Catalysis

Metal/organocatalyst dual catalysis is a privileged catalytic strategy which involves both a metal-based catalyst and an organocatalyst to catalyze the organic transformation. Based on the type of activation of substrates with both catalysts, there are seven kinds of dual catalysis; namely cooperative catalysis, cascade catalysis, sequential catalysis, double activation catalysis, restorative catalysis, bifunctional catalysis, and multiple relay catalysis. The generic activation of the metal-based catalyst and the organocatalyst applied in the dual-catalytic system is summarized. In these dual-catalytic approaches, the advantages of both metal catalysis and organocatalysis are converged to achieve many transformations that were previously inaccessible or challenging by any single-catalyst paradigm, to develop new reactions, to discover unique reaction mechanisms, and even to allow for stereodivergent synthesis.