Metal-Mediated Reductive C–C Coupling of π Bonds

Molecular complexity is, to a large extent, dependent on the linkage- and functionality-complexity of the molecule's backbone. In many cases, the formation of relatively inert C–C bond is a limiting factor on the synthetic accessibility to complex molecules. 1–3 Metal-mediated reductive coupling of π bonds is an important method to construct carbon backbones efficiently and atom-economically from simpler fragments. Metals can play multiple roles in reductive coupling reactions—as electron donors, directing groups, or activating the π system of substrates. Metal-mediated reductive coupling has attracted enduring research interest in the past decades, while some challenges remain unsettled. In this chapter, we will discuss both stoichiometric and catalytic reductive coupling in the categories of the metals and the coupling partners involved. The chapter will include the recent (~15 years) advances in both intra- and intermolecular reductive coupling.