Abstract
AbstractIn the area of C—H functionalization, cross-dehydrogenative coupling (CDC) represents the most atom-efficient coupling reaction, since it obviates the need for substrate prefunctionalization. The CDC strategy enables the construction of C—C bonds of diverse hybridization directly from C—H bonds present in the precursors, with formal loss of dihydrogen. C(sp2)—C(sp3) bond formation via selective C(sp3)—H/C(sp2)-H cross coupling is generally difficult to achieve owing to the inertness of C(sp3)-H bonds and their ubiquity in organic molecules. This review describes the different strategies developed over the years in overcoming the aforesaid challenges to enable C(sp2)—C(sp3) bond formation by CDC. Utilization of directing-group-assisted C(sp3)—H metalation with the aid of ligands has largely been the key for selective alkenylation at both proximal and distal positions. Non-directed protocols have also been developed that proceed by selective radical formation using a metal/oxidant combination, or just an oxidant. The developments made in terms of ligand design, scope, mechanistic aspects, and the potential applications of the different methodologies for the CDC between C(sp3)—H and C(sp2)—H bonds are portrayed in this chapter.