Co(III), Rh(III) & Ir(III)-Catalyzed Direct C-H Alkylation/Alkenylation/Arylation with Carbene Precursors.

Metal carbenes play a pivotal role in transition-metal-catalyzed synthetic transfer reactions. The metal carbene is generated either from a diazo compound through facile extrusion of N with a metal catalyst or in situ generated from other sources like triazoles, pyriodotriazoles, sulfoxonium ylides and iodonium-ylide. On the other hand, Co(III), Rh(III) & Ir(III)-catalyzed C-H functionalizations have been well established as a key synthetic step to enable the construction of various synthetic transformations. Interestingly, in recent years, merging of these two concepts C-H activation and carbene migratory insertion gained much attention, in particular group 9 metal-catalyzed arene C-H functionalizations with carbene precursors via carbene migratory insertion. In this review, we summarize recent advances in Co(III), Rh(III) & Ir(III)-catalyzed direct C-H alkylation/alkenylation/arylation with carbene precursors and also discuss key synthetic intermediates within the catalytic cycles.