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 N2 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. Individually, the fields of metal carbenes and transition‐metal‐catalyzed C−H activation have become very familiar in organic synthesis. Merging these two concepts, carbene migratory insertions via C−H activation methods, are still in early stage. This review summarizes the recent advances in Co(III), Rh(III) & Ir(III)‐catalyzed direct C−H alkylation/alkenylation/arylation with carbene precursors and current developments of this emerging research area.