Catalyst‐Controlled Regiodivergent Alkyne Insertion in the Context of C−H Activation and Diels–Alder Reactions: Synthesis of Fused and Bridged Cycles

Catalyst-Controlled C-H activation of indoles and coupling with 1,6-enynes is discussed. Under Rh(III) catalysis, the alkyne insertion follows 2,1-regioselectivity with subsequent type-I intramolecular Diels-Alder reaction (IMDA) to afford [6,5]-fused cycles. When catalyzed by the Co(III) congener, 1,2-insertion of alkyne is preferred, followed by rare type-II IMDA leading to bridged [3,3,1]-cycles. This selectivity of the alkyne insertion was mainly tuned by the steric sensitivity of the catalyst.