Manganese-Catalysed C−H Activation: A Regioselective C−H Alkenylation of Indoles and other (hetero)aromatics with 4-Hydroxy-2-Alkynoates Leading to Concomitant Lactonization

A manganese-catalyzed C−H bond alkenylation of indoles at C2-position with 4-hydroxy-2-alkynoates leading to concomitant lactonization under removable directing group strategy has been disclosed. This lactonization strategy exhibits regioselectivity, a broad substrate scope, and a good functional group tolerance furnishing the products in low to high yields. The regioselectivity is guided by the electronic effect of the ester group as well as the steric bulk at the C4-position of the 4-hydroxy-2-alkynoates. After the reaction, the directing group has been readily removed to obtain N−H free indole. (Figure presented.).