Catalyst-Guided C=Het Hydroarylations by Manganese-Catalyzed Additive-Free C−H Activation

Expedient hydroarylations of C=Het bonds (Het=heteroatom) were accomplished by user‐friendly organometallic C−H activation in a positional‐selective manner. The broadly applicable C−H functionalization platform enabled the step‐economical transformation of aldehydes, ketones, and imines under additive‐free reaction conditions. In contrast to palladium, rhodium, ruthenium, rhenium, iridium, nickel, and cobalt catalysis, solely manganese(I) complexes outcompeted the innate substrate control, clearly highlighting the unique power of manganese(I) C−H activation catalysis. One catalyst to rule them all: The unique selectivity of manganese(I) catalysis in heteroarene C−H activation set the stage for positional selective hydroarylations with ample scope under additive‐free conditions, outcompeting palladium, rhodium, ruthenium, rhenium, iridium, nickel, iron, and cobalt catalysts.