Manganese‐Catalyzed C−H Functionalizations: Hydroarylations and Alkenylations Involving an Unexpected Heteroaryl Shift

A manganese‐catalyzed regio‐ and stereoselective hydroarylation of allenes is reported. The C−H functionalization method provides access to various alkenylated indoles in excellent yields. Moreover, a hydroarylation/cyclization cascade involving an unexpected C−N bond cleavage and aryl shift has been developed, which provides a new synthetic approach to substituted pyrroloindolones. Which way to go: An efficient, scalable, regio‐, and stereoselective manganese‐catalyzed C−H arylation of allenes is reported. When trisubstituted allenes are used, a C−H functionalization/C−N bond cleavage/cyclization cascade affords pyrroloindolones. Mechanistic studies suggest that a manganacycle is formed during the catalytic cycle.