Mn(I)-Catalyzed nucleophilic addition/ring expansion via C–H activation and C–C cleavage.

Mn(I)-Catalyzed synthesis of seven- or eight-membered carbocycles is disclosed via C–H activation of heteroarenes and coupling with alkyne-functionalized 1,3-cyclopentadiones or 1,3-cyclohexadiones. This n to n + 2 (n = 5, 6) ring expansion reaction proceeded via a C–H alkenylation/carbonyl addition/retro-Aldol cascade. Structurally diverse mid-sized carbocycles were constructed via cleavage of both C–H and C–C bonds in a single operation. [ABSTRACT FROM AUTHOR]