The oxidative functionalization of the benzylic C-H bonds in tetrahydroisoquinolines and tetrahydro-β-carboline derivatives was investigated. C-C bond forming reactions proceeded with a range of nucleophiles (nitroalkane, enol silyl ether, indole, allylstannane, and tetrabutylammonium cyanide) under metal-free conditions and an oxygen atmosphere. Acetic acid caused a significant acceleration effect.