Rhodium(III‐Catalyzed C8‐Selective C−H Alkenylation and Alkylation of 1, 2, 3, 4‐Tetrahydroquinolines with Styrenes and Allylic Alcohols

Rh(III)-catalyzed chelation-assisted C8-selective C-H alkenylation and alkylation of 1,2,3,4-tretrahydroquinolines with styrenes and allylic alcohols have been realized. The cationic Rh(III) catalytic system in combination with a catalytic amount of copper acetate uses oxygen as the terminal oxidant and catalyzes the stereoselective C8-alkenylation of 1,2,3,4-tetrahydroquinolines with styrenes to give the corresponding products in 56-93% yields with wide substrate scope and broad functional group compatibility. The reaction can be scaled up. Moreover, this protocol can be extended to the C8-alkylation of 1,2,3,4-tetrahydroquinolines with allylic alcohols, providing access to various 8-(3-oxoalkyl)-1,2,3,4-tetrahydroquinolines in 77-90% yields. The selection of N-directing group is essential for catalysis, and the readily installable and removable N-(2-pyrimidyl) group proves to be optimal choice. Preliminary mechanistic studies are performed to gain insights into the reaction mechanism.