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.

Automated summary

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 achieved using a cationic Rh(III) catalytic system. The reaction proceeds with oxygen as the terminal oxidant and shows good substrate scope and functional group compatibility, providing the corresponding products in moderate to high yields. The choice of N-directing group is crucial for the catalysis, and the N-(2-pyrimidyl) group proves to be the optimal choice. Preliminary mechanistic studies have been conducted to gain insights into the reaction mechanism.