Microwave-assisted Rhodium(I)-Catalyzed C8-Regioselective C-H Alkenylation and Arylation of 1,2,3,4-Tetrahydroquinolines with Alkenyl and Aryl Carboxylic Acids

Rh(I)-catalyzed C8-selective C-H alkenylation and arylation of 1,2,3,4-tetrahydroquinolines with alkenyl and aryl carboxylic acids under microwave assistance have been realized. Using [Rh(CO)2(acac)] as the catalyst and Piv2O as the acid activator, 1,2,3,4-tetrahydroquinolines undergo C8-selective decarbonylative C-H alkenylation with a wide range of alkenyl and aryl carboxylic acids, affording the C8-alkenylated or arylated 1,2,3,4-tetrahydroquinolines. This method enables the synthesis of C8-alkenylated 1,2,3,4-tetrahydroquinolines that would otherwise be difficult to access by means of conventional C-H alkenylation protocols. Moreover, this catalytic system also works well in C8-selective decarbonylative C-H arylation of 1,2,3,4-tetrahydroquinolines with aryl carboxylic acids. The catalytic activity strongly depends on the choice of the N-directing group, with the readily installable and removable N-(2-pyrimidyl) group being optimal. The catalytic pathway is elucidated by mechanistic experiments. + image