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

Abstract 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 Piv 2 O 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.