Ru(II)-Catalyzed Regioselective C-H Alkenylation of Indoles Using Cyanomethyl Directing Group

A ruthenium-catalyzed C(2)-alkenylation of indole derivatives by employing cyanomethyl as the directing group was developed for the first time. Site-selective alkenylation was achieved for a broad scope of alkenes as coupling partners with a large number of indoles bearing synthetically useful functional groups. The protocol represents a novel method for C(2)-alkenylation of indoles affording biologically relevant indolic compounds. The reaction conditions were mild and it showed good substrate scope and functional group compatibility. Ester group, cyano group, iodine, bromine, fluorine and trifluoromethyl were all well compatible. The directing group can be easily removed under relatively mild conditions to form N-H indoles.