Switchable regioselective hydroalkylation of 2-arylindoles with maleimides.

A condition-based switchable regioselective hydroalkylation of 2-arylindoles with maleimides has been developed. The reaction in the presence of a Ru(ii)-catalyst resulted in hydroalkylation at the ortho-position of the C2-aryl ring via C-H activation whereas the reaction in the absence of the catalyst in TFE resulted in C3-hydroalkylation. Various functional groups both on the indole ring and on the 2-phenyl ring were tolerated and a wide range of hydroalkylated products were obtained in moderate to high (37-88%) yields.