Direct Access to Dihydrobenzoimidazo[2,1-a]isoquinolines through Ruthenium-catalyzed Formal [4+2] Annulation

A facile and straightforward synthesis of benzoimidazo[2,1-a]isoquinolines through Ru(II)-catalyzed [4+2] annulation reaction of 2-aryl benzimidazole and styrene has been explored. Tentative mechanistic studies imply the current reaction involves sequential C-C/C-N bond formation through the ortho C-H activation of 2-aryl benzimidazole followed by C-N reductive elimination. This newly developed strategy is widely applicable and tolerates various 2-arylbenzimidazole and vinyl derivatives, and allows the attractive vehicle for direct construction of diverse C6-substituated benzoimidazoisoquinoline scaffold in good yields.