Transition Metal Rhodium-Catalyzed Regioselective C-H Olefination Of 2-arylindoles

Over the past decades,transition-metal-catalyzed C-H bond functionalization has been attracted considerable attention and has been become the most powerful alternatives for the transformation of unfunctionalized compound into varieties of bioactive compounds,pharmaceuticals and functional materials.Since the seminal work of Fujiwara and Moritani in 1967,transition-metal-catalyzed C-H direct olefination has emerged as powerful tool to construct(hetero)arylalkenes.The indole motif is ubiquitous featured at the core of natural products and biologically active intermediates.In this context,the development of methods for the regioselective C-H olefination of indoles has received intensive and continued attention.In this dissertation,systematic explorations have been carried out on the rhodium-catalyzed regioselective olefination of 2-arylindoles with alkenes.We have developed a general rhodium-catalyzed ortho-selective olefination of 2-arylindoles via NH-indole-directed C-H bond cleavage.The C-H olefination was carried out by employing 1.0 equiv of 2-arylindoles,2.0 equiv of alkenes,2.5 mol%of[Cp*RhCl2]2,2 equiv of Cu(OAc)2 in EtOAc at 140℃.This cross-dehydrogenative-coupling proved to be broad in substrate scope,tolerating a variety of functional groups.The synthesis of 6H-isoindolo[2,11-a]indoles via rhodium-catalyzed ortho C-H olefination and subsequent intramolecular aza-Michael reaction of 2-arylindoles was also demonstrated.The present research work has extended regioselective C-H oxidative Heck reaction of indole-containing compounds.A novel rhodium-catalyzed approach for the direct synthesis of benzo[a]carbazole from 2-arylindoles via regioselective double successive oxidative Heck reaction has been achieved.The optimum reaction conditions thus far developed employ 1.0 equiv of 2-arylindoles,2.0 equiv of alkenes,2.5 mol%of[Cp*RhCl2]2,5 equiv of AgOAc,16 equiv of HOAc,40 mol%PivOH in xylene at 140℃.