Rhouidm(?)-catalyzed Indole-directed Carbenoid Aryl C-H Insertion/Cyclization: Access To 1,2-Benzocarbazoles

Fused arenes have been referred to as privileged structures in complex natural products,pharmaceutical molecules and organic functional materials.The synthesis of these compounds has continuosly been one of the hotspots in organic chemistry.For example,the classical Diels-Alder reaction,Robinson cyclization reaction and Skraup reaction colud effectively construct the diversity fused ring compounds.In recent years,transition-metal catalyzed C-H bond functionalization has provided high-atom and high-step economic methods for assembling fused arenes.In view that carbazoles and their derivatives could be used in the field of optoelectronic material due to their exceptional unique electronic.So,developing more efficient methods to construct this kind of compounds remains highly desirable and challenging.In this paper we designed and synthesized a series of 2-phenylindole substrates and systematically studied a rhodium(III)-catalyzed cyclization coupling of 2-phenylindoles with diazo compounds using the amine(NH)group on the indole ring as a directed group.The methodically optimization of the reaction parameters showed that [Cp*RhCl2]2/CuCl catalytical system could efficiently afford 1,2-benzocarbazols via [4 + 2] coupling cyclization of 2-arylindole(1.0 eq)and diazo(2.0 eq),and this transformation could tolerate a broad range of functional groups.On the contrary,[Cp*RhCl2]2/AgOAc catalytical system could assembly the fused ring isoquinoline [2,1,8-lma] carbazole via carbenoid insertion C-H bond/cascade annulations reaction in moderate yield.This novel strategy could efficiently construct isoquinoline [2,1,8-lma] carbazoles in which three C-C bonds and one C-N bond could from simultaneously through one-step of chemical transformation.The corresponding control experiments and kinetic isotope effect(KIE)showed that the [4 + 2] cyclization involved in aryl C-H bond activation process and the aryl C-H bond cleavage belongs to the whole rate-limiting step.The selected carbazole compounds have been demonstrated to be promising molecules which could be further used in the filed of optoelectronic materials.