Study On Rhodium-Catalyzed Synthesis Of 2-Substituted Indoles

Indoles,as important building blocks in organic synthesis,are common encountered in natural products,pharmaceutical molecules and functional materials.The importance of indoles has driven chemists to continue developing new strategies to build functionalized indole skeleton.Arguably,the traditional Fischer indole synthesis has remained one of the most commonly employed methods.Recently,the direct synthesis of indoles based on transition-metal-catalyzed C–H bond activation has drawn much attention due to its outstanding atom-economical and environmentally benign merits.In particularly,a great breakthrough has been made recently on the catalytic carbenoid insertion reaction as a novel approach toward C-H functionalization of the synthesis of indole.It is well-known that diazo or azide compounds as carbene precursors have taken a larger role in C-H activation for direct C-C bond formation.More importantly,sulfoxonium ylide could replace them perfectly owing to its considerable higher security and better usability.The process of cyclization from sulfoxonium ylide involves transition-metal-catalyzed a C-H alkylation-nucleophilic cyclization cascade reactions.Therefore,it is of great significance to explore and enrich the application of sulfoxonium ylide and the synthesis of indole.In this thesis,we have developed a rhodium(III)-catalyzed C-H alkylation-nucleophilic cyclization of anilines with sulfoxonium ylides toward 2-substituted indole.Notably,this transformation could smoothly proceed with high yields,good regioselectivity,and features broad group tolerance and under redox-neutral condition to avoid external oxidants,providing an effective route for the preparation of bioactive indoles.Based on the results obtained and the literature,a possible reaction mechanism is proposed,which is shown in Scheme 2.