Silver-Catalyzed Direct Nucleophilic Cyclization: Enantioselective <i>De Novo</i> Synthesis of C–C Axially Chiral 2-Arylindoles
Liangbin Yu, Junjun Liu, Shiyu Xiang, Taotao Lu, Ma Ping, Qingyang Zhao
Abstract
Atropisomeric indoles widely exist in natural products, pharmaceuticals, functional materials, and catalysts for their featured biological activities, photoelectric properties, and catalytic activities, while facile and de novo construction of this motif remains underexplored. Herein, we report a chiral silver phosphate-catalyzed direct 5- endo - dig nucleophilic cyclization of 2-alkynylanilins under mild conditions, affording various C–C axially chiral 2-arylindoles in high to excellent yields and enantioselectivities. Control experiments implied the cooperative catalysis of AgOAc and chiral phosphoric acid, wherein the former accelerated the desired transformation while the latter improved the enantioselectivity. In addition, as the first example of silver-catalyzed enantioselective de novo synthesis of C–C axially chiral indole skeletons, synthetic applications and products’ thermal stability have been investigated.