Catalytic (3 + 2) annulation of donor–acceptor aminocyclopropane monoesters and indoles

Abstract

A catalytic dearomatization of indoles with D–A aminocyclopropane monoesters for the synthesis of highly substituted indolines.The efficient catalytic activation of donor–acceptor aminocyclopropanes lacking the commonly used diester acceptor is reported here in a (3 + 2) dearomative annulation with indoles. Bench-stable tosyl-protected aminocyclopropyl esters were converted into cycloadducts in 46–95% yields and up to 95 : 5 diastereomeric ratio using catalytic amounts of triethylsilyl triflimide. Tricyclic indoline frameworks containing four stereogenic centers including all-carbon quaternary centers were obtained.