Temperature-Controlled Dearomative [5+1] Spiroannulation and Formal [5+2] Cyclization of Indoles with Enynones: Divergent Synthesis of Spiro-Indolenines and Dihydrocyclohepta[b]Indolones

Abstract

We developed a temperature-controlled intermolecular dearomative [5+1] spiroannulation and [5+2] cyclization of indoles with enynones, smoothly delivering a variety of spiroindolenines and dihydrocyclohepta[b]indolones under 40 °C and 80 °C, respectively. A three-step cascade reaction was also realized by using OTBS or NHBoc containing enynones in the reaction with the indole under the identical condition. And a novel valuable highly-oriented three-dimensional indole-based tetracyclic scaffold was produced in high yields with excellent diastereoselectivities. Additionally, various spiroindolines and spirooxindoles were facilely produced through simple operations. This highly efficient domino-reaction represents an emblematic method for the preparation of indole-based polycycles through the intermolecular pathway.