Copper catalyzed dearomatization by Michael-type addition of indolyl ynones: divergent synthesis of functionalized spiroindoles and cyclopenta[c]quinolin-3-ones

Abstract

Described herein is a novel copper-catalyzed multifunctionalization of alkyne-tethered indoles, allowing the practical and efficient synthesis of a diverse array of valuable dihalogen-substituted spiroindoles containing tetrasubstituted alkenes which can be readily functionalized further to obtain various spiroindolines. The construction of synthetically challenging quaternary spirocyclic carbons and tetrasubstituted alkenes is easily achieved in a single operation. Importantly, an unexpected dearomatization of alkyne-tethered indoles via Michael-type addition is involved in this tandem sequence. Furthermore, this Cu catalysis is also applicable to the regioselective synthesis of cyclopenta[c]quinolin-3-ones from readily available indolyl ynone homologues by skeletal rearrangement.