Cu-Catalyzed radical-triggered spirotricyclization of enediynes and enyne-nitriles for the synthesis of pentacyclic spiroindenes

Abstract

A new copper-catalyzed radical-triggered fluoromethylation-spirotricyclization of enediyne- and enyne-nitrile-containing para-quinone methides (p-QMs) was reported for the first time, and used to produce a series of hitherto unreported cyclohexadienone-based pentacyclic spiroindenes with moderate to good yields and complete regioselectivity. The reaction proceeds through a complex difluoromethyl or trifluoromethyl radical-induced 1,6-addition/5-exo-dig, 6-exo-dig, 6-endo-trig tricyclization/single electron transfer (SET) process, resulting in the direct formation of up to three new rings and four chemical bonds in one step. The present Cu-catalyzed strategy accommodates a good substrate scope and is distinguished by its high bond-forming efficiency, annulation efficiency, and high regioselectivity.