Copper-Catalyzed Annulation–Cyanotrifluoromethylation of 1,6-Enynes Toward 1-Indanones via a Radical Process

A new Cu(II)-catalyzed annulation–cyanotrifluoromethylation of 1,6-enynes with Togni's reagent and trimethylsilyl cyanide (TMSCN) has been established, enabling the direct construction of trifluoromethylated 1-indanones with an all-carbon quaternary center in good yields. This reaction was performed by using low-cost Cu(OTf)(2) as the catalyst and Togni's reagent as both the radical initiator and a CF(3) source, providing an efficient protocol for building up an 1-indanone framework with wide functional group compatibility. The reaction mechanism was proposed through a radical triggered addition/5-exo-dig cyclization/oxidation/nucleophilic cascade.