Visible-Light-Promoted Cascade Alkene Trifluoromethylation and Dearomatization of Indole Derivatives via Intermolecular Charge Transfer

An intramolecular dearomatization of indole derivatives has been developed via an electron donor-acceptor complex formed between indole derivatives and Umemoto's reagent. Without the requirement of any catalyst and additive, diverse trifluoromethyl-substituted spiroindolenines bearing a quaternary stereogenic center were obtained in good yields (up to 90%) merely upon the illumination of two starting materials in 1,2-dichloroethane solution at room temperature. This work provides facile access to spiroindolenines bearing a trifluoromethyl group enabled by visible light.