Regioselective Synthesis of 2-Substituted Indoles from Benzotriazoles and Alkynes by Photoinitiated Denitrogenation

Herein, we describe a photoinitiated and regioselective synthesis of 2-substituted indoles under mild reaction conditions. This biologically privileged scaffold was accessed in good yields from N-aroylbenzotriazoles, a quencher class previously identified using our mechanism-based luminescence screening, and terminal alkynes in the presence of a photocatalyst and blue light irradiation. This straightforward protocol displays a broad substrate scope and functional group tolerance. Furthermore, the mildness and robustness of the reaction were assessed by the application of an additive-based robustness screen. The determination of the reaction quantum yield and Stern–Volmer studies support the proposed photoinitiated radical chain mechanism.