Blue Light-Induced C─X Insertion and Halogenation Reaction of 3-Diazo-3H-Indoles With Halohydrocarbons.

Visible light-induced free carbene transfer reactions have attracted much attention over the past decades. Whereas photoinduced C─X insertion and halogenation reactions with halohydrocarbons are rare due to many other competitive carbene transformations. Herein, we disclose a blue light-induced C─X (X = Cl, Br, I) insertion reaction of 3-diazo-3H-indoles with halohydrocarbons, leading to the gem-haloalkylation products in moderate to good yields under mild and neutral conditions. Moreover, starting from the same reagents, the halogenation products could be obtained selectively under acidic conditions in the presence of quantitative AcOH. This method offers a complementary approach for the synthesis of halogenated indoles, which are useful synthetic building blocks and essential structural motifs in bioactive molecules. Further synthetic applications could be envisioned for the construction of C─C and C─X bonds via visible light-induced free carbene transfer reactions.