C-H Functionalization Reactions of Unprotected N-Heterocycles by Gold-Catalyzed Carbene Transfer

The C-H functionalization reaction of N-heterocycles with an unprotected N-H group is one of the most step-economic strategies to introduce functional groups without the need for installation and removal of protecting groups. Despite recent significant advances in C-H functionalization chemistry, this strategy remains unsatisfactorily developed. In this report, we disclose a simple and straightforward protocol to allow for the selective C-H functionalization of unprotected double-benzannellated N-heterocycles via gold-catalyzed carbene-transfer reactions (29 examples, up to 86% yield). The scope of the reaction can also be expanded to the corresponding protected heterocycles (37 examples, up to 98% yield), further demonstrating the generality of this method. Mechanistic studies by density functional theory (DFT) calculations underpin the importance of the gold catalyst and reveal that the selectivity of this reaction is driven by trace amounts of water present in the reaction mixture.