Copper‐Catalyzed C–H Insertion of N ‐Heterocycles Into Diazo Arylidene Succinimides

Copper(II) triflate is found to be an effective catalyst for the regioselective C–H insertion of heteroaromatic compounds into diazo arylidene succinimide‐based carbene precursors. Preferential C3–H insertion occurs in N ‐substituted and unsubstituted indoles, while selective C2–H insertion occurs when the C3 site is blocked. This technique was extended to other heteroaromatic compounds, such as carbazoles, phenothiazines and pyrrole, and all of them yielded the respective C–H insertion products in good yields.