Nucleophilic Iron Complexes in Proton‐Transfer Catalysis: An Iron‐Catalyzed Dimroth Cyclocondensation

The nucleophilic iron complex Bu₄NFe(CO)₃(NO)] (TBAFe]) is an active catalyst in C?H‐amination but also in proton‐transfer catalysis. Herein, we describe the successful use of this complex as a proton‐transfer catalyst in the cyclocondensation reaction between azides and ketones to the corresponding 1,2,3‐triazoles. Cross‐experiments indicate that the proton‐transfer catalysis is significantly faster than the nitrene‐transfer catalysis, which would lead to the C?H amination product. An example of a successful sequential Dimroth triazole–indoline synthesis to the corresponding triazole‐substituted indolines is presented.