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

Abstract

The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) 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.