Ligand-Promoted Iron-Catalyzed Nitrene Transfer for the Synthesis of Hydrazines and Triazanes through N-Amidation of Arylamines

Herein, we report that bulky alkylphosphines such as PtBu3 can switch the roles from actor to spectator ligands to promote the FeCl2-catalyzed N-amidation reaction of arylamines with dioxazolones, giving hydrazides in high efficiency and chemoselectivity. Mechanistic studies indicated that the phosphine ligands could facilitate the decarboxylation of dioxazolones on the Fe center, and the hydrogen bonding interactions between the arylamines and the ligands on Fe nitrenoid intermediates might play a role in modulating the delicate interplay between the phosphine ligand, arylamine, and acyl nitrene N, favoring N-N coupling over N-P coupling. The new ligand-promoted N-amidation protocols offer a convenient way to access various challenging triazane compounds via double or sequential N-amidation of primary arylamines.

Automated summary

In this work, we demonstrate that bulky alkylphosphines such as PtBu3 can switch from being active ligands to being spectator ligands, promoting the FeCl2-catalyzed N-amidation reaction of arylamines with dioxazolones to yield hydrazides with high efficiency and chemoselectivity. Mechanistic studies show that the phosphine ligands can enhance the decarboxylation of dioxazolones on the iron center, and hydrogen bonding interactions between the arylamines and the ligands on Fe nitrenoid intermediates might play a role in tuning the delicate interplay between phosphine ligand, arylamine, and acyl nitrene N, thereby favoring N-N coupling over N-P coupling. The ligand-promoted N-amidation protocols presented here provide a convenient approach to access various challenging triazane compounds through double or sequential N-amidation of primary arylamines.