Synthesis of Aziridines from Alkenes and Aryl Azides with a Reusable Macrocyclic Tetracarbene Iron Catalyst

A new iron aziridination catalyst supported by a macrocyclic tetracarbene ligand has been synthesized. The catalyst, [(Me,EtTCPh)Fe(NCCH3)2](PF6)2, was synthesized from the tetraimidazolium precursor (Me,EtTCPh)(I)4 and characterized by NMR spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. This iron complex catalyzes the aziridination of electron-donating aryl azides and a wide variety of substituted aliphatic alkenes, including tetrasubstituted ones, in a “C2 + N1” addition reaction. Finally, the catalyst can be recovered and reused up to three additional times without significant reduction in yield.