Aziridination and Diamination

The first reports on iron-catalyzed aziridinations date back to 1984, when Mansuy et al. reported that iron and manganese porphyrin catalysts were able to transfer a nitrene moiety on to alkenes [90]. They used iminoiodinanes PhIN=R (R = tosyl) as the nitrene source. However, yields remained low (up to 55% for styrene aziridination). It was suggested that the active intermediate formed during the reaction was an Fev=NTs complex and that this complex would transfer the NTs moiety to the alkene [91-93]. However, the catalytic performance was hampered by the rapid iron-catalyzed decomposition of PhI=NTs into iodobenzene and sulfonamide. Other reports on aziridination reactions with iron porphyrins or corroles and nitrene sources such as bromamine-T or chloramine-T have been published [94], An asymmetric variant was presented by Marchon and coworkers [95]. Biomimetic systems such as those mentioned above will be dealt with elsewhere. 

Another non-heme system made use of hexadentate phenol ligands [98]. However, the catalytically active species was only formed upon ligand oxidation by excess of PhI=NTs. Furthermore, a large excess of the alkene was required (2000 equiv. vs. PhI=NTs). The reaction of cyclooctene and 1-hexene gave yields of about 50%, which represents a significant improvement over the earlier described copper systems [99]. 

Attempts to aziridinate alkenes with iron catalysts in an asymmetric manner have met with only limited success to date [101], In an early report on the use of various chiral metal salen complexes, it was found that only the Mn complex catalyzed the reaction whereas all other metals investigated (Cr, Fe, Co, Ni etc.) gave only unwanted hydrolysis of the iminoiodinane to the corresponding sulfonamide and iodoben-zene [102], Later, Jacobsen and coworkers and Evans et al. achieved good results with chiral copper complexes [103]. 

The iron-catalyzed nitrene transfer to alkenes is a challenging field of research. Remarkable results have been reported but much more effort has to be made to develop further this area of catalysis. 

3 Named after Gif-sur-Yvette, France, where it was developed. D. H. R. Barton, A. K. Goktiirk, J.W. Morzycki, W. B. Motherwell, J. Chem. Soc., Perkin Trans. 1985, 1, 583. 

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