Design of Stereogenic‐at‐Iron Catalysts with a (3+2+1)‐Ligand Sphere

Abstract

AbstractA stereogenic‐at‐iron(II) catalyst scaffold is introduced which contains one coordinated meridional tridentate imidazolidin‐2‐ylidene‐functionalized 2,2′‐bipyridine, one bidentate pyrazolylpyridine, and one monodentate acetonitrile ligand. This (3+2+1)‐coordination sphere implements a stereogenic iron center. A carbon stereocenter in the N‐heterocyclic carbene moiety controls the absolute metal‐centered configuration. The bench‐stable diamagnetic iron(II) complexes can be synthesized in a highly diastereoselective fashion from iron dibromide in an efficient one‐pot coordination reaction. The obtained enantiopure complexes were applied as chiral catalysts in the ring contraction of an isoxazole to a chiral 2H‐azirine (quantitative yields, up to 90 : 10 er).