A class of stereogenic-at-iron
catalysts is introduced and applied
to asymmetric 3d-transition metal catalysis. The pentadentate coordination
of a tripodal ligand creates a stereogenic iron center, while an isopropyl
group in the ligand backbone serves as a chiral lever to thermodynamically
favor one diastereomer (>20:1 dr) of the obtained iron complexes.
The coordination sphere is completed with a labile acetonitrile ligand.
Ligand coordination and dynamics were studied by NMR spectroscopy.
A modular design of the tripodal ligand enables the convenient implementation
of different modifications, which have been incorporated and investigated
in this work. The catalytic performance of the obtained complexes
was evaluated in the ring contraction of isoxazoles to chiral 2H-azirines in up to 99% yield and with up to 93% ee and
features a remarkably high catalytic activity with up to 10,000 turnover
numbers (TON).