Chiral Bis(imidazolidine)pyridine-Cu(OTf)2: Catalytic Asymmetric Endo-Selective [3+2] Cycloaddition of Imino Esters with Nitroalkenes

The novel C-2-symmetric bis(imidazolidine)pyridine (PyBidine) ligand was easily synthesized in a single condensation of 2,6-pyridyl aldehyde and optically active (S,S)diphenylethylenediamine. In the C-2-symmetric PyBidine-Cu(OTf)(2) complex, imidazolidine rings act as chiral fences to shield the first and third quadrants. Use of the PyBidine-Cu(OTf)(2) complex as a catalyst enabled the highly endo-selective reaction of imino esters and nitroalkenes to give the adducts in up to 99% ee.