Chiral Bicyclic NHC/Rh Complexes and Their Application to Catalytic Asymmetric Ring-Opening Reaction of Oxabenzonorbornadienes with Amines.

Abstract

A rhodium complex bearing a chiral bicyclic NHC ligand, [RhCl(3az)(cod)] 4az, was synthesized and fully characterized by X-ray diffraction analysis, high-resolution mass spectrometry, and multinuclear NMR spectroscopy. The electronic and steric properties of NHC ligand 3az were evaluated by IR measurement and X-ray diffraction analysis of dicarbonyl complex [RhCl(3az)(CO)2] 5az, which was prepared by replacing the COD ligand of 4az with CO. The potential of novel complex 4az as a chiral catalyst was investigated in the Rh-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadienes with amines, and the corresponding products were afforded in good yields with good enantioselectivities (up to 81% ee).