ChemInform Abstract: Conformationally Rigid Chiral Bicyclic Skeleton-Tethered Bipyridine N,N′-Dioxide as Organocatalyst: Asymmetric Ring Opening of meso-Epoxides

The conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′-dioxide (−)-9 has been designed, synthesized and examined as an organocatalyst in the enantioselective ring opening of meso-epoxides using tetrachlorosilane (SiCl4). The catalyst (−)-9 is found to exhibit good enantioselectivity for substituted cis-stilbene epoxides; whereas, the saturated cyclic meso-epoxides display a moderate enantioselectivity. At −30 °C in chloroform, the catalyst (−)-9 with 0.5 mol % loading generated the chlorohydrins in up to 97 % yield with up to 93 % ee. The possible creation of transient axial chiral environment around hypervalent silicon species due to the presence of conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′-dioxide may be responsible for such enantioselectivity observed in the desymmetrization of meso-epoxides.