A new synthetic route to enantiomerically pure axially chiral 2,2′-bipyridine N,N′-dioxides.: Highly efficient catalysts for asymmetric allylation of aldehydes with allyl(trichloro)silanes

New axially chiral 2,2'-bipyridine NIT-dioxides 1 were obtained in an enantiomerically pure form by way of cyclic diesters 6 or 7 which were formed by the esterification of diols 2 with (R)-2,2'-bis(chlorocarbonyl)-1,1'-binaphthalene (5). Epimerization of the kinetic products at the ester formation (R-nap,S-pyr)-6 to the thermodynamically stable isomers (R-nap,R-pyr)-7 was observed in refluxing toluene or in the presence of trifluoroacetic acid. One of the N,N'-dioxides la which is substituted with phenyl groups at the 6 and 6' positions was found to be highly catalytically active and enantioselective for the asymmetric allylation of aldehydes with allyl(trichloro)silane giving homoallyl alcohols.