A New Synthetic Route to Enantiomerically Pure Axially Chiral 2,2‘-Bipyridine <i>N,N</i><i>‘</i>-Dioxides. Highly Efficient Catalysts for Asymmetric Allylation of Aldehydes with Allyl(trichloro)silanes

Abstract

New axially chiral 2,2'-bipyridine N,N'-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 1a 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.