Interannular Diastereoselectivity in the Hydroboration of Functionalized 1-Cyclohexylcyclohexenes

Article abstract of DOI:10.1021/jo00269a042

The reactions of thexylborane with 2-(1-cyclohexen-1-yl)cyclohexanone, cis-2,6-di(1-cyclohexen-1-yl)cyclohexanone, and related alcohols and ketals were investigated.All reactions are selective for products with erythro linkages between cyclohexyl rings, diastereoselectivities ranging from 66 to 97percent.Greatest erythro selectivities were observed for equatorial homoallylic alcohols and ethylene ketals.The configurations of all products were unambiguously assigned by correlation with <1,1'-bicyclohexyl>-2,2'-diones and an erythro, erythro triketone (25), the configuration of which was determined by X-ray crystallography.The diastereoselectivities of these hydroborations and related examples from the literature can be qualitatively rationalized by the Houk transition structure model.