Hydroxyl-Directed Stereoselective Diboration of Alkenes

ABSTRACT: An alkoxide-catalyzed directed diboration of alkenyl alcohols is described. This reaction occurs in a stereoselective fashion and is demonstrated with cyclic and acyclic homoallylic and bishomoallylic alcohol substrates. After oxidation, the reaction generates 1,2-diols such that the process represents a method for the stereoselective directed dihydroxylation of alkenes. The olefin diboration reaction is a useful strategy for theconversion of alkenes into a range of important building blocks.1 In this connection, we2 and others3 have developed strategies for the catalytic enantioselective addition of diboron reagents to prochiral isolated alkenes. While these reactions occur selectively with monosubstituted, trans-1,2-disubstituted, and trisubstituted alkenes, the minimally biased prochiral π-faces of cis-1,2-disubstituted and 1,1-disubstituted alkenes render selective reactions of these substrate classes muc