Diisopropyl tartrate modified (E)-γ-[(cyclohexyloxy)dimethylsilyl]- and (E)-γ-(dimethylphenylsilyl)allylboronates: Chiral Reagents for the Enantio- and Diastereoselective synthesis of anti 1,2-diols and 2-butene-1,4-diols via the formal α- and γ-hydroxyallylation of aldehydes

Abstract

Enantioselective synthesis of 4-substituted (E)-2-butene-1,4-diols and anti 1,2-diols are described. Highly diastereoselective reactions of aldehydes and the chiral PhMe 2Si- and (C 6H 11O)Me 2Si- substituted allylboronates 25 and 26 provide anti homoallylic 29 and 50, respectively. Epoxidation of 29 with dimethyl dioxirane followed by acid catalyzed Petersen rearrangement of the intermediate epoxysilanols provides butene-1,4-diols 27 with excellent enantioselectivity (81–87% e.e.). Tamao oxidation of 50 provides anti diols 22 (64–72% e.e). These procedures give excellent results especially in matched double asymmetric reactions with a range of oxygenated, chiral aldehydes (Figures 1 and 2). These methods promise to find application in diastereoselective syntheses of carbohydrates from acyclic precursors.