Stereoselective Tandem Synthesis of syn-1,3-Diol Derivatives by Integrating Olefin Cross-Metathesis, Hemiacetalization, and Intramolecular Oxa-Michael Addition.

Stereoselective tandem synthesis of syn-1,3-diol motifs, abundantly present in polyketide natural products and relevant pharmaceuticals, was achieved from homoallylic alcohols, α,β-unsaturated ketones, and aldehydes. Olefin cross-metathesis of homoallylic alcohols with α,β-unsaturated ketones, hemiacetalization of the resultant alcohols with aldehydes, and subsequent intramolecular oxa-Michael addition of the derived hemiacetals furnished syn-1,3-dioxane derivatives in good to excellent yields without isolation of any intermediates. The acetal moiety of the resultant syn-1,3-dioxanes could be cleaved chemoselectively/regioselectively under mild conditions in subsequent transformations.