Enantioselective synthesis of allylboronates and allylic alcohols by copper-catalyzed 1,6-boration

Article abstract of DOI:10.1002/anie.201310380

Chiral secondary allylboronates are obtained in high enantioselectivities and 1,6:1,4 ratios by the copper-catalyzed 1,6-boration of electron-deficient dienes with bis(pinacolato)diboron (B₂(pin)₂). The reactions proceed efficiently using catalyst loadings as low as 0.0049 mol %. The allylboronates may be oxidized to the allylic alcohols, and can be used in stereoselective aldehyde allylborations. This process was applied to a concise synthesis of atorvastatin, in which the key 1,6-boration was performed using only a 0.02 mol % catalyst loading. 1,6-Borations of electron-deficient dienes with bis(pinacolato)diboron using copper catalyst loadings as low as 0.0049 mol % provided chiral allylboronates that, after oxidation, result in allylic alcohols in high enantioselectivities and 1,6:1,4 ratios. The allylboronates can also be used in stereoselective allylations of aldehydes. This process was applied to a concise synthesis of atorvastatin.