Enantioselective Synthesis of Allylboronates and Allylic Alcohols by Copper-Catalyzed 1,6-Boration

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 (B-2(pin)(2)). The reactions proceed efficiently using catalyst loadings as low as 0.0049mol%. 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 0.02mol% catalyst loading.