Novel isomerically pure tetrasubstituted allylboronates: Stereocontrolled synthesis of α-exomethylene γ-lactones as aldol-like adducts with a stereogenic quaternary carbon center

Article abstract of DOI:10.1021/ja016391e

In spite of their inherent isomerization tendency and low reactivity, 1-alkoxycarbonyl vinylcopper(I) intermediates from the conjugate addition of organocuprates onto acetylenic esters were trapped with very high cis-addition selectivity with iodomethylboronic esters in the presence of HMPA. The resulting isomerically pure 3,3-disubstituted allylboronates react with aldehydes in a highly diastereo- and enantioselective manner, providing α-exomethylene γ-lactones with a stereogenic quaternary β-carbon center. Copyright