Stereospecific Conversion of Boronic Esters into Enones using Methoxyallene: Application in the Total Synthesis of 10-Deoxymethynolide

Abstract

Enones are widely utilized linchpin functional groups in chemical synthesis and molecular biology. We herein report the direct conversion of boronic esters into enones using commercially available methoxyallene as a three-carbon building block. Following boronate complex formation by reaction of the boronic ester with lithiated-methoxyallene, protonation triggers a stereospecific 1,2-migration before oxidation generates the enone. The protocol shows broad substrate scope and complete enantiospecificity is observed with chiral migrating groups. In addition, various electrophiles could be used to induce 1,2-migration and give a much broader range of α-functionalized enones. Finally, the methodology was applied to a 14-step synthesis of the enone-containing polyketide 10-deoxymethynolide.