Enantioselective Ruthenium-BINAP-Catalyzed Carbonyl Reductive Coupling of Alkoxyallenes: Convergent Construction of <i>syn-sec,tert</i>-Diols via (<i>Z</i>)-σ-Allylmetal Intermediates

Abstract

The first catalytic enantioselective ruthenium-catalyzed carbonyl reductive couplings of allene pronucleophiles is described. Using an iodide-modified ruthenium-BINAP-catalyst and <i>O</i>-benzhydryl alkoxyallene <b>1a</b>, carbonyl (α-alkoxy)allylation occurs from the alcohol or aldehyde oxidation level to form enantiomerically enriched <i>syn</i>-<i>sec,tert</i>-diols. Internal chelation directs intervention of (<i>Z</i>)-σ-alkoxyallylruthenium isomers, which engage in stereospecific carbonyl addition.