Catalytic asymmetric isomerization/hydroboration of silyl enol ethers

Abstract

Asymmetric remote hydroboration of olefins has emerged as an efficient strategy for the construction of chiral boronic esters. Conventional asymmetric alkene isomerizations rely on directing groups (OH, NR₂, carbonyl) for thermodynamic control via (hyper)conjugation, but their use restricts substrate scope and risks β-heteroatom elimination with transition-metal catalysts. We here reported a catalytic asymmetric isomerization/hydroboration of silyl enol ethers under mild conditions, enabling the efficient synthesis of enantioenriched boryl ethers. The chiral borylether products enable efficient access to valuable 1,n-diols and 1,n-amino alcohols, prevalent in bioactive molecules, and facilitate late-stage functionalization of complex architectures. Preliminary mechanistic studies reveal that this reaction involves a nondissociative chain-walking process and that the β-H elimination may contribute to the rate-limiting step.