Stereoselective Dehydroxyboration of Allylic Alcohols to Access (E)-Allylboronates by a Combination of C-OH Cleavage and Boron Transfer under Iron Catalysis

LiOtBu-Promoted trans-Stereoselective and β-Regioselective Hydroboration of Propargyl Alcohols

A convenient and efficient trans-stereoselective and β-regioselective hydroboration of propargyl alcohols was achieved simply with LiOtBu as the base and (Bpin)2 as the boron reagent in dimethyl sulfoxide at room temperature. Both terminal and internal propargyl alcohols with diverse structures and functional groups underwent the transformation smoothly to produce β-Bpin-substituted (E)-allylic alcohols, of which the synthetic potentials were demonstrated by the downstream conversions of boronate, alkenyl, and hydroxyl groups.

Synthesis of vinyl-substituted alcohols using acetylene as a C2 building block

Vinyl-substituted alcohols represent a highly useful class of molecular skeletons. The current method typically requires either stoichiometric metallic reagents or preformed precursors. Herein, we report a nickel catalysis-enabled synthesis of vinyl-substituted alcohols via a 5-membered oxa-metallacycle. In this protocol, acetylene, the simplest alkyne and abundant feedstock, is employed as an ideal C2 synthon. The reaction features mild conditions, good functional group tolerance and broad substrate scope. Mechanistic exploration implies that the oxa-metallacycle originated from the cyclometallation of aldehyde and acetylene is the key intermediate for this transformation, which is then terminated by a silane-mediated σ-bond metathesis and subsequent reductive elimination.

Direct deoxygenative borylation

Direct deoxygenative borylation is a highly enabling chemical transformation considering the attractive synthetic features of oxygenous feedstocks and organoboron compounds. Despite ranking among the synthetic ideality in different settings, such chemical space remained largely uncharted and underutilized until recent decades. This short review will summarize some key advances in the field of direct deoxy-borylation of alcohols, ethers, aldehydes, ketones, and carboxylic acids and organize these contributions based on substrate classes. In each representative, the general features, including reaction conditions, product scopes and mechanistic insights, will be highlighted and discussed.