Catalytic Asymmetric Synthesis of Chiral Propargylic Boron Compounds through B-H Bond Insertion Reactions

Chiral propargylic boron compounds have a diverse array of potential applications. Although numbers of highly enantioselective methodologies for the synthesis of other organoboron compounds are well established, highly enantioselective synthesis of chiral propargylic boron compounds remains unknown. Herein, we report a catalytic method for the construction of chiral propargylic boron compounds by means of highly enantioselective dirhodium-catalyzed B-H bond insertion reactions using aryl propargylic sulfonylhydrazones as carbene precursors. This method enables the straightforward synthesis of a wide range of stable chiral propargylic boron compounds in yields up to 99% with enantioselectivities up to 97% ee. The operationally simple method features a broad substrate scope, good functional group tolerance, and mild reaction conditions. The boron compounds prepared in this study are inaccessible by other known methods and exhibit high potential utility because they could be efficiently transformed into allenyl borates, triazole borane compounds, and homopropargylic and propargylic alcohols with good enantiomeric fidelity. Our work expands the library of catalytic B-H bond insertion reactions, increases the variety of chiral organoboron compounds that can be synthesized, and provides preliminary information about possible transformations of chiral propargylic boron compounds, thus laying the foundation for wide application of these compounds.

Automated summary

Chiral propargylic boron compounds have a wide range of potential applications, but the synthesis of these compounds with high enantioselectivity is still unknown. This study reports a catalytic method for the construction of chiral propargylic boron compounds with high enantioselectivity.