Search

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. © 2022 American Chemical Society.

The scarcity of reliable methods for synthesizing chiral gem-diarylmethine borons limits their applications. Herein, we report a method for highly enantioselective dirhodium-catalyzed B−H bond insertion reactions with diaryl diazomethanes as carbene precursors. These reactions afforded chiral gem-diarylmethine borane compounds in high yield (up to 99 % yield), high activity (turnover numbers up to 14 300), high enantioselectivity (up to 99 % ee) and showed unprecedented broad functional group tolerance. The borane compounds synthesized by this method could be efficiently transformed into diaryl methanol, diaryl methyl amine, and triaryl methane derivatives with good stereospecificity. Mechanistic studies suggested that the borane adduct coordinated to the rhodium catalyst and thus interfered with decomposition of the diazomethane, and that insertion of a rhodium carbene (generated from the diaryl diazomethane) into the B−H bond was most likely the rate-determining step. © 2021 Wiley-VCH GmbH

A highly enantioselective and diastereoselective nickel-catalyzed desymmetrizing cyclization of 1,6-dienes was developed by using chiral spiro phosphoramidite ligands. The reaction provides a new atom- and step-economical approach to chiral spiro lactones and analogues bearing a quaternary stereocenter. ©

Chiral propargylsilanes and chiral allenylsilanes have emerged as versatile building blocks for organic synthesis. However, efficient methods for preparing these organosilicon compounds are lacking. We herein report a highly enantioselective method for synthesis of chiral propargylsilanes and chiral allenylsilanes from readily available alkynyl sulfonylhydrazones. Specifically, chiral spiro phosphate dirhodium complexes were used to catalyze asymmetric insertion of alkynyl carbenes into the Si-H bonds of silanes to afford a variety of chiral propargylsilanes with excellent enantioselectivity. Subsequently, a platinum catalyst was used for stereospecific isomerization of the chiral propargylsilanes to the corresponding chiral allenylsilanes. ©

Catalytic enantioselection usually depends on differences in steric interactions between prochiral substrates and a chiral catalyst. We have discovered a carbene Si-H insertion in which the enantioselectivity depends primarily on the electronic characteristics of the carbene substrate, and the log(er) values are linearly related to Hammett parameters. A new class of chiral tetraphosphate dirhodium catalysts was developed; it shows excellent activity and enantioselectivity for the insertion of diarylcarbenes into the Si-H bond of silanes. Computational and mechanistic studies show how the electronic differences between the two aryls of the carbene lead to differences in energies of the diastereomeric transition states. This study provides a new strategy for asymmetric catalysis exploiting the electronic properties of the substrates.