Vicinal Diboronates in High Enantiomeric Purity through Tandem Site-Selective NHC−Cu-Catalyzed Boron−Copper Additions to Terminal Alkynes
- 7 December 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 131 (51), 18234-18235
- https://doi.org/10.1021/ja9089928
Abstract
A Cu-catalyzed protocol for conversion of terminal alkynes to enantiomerically enriched diboronates is reported. In a single vessel, a site-selective hydroboration of an alkyne leads to the corresponding terminal vinylboronate, which undergoes a second site-selective and enantioselective hydroboration. Reactions proceed in the presence of 2 equiv of commercially available bis(pinacolato)diboron [B2(pin)2] and 5−7.5 mol % loading of a chiral bidentate imidazolinium salt, affording diboronates in 60−93% yield and up to 97.5:2.5 enantiomeric ratio (er). The enantiomerically enriched products can be functionalized to afford an assortment of versatile organic molecules. Enynes are converted to unsaturated diboronates with high chemo- (>98% reaction of alkyne; <2% at alkene) and enantioselectivity (e.g., 94.5:5.5 er).Keywords
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