Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
J Am Chem Soc. 2009 Dec 30;131(51):18234-5. doi: 10.1021/ja9089928.
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 [B(2)(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).
报道了一种铜催化的将末端炔烃转化为对映体富集的二硼酸酯的方法。在一个单一的容器中，炔烃的选择性氢硼化导致相应的末端乙烯基硼酸酯，其经历第二次的选择性和对映选择性氢硼化。反应在 2 当量的商业可得的双(频哪醇)二硼 [B(2)(pin)(2)] 和 5-7.5 mol%的手性双齿咪唑啉鎓盐的存在下进行，以 60-93%的收率和高达 97.5:2.5 的对映体过量（ee）得到二硼酸酯。对映体富集的产物可以官能化得到各种多功能有机分子。烯炔烃被转化为具有高化学选择性（>98%炔烃反应；<2%烯烃）和对映选择性（例如，94.5:5.5ee）的不饱和二硼酸酯。
