borane-mediated reduction of a series of symmetrical alk-2-yne-1,4-diones (5) in the presence of the oxazaborolidine (R)-6 to afford (R,R)-alk-2-yne-1,4-diols ((R,R)-1) in good yields and high stereoselectivities (up to 99.9% ee). In some cases, the stereochemical purity of 1 was improved by a two-step process: (i) temporary transformation of 1 into its vic-dibromo derivatives 9, which allowed us to remove
我们在
恶唑硼烷(R)-6存在下进行了
硼烷介导的一系列对称的alk-2-yne-1,4-diones(5)的
硼烷介导还原反应,得到(R,R)-alk-2-yne -1,4
-二醇((R,R)-1)收率高,立体选择性高(ee高达99.9%)。在某些情况下,可通过两步过程提高1的立体
化学纯度:(i)将1暂时转化为其vic -dibromo衍
生物9,这使我们能够除去次要内消旋体通过色谱分离异构体,和(ii)用SmI 2再生对映体富集的二醇1。由5衍生的六羰基二
钴络合物8的还原也是成功的。