New chiral borohydrides. 3. Preparation and asymmetric reducing properties of potassium 9-O -(1,2-isopropylidene-5-deoxy-α-D-xylofuranosyl)-9-borata-bicyclo[3.3.1]nonane
作者:Byung Tae Cho、Yu Sung Chun
DOI:10.1016/s0957-4166(00)82314-9
日期:1992.1
A stable, new chiral borohydride, potassium 9-O- (1,2-O-isopropylidene-5- deoxy-α-D-xylofuranosyl)-9-boratabicyclo[3.3.1]nonane (K xylide,1D) using a xylose derivative as a chiral auxiliary was prepared by the treatment of the corresponding borinic ester3D with potassium hydride in THF. The reagent provided high optical induction for asymmetric reduction of prochiral ketones, such as relatively hindered
一种稳定的,新的手性硼氢化钾,使用木糖形成的钾9- O-(1,2- O-异亚丙基-5-脱氧-α-D-木呋喃糖基)-9-硼双双环[3.3.1]壬烷(K xylide,1D)通过处理相应的硼酸酯3D制备作为手性助剂的衍生物用氢化钾的四氢呋喃溶液。该试剂为不对称还原前手性酮(例如相对受阻的酮,烷基芳族酮和α-卤代酮)提供了较高的光诱导能力。因此,4-甲基-2-戊酮,3,3-二甲基-2-丁酮和2,2-二甲基环戊酮的还原分别提供了相应的醇,分别为65%ee,76%ee和80%ee。未受阻的脂肪族酮的光诱导很低,例如2-庚酮的ee为36%,3-甲基-2-丁酮的ee为46%。烷基芳族酮的减少提供了高的光诱导性,例如苯乙酮为70%ee,丁苯酮为82%ee,异丁苯酮为89%ee,新戊苯酮为99%ee,2'-甲基苯乙酮为93%ee。对于某些功能化的酮,