(+/-)-4-Bromo-2-methylene-3-cyclohexen-1-ol acetate | 151053-18-8

• 分子结构分类: 有机化合物 - 有机氧化合物
• 英文名称: (+/-)-4-Bromo-2-methylene-3-cyclohexen-1-ol acetate
• CAS: 151053-18-8
• 化学式: C₉H₁₁BrO₂
• 分子量: 231.089
• InChiKey: YBPLBOHABBLURO-UHFFFAOYSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  2.55
• 重原子数：
  12.0
• 可旋转键数：
  1.0
• 环数：
  1.0
• sp3杂化的碳原子比例：
  0.44
• 拓扑面积：
  26.3
• 氢给体数：
  0.0
• 氢受体数：
  2.0

反应信息

• 作为反应物：
  描述：

  (+/-)-4-Bromo-2-methylene-3-cyclohexen-1-ol acetate 在 吡啶 、 4-二甲氨基吡啶 、 sodium hydroxide 、 四氧化锇 、 cerium(III) chloride 、 叔丁基锂 、 N-甲基吗啉氧化物 、 三乙胺 、 N,N-二异丙基乙胺 作用下， 以 四氢呋喃 、 甲醇 、 二氯甲烷 为溶剂， 反应 75.67h， 生成 (+/-)-(1R^*,2S^*,4R^*)-7,7-Dimethoxy-2-<(1R^*,6S^*)-1-(methoxymethoxy)-7-oxabicyclo<4.2.0>oct-2-en-3-yl>-5-norbornen-2-ol
  参考文献：
  名称：

  Synthetic equivalents of the taxol C,D ring system. Examination of nucleophilic bicyclic oxetanes and less-strained acetonide equivalents

  摘要：

  A procedure is described for the conversion of 3-bromo-2-cyclohexenone into the functionalized bicyclic oxetanes 13a and 13b. These heterocycles undergo halogen-metal exchange readily in the presence of tert-butyllithium at -78-degrees-C, and the resulting vinyl anions are capable of nucleophilic addition to ketones either directly or via cerate intermediates without complication. Whereas norbornenol 20 smoothly undergoes anionic oxy-Cope rearrangement at 0-degrees-C when transformed into its potassium salt, alcohols 23 and 24 are especially prone to aromatization with loss of the oxetane subunit under the same conditions. Thermal activation of these substrates results in fragmentation via an oxy-ene reaction. In order to skirt these complications, attention was directed to O-benzylation of the hydroxy diacetates 9/10, followed by saponification and acetalization with 2,2-dimethoxypropane. This has made available the pair of bromo acetonides 36 and 37. Sequential treatment of 36 with tert-butyllithium and anhydrous cerium trichloride gave the corresponding organocerate that added stereoselectively to the endo surface of the carbonyl group in optically pure ketone 22. The individual diastereomers thus produced were subjected to anionic oxy-Cope rearrangement in the presence of potassium hexamethyldisilazide and air. In this way, the highly reactive enolates formed by [3,3] sigmatropy were directly oxygenated. The resulting alpha-hydroxy ketones were examined for their ability to experience dehydration. While 42 underwent spontaneous regiospecific conversion to alpha,beta-unsaturated ketone 43 during formation of its mesylate, 41 proved resistant to the loss of water. This striking difference in reactivity has been analyzed on the basis of the conformational features of the two diastereomers as deduced by molecular mechanics calculations and X-ray crystallography.

  DOI：

  10.1021/jo00070a036
• 作为产物：
  描述：

  甲基三苯基溴化膦 、 6-acetoxy-3-bromocyclohex-2-enone 在 正丁基锂 作用下， 生成 (+/-)-4-Bromo-2-methylene-3-cyclohexen-1-ol acetate
  参考文献：
  名称：

  Synthetic equivalents of the taxol C,D ring system. Examination of nucleophilic bicyclic oxetanes and less-strained acetonide equivalents

  摘要：

  A procedure is described for the conversion of 3-bromo-2-cyclohexenone into the functionalized bicyclic oxetanes 13a and 13b. These heterocycles undergo halogen-metal exchange readily in the presence of tert-butyllithium at -78-degrees-C, and the resulting vinyl anions are capable of nucleophilic addition to ketones either directly or via cerate intermediates without complication. Whereas norbornenol 20 smoothly undergoes anionic oxy-Cope rearrangement at 0-degrees-C when transformed into its potassium salt, alcohols 23 and 24 are especially prone to aromatization with loss of the oxetane subunit under the same conditions. Thermal activation of these substrates results in fragmentation via an oxy-ene reaction. In order to skirt these complications, attention was directed to O-benzylation of the hydroxy diacetates 9/10, followed by saponification and acetalization with 2,2-dimethoxypropane. This has made available the pair of bromo acetonides 36 and 37. Sequential treatment of 36 with tert-butyllithium and anhydrous cerium trichloride gave the corresponding organocerate that added stereoselectively to the endo surface of the carbonyl group in optically pure ketone 22. The individual diastereomers thus produced were subjected to anionic oxy-Cope rearrangement in the presence of potassium hexamethyldisilazide and air. In this way, the highly reactive enolates formed by [3,3] sigmatropy were directly oxygenated. The resulting alpha-hydroxy ketones were examined for their ability to experience dehydration. While 42 underwent spontaneous regiospecific conversion to alpha,beta-unsaturated ketone 43 during formation of its mesylate, 41 proved resistant to the loss of water. This striking difference in reactivity has been analyzed on the basis of the conformational features of the two diastereomers as deduced by molecular mechanics calculations and X-ray crystallography.

  DOI：

  10.1021/jo00070a036