rel-(2S,4R,6S)-2-n-hexyl-4,6-dimethyl-1,3-dioxane | 137694-23-6

• 分子结构分类: 有机化合物 - 有机杂环化合物 - 二恶烷
• 英文名称: rel-(2S,4R,6S)-2-n-hexyl-4,6-dimethyl-1,3-dioxane
• CAS: 137694-23-6
• 化学式: C₁₂H₂₄O₂
• 分子量: 200.321
• InChiKey: BSNWHBPLTGXHBY-ZSBIGDGJSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  3.5
• 重原子数：
  14.0
• 可旋转键数：
  5.0
• 环数：
  1.0
• sp3杂化的碳原子比例：
  1.0
• 拓扑面积：
  18.46
• 氢给体数：
  0.0
• 氢受体数：
  2.0

反应信息

• 作为反应物：
  描述：

  rel-(2S,4R,6S)-2-n-hexyl-4,6-dimethyl-1,3-dioxane 、 烯丙基三甲基硅烷 在 四氯化钛 作用下， 以 二氯甲烷 为溶剂， 反应 0.5h， 生成 (2S,4R)-4-((S)-1-Allyl-heptyloxy)-pentan-2-ol 、 (2R,4S)-4-((S)-1-Allyl-heptyloxy)-pentan-2-ol
  参考文献：
  名称：

  Studies on the mechanism and origin of stereoselective opening of chiral dioxane acetals

  摘要：

  A systematic examination of the mechanism and origin of stereoselection in the reaction of dioxane acetals with allyltrimethylsilane was undertaken. Experimental tests for two limiting mechanisms, synchronous (S(N)2-like) and dissociative (S(N)1-like) substitution processes, were investigated. The meso 2,4,6-trisubstituted 1,3-dioxane acetals cis- and trans-1 provided an interesting opportunity to test the timing of bond breaking and making in the substitution reaction. The modest and C(2)-substituent-dependent selectivity excluded the possibility of a direct S(N)2-type attack on a complexed acetal. Further, the enol ethers 3 and 5 and acyclic acetal 7 were studied as precursors of the putative oxocarbenium ion intermediate in the dissociative limit. The weak and inverted selectivity observed with these substrates ruled out the intermediacy of the extended, separated ion in reactions of the cyclic acetals under similar conditions. A unified mechanistic scheme involving three distinct ion pairs is proposed to explain the dependence of allylation selectivity on structural and experimental variables. The three species are analogous to those proposed in the classic Winstein scheme: (1) an intimate ion pair, (2) an external ion pair, and (3) a separated ion. Each of these proposed intermediates has a different stereochemical profile and the ultimate outcome is a composite of those factors that balance the contribution of the different intermediates. The influence of C(2) substituent, acetal configuration, Lewis acid type and stoichiometry, allylsilane stoichiometry, concentration, solvent, and temperature were investigated and integrated in the proposed mechanistic scheme.

  DOI：

  10.1021/ja00021a040
• 作为产物：
  描述：

  庚醛 、 2,4-戊二醇 在 对甲苯磺酸 作用下， 以 苯 为溶剂， 反应 8.5h， 以47.7%的产率得到rel-(2S,4R,6S)-2-n-hexyl-4,6-dimethyl-1,3-dioxane
  参考文献：
  名称：

  Studies on the mechanism and origin of stereoselective opening of chiral dioxane acetals

  摘要：

  A systematic examination of the mechanism and origin of stereoselection in the reaction of dioxane acetals with allyltrimethylsilane was undertaken. Experimental tests for two limiting mechanisms, synchronous (S(N)2-like) and dissociative (S(N)1-like) substitution processes, were investigated. The meso 2,4,6-trisubstituted 1,3-dioxane acetals cis- and trans-1 provided an interesting opportunity to test the timing of bond breaking and making in the substitution reaction. The modest and C(2)-substituent-dependent selectivity excluded the possibility of a direct S(N)2-type attack on a complexed acetal. Further, the enol ethers 3 and 5 and acyclic acetal 7 were studied as precursors of the putative oxocarbenium ion intermediate in the dissociative limit. The weak and inverted selectivity observed with these substrates ruled out the intermediacy of the extended, separated ion in reactions of the cyclic acetals under similar conditions. A unified mechanistic scheme involving three distinct ion pairs is proposed to explain the dependence of allylation selectivity on structural and experimental variables. The three species are analogous to those proposed in the classic Winstein scheme: (1) an intimate ion pair, (2) an external ion pair, and (3) a separated ion. Each of these proposed intermediates has a different stereochemical profile and the ultimate outcome is a composite of those factors that balance the contribution of the different intermediates. The influence of C(2) substituent, acetal configuration, Lewis acid type and stoichiometry, allylsilane stoichiometry, concentration, solvent, and temperature were investigated and integrated in the proposed mechanistic scheme.

  DOI：

  10.1021/ja00021a040

文献信息

• On the stereoselectivity opening of achiral dioxane acetals
  作者：Scott E. Denmark、Neil G. Almstead

  DOI：10.1021/jo00022a043

  日期：1991.10

  The stereoselectivity of allylation of achiral dioxane acetals cis- and trans-3 and cis- and trans-5 was found to be highly dependent on the nature of the allylmetal reagent, Lewis acid, and stoichiometry. Using TiCl2(O-i-Pr)2 as the Lewis acid in conjunction with allyltrimethylsilane and allyltri-n-butylstannane the selectivity of opening ranged from 1/1 to 18.6/1. In reactions with allyltrimethylsilane, the lack of selectivity for both the cis and trans series (1-2.4/1) was shown to arise from rapid equilibration of ion pairs. Control experiments revealed that the acetals underwent opening faster than isomerization. The reactions with allyltri-n-butylstannane were more selective and dependent on reagent stoichiometry. Moreover, the sense of asymmetric induction for the cis and trans series was opposite. Control experiments again established that isomerization of the acetals occurs slower than reaction with the stannane. These experiments unambiguously rule out the possibility that the opening proceeds via equilibrating ion pairs. The meso dioxane acetal cis-9 reacted with significantly reduced selectivity compared to the 2,4,6-trisubstituted analogue cis-7. On the other hand, the chiral acetal (+/-)-13 reacted much more selectively than the 2,4,6-trisubstituted analogue (+/-)-11. These reactions illustrate the sensitivity of stereochemical outcome to structural and experimental variables and demonstrate the ability to intercept reactive ion pairs under conditions of kinetic control.
• Studies on the mechanism and origin of stereoselective opening of chiral dioxane acetals
  作者：Scott E. Denmark、Neil G. Almstead

  DOI：10.1021/ja00021a040

  日期：1991.10

  A systematic examination of the mechanism and origin of stereoselection in the reaction of dioxane acetals with allyltrimethylsilane was undertaken. Experimental tests for two limiting mechanisms, synchronous (S(N)2-like) and dissociative (S(N)1-like) substitution processes, were investigated. The meso 2,4,6-trisubstituted 1,3-dioxane acetals cis- and trans-1 provided an interesting opportunity to test the timing of bond breaking and making in the substitution reaction. The modest and C(2)-substituent-dependent selectivity excluded the possibility of a direct S(N)2-type attack on a complexed acetal. Further, the enol ethers 3 and 5 and acyclic acetal 7 were studied as precursors of the putative oxocarbenium ion intermediate in the dissociative limit. The weak and inverted selectivity observed with these substrates ruled out the intermediacy of the extended, separated ion in reactions of the cyclic acetals under similar conditions. A unified mechanistic scheme involving three distinct ion pairs is proposed to explain the dependence of allylation selectivity on structural and experimental variables. The three species are analogous to those proposed in the classic Winstein scheme: (1) an intimate ion pair, (2) an external ion pair, and (3) a separated ion. Each of these proposed intermediates has a different stereochemical profile and the ultimate outcome is a composite of those factors that balance the contribution of the different intermediates. The influence of C(2) substituent, acetal configuration, Lewis acid type and stoichiometry, allylsilane stoichiometry, concentration, solvent, and temperature were investigated and integrated in the proposed mechanistic scheme.