Stereoretentive chlorination of cyclic alcohols catalyzed by titanium(IV) tetrachloride: evidence for a front side attack mechanism.
Stereoretentive chlorination of cyclic alcohols catalyzed by titanium(IV) tetrachloride: evidence for a front side attack mechanism.
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DOI：
10.1021/jo3023439
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发表时间：
2013-03-01
期刊：
影响因子：
--
通讯作者：
Lepore SD
中科院分区：
文献类型：
--
作者：
Mondal D;Li SY;Bellucci L;Laino T;Tafi A;Guccione S;Lepore SD
用经典的亚硫酰氯试剂和添加催化氯化钛(IV)进行了温和的醇氯化反应。这些反应进行得很快，以优异的产率和对保持构型的偏好提供了氯化产物。对于各种手性环二次底物，包括空间受阻体系，立体选择性都很高。氯亚硫酸盐首先在原位生成，并在四氯化钛的作用下转化为烷基氯，四氯化钛被认为是螯合离开氯亚硫酸盐的基团，并从正面输送卤素亲核试剂。为了更好地理解这一新的反应途径，采用两种不同的计算方法在密度泛函理论水平上进行了从头算研究。这一计算证据表明，当反应通过碳正离子中间体进行时，这种带电物种可能保留了金字塔几何结构，作为通过超共轭稳定的构象异构体(超共轭)存在。然后，这些碳正离子在亲核捕获时基本上被冻结在它们的原始构型中。
A mild chlorination reaction of alcohols was developed using the classical thionyl chloride reagent but with added catalytic titanium (IV) chloride. These reactions proceeded rapidly to afford chlorination products in excellent yields and with preference for retention of configuration. Stereoselectivities were high for a variety of chiral cyclic secondary substrates including sterically hindered systems. Chlorosulfites were first generated in situ and converted to alkyl chlorides by the action of titanium tetrachloride which is thought to chelate the chlorosulfite leaving group and deliver the halogen nucleophile from the front face. To better understand this novel reaction pathway, an ab initio study was undertaken at DFT level of theory using two different computational approaches. This computational evidence suggests that while the reaction proceeds through a carbocation intermediate, this charged species likely retains pyramidal geometry existing as a conformational isomer stabilized through hyperconjugation (hyperconjomers). These carbocations are then essentially “frozen” in their original configurations at the time of nucleophilic capture.
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影响因子：
2.8
作者：
Mondal, Deboprosad;Bellucci, Luca;Lepore, Salvatore D.
通讯作者：
Lepore, Salvatore D.
影响因子：
--
作者：
GONZALEZ, C;SCHLEGEL, HB
通讯作者：
SCHLEGEL, HB
影响因子：
15
作者：
BOOZER, CE;LEWIS, ES
通讯作者：
LEWIS, ES
DOI：
10.1039/p19760000754
发表时间：
1976-01-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1
影响因子：
--
作者：
HEPBURN, DR;HUDSON, HR
通讯作者：
HUDSON, HR
影响因子：
4.4
作者：
Heyden, A;Bell, AT;Keil, FJ
通讯作者：
Keil, FJ