Electrolytic Partial Fluorination of Organic Compounds. 17. Regiospecific Anodic Fluorination of Sulfides Bearing Electron-Withdrawing Substituents at the Position .alpha. to the Sulfur Atom
摘要:
Regiospecific monofluorination of various sulfides bearing electron-withdrawing substituents, cyano, ester, acyl, amino, and phosphonate groups,at their alpha-positions was successfully carried out by the anodic oxidation of the sulfides in Et(3)N . 3HF/MeCN using an undivided cell. Fluorine was introduced at the position alpha to the sulfur atom selectively. Fluorination of alpha-(phenylthio)-substituted cyclic carbonyl compounds was also successful. Furthermore, anodic alpha,alpha-difluorination of ethyl alpha-(phenylthio)acetate was also successfully carried out although a large amount of electricity was required.
高反应性试剂烯丙基卤化镁与α-取代的无环手性酮的加成具有高立体选择性。立体选择性无法通过常规立体化学模型进行分析,因为这些反应不符合这些模型的要求。相反,立体选择性是由于亲核试剂接近酮的最低能量构象的最容易接近的非对映面而产生的。预期具有高立体选择性,并且可以预测立体化学结果,其中构象偏向的酮具有空间上可区分的非对映面,其中只有一个面可进行亲核加成。酮的构象可以通过计算建模和在某些情况下通过 X 射线晶体学确定结构的组合来确定。
Nucleophilic Substitution Reactions of Sulfur-Substituted Cyclohexanone Acetals: An Analysis of the Factors Controlling Stereoselectivity
作者:Susan B. Billings、K. A. Woerpel
DOI:10.1021/jo060077r
日期:2006.7.1
The reactions of cyclohexanone acetals substituted with thiophenyl groups (and other heteroatoms) at C-2 demonstrate the powerful influence that these substituents have on the stereoselectivity of nucleophilic substitution reactions. The trans selectivities of these reactions correlate with the behavior of the corresponding ketones. These experiments lend support to the possibility that the reactions