在温和的反应条件下,使用碳酸氢钠-过氧化氢作为氧化剂,探索了基于Mn III-卟啉的催化体系进行烯烃环氧化。Mn(TPP)OAc /咪唑/ NaHCO 3体系有效地催化了H 2 O 2对烯烃的环氧化。环烯烃以优异的收率(80–100%)和选择性(87–100%)转化,获得的选择性和收率比没有碳酸氢盐时观察到的要好得多。在过量的底物存在下,用Mn(TPP)OAc / Im / NaHCO 3 / H 2 O 2获得转换数42862小时后系统。碳酸氢盐活化的氧化系统是其他氧化剂和过氧酸的一种简单,便宜且相对无毒的替代品,可用于需要中性,中性pH氧化剂的各种氧化反应中。 由于溶剂,反应温度,咪唑/ NaHCO 3 / H 2 O 2的化学计量比,烯烃的氧化等多种因素的影响,采用Taguchi系统优化方法确定了贡献率(%P)。每个因素。发现该溶剂对氧化的影响最大(30.051%),并且咪唑的量排在第二位(22
The use of trialkylorganozincates and tetraalkylaluminates allows regioselective SN2 nucleophilic opening of vinylic epoxides. The reaction occurs with an anti-substitution pattern and can be applied to a wide range of substrates. We also show that the solvent and the structure of the epoxide have an influence on the substitution products ratio.
newly proposed hypothesis on the mechanism of asymmetric induction, highly efficient (salen)manganese(III) complex (3) was constructed as a catalyst for asymmetric epoxidation. With this catalyst, the highest level of enantioselectivity was realized in the epoxidation of various conjugated cis-olefins.
In the Mn-salen catalyzed asymmetricepoxidation of some olefins, non-linear relationship between reaction temperature and enantioselectivity was observed. For example, the epoxidation of 1,3-cycloalkadiene with complex 3a as a catalyst showed the maximum enantioselectivity at 0 °C. It was also found that the electronic nature of the aromatic substituent in the salen ligand affects enantioselectivity
The reaction of dimethyldioxirane with 1,3-cyclohexadiene and 1,3-cyclooctadiene: monoepoxidation kinetics and computational modeling
作者:Davita McTush-Camp、Pedro C. Vasquez、Alfons L. Baumstark
DOI:10.1515/hc-2014-0211
日期:2015.2.1
monoepoxidations. As expected, the calculations were consistent with a concerted, electrophilic process with a spiro-transition state. As found for the epoxidation of simple alkenes, the calculated transition-state geometry showed a slight asynchronous tilt of the dioxirane plane relative to that of the remaining alkene portion of the diene and a slight tilt back from the face of the diene. Relative reactivities
Stereoselective synthesis of syn-meso-cyclooctanetetraol, bromo-, and oxabicyclic amino-alcohol derivatives
作者:Emine Salamci、Ufuk Nusret Karavaizoglu
DOI:10.1016/j.tetlet.2023.154759
日期:2023.10
The first synthesis of syn-meso-cyclooctane-1,2,3,4-tetraol isomer, a new bromocyclooctanetriol, and oxabicyclic amino-alcohol derivatives of them starting from cis,cis-1,3-cyclooctadiene is described. For the construction of a cyclooctane-1,2,3,4-tetraol skeleton with all the syn hydroxyl groups, cyclooctene endoperoxide was used as the key compound. Epoxidation of the endoperoxide followed by hydrogenation