Wittig Reactions in Water Media Employing Stabilized Ylides with Aldehydes. Synthesis of α,β-Unsaturated Esters from Mixing Aldehydes, α-Bromoesters, and Ph<sub>3</sub>P in Aqueous NaHCO<sub>3</sub>
作者:Amer El-Batta、Changchun Jiang、Wen Zhao、Robert Anness、Andrew L. Cooksy、Mikael Bergdahl
DOI:10.1021/jo070665k
日期:2007.7.1
range of stabilized ylides and aldehydes. Despite sometimes poor solubility of the reactants, good chemical yields normally ranging from 80 to 98% and high E-selectivities (up to 99%) are achieved, and the rate of the reactions in water is unexpectedly accelerated. The efficiency of water as a medium in the Wittig reaction is compared to conventional organic solvents ranging from carbon tetrachloride
事实证明,水是在多种稳定的乙炔和醛上进行维蒂希反应的有效介质。尽管有时反应物的溶解度较差,但通常可获得80-98 %的良好化学收率和较高的E选择性(高达99%),并且在水中的反应速度出乎意料地加快了。将水作为Wittig反应介质的效率与常规有机溶剂(从四氯化碳到甲醇)进行了比较。当存在大量疏水性实体(例如芳香族,杂环芳香族甲醛和长链脂族醛与三苯基膦)时,维蒂希水溶液反应最有效。该Ë / ž维蒂希产物的β-异构体比例取决于电子接受/给体能力和存在于芳环中的取代基的位置。研究了添加剂(例如苯甲酸,LiCl和十二烷基硫酸钠(SDS))对Wittig反应的影响。Wittig反应也可以在酸性实体例如苯酚和羧酸的存在下进行。另外,脂族醛中的大α-取代基不会危害反应。还证明了醛的水合物可以直接在含水维蒂希反应中用作底物。Wittig水溶液的反应范围扩展到Ph 3的一锅混合物的24个例子碳酸氢钠溶液中的P