描述了有关双相溶剂体系中迈森海默加合物形成的详细研究。该方法依赖于利用显着的亲脂性季铵盐在含有电子不足的芳族底物的水层和有机层之间转移亲核试剂(例如氢氧根离子)。如果有机层足够非极性,则所得的迈森海默加合物相当稳定,这很可能是大的可极化阴离子络合物和带扩散电荷的四烷基铵阳离子之间强烈的离子对相互作用的结果。以3,5-二硝基苯甲酸的二乙酰胺为模型化合物,研究了离子对试剂和溶剂对加合物形成的影响。相对于在单相系统中生成的相同加合物,在双相介质(例如苯/ 2 M NaOH)中观察到了迈森海默加合物的平衡形成的急剧增加。该加合物的光谱研究与在单相极性或偶极非质子溶剂中进行的研究一致。该方法扩展到对几种消旋的电子缺陷型酰胺进行高度对映选择性的双相动力学拆分。
Simple Synthesis of Amides and Weinreb Amides Using PPh3 or Polymer-Supported PPh3 and Iodine
作者:Amit Kumar、Hari Kiran Akula、Mahesh K. Lakshman
DOI:10.1002/ejoc.200901420
日期:2010.5
range of carboxylic acids to 2 degrees , 3 degrees , and Weinrebamides. Simplification of the procedure was possible with the use of polymer-supported PPh3/I2. Weinrebamides produced via the use of polymer-supportedPPh3 could be filtered through a short silica gel plug and used in further transformations. Thus, use of polymer-supportedPPh3 offers potential applicability to diversity-oriented reactions
已经证明,PPh 3 / I 2的组合对于将一系列羧酸转化为2度,3度和Weinreb酰胺是有效的。使用聚合物负载的PPh3 / I2可以简化程序。通过使用聚合物负载的PPh3制备的Weinreb酰胺可以通过短硅胶塞过滤,并用于进一步的转化。因此,使用聚合物负载的PPh3可为面向多样性的反应提供潜在的适用性。通过使用这种酰胺形成方法,已经完成了载脂蛋白和普拉托恩的正式全部合成,以及脱水胆碱酮和马来帕定的合成。已尝试获得对该反应的了解。
Acid anhydrides and the unexpected N,N-diethylamides derived from the reaction of carboxylic acids with Ph3P/I2/Et3N
high yields within 5–10 min. However, for nitro-substituted derivatives, unexpectedly, N,N-diethylamides were isolated without anhydride formation. These results indicated the pronounced effect of substituents in governing these potential side reactions which can significantly affect the yields of acylation reactions promoted by phosphonium species.
研究了由磷介导的羧酸活化作用形成酸酐。在各种体系下,取决于试剂的反应性,在碱的存在下苯甲酸的活化导致苯甲酸酐以不同的速率形成。使用Ph 3 P–I 2 / Et 3 N组合,大多数芳酸在5–10分钟内即可高产率转化为相应的酸酐。然而,对于硝基取代的衍生物,出乎意料的是,N,N分离了-二乙酰胺而没有酸酐形成。这些结果表明取代基在控制这些潜在的副反应中具有显着的作用,其可显着影响由phospho物种促进的酰化反应的产率。
A Convenient and Inexpensive Method for Conversion of Thiocarbonyl Compounds to Their Oxo Derivatives Using Oxone Under Solvent-Free Conditions
作者:Iraj Mohammadpoor-Baltork、Majid M. Sadeghi、Karim Esmayilpour
DOI:10.1081/scc-120016359
日期:2003.1.4
Abstract A series of thioamides, thioureas and thioesters are transformed to their corresponding carbonyl compounds in good to excellent yields with oxone under solid phase conditions, while thioketones remained unchanged under these conditions.
Efficient and Convenient Deprotection of Thiocarbonyl to Carbonyl Compounds Using 3-Carboxypyridinium and 2,2'-Bipyridinium Chlorochromates in Solution, Dry Media, and under Microwave Irradiation
deprotection reactions is reported. Different types of thioamides, thioureas, thiono esters, and thioketones are deprotected to their corresponding carbonyl compounds with these reagents in good to excellent yields. The reactions were carried out in solution, under solvent-free conditions, and under microwave irradiation. The results show that with both reagents the rates of the reactions and the yields
12-Tungstosilicic acid (H4SiW12O40) is applied for the conversion of a series of thioamides to their corresponding oxo analogues in excellent yields in acetonitrile. In the case of thioketones, no reaction is observed under these conditions. The reusability of the catalyst also is investigated.