The direct esterification of phosphinicacids has been extended to the preparation of thiophosphinates using thiols, but the conversions are only ca. 50%. The outcome is in agreement with the unexpectedly high enthalpy of activation and endothermicity suggested by quantum chemical calculations. At the same time, formation of the thiophosphinates confirms the AAC2 (phosphinylation) mechanism and excludes
次膦酸的直接酯化作用已扩展到使用硫醇制备硫代次膦酸酯的过程,但转化率仅为约2。50%。结果与量子化学计算所暗示的活化焓和吸热性出乎意料的高一致。同时,硫代次膦酸酯的形成证实了A AC 2(次膦酸酯化)的机理,并且排除了S N反应路径。在实验条件下也排除了在反应条件下形成烯烃中间体的可能性。
Direct Estirification and Amidation of Phosphinic Acids Under Microwave Conditions
Abstract Phosphinic acids may be efficiently esterified in microwave-assisted reactions with alcohols. Especially alcohols with longer alkyl chain are suitable reagents for direct esterifications. At the same time, the directamidation cannot be complete under such conditions. Hence, the tradional amidations via the phosphinic chloride intermediates have to be applied. The values of activation enthalpies
the alkylatingesterification of the corresponding 1-hydroxy derivatives under phase transfer catalytic, microwave, and solventlessconditions using alkyl halides as the reactants and potassium carbonate as the base. In the case of alkylating agents of increased reactivity, there was no need for the use of phase transfer catalyst. Regarding the phosphinic acids, the 3-methyl-3-phospholene oxides were
1-Hydroxy-phospholene 1-oxides (1 and 3) and 1-hydroxy-phospholane oxides (5 and 7) undergo fast and efficient esterification with a series of alcohols, at room temperature, in the presence of 1.1 equiv of propylphosphonic anhydride (T3P (R)). (C) 2013 Elsevier Ltd. All rights reserved.