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首页> 外文期刊>Chemistry: A European journal >Alkali-metal-ion catalysis and inhibition in the nucleophilic displacement reaction of Y-substituted phenyl diphenylphosphinates and diphenylphosphinothioates with alkali-metal ethoxides: effect of changing the electrophilic center from P=O to P=S
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Alkali-metal-ion catalysis and inhibition in the nucleophilic displacement reaction of Y-substituted phenyl diphenylphosphinates and diphenylphosphinothioates with alkali-metal ethoxides: effect of changing the electrophilic center from P=O to P=S

机译：Y取代的苯基二苯基次膦酸酯和二苯基膦硫代酸酯与碱金属乙醇化物的亲核取代反应中的碱金属离子催化及其抑制：将亲电中心从P = O变为P = S的作用

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摘要

A kinetic study of the nucleophilic substitution reaction of Y-substituted phenyl diphenylphosphinothioates 2a-g with alkali-metal ethoxides (MOEt; M=Li, Na, K) in anhydrous ethanol at (25.0?±0.1)°C is reported. Plots of pseudo-first-order rate constants (k _(obsd)) versus [MOEt], the alkali ethoxide concentration, show distinct upward (KOEt) and downward (LiOEt) curvatures, respectively, pointing to the importance of ion-pairing phenomena and a differential reactivity of dissociated EtO - and ion-paired MOEt. Based on ion-pairing treatment of the kinetic data, the k _(obsd) values were dissected into kEtO- and k _(MOEt), the second-order rate constants for the reaction with the dissociated EtO - and ion-paired MOEt, respectively. The reactivity of MOEt toward 2b (Y=4-NO _2) increases in the order LiOEtNaOEt>KOEt>EtO ~-. The current study based on Yukawa-Tsuno analysis has revealed that the reactions of 2a-g (P=S) and Y-substituted phenyl diphenylphosphinates 1a-g (P=O) with MOEt proceed through the same concerted mechanism, which indicates that the contrasting selectivity patterns are not due to a difference in reaction mechanism. The P=O compounds 1a-g are approximately 80-fold more reactive than the P=S compounds 2a-g toward the dissociated EtO ~- (regardless of the electronic nature of substituent Y) but are up to 3.1×10 3-fold more reactive toward ion-paired LiOEt. The origin of the contrasting selectivity patterns is further discussed on the basis of competing electrostatic effects and solvational requirements as a function of anionic electric field strength and cation size (Eisenman's theory). Concerted effort: The reactions of Y-substituted phenyl diphenylphosphinates (1a-g; see scheme) and diphenylphosphinothioates (2a-g) proceed through a concerted mechanism with TS _1 as a transition state. The nature of X and M in TS _1 determines whether metal-ion catalysis or inhibition occurs.
机译：报道了Y-取代的苯基二苯基硫代磷酸酯2a-g与碱金属乙醇盐（MOEt; M = Li，Na，K）在无水乙醇中（25.0？±0.1）℃的亲核取代反应的动力学研究。伪一阶速率常数（k _（obsd））与[MOEt]（碱式乙醇浓度）的关系图分别显示出明显的向上（KOEt）和向下（LiOEt）曲率，指出了离子对现象的重要性以及离解的EtO-和离子配对的MOEt的差异反应性。根据动力学数据的离子配对处理，将k _（obsd）值分解为kEtO-和k _（MOEt），以及与解离的EtO-和离子配对的MOEt反应的二级速率常数，分别。 MOEt对2b（Y = 4-NO _2）的反应性按照LiOEt NaOEt> KOEt> EtO〜-。基于Yukawa-Tsuno分析的当前研究表明，2a-g（P = S）和Y取代的苯基二苯基次膦酸酯1a-g（P = O）与MOEt的反应是通过相同的协同机理进行的，这表明相反的选择性模式不是由于反应机理的差异。 P = O化合物1a-g对PtS化合物2a-g的离解EtO〜-反应性约为80倍（无论取代基Y的电子性质如何），但最高可达3.1×10 3倍对离子配对的LiOEt更具反应性。在竞争性静电效应和溶剂需求的基础上，进一步讨论了形成对比的选择性图形的起源，这是阴离子电场强度和阳离子尺寸的函数（艾森曼理论）。齐心协力：Y取代的苯基二苯基次膦酸酯（1a-g;参见方案）和二苯基次硫代膦酸酯（2a-g）的反应通过一致的机理进行，其中TS _1为过渡态。 TS _1中X和M的性质决定是否发生金属离子催化或抑制。

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