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首页> 外文期刊>Chemistry: A European journal >Determination of the Electrophilicity Parameters of Diethyl Benzylidenemalonates in Dimethyl Sulfoxide: Reference Electrophiles for Characterizing Strong Nucleophiles
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Determination of the Electrophilicity Parameters of Diethyl Benzylidenemalonates in Dimethyl Sulfoxide: Reference Electrophiles for Characterizing Strong Nucleophiles

机译：亚乙基苯二甲基丙二酸酯在二甲基亚砜中的亲电参数的确定：表征强亲核试剂的参考亲电试剂

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The second-order rate constants of the reactions of nine substituted diethyl benzylidenemalonates 1 a-i with the carbanions 2a-e have been determined spectrophotometrically in dimethyl sulfoxide (DMSO). Product show that the nucleophiles attack regioselectively at the electro-philic C=C double bond of the Michael acceptors to form the carbanionic adducts 4. The correlation log k(20 degrees C) = s(N+E) allows the determination of the electrophilicity parameters E for the electrophiles 1a-i from the rate constants determined in this work and the previously published N and s parameters for the nucleophiles 2a-e. The electrophilicities E for compounds 1 a-i cover a range of six units (-17.7> E >-23.8) and correlate excellently with Hammett's substituent constants sigma(p), The title compounds are roughly ten orders of magnitude less reactive than analogously substituted benzylidene Meldrum's acids, their cyclic analogues. Due to their low reactivities. compounds 1a-i are suitable reference electrophiles for determining the reactivities of highly reactive nucleophiles, such as carbanions with 16 < N < 30.
机译：已经在二甲基亚砜（DMSO）中用分光光度法确定了9个取代的亚苄基丙二烯二丙二酸二乙酯与碳负离子2a-e反应的二级速率常数。产品显示，亲核试剂在迈克尔受体的亲电C = C双键上发生区域选择性攻击，形成碳负离子加合物4。相关性log k（20°C）= s（N + E）可以确定亲电性从这项工作中确定的速率常数和亲核试剂2a-e的先前发布的N和s参数，确定亲电试剂1a-i的参数E。化合物1 ai的亲电子性E涵盖六个单位的范围（-17.7> E> -23.8），并且与哈米特的取代基常数sigma（p）密切相关。标题化合物的反应活性比类似取代的亚苄基Meldrum's低约十个数量级。酸，其环状类似物。由于它们的反应性低。化合物1a-i是确定高反应性亲核试剂（例如16

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