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Puente, Ángel; He, Shanshan; Corral-Bautista, Francisco; Ofial, Armin R.; Mayr, Herbert (2016): Nucleophilic Reactivities of 2-Substituted Malonates. In: European Journal of Organic Chemistry, No. 10: pp. 1841-1848
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Abstract

Kinetics of the reactions of 2-substituted malonate anions and 5-substituted Meldrum's acid anions with benzhydrylium ions and structurally related quinone methides have been monitored in dimethyl sulfoxide solution at 20 degrees C. The resulting second-order rate constants followed the correlation lg k(20 degrees C) = s(N)(E + N), which allowed the nucleophile-specific parameters N and s(N) to be calculated for these highly stabilized carbanions and to integrate them in our comprehensive nucleophilicity scale. Given that the reactions of the benzhydrylium ions with the anions derived from 5-aryl-substituted Meldrum's acids did not proceed to completion, the corresponding equilibrium constants could be determined. In combination with available data for pyridines and benzoate ions, these equilibrium constants provide a direct comparison of the strengths of C-, N-, and O-centered Lewis bases with respect to C-centered Lewis acids.