6768-19-0Relevant academic research and scientific papers
Determination of the electrophilicity parameters of diethyl benzylidenemalonates in dimethyl sulfoxide: Reference electrophiles for characterizing strong nucleophiles
Kaumanns, Oliver,Lucius, Roland,Mayr, Herbert
supporting information; experimental part, p. 9675 - 9682 (2009/09/29)
The second-order rate constants of the reactions of nine substituted diethyl benzylidenemalonates 1a-i with the carbanions 2a-e have been determined spectrophotometrically in dimethyl sulfoxide (DMSO). Product studies show that the nucleophiles attack regioselectively at the electrophilic C=C double bond of the Michael acceptors to form the carbanionic adducts 4. The correlation log k(20°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 1a-i cover a range of six units (-17.7> E >-23.8) and correlate excellently with Hammett's substituent constants σp. 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 16N30.
Tandem Knoevenagel-Michael addition of aryl sulfonimines with diethyl malonate for synthesis of arylidene dimalonates
Fan, Renhua,Wang, Weizi,Pu, Dongming,Wu, Jie
, p. 5905 - 5907 (2008/02/10)
(Chemical Equation Presented) A highly efficient, one-flask tandem Knoevenagel-Michael addition reaction of sulfonimines with diethyl malonate in the presence of a catalytic amount of base affords the corresponding arylidene dimalonates in good to excellent yields.
Lewis acidic ionic liquids for the synthesis of electrophilic alkenes via the Knoevenagel condensation
Harjani, Jitendra R,Nara, Susheel J,Salunkhe, Manikrao M
, p. 1127 - 1130 (2007/10/03)
1-Butyl-3-methylimidazolium chloroaluminate, [bmim]Cl·AlCl3, N = 0.67 and 1-butylpyridinium chloroaluminate, [bpy]Cl·AlCl3, N = 0.67 ionic liquids were found to work well as the Lewis acid catalyst and solvent in the Knoevenagel condensations of benzaldehyde and substituted benzaldehydes with diethyl malonate to give benzylidene malonates. The benzylidene malonates subsequently underwent Michael additions with diethyl malonate. The extent of Michael product formed during the reaction was found to vary with the Lewis acidity and the molar proportion of ionic liquid. The influence of Lewis acidity of the ionic liquid on the Knoevenagel and Michael products is demonstrated. In the case of 2-hydroxyarylaldehydes, the reactions led to the formation of 3-ethoxycarbonyl coumarins under ambient conditions.
