6771-51-3Relevant 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.
