Electrophilicities of trans-β-nitrostyrenes.

The kinetics of the reactions of the trans-β-nitrostyrenes 1a-f with the acceptor-substituted carbanions 2a-h have been determined in dimethyl sulfoxide solution at 20 °C. The resulting second-order rate constants were employed to determine the electrophile-specific reactivity parameters E of the trans-β-nitrostyrenes according to the correlation equation log k(2)(20 °C) = s(N)(N + E). The E parameters range from -12 to -15 on our empirical electrophilicity scale (www.cup.lmu.de/oc/mayr/DBintro.html). The second-order rate constants for the reactions of trans-β-nitrostyrenes with some enamines were measured and found to agree with those calculated from the electrophilicity parameters E determined in this work and the previously published N and s(N) parameters for enamines.