Nucleophilic reactivities of benzenesulfonyl-substituted carbanions

Abstract

Kinetics of the reactions of four benzenesulfonyl-stabilized carbanions (1a–d)⁻ with reference electrophiles (quinone methides 2 and diarylcarbenium ions 3) have been determined in dimethyl sulfoxide solution at 20 °C in order to derive the reactivity parameters N and s according to the linear free-energy relationship log k(20 °C) = s(N + E) (eqn (1)). The additions of (1a–d)⁻ to ordinary Michael acceptors (e.g., benzylidene Meldrum's acid 4a, benzylidenebarbituric acids 5a–c, and benzylidene-indan-1,3-diones 6a–d) were also studied kinetically and found to be 5–24 times slower than predicted by eqn (1).