Electrophilic reactivities of 1,2-diaza-1,3-dienes

The kinetics of the reactions between 1,2-diaza-1,3-dienes 1 and substituted carbanions 2 have been studied at 20 °C. The reactions follow a second-order rate law and can be described by the linear free energy relationship log k2(20 °C) = s(N+E). With the so determined E-parameters of the Michael acceptors 1, the rates of their reactions with phosphines 3, enamines 4, and amines 5 can be predicted. With E-parameters in the range of -13.3 to -15.4, the electrophilic reactivity of 1 can be compared to those of benzylidenemalononitriles, benzylideneindandiones, benzylidene Meldrum’s acid and benzylidenebarbituric acids