✍ Scribed by Dipl.-Chem. Tanja Kanzian; Dr. Simona Nicolini; Dr. Lucia De Crescentini; Prof. Dr. Orazio A. Attanasi; Dr. Armin R. Ofial; Prof. Dr. Herbert Mayr
No coin nor oath required. For personal study only.
The kinetics of the reactions of 1,2‐diaza‐1,3‐dienes 1 with acceptor‐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 k(20 °C)=s(N+E) [Eq. (1)]. With Equation (1) and the known nucleophile‐specific parameters N and s for the carbanions, the electrophilicity parameters E of the 1,2‐diaza‐1,3‐dienes 1 were determined. With E parameters in the range of −13.3 to −15.4, the electrophilic reactivities of 1 a–d are comparable to those of benzylidenemalononitriles, 2‐benzylideneindan‐1,3‐diones, and benzylidenebarbituric acids. The experimental second‐order rate constants for the reactions of 1 a–d with amines 3 and triarylphosphines 4 agreed with those calculated from E, N, and s, indicating the applicability of the linear free energy relationship [Eq. (1)] for predicting potential nucleophilic reaction partners of 1,2‐diaza‐1,3‐dienes 1. Enamines 5 react up to 10^2^ to 10^3^ times faster with compounds 1 than predicted by Equation (1), indicating a change of mechanism, which becomes obvious in the reactions of 1 with enol ethers.
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