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

Chemistry - A European Journal, ISSN: 0947-6539, Vol: 16, Issue: 39, Page: 12008-12016
2010
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Article Description

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 logk(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 1a-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 1a-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 to 10 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. Electrophilicities quantified: The kinetics of the reactions of 1,2-diaza-1,3-dienes 1 with carbanions have been studied photometrically at 20°C (see figure). The second-order rate constants were used to calculate the electrophilicity parameters E of compounds 1 according to the linear free energy relationship logk(20°C)= s(N+E). These parameters were employed to define the scope and limitations of the reactions of 1,2-diaza-1,3-dienes 1 with various nucleophiles. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bibliographic Details

Kanzian, Tanja; Nicolini, Simona; De Crescentini, Lucia; Attanasi, Orazio A; Ofial, Armin R; Mayr, Herbert

Wiley

Chemical Engineering; Chemistry

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