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 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(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.

In situ derived acyclic and cyclic 1,2-diaza-1,3-dienes (DDs) were engaged in interceptive [4 + 1] annulation strategy with diazo esters (DEs). The catalytic activity of inexpensive copper(II) chloride allows the direct synthesis of mono-, bi-, and tricyclic 4,5-dihydropyrazole-5-carboxylic acid derivatives in a process that circumvents the use of an anhydrous and inert atmosphere.

1,2-Diaza-1,3-dienes (DDs) react as Michael acceptors with primary amines to afford α-aminohydrazone derivatives that were in situ coupled with isocyanates. Intramolecular ring closure of the asymmetric urea derivatives so formed allows for a selectively substituted hydantoin ring to be obtained. The hydrazone side chain introduced by the conjugated heterodiene system at the 5-position of the heterocycle represents a valuable functionality for accessing novel 5-acyl derivatives difficult to obtain by other methods.

Abstract:The zinc(II) triflate-catalyzed synthesis of highly functionalized pyrroles is described. The sequence involves the preliminary preparation of aaminohydrazones by Michael addition of primary amines to 1,2-diaza-1,3-dienes. The treatment of these intermediates with dialkyl acetylenedicarboxylates produces a-(N-enamino)-hydrazones that are converted into the corresponding pyrroles. The substituents on the carbon in position four of 1,2-diaza-1,3-dienes drive the regioselectivity of the ring closure process. Starting from 4-aminocarbonyl-1,2-diaza-1,3-dienes only dialkyl 1-substituted 5-aminocarbonyl-1H-pyrrole-2,3-dicarboxylates are achieved by Lewis acid-catalyzed ring closure. A screening of several Lewis/Brønsted acid catalysts is performed. Zinc(II) triflate is the most efficient catalyst. Under similar reaction conditions, employing 4-alkoxycarbonyl-1,2-diaza-1,3-dienes, only 4-hydroxy-1H-pyrrole-2,3-dicarboxylates are synthesized. These latter reactions can be accomplished regioselectively also in one pot. Using 4-aminocarbonyl-1,2-diaza-1,3-dienes, diamines and dialkyl acetylenedicarboxylates the sequence provides the corresponding a,w-di(Npyrrolyl)alkanes.

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