Cyclisation reactions of some pyridazinylimidoylketenes?

New Journal of Chemistry Pub Date: 2009-11-10 DOI: 10.1039/B9NJ00474B

Abstract

Flash vacuum pyrolysis (FVP) of aminopyridazinone derivatives of Meldrum’s acid at 600 °C (0.02 Torr) results in generation of an imidoylketene intermediate followed by cyclisation. In the case of the 5-amino derivatives, the products are pyrido[2,3-d]pyridazines, whereas the 4-amino compounds lead to mixtures of pyrido[2,3-d]pyridazines and pyrrolo[3,2-c]pyridazines. The feasibility of the 1,5-sigmatropic shift of a chlorine atom, required for the formation of two of the pyrido[2,3-d]pyridazines, was supported by the corresponding reaction of a corresponding 2,6-dichloroaniline derivative. The feasibility of the decarboxylation mechanism required for the formation of the pyrrolo[3,2-c]pyridazines, was supported by related processes in the FVP reactions of model compounds and by DFT calculations.

Graphical abstract: Cyclisation reactions of some pyridazinylimidoylketenes
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