Enaminones as Building Blocks in Heterocyclic Syntheses: Reinvestigating the Product Structures of Enaminones with Malononitrile. A Novel Route to 6-Substituted-3-Oxo-23-Dihydropyridazine-4-Carboxylic Acids

摘要

The reported structures of reaction products of enaminones with malononitrile in ethanolic piperidine are revised. A novel route to 2,3-dihydropyridazine-4-carboxylic acids >4a-c via reactions of 2-cyano-5-(dimethylamino)-5-arylpenta-2,4-dienamides >8a-c with nitrous acid or with benzenediazonium chloride is reported. Compounds >8a-c are converted to 1,2-dihydropyridine-3-carboxylic acid and 1,2-dihydropyridine-3-carbonitrile derivatives upon reflux in EtOH/ HCl and in AcOH.