Further studies on the reaction of ethyl benzoylacetate with malononitrile: synthesis of some novel pyridine and pyridazine derivatives

2-Cyano-5-phenyl-3,5-dioxopentanonitrile undergoes alcoholysis followed by Knoevenagel condensation to afford ethyl 4,4-dicyano-3-phenyl-3-butenoate, a thermo dynamically controlled product, which undergoes cyclization in acid medium to afford 2,6-dihydroxy-4-phenylnicotinonitrile. Some azo derivatives of nicotinonitriles and of 2-aminopyran are described. 5-Arylazo-2-aminopyrans are transformed by acid treatment into pyridazine derivatives, whereas without the arylazo substituent pyridines are obtained.