Studies with functionally substituted heteroaromatics: The chemistry of N-phenylhydrazonylalkylpyridinium salts and of phenylhydrazonylalkylbenzoazoles

2-Pyrid-1-yliniumacetonitrile bromide la and 2-pyrid-1-ylinium-1 -phenyleth anone bromide Ib coupled with benzenediazonium chloride to yield the corres ponding phenylhydrazones 3a, b. Similarly, compounds 2a-c also coupled with aryldiazonium chloride, yielding the arylhydrazones 10a-b, which were used as precursors for the synthesis of azolypyridazinones 11a, b. Compounds 3a , b were converted into 1,2,4,5-dihydrotetrazines 4a, b on refluxing in ace ronitrile in the presence of ammonium acetate. Refluxing 3a in dimethylform amide resulted in the formation of the 3-cyanoindazole 6. Compound 3a was c onverted to pyrazole 8 on treatment with the enaminone 7, and to hydrazonyl bromide 9 on heating in dioxane/acetonitrile. Compound 12 was synthesized from the reaction of 10b with ethanolic aqueous sodium hydroxide.