Studies with Functionally Substituted Heteroaromatics: The Chemistry of N-Phenylhydrazonylalkylpyridinium Salts and of Phenylhydrazonylalkylbenzoazoles

Abstract

2-Pyrid-1-yliniumacetonitrile bromide 1a and 2-pyrid-1-ylinium-1-phenylethanone bromide 1b coupled with benzenediazonium chloride to yield the corresponding 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 acetonitrile in the presence of ammonium acetate. Refluxing 3a in dimethylformamide resulted in the formation of the 3-cyanoindazole 6. Compound 3a was converted 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.