The properties and reactions of 4-aryl-3,5- dihydroxypyrazoles are summarized and discussed. These heterocycles react with 1,3- diketones and phenylmalononitrile derivatives to yield a novel diazapentalene betainic system. The colored heterocyclic compounds thus obtained were named “paraionic” because the cationic and anionic parts coexist parallel to one another. The interaction between the cationic part and the anionic part is in the excited state only. The acidity and structure and reactivity of 4-Aryl-3,5-dihydroxypyrazoles is compared to that of 4-aryl- 3,5-dihydroxyisoxazoles. The structure and properties of a series of paraionic heterocycles is explained and discussed.
Buy this Article