Add time:09/24/2019         Source:sciencedirect.com

Publisher SummaryAll pyrazolones are named according to the International Union of Pure and Applied Chemistry (IUPAC) recommendations as pyrazol-3-ones and not as pyrazol-5-ones. The IUPAC nomenclature numbers the ring clockwise, whereas most organic chemists are used to an anti-clockwise numbering. Alkylation of pyrazol-3-ones usually occurs not only on side-chain substituents, such as primary amino groups, but also on the nitrogen atom of the unsubstituted lactam group. Alkylation can also occur on a stabilized carbanion generated from a methyl group by a strong base. Most of the acylation reactions are carried out with 4-amino-1,2-dihydro-1,5-dimethyl-2- phenyl-3H-pyrazol-3-one (4-aminoantipyrine). The acid chlorides are prepared separately or generated in situ from the corresponding carboxylic acid in the presence of the aminopyrazol-3-ones. The only halogenation reactions of the ring substituents of pyrazol-3-ones known are those with bromine, N-bromosuccinimide, and hydrogen bromide. Sulfonation of 5-aminopyrazol-3-ones is described. Coupling the diazonium salts with carbon nucleophiles is the most common reaction. Condensation reactions are discussed. One of the categories of reactions may involve nucleophilic addition either by or to the pyrazol-3-one side-group. A variety of nucleophilic substitution reactions are discussed. Pyrazol-3-ones are oxidized by a variety of oxidizing agents. The reduction of functional groups, such as aldehyde, nitro, nitroso, alkene, and imino as well as deamination of amines and cleavage of amides are accomplished by various reducing agents without affecting the pyrazol-3-one ring. Some miscellaneous reactions are discussed.

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