4- Methyl-2-phenyl-3-pyrazolidinone

Hydroquinone and A-methyl-p-aminophenol (Metol) form superadditive mixtures and a complex, Metoquinone , consisting of one hydroquinone and two Metol molecules, was proposed by Lumiere, Lumiere and Seyewtz [44] to be the species with higher activity than the separate agents. A similar complex between hydroquinone and l-phenyl-3-pyrazolidinone (Phenidone) consisting of one molecule of hydroquinone and one molecule of Phenidone has been observed in the solid state by Kurosaki [45] and Mutter and Schneider [46]. Although these complexes can be crystallized from concentrated solutions of hydroquinone and Metol, and hydroquinone and Phenidone, there is no evidence of their existence in solution. 

The few 3-acyloxy-5-imino-2-pyrazolines known are prepared by acylation of 5-imino-3-pyrazolidinones.391,594,1599 Crippa and Gau-meri32 have treated 3-methyl-l-phenyl-5-imino-2-pyrazoline with p-nitrophenylsulfenyl chloride to obtain a 4-arylmercapto compound. These compounds are listed in Table XII. 

Axford762 have found that the reaction of various esters with phenyl-hydrazine in the presence of sodium ethoxide led to the 1-isomers (eq. 4). Under somewhat similar conditions, but using sodium methoxide as the condensing agent, Vystrcil and Stejskal1569 found that methyl croto-nate and phenylhydrazine did not give a 3-pyrazolidinone but rather pyrazolinones. These latter authors studied the condensation of methyl methacrylate and methyl crotonate with phenylhydrazine in the presence of hydroquinone. The chief products were the 2-isomers (eq. 244), but 1-isomers were usually formed in very small yields. 

The reaction of 2-phenyl-4-benzylidene-5-oxazolone with hydrazine forms 4-benzamido-5-phenyl-3-pyrazolidinone.319,1342 Both 2-pyrazolin-5-ones and 3-pyrazolin-5-ones have been reduced catalytically to 3-pyrazolidinones.1491,1592 Heymons and Rohland647 have treated 3-methyl-l,2-diphenyl-3-pyrazolin-5-one with sodium and carbon dioxide and claimed to have obtained a carboxylic acid, presumably by intermediate addition of sodium to the double bond (eq. 246). A number of... 

Dimethyl-2-phenyl-3,4-pyrazolidinedione and its 1,5-diphenyI-2-methyl analog are the only compounds of their class known. The former has been synthesized by treatment of l-(2,3-dioxobutyryl)-l-phenyl-2-methyl-2-nitrosohydrazine hydrate with sodium bisulfite" and by methylation of 4-hydroxy-3-methyl-l-phenyl-2-pyrazolin-5-one.820 The latter compound has been prepared in the same way.1243 The dimethyl phenyl compound has also been isolated from urine as a metabolic product of 4-dimethylamino-2,3-dimethyl-l-phenyl-3-pyra-zolin-5-one617 and it is formed by treatment of the same compound with sulfuric acid.618 The 4-thiono analog is also known. Reduction of 2-3-dimethyl-l-phenyl-5-oxo-3-pyrazolin-4-sulfonic acid using zinc in acid gives l,5-dimethyl-2-phenyl-4-thiono-3-pyrazolidinone.1249... 

There are reactions that seemingly contradict Baldwin s rules. Fountain showed that A-methyl-O-cinnamoyl hydroxylamine gave 5-phenyl-3-pyrazolidinone (180, which exists as the two valence tautomers shown) under forcing conditions (15 h in refluxing dichlorobenzene), via the disfavored 5-endo-trig pathway. This simply illustrates that the rules say favored or disfavored, not allowed or forbidden. It does point out, however,... 

Phenidone (i-phenyl-3-pyrazolidinone) is a black-and-white film-developing agent often listed among allergens but, to the best of my knowledge, no case of contact allergy has been reported (Liden 1984a, 1989). Related substances in limited use are dimezone (i-phenyl-4,4-dimethyl-3-pyrazolidinone) and 4-hy-droxymethyl-4-methyl-i-phenyl-3-pyrazolidinone (Sc-heman and Katta 1997). 

A most unusual photochemical oxidation occurred on 5-methyl-2-phenyl-3-pyrazolidinone (158) in acetone to give the spiroepoxide product (159). The structure of the epoxide (159) was confirmed by MCPBA epoxidation of the olefin (160). The oxidation of salicyl alcohol with sodium periodate... 

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