Pyrazolinone derivatives

Some substances, e. g. penicillin and pyrazolinone derivatives, are poorly detected by iodine staining with detection limits of 2-4 pg substance per chromatogram zone [6, 7]. The limits for lipids and for opium alkaloids lie with 50-500 ng [8] in the middle nanogram range [9]. 

Purpuric acid lb 174 Pyrazolidine derivatives la 426 3,5-Pyrazolidindione derivatives lb 20 Pyrazolinone derivatives lb 277 Pyrazolin-5-one derivatives lb 327,329 Pyrazone lb 332 Pyrene lb 379 PyrethrinI lb 18 Pyrethrin II lb 18 Pyrethroids lb 86,87 Pyrethroid insecticides la 359 Pyridine alkaloids la 66 lb 279 Pyridine derivatives lb 119,244 Pyridinium carbinols lb 65 Pyridinium glycols lb 65 Pyridoxal la 157,158,253 Pyridoxamine la 253 Pyridoxine la 253... 

The stability of the pyrazolinone tautomers was related to their scale of aromaticity.Experimental values for the tautomerism of pyrazolinone derivatives were obtained by flash vacuum pyrolysis (FVP), which allowed the calculation of the effect of the temperature on the equilibrium between tautomers. The variation of Kj with the temperature was determined by H NMR in solution for the model compound l-phenyl-3-methyl-2-pyrazolin-5-one (Scheme 25), showing that at 0 K the only tautomers present are either the NH or the OH ones. Temperature and solvent effects on the prototropic equilibrium of the model compound in solution showed that... 

Aminotriazole is carboxylated at the 5-position by heating with aqueous sodium bicarbonate in a Kolbe-type reaction (7lJCS(C)l50l). 2-Thiazolinones undergo the Gatter-mann and Reimer-Tiemann reactions at the 4-position, and 3- and 4-pyrazolinone anions on alkylation give 4-alkyl as well as O- and N-alkyl derivatives. 

Formally, these are derived from the monocationic structures (22) and (23) by replacing one of the CR groups by a negatively charged heteroatom (generally 0 , S or RN ). Two groups of unequal importance are included here the pyrazolinones and the betaines. 

The spectra of pyrazolinones have been used in tautomeric studies (Section 4.04.1.5.2). The chemical shifts shown in Table 11 are representative of the three classes of fixed derivatives [OR (63) and (64), NR (65) and CR (66)], and many others are discussed in (76AHC(Sl)l). Some tautomeric compounds are also included in Table 11. 

Irradiation of 4-hydroxy- and 4-alkoxy-3-pyrazolin-5-one derivatives (163 R = OH, OR) leads to ring cleavage with the formation of /3-diamides (165) 69TL271). The methylene blue sensitized rearrangement of the same pyrazolinone (R = H) to the oxindole (166) also... 

The trihydroxypropyl derivative 63 was prepared from dehydro-L-ascorbic acid phenylosazone (62) by opening the lactone ring with warm alkali and acidifying the mixture after a few minutes, whereupon the pyrazolinone 63 separated immediately.63 The structure of this compound was established by degradation,63 and confirmed by a study of its n.m.r. spectrum.64 The p-tolyl-, p-(bromophenyl)-, and p-(iodophenyl)-osazones of dehydro-L-ascorbic acid were also converted into the corresponding l-aryl-4-phenylazo-3-(trihydroxy-propyl)-5-pyrazolinone, and their acetylation and benzoylation products were prepared.64... 

Direct nitrosation of pyrazoles cannot be accomplished to obtain 4-nitrosopyrazoles, j9-diketones are nitrosated and then treated with hydrazine or a hydrazine derivative.594 Nitrosation of 3- and 5-hydroxypyrazoles (pyrazolinones) takes place readily in the 4-position,595 but 4-hydroxypyrazoles yield 5-nitroso derivatives.598 The following compounds are also nitrosated at the 4-position 1,3-dimethyl-5-methylthiopyrazole,542 3-methyl-5-ethoxypyrazole,597... 

Under alkaline conditions, alkyl nitrites nitrosate imidazoles that possess a free NH group, at the 4-position. Nitrosation of 3,5-dimethylpyrazoles gives the 4-diazonium salt by further reaction of the nitroso compound with more NO+. 4-Nitrosopyrazoles 188 can be used as spin traps. 5-Pyrazolinones are nitrosated readily at the 4-position. Imidazo[l,2-tf] benzimidazoles are nitrosated with NaN02 in acetic acid giving 3-nitrosoderivatives 189. Nitrosation of 2-(dimethyla-mino)thiazoles under acid conditions gives 5-nitroso-derivatives 190. 3-Alkyl-5-acetamidoisothiazoles undergo 4-nitrosation. 

Alkenes conjugated with are electron-deficient and hence do not react readily with organic peroxy acids. The observation that the stereochemistry of the pyrazolinone (109) is not retained in the epoxidadon product (110) is interesting (equation 38). The epoxide (110) is not fomaed directly fiom (109). Since the double brad in (109) is electron-deficient its peroxy acid epoxidadon to furnish (111) is a slow process. The isomerizadon the (Z)-pyrazolinfast process. MCPBA epoxidadon of the ( )-isomer derived from (109) Amishes (110). 

The transformation of an active CH compound into the corresponding diazo derivative with -toluenesulfonyl azide has been designated a diazo transfer reaction and possesses a variety of preparative uses. The method has been useful for the syntheses of diazo derivatives of cyclopentadiene, 1,3-dicar-bonyl compounds, 1,3-disulfonyl compounds,1,3-keto-sulfonyl compounds, ketones, " carboxylic acid esters, and /3-keto imines. Further reaction of these diazo intermediates can lead to azo compounds,"- " 1,2,3-triazoles, and pyrazolinones. ... 

Cycloaddition of nitrones and pyrazolinones with a copper catalyst and a chiral ligand leads to pyrrolidine derivatives with good enantioselectivity. 

Pyrazolinones and pyrazolidinones are oxo derivatives of pyrazo-lines and pyrazolidines, respectively, and are so named in Chemical Abstracts at present. However, the usual method of naming in the earlier literature is the pyrazolone-pyrazolidone system. Although a large number of tautomeric structures are possible for pyrazolinones, the usual assignment of ring structures is as shown in (I), (II) and (III). The Chemical Abstracts names for these are (I) 2-pyrazolin-5-one, (II)... 

All of these derivatives of 2-pyrazolin-5-ones have a nitrogen atom substituted at the 4-position as the 3-nitrogen-substituted-2-pyrazolin-5-ones are tautomeric with the 5-imino-3-pyrazolidinones and are considered as such in this discussion. The 4-nitrogen-substituted-2-pyrazolin-5-ones are not usually prepared by cyclization directly to the desired pyrazolinone ring but rather by modification of already formed pyrazolinones. The methods used are usually those employed in... 

---