Pyrazolinone

C3N2 N N — — — Pyrazole substituted pyrazoles A - and A -pyrazolines pyrazolinones pyrazolidines pyrazolidinones... 

As expected, nitration is facilitated by activating groups such as an amino group for example, nitration of (115) occurs at about 20 °C (HNO3/H2SO4). Sydnones (116) are nitrated readily. The pyrazolinone (117) is nitrated as indicated, and 1,2,4-triazolinones have also been ring nitrated. 

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. 

Under alkaline conditions, alkyl nitrites nitrosate imidazoles which possess a free NH group in the 4-position (70AHC(12)103). Nitrosation of 3,5-dimethylpyrazole gives the 4-diazonium salt by further reaction of the nitroso compound with more NO". 5-Pyrazolinones are often nitrosated readily at the 4-position. 3-Alkyl-5-acetamidoisothiazoles undergo 4-nitrosation. 

Electrophilic substitution occurs readily in Af-phenyl groups, e.g. 1-phenyI-pyrazoIes, -imidazoles and -pyrazolinones are all nitrated and halogenated at the para position. The aryl group is attacked preferentially when the reactions are carried out in strongly acidic media, where the azole ring is protonated. 

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 pyrazolinones (11) (pyrazolinethiones and iminopyrazolines) correspond to the replacement of R or R in (22) by 0 , and are normally represented by their neutral structure, but it is important to bear in mind their dipolar formula (26) when discussing their reactivity. Similarly, the indazolinones (12) (27) result from the indazolium salts (23). 

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. 

Figure 14 C chemical shifts (p.p.m.) of pyrazolinones, pyrazolinethiones and pyrazolidinediones...

Hi) Pyrazole rings containing carbonyl groups In this subsection compounds with a pyrazole C—O bond will be discussed independently of their aromatic character. In solution the tautomers of pyrazolinones, e.g. (78a), (78b) and (78c), are easily identified by their IR spectra (Figure 18) (76AHC(Sl)l). 

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... 

Pyrazolin-5-one, 3-methyl-1-phenyl-in colour photography, 5, 299 Pyrazolinones C NMR, 5, 193 H NMR, 5, 185, 187 colour couplers... 

Carpino et al. recently disclosed the synthesis of the fused pyrazolinone-piperidine dipeptide 56 with potent growth hormone secretagogue activity. The synthesis of the intermediate pyrazolone was accomplished by reacting the ketoester 54 with methyl hydrazine in refluxing ethanol. ... 

Pyrazolinones and other five-membered compounds (functional tautomerism). These studies have often used the most simple but rather experimentally neglected pyrazolin-5-one 19. Its four tautomers are called CH 19a, NH 19b, 5-OH 19c, and 3-OH 19c (Scheme 10) [76AHCS1, p. 313]. 

The authors claim that these associations, which are destroyed in fixed compounds, play an important role in the calculation of Ty.The cases of 1,2,4-triazole-5-thiones 74 [97SA(A)699] and of pyridone dimers 15a-15a and 15a-15b were also studied [96MI(13)65]. (3) The recording of IR spectra in solution at different temperatures to determine the effect of the temperature on Kj-, for instance, in pyrazolinones [83JPR(325)238] and in cytosine-guanine base pairs [92MI(9)881]. (4) The determination of the equilibrium 2-aminopyridine/acetic acid 2-aminopyridinium acetate (see Section III.E) in the acid-base complex was carried out by IR (97NKK100). 

The predominance in the gas phase of the CH tautomers in the case of several pyrazolinones including one 3-aminopyrazolin-5-one was demonstrated by PES [88JCS(P2)641] this result is consistent with previous findings (76AHCS1, p. 325). The same technique was applied to the study of the amino/imino equilibrium in 9-amino and 9-(methylamino)acridines [91MI(61)166] although both tautomers have similar stabilities, the experimental data are in better agreement with the amino tautomer. 

The equilibrium in pyrazolin-5-ones, containing one or more carboxylate or sulfonate group, is extremely sensitive to the pH of the medium. For example, pyrazolinone 105c, which exists in D2O solution at pH 2 as an enol... 

There are four possible pyrazol-3-(Mie structures I-IV. The nomenclature most frequently used in the literature has been taken from Chemical Abstracts, wlwre for example, structure I is named 2,3-dihydropyrazol-3(lW)-(Mie and structure II is named 4,5-dihydropyrazol-5(l//)-one. Compounds I and II have also been named as pyrazolinones. Compounds with structure IV have been referred to as 2,3-diaza-2,4-cyclopentadienones. To avoid this needless confusion, the nomenclature used throughout this review is in accord with the recommendations set forth by lUPAC. 

The pyrazolinone should be colorless. If it is not, it may be washed with a minimum of ice-cold ethanol. This procedure is convenient and yields material of adequate purity for the subsequent reaction. Additional pyrazolinone may be obtained by evaporating the filtrate and recrvstallizing the residue from ethanol. 

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... 

Four-equivalent couplers, 19 249 Four-equivalent pyrazolinones, 19 255 Af elements, 14 630. See also Lanthanide entries... 

Pyrazoles, 13 599 Pyrazolinone couplers, 19 254-255 Pyrazolo-(3,2,-c)-5-triazole couplers, 19 256 Pyrazolobenzimidazole couplers, 19 256 Pyrazolone dyes, 19 285 Pyrazolone Orange, 19 435 pigment for plastics, 7 367t Pyrazolone reds, 19 437 Pyrazolones, 9 283 13 599... 

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