3-Methylpyrazole

The pyrazole ring is generally stable to oxidation and side chains are oxidized to carbonyl groups (66AHC(6)347). l-Aryl-3-methylpyrazoles (134) react with ozone to yield 1,3,4-oxadiazolinones (135) (66AHC(7)183). 

Cu(H) Dimethylbis(3-methylpyrazol-l -yl)gallate [GaMe2(MPz)2] CuO[GaMe2(MPz)2](3MPz) 2 76CJC343 G... 

Mepirizole — see also Pyrimidine, 4-methoxy-2-(5-methoxy-3-methylpyrazol-l-yl)-6-methyl-metabolism, 5, 301, 302 Mepitiostane, 7, 182, 183 Mepivacaine... 

Pyrimidine, 4-methoxy-2-( 5-methoxy-3-methylpyrazol-I-yl)-6-methyl-analgesic activity, 5, 294 Pyrimidine, 2-methoxy-5-methyI-rearrangement, 3, 93 Pyrimidine, 4-methoxy-6-methyl-N-oxides... 

ICA 97)19]. Compound 163 (R = Br) and perchloric acid yield 164, where the monodentate pyrazolate ligand is protonated. Potassium hydroxide regenerates 163 (R = Br). Dicationic complexes of the type 164 can alternatively be produced from [Rh2(r/ -Cp )2(/x-0H)3]Cl04 and perchloric acid in the presence of excess pyrazole, 4-bromopyrazole, 3-methylpyrazole, or 3,5-dimethylpyrazole. 

Complex (NBu4)2[Pd(QCl5)2(/x.-OH)]2 behaves differently in the presence of an alkali with respect to pyrazole and 3-methylpyrazole, on the one hand, and... 

The NMR spectra for several alkynylpyrazoles have been measured, and selected data are presented in this section. The signals of the C=C atoms in the NMR spectraresonate in the range 70-95 ppm. For l-ethynyl-3-methylpyrazole the chemical shift of C=CH atom appears at 58.3 ppm the chemical shift of the C=CH atom is 61.7. For l-ethynyl-5-methylpyrazole the chemical shift of the C=CH atom is 58.3 ppm, and the chemical shift of the C=CH atom is 61.7 ppm (94AJC991). The direct spin-spin coupling constant of ( 7c c) is 179.9... 

In the reactions of nucleophilic addition to diacetylene, monoalkylhydrazines behave in two ways (71AKZ743). In an anhydrous medium at 40-50°C, the reaction with methyl- and ethylhydrazines proceeds in such a way that a more nucleophilic disubstituted nitrogen atom attacks the terminal carbon atom of diacetylene to form l-alkyl-3-methylpyrazoles (17), the content of isomeric 1-alkyl-5-methylpyrazoles being 15% according to GLC (71AKZ743 73DIS 77AKZ332). 

In aqueous solutions, the prevailing process is the primary attack of the unsubstituted nitrogen atom of alkylhydrazines at the terminal carbon atom of diacetylene with predominant formation of l-alkyl-5-methylpyrazoles (18) (73DIS). The content of isomeric l-alkyl-3-methylpyrazoles is less than 10% (GLC). In the authors opinion, this different direction of the attack at diacetylene in aqueous media is related to the hydration of alkylhydrazines and the formation of ammonium base RN" H2(0H) NH2, in which the primary amino group becomes the major nucleophilic center. 

Synthesis of l-guanyl-3-methylpyrazole (29) (86% yield) from pyrazole 13 and aqueous cyanamide has been claimed (94GEP4237687). 

Likewise, the ynaminoketones with phenylhydrazine give a similar mixture of isomerie l-phenyl-3-dialkylammo-5-methylpyrazoles (369) and l-phenyl-5-dialkylamino-3-methylpyrazoles (370) in the same 3 4 ratio (87ZOR1635). 

---