Sodium 3,5-dimethylpyrazolate, reaction with

The synthesis of N-(2-mercaptoethyl)-3,5-dimethylpyrazole and the workup procedure are performed in air, but the resultant thiol can best be stored under a nitrogen atmosphere. In air, the thiol is resistant to oxidation for several weeks, but the disulfide slowly crystallizes from the oil. According to the NMR spectra, the product is quite pure, but may still contain a small amount of 1,1,3,3-tetramethylurea (up to 5%). The reaction with 1,3-dichloro-2-propanol was carried out in a water/tetrahydrofuran mixture with sodium hydroxide, and appeared to proceed smoothly and in almost quantitative yields.2 This new reaction path to pyrazole-thioether ligands opens the road to the development of new chelating ligands. 

The chemical properties of 1,4-dinitropyrazole [654] and l,4-dimethyl-3,5-dini-tropyrazole obtained by the nitration of 1,4-dimethylpyrazole [655], nitrotriazoles [656-663], and other nitroazoles [662, 664-666] have been studied. 1,4-Dinitro-pyrazole undergoes ring transformation reactions with primary amines, hydrazines, hydroxylamine, and amidines [654], Acid hydrolysis of dinitropyrazole leads to (l-methyl-3,5-dinitropyrazol-4-yl)acetaldehyde, and the reaction with sodium nitrite in hydrochloric acid furnishes 2-hydroxymino-2-(l-methyl-3,5-dinitropyra-zol-4-yl)acetaldehyde [655],... 

It should be noted that the reaction of K[BHJ with pyrazole cannot be stopped at the K[H3B(pz)] stage from an incomplete reaction only K[BHJ and K[H2B(pz)2] could be isolated. It has been possible, though, to synthesize the ion [H3B pz-3,5-(CHj) ] by reaction of the borane adduct of 3,5-dimethylpyrazole with sodium hydride, and from it by a carefully controlled reaction with pyrazole in N,N-dimethyl-acetamide to prepare the first example of an asymmetric poly(l-pyrazolyl)borate ligand, i.e., Na[H2B(pz) pz-3,5-(CH3)2 ]... 

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