Pyrazole Blue

The nomenclature used in this discussion will generally be in accordance with Chemical Abstracts, although some trivial names will be used since these are very common among pyrazolinones and are frequently well known. Examples of such names are antipyrine, pyrazole blue and aminopyrine. The numbering is as shown in formulas... 

Only a very few 4,4 -bis(2-pyrazolin-5-ones) linked by a double bond have been prepared. The parent compound of this series, 4-(3-methyl -1 -phenyl - 5 - oxo - 2 - pyrazolin - 4-ylidene)-3-methyl-l-phenyl-2-pyrazolin-5-one (XXII-D), is known as pyrazole blue.323,807,809,816, 1090,1091 was so nameci by Knorr because of its great resemblance to indigo blue. All these compounds are strongly colored. The usual synthesis is by ferric chloride oxidation of monomeric 2-pyrazolin-5-ones (eq. 61)296,809 or by oxidation of the corresponding bis compounds... 

Westoo has reported the synthesis of complex bispyrazolinones which he has called furlones.1608,1610,1611 These have two 2-pyrazolin-5-one rings connected through a dihydrofuran ring which in turn is fused with a pyrazole ring. These were prepared by condensation of 4-halogenated-2-pyrazolin-5-ones, together, with l-aryl-2-pyrazolin-5-ones, or with pyrazole blue (XXII-D) in the presence of a base and copper sulfate (eq. 87). These compounds are listed in Table X. 

A few bis(2-pyrazolin-5-ones) having alkoxy substituents are known and are listed in Table III. These are prepared by addition of alcohols to the double bond connecting the pyrazolinone rings in pyrazole blue. 

The cyanide (CN ) is converted to cyanogen chloride (CNCl) at pH < 8, without hydrolyzing to the cyanate, by reaction with the Chloramine-T which acts as a source of hypochlorous acid (HOCl). After the reaction is complete, the CNCl forms a blue dye (pyrazole blue) on the addition of the pyridine-pyrazalone reagent. 

The behaviour of pyrazoles towards nitrosation is similar to their behaviour described above towards diazo coupling, i.e. aminopyrazoles and pyrazolones readily react with nitrosation agents, like alkyl nitrites (81FES1019), to afford stable nitroso derivatives. Some simple nitrosopyrazoles have been isolated, for example the blue-green 3,5-dimethyl-4-nitrosopyrazole, and many others have been proposed as reactive intermediates in the direct conversion of pyrazoles into diazonium or diazo derivatives (Scheme 25) (B-76MI40402). 

Chelated species are less common. The substituted thiourea 7V-ethoxycarbonyl-/V-[3-(/>-anisyl) pyrazol-5-yl]thiourea (eatu) acts as a monoanionic 0,S-chelate to cobalt(II), forming Co(eatu)2.506 Whereas ethylenethiourea (etu) has been observed to act as a S-donor monodentate in Co (etu)2X2(H20)2 (X = C1, Br), it binds as an S,N-chelate in Co(etu)2(OOCCH3)2.507 Both violet octahedral and blue tetrahedral cobalt(II) compounds Co(pptu)2Cl2 and Cp(pptu)Cl2 respectively were prepared with bidentate A -2-(5-pico 1 y 1)- A"-pheny 11hiourea (pptu) chelated.508 Refluxing Co powder with thiourea in 4-methylpyridine provides a route to isothiocyanates, which form by decomposition of thiourea to ammonium thiocyanate509 with one product, Co(pic)4(NCS)2, characterized by a crystal structure. 

The average of the coefficients of the hydrophobic term is approximately equal to one (average = 0.97) suggesting complete desolvation about substituent X. Figure 6 shows con lete desolvation by the enzyme ADH (hydrophobic space red polar space - blue) around substituent X of the pyrazole (green). 

Copper(I) pyrazolates react with neutral ligands (L), such as 1,10-phenan-throline and cyclohexyl isocyanide, giving binuclear complexes of general formula [Cu(pzXL)]2.9,10 Solutions of [Cu(dmpz)]3 in pyridine rapidly absorb oxygen in the presence of water, giving the blue octanuclear hydroxo-... 

The possibility of formation of an O—O bond at a single Mn site of the OEC, on the other hand, seems remote, but nevertheless, two mononuclear model Mn-peroxo complexes, a peroxo-Mnm porphinato 64 [157] and a peroxo-Mn111 pyrazolylborato complex 65 [158], have been structurally characterized. Both complexes contain side-on peroxo groups. Complex 65 has been crystallized in two forms, one brown and one blue. A peroxo-H—N (pyrazole) hydrogen bond is found only in the blue form (Figure 29). 

To a stirred solution of 1.00 gram of 17p-hydroxy-17a-methyl-4-androsteno[3,2-c]pyrazole in 200 ml of tetrahydrofuran and 400 ml of liquid ammonia was added 2.12 grams of lithium wire during 5 minutes. The dark blue mixture was stirred for 45 minutes. A solution of 40 ml of tertiary-butyl alcohol in 160 ml of diethyl ether was added with stirring. 

PYRAZOL FAST BRILLIANT BLUE VP SHIKISO DIRECT SKY BLUE 6B TERTRODIRECT BLUE FF VONDACELBLUEFF... 

PYRAZOL FAST BRILLIANT BLUE VP see CMN750 PYRAZOLIDIN see BRF500... 

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