1.2.4- Triazole - from dioxide

Sulfolene (172) on treatment with phenyl azide yielded 3a,5,6,6a-tetrahydro-l/f-thieno[2,3-d]-1,2,3-triazole 4-dioxide (173) together with an aziridine, presumably resulting from the thermal decomposition of triazoline (173) <74UKZ433>. 

The photoelimination of carbon dioxide from esters and lactones is a process that has been the subject of detailed investigations. Discussion here is limited to nitrogen containing systems. 3,4-Diphenylsydnone (464), on irradiation in benzene, is converted via the nitrile imine 465 into 2,4,5-triphenyl-1,2,3-triazole (466)388 initial bond formation between N-2 and C-4 followed by loss of carbon dioxide to give the diazirine 467 is proposed to account for the formation of the nitrile imine. Nitrile imines generated in this way have been trapped with alkenes and alkynes to give pyrazoles389... 

In the presence of various metal ions, 2-(fluoroenone)benzothiazoline has been found to rearrange to A-2-mercaptophenylenimine, while a free radical mechanism involving the homolysis of C-S and C-N bonds has been invoked to explain the formation of 3-phenyl-1,2,4-triazole derivatives from the thermal fragmentation and rearrangement of 2-(arylidenehydrazino)-4-(5//)-thiazolone derivatives. The cycloadducts (36) formed from the reaction of 3-diethylamino-4-(4-methoxyphenyl)-5-vinyl-isothiazole 1,1-dioxide (34) with nitric oxides or miinchnones (35) have been found to undergo pyrolytic transformation into a, jS-unsaturated nitriles (38) by way of pyrrole-isothiazoline 1,1-dioxide intermediates (37). 

Aminotriazoles and their derivatives can be prepared from bis hydrazones and from substituted bis hydrazones of a-diketones. The bis hydrazones may in some cases be prepared more conveniently from -bromoketones than from a-diketones. Oxidation with mercuric oxide or with manganese dioxide gives the 1-aminotriazoles directly (Scheme m-ns Although two isomeric triazoles would be ex-... 

Irradiation of A -cyclohexyl-C-phenylsydnone (1, R = cyclohexyl, R = phenyl) in benzene under a nitrogen atmosphere gave the 1,3,4-oxadiazolin-5-one (317, R = cyclohexyl, R = phenyl 15%), the bisazoethylene (318, R = cyclohexyl, R = phenyl 15%), and the triazole (320, R = cyclohexyl, R = phenyl 12%). When the nitrogen atmosphere was replaced by carbon dioxide, then the yield of the 1,3,4-oxadiazolin-5-one was increased from 15% to 47%. These results provide good support for the general mechanistic proposals given in Fig. 4. 

Cycloadditions have been carried out to 37/-indoles (222, 223) (125,126), N-arylmaleimides (224) (127,128), l,2), -azaphospholes (225) (129), 5(47/)-oxazo-lones (226) (130), and 4,5-dihydrooxazoles (230) (131). The primary cycloadducts from the reaction of oxazolones (e.g., 226 with diaryl nitrile imines), derived from tetrazoles in refluxing anisole, do not survive. They appear to lose carbon dioxide and undergo a dimerization-fragmentation sequence to give the triazole 228 and the diarylethene 229 as the isolated products (130). In cases where the two aryl substituents on the oxazole are not the same, then, due to tautomerism, isomeric mixtures of products are obtained. 

Erba et al. (102) observed a novel formation of pyrrole imines 181 from the 1,3-dipolar cycloaddition of mtinchnones 179 and 5-amino-l-aryl-4,5-dihydro-4-methylene-1,2,3-triazoles 180 (Table 10.4). Treatment with benzaldehyde yielded 3-formylpyrroles (182). The reaction presumably involves loss of carbon dioxide, nitrogen, and morpholine from the initial cycloadduct. Unsymmetrical mtinchnones behave regioselectively and furnish products derived from bonding between C(2) of... 

Chloro-2-(3-methyl-4H-l,2,4-triazol-4-yl)benzophenone (Oxidation of 7-chloro-l-methyl-5-phenyl-s-trizolo[4,3-a]quinoline) A stirred suspension of 7-chloro-l-methyl-5-phenyl-s-triazolo[4,3-a] quinoline (2,94 g, 0.01 mol) in acetone (110 ml) was cooled in an ice-bath and treated slowly with a solution prepared by adding sodium periodate (2 g) to a stirred suspension of ruthenium dioxide (200 mg) in water (35 ml). The mixture became dark. Additional sodium periodate (8 g) was added during the next 15 minutes. The ice-bath was removed and the mixture was stirred for 45 minutes. Additional sodium periodate (4 g) was added and the mixture was stirred at ambient temperature for 18 hours and filtered. The solid was washed with acetone and the combined filtrate was concentrated in vacuum. The residue was suspended in water and extracted with methylene chloride. The extract was dried over anhydrous potassium carbonate and concentrated. The residue was chromatographed on silica gel (100 g) with 10% methanol and 90% ethyl acetate 50 ml fractions were collected. The product was eluted in fractions 10-20 and was crystallized from ethyl acetate to give 0.405 g of melting... 

Hydrogenation was conducted in 10 ml of ethyl acetate and 10 ml of water at room temperature for 30 min by using 45 mg of benzhydryl 2-oc-methyl-2-p-(l,2,3-triazol-l-yl)methylpenam-3-a-carboxylate-l,1-dioxide, 15 mg of 10% palladium charcoal and 16 mg of sodium hydrogen carbonate. The aqueous layer was separated from the reaction mixture and washed once with ethyl acetate. The aqueous solution was then purified with an MCI gel, CHP-20P (product of Mitsubishi Kasei Co., Ltd., Japan). After freeze-drying, there was obtained an amorphous product of sodium 2-a-methyl-2-p-(l,2,3-triazol-l-yl)methylpenam-3-a-carboxylate-l,1-dioxide with a melting point 170°C, dec. 

Abstract Synthesis methods of various C- and /V-nitroderivativcs of five-membered azoles - pyrazoles, imidazoles, 1,2,3-triazoles, 1,2,4-triazoles, oxazoles, oxadiazoles, isoxazoles, thiazoles, thiadiazoles, isothiazoles, selenazoles and tetrazoles - are summarized and critically discussed. The special attention focuses on the nitration reaction of azoles with nitric acid or sulfuric-nitric acid mixture, one of the main synthetic routes to nitroazoles. The nitration reactions with such nitrating agents as acetylnitrate, nitric acid/trifluoroacetic anhydride, nitrogen dioxide, nitrogen tetrox-ide, nitronium tetrafluoroborate, V-nitropicolinium tetrafluoroborate are reported. General information on the theory of electrophilic nitration of aromatic compounds is included in the chapter covering synthetic methods. The kinetics and mechanisms of nitration of five-membered azoles are considered. The nitroazole preparation from different cyclic systems or from aminoazoles or based on heterocyclization is the subject of wide speculation. The particular section is devoted to the chemistry of extraordinary class of nitroazoles - polynitroazoles. Vicarious nucleophilic substitution (VNS) reaction in nitroazoles is reviewed in detail. 

The oxidative desulfurisation of 1,2,4-triazole thiones is a type of reaction common to other electron-deficient nitrogen heterocycles nitric acid is the oxidant in the example below. The process involves loss of sulfur dioxide from an intermediate sulfinic acid. ... 

The iron compound can be prepared from any soluble iron(U) salt. It is most convenient to start with hydrated iron(U) perchlorate. Hexaaquairon(U) perchlorate (0.05 mole, 18.14 g) is dissolved in about 100 mL of degassed water. Ammonium thiocyanate (0.1 mole 7.61 g) dissolved in about 50 mL of degassed water is added the color of the solution turns red as a result of small amounts of iron(Ul) present. This solution is saturated with sulfur dioxide (to reduce any Fe(Ul) present) and a few drops of nitric acid are added. Next, 1,2,4-triazole (0.1 mole, 6.91 g), dissolved in 50 mL water, is added. At this stage the color of the solution may still be (dark) brown. 

CAs are ubiquitous metalloenzymes that catalyze the reversible synthesis of bicarbonate ion and proton from carbon dioxide and water. This family includes 15 isoenzymes (1-XlV, V further subclassified as VA and VB) endowed with different molecular features, cellular localization, distribution in organs and tissues, and kinetic properties. It has been demonstrated that the dysfunction of these enzymes is related to different pathologies such as cancer (CAs Vll, IX, XII), neurodegeneration (CA VIII), obesity (CAs VA and VB), and sterility (CA XIII) [36]. Based on the knowledge that coumarin derivatives are CA inhibitors [37], a library of suflbcoumarin derivatives 21 bearing a triazole moiety was synthesized (Scheme 2.3). These compounds 21 (R = Ph) were found to... 

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