Benzo-l,2,3-thiadiazoles

Synthesis.—Syntheses of 1,2,4-thiadiazoles reported in the period under review are mostly adaptations or extensions of the classical routes. However, they have improved and diversified the accessibility of compounds of this ring system. 

Substituted 1,2,4-thiadiazoles of type (27), for example, have been synthesized from ethyl cyanoglyoxalate arylhydrazones (26), by an extension of Tiemann s synthesis of 1889, employing the successive action of hydroxylamine and aromatic isothiocyanate esters.  

5-Substituted 3-amino-l,2,4-thiadiazoles (30) are obtainable from acylguanidines (28) by treatment with phosphorus pentasulphide in pyridine, followed by oxidative cyclization in situ of the intermediate labile thioacylguanidine (29). The use of hydrogen peroxide affords moderate to poor yields [53% for (30 = Ph), but less than 1% for (30  

Dipotassium cyanodithioimidoearbonate (31) reacts with chlorine in methylene chloride to yield 3-chloro-I,2,4-thiadiazol-5-yl sulphenyl chloride (32) (85—100%) as a stable yellow solid which is reversibly 

The dipotassium sail of 3,5-dimercapto-l,2,4-thiadiazole ( perthiocyanic acid ) (36) is most conveniently prepared by refluxing a solution of (31) in methanol with sulphur. The salt is readily chlorinated to the stable bis(sulphenylchloride) (37). The observations supplement and further clarify previous work on the synthesis of 1,2,4-thiadiazoles from thiocyanic acid (see Volume 1, p. 448 and ref. 15). 

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The structure of the isomeric benzo-l,2,3-thiadiazole 11.30 is unknown, but the 1 1 adduct with AsFs (11.31) has been structurally characterized. The AsFs molecule is coordinated to the carbon-bonded nitrogen atom. Cycloocteno-l,2,3-selenadiazole is an effective source of selenium for the production of semi-conductors such as cadmium selenide." ... 

The bond lengths and bond angles found for benzo-l,2,3-thiadiazole by X-ray diffraction are listed in Table 3. These values are quite close to those published for a substituted 1,2,3-benzothiadiazole <1984CHEC(6)447>. 

Ammonium 2,4,6-tris(dioxoselena)hexahydrotriazine-l,3,5-triide Benzo-l,2,3-thiadiazole, 2199 Benzo-l,2,3-thiadiazole 1,1-dioxide, 2191 Bis(S,S-difluoro-N-sulfimido)sulfur tetrafluoride, 4381 Bis(dimethylamino) sulfoxide, 1757... 

Narrowing the bandgap of copolymers by alternation of electron-rich thiophene and electron-deficient benzo-l,2,3-thiadiazole units was used in the design of several LEPs whose optical and electronic properties could be tuned through such a modification. Cao and coworkers synthesized copolymers 599 and 600 (02MI2887 04MM6299), exploiting random copolymerization. 

Ammonium thiosulfate, 4568 Benzo-l,2,3-thiadiazole, 2192 Benzo-l,2,3-thiadiazole 1,1-dioxide, 2184... 

Benzyne precursors 1-Aminobenzotriazole. Benzenediazonium-2-carboxylate. Benzo-l,2,3-thiadiazole-l,l-dioxide. o-Bromofluorobenzene. o-Bromoiodobenzene. Diphenylio-donium-2-carboxylate monohydrate. 

Bei der Photolyse von Benzo-l,2,3-thiadiazolen entsteht neben PolymerenausschlieBlich Thianthren (bis 18% d.Th.)1-3. Benzo-l,2,3-thiadiazol-l,l-dioxid wird bei Bestrahlung in Methanol zu Methoxy-benzol abgebaut4. 1,2,5-Thiadiazole fragmentieren zu Carbonsaure-nitrilen6. 

Benzo-l,2,3-thiadiazole reacts with phenyl isothiocyanate to give the 2-phenylimino-l,3-benzodithiole (200), which was not isolated but converted into the quaternary ammonium salt with methyl iodide. A series of 4,6-dialkyl-... 

It was noticed that S-methyl benzo-l,2,3-thiadiazole-7-carboxylate (BTH), the first commercial SAR activator for plants, could induce a similar defense response to salicylic acid in signal transduction. Therefore, itwas interesting to investigate whether or not BTH derivatives could also induce seeondary... 

Dithiins and It4-Di elenins.—1,4-Dithiins (36) are among the photolysis products of biaryl- and benzo-l,2,3-thiadiazoles. The postulated intermediate biradicals (35) dimerize in the direction shown. Thermolysis of cycloalkeno-l,2,3-selenadiazoles produces 1,4-diselenins (37) together with cycloalkynes. A structure determination of 2,5-diphenyl-l,4-dithiin 1-oxide reveals a boat-shaped configuration (Figure) with the sulphur... 

Benzo-l,2,3-thladiazoles.—A number of conventional reactions of 5-amino-benzo-l,2,3-thiadiazole (25) have been described. They concern the amino-benzene moiety of the condensed heteroaromatic system and are outlined in Scheme 1. ... 

A series of azo-dyes (46), (47) incorporating the benzo-l,2,3-thiadiazole structure have been produced from the 5-amino-heterocycle by conventional methods, and their properties as dyes evaluated. ... 

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