Researches on 2,1,3-thia- and selenadiazole XLV. Nitration of 4-hydroxy- and 4-ethoxybenzo-2,1,3-thiadiazoIe

Nitration of 4-hydroxybenzo-2,1,3-thiadiazole under conditions generally used for phenols, gave a high yield of 4-hydroxy-5-nitrobenzo-2,1,3-thiadiazole. The latter is readily reduced to 4-hydroxy-S-aminobenzo-2,1,3-thiadiazole which on treatment with orthoformic ester gives oxazolo [5,4-e]benzo-2,1,3-thiadiazole. 4-Ethoxybenzo-2,1,3-thiadiazole is nitrated under similar conditions, giving a high yield of a mixture of equal quantities of 4-ethoxy-S-nitro- and 4-ethoxy-7-nitrobenzo-2,1,3-thiadiazole.     

Investigations in the field of 2,1,3-thiadiazole and 2,1,3-selenadiazole

The action of sodiomalonic ester on 4-bromomethylbenzo-2,1,3-thiadiazole forms a malonate which is converted by acid hydrolysis into 4-(-carboxyethyl)benzo-2,1,3-thiadiazole. When this reaction is carried out with 5-bromomethylbenzo-2,1,3-thiadiazole, mono- and disubstituted malonic esters are formed the acid hydrolysis of which gives the corresponding acids. The nitration of 4-and 5-(-carboxyethyl)benzo-2,1,3-thiadiazoles forms, respectively, 4-(-carboxyethyl)-5,7-dinitrobenzo-2,1,3-thiadiazole and 5-(-carboxyethyl)4-nitrobenzo-2,1, 3-thiadiazole. The reaction of 4-bromomethylbenzo-2,1, 3-thiadiazole with potassium cyanide forms two products: 4-cyanomethylbenzo-2,1, 3-thiadiazole and 1,2-di(benzo-2,1, 3-thiadiazole-4-yl)-2-cyanoethane.For part LVIII, see [1].     

Researches on 2,1,3-thia-and selenadiazole

Chlorination of benzo-2,1,3-thiadiazole (I) in the presence of iron and paraform gives only 4-chlorobenzo-2,1,3-thiazole. Chlorination of 5,6-dimethylbenzo-2,1,3-thiadiazole (II) under exactly the same conditions gives only 5,6-dimethyl-4,7-dichlorobenzo-2,1,2-thiadiazole. Similarly chloromethylation of II in the presence of paraform gives only 5,6-dimethly-4,7-di(chloromethyl)benzo-2,1,3-thiadiazole. Chlorination and chloromethylation of I proceed through the intermediate formation of monosubstituted compounds which change into disubstimted ones.It is known [2,3] that Chlorination of benzo-2,1,3-thiadiazole (I) and its 5,6-dimethyl derivative (II) with chlorine in the presence of iron gives mainly the 4,7-dichloro substitution products III and IV respectively.It was previously shown [4] that chloromethylation of I with dichlorodimethyl ether in the presence of anhydrous aluminum chloride also gives mainly 4,7-di(chloromethyl)benzo-2,1,3-thiadiazole (V). Bases and pseudo-bases (paraform, urotropine. dimethylformamide) have a retarding effect on chloromethylation. When the reaction is run in the presence of these latter the products comprise besides V, 4-chloromethyl-2,1,3-thiadiazole (VI), or else, if enough base is added, there is no reaction.For Part XLII see [1].     

Investigations of 2,1,3-thia- and selenadiazoles

All three possible isomeric amines are obtained by the reaction of 4- or 5-methylbenzo-2,1,3-thiadiazoles with hydroxylamine sulfate in concentrated sulfuric acid. Under similar conditions, 5,6-dimethyl-4-aminobenzo-2,1,3-thiadiazole is obtained from 5,6-dimethylbenzo-2,1,3-thiadiazole.See [1] for communication LXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 601–602, May, 1971.     

Oxidation of halohydroxybenzo-2,1,3-thiadiazoles with nitric acid

4,5-Dioxobenzo-2,1,3-thiadiazole has been synthesized. Its structure was proven by conversion to the known 4,5-dioximinobenzo-2,1,3-thiadiazole and to 2,1,3-thiadiazolo[4,5-a]phenazine, and by reduction to 4,5-dihydroxybenzo-2,1,3-thiadiazole. Oxidation of 5,6-dichloro-4,7-dihydroxy- and 5,7-dichloro-4-hydroxy-benzo-2,1,3-thiadiazoles forms 5,6-dichloro-4,7-dihydroxybenzo-2,1,3-thiadiazole, of known structure, and 7-chloro-4,5-dioxobenzo-2,1,3-thiadiazole; the latter by reaction with ortho-phenylene diamine is converted to 4-chloro-2,1,3-thiadiazolo[4,5-a]phenazine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 850–852, June, 1987.     

Studies in the field of 2,1,3-thia- and selenadiazoles

The reaction of benzo-2,1,3-thiadiazole with hydroxylamine sulfate in concentrated sulfuric acid at 150° C for 1–10 hr has been studied. It has been shown that under these conditions mixtures of different amounts of 4- and 5-aminobenzo-2,1,3-thiadiazoles are formed.For part LII, see [1].     

Fries reaction and dakin rearrangement in benzo-2,1,3-thiadiazoles

The Fries rearrangement of 4- and 5-acetoxybenzo-2,1,3-thiadiazoles has given 4-hydroxy-7-acetyl- and 5-hydroxy-4-acetylbenzo-2,1,3-thiadiazoles, which on oxidation afford mixtures of 5-chloro-4,7-dioxo- and 5,6-dichloro-4,7-dioxobenzo-2,1,3-thiadiazole and of 6-chloro-4,5-dioxo- and 6,7-dichloro-4,5-dioxobenzo-2,1,3-thiadiazole. Reaction of 6,7-dichloro-4,5-dioxobenzo-2,1,3-thiadizole with ortho-phenyl-enediamine gives 4,5-dichloro-2,1,3-thiadiazolo[4,5-a]phenazine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1683–1687, December, 1987.     

Oxidation and reduction of some derivatives of benzo-2,1,3-thiadiazole

In the reduction of 4-hydroxy-7-phenylazobenzo-2,1,3-thiadiazole and of 4-hydroxy-7-nitro-benzo-2,1, 3-thiadiazole with sodium hydrosulfite, 7-amino-4-hydroxybenzo-2,1,3-thiadiazole is obtained. The reduction of 4-hydroxybenzo-2,1,3-thiadiazole leads to 2,3-diaminophenol which forms 5-hydroxyquinoxaline with the bisulfite derivative of glyoxal. The oxidation of 4-hydroxy- and 4-aminobenzo-2,1,3-thiadiazoles with potassium dichromate in an acid medium has yielded 4,7-dioxo-4,7-dihydrobenzo-2,1,3-thiadiazole, which has been converted into 4,7-dihydroxybenzo-2,1,3-thiadiazole and 4,7-di(hydroxyimino)-4,7-dihydrobenzo-2,1,3-thiadiazole.Translated from Khimiya Geterotsikliches-kikh Soedinenii, No. 7, pp. 926–929, July, 1973.     

Studies in the field of 2,1,3-thia- and -selenadiazoles

The results of studies on 2,1,3-thiadiazole, benzo-2,1,3-thiadiazole, benzo-2,1,3-selenadiazole, and their derivatives by chemical, physicochemical, and physical methods give no grounds for assuming that they have a quinoid structure. These results permit the statement that these heterocycles containing quatervalent sulfur or selenium are typical heteroaromatic systems satisfying Hückel's (4n+2) rule.For part LV, see [1].     

Studies in the field of 2,1,3-thia- and selenadiazoles

The reaction of benzo-2,1,3-thiadiazole with hydroxylamine sulfate in concentrated sulfuric acid at 150° C for 1–10 hr has been studied. It has been shown that under these conditions mixtures of different amounts of 4- and 5-aminobenzo-2,1,3-thiadiazoles are formed.     

Bromination of 2,1,3-benzothiadiazoles

The bromination of 2,1,3-benzothiadiazoles in 47% hydrobromic acid at elevated temperature has led to a general preparative method for the synthesis in high yield of otherwise difficulty accessible brominated 2,1,3-benzothiadiazoles. The typical addition reaction is apparently eliminated under these reaction conditions and substitution takes place exclusively. Bromination of 2,1,3-benzothiadiazole occurs successively at positions 4 and 7. 4-Substituted 2,1,3-benzothia-diazoles are selectively brominated at position 7. 5-Bromo- and 5-methyl-2,1,3-benzothiadiazole are brominated consecutively at positions 4 and 7.     

Researches on 2,1,3-thia-and selenadiazoles

Chloromethylation of 4- and 5-chlorobenzo-2,1,3-thiadiazoles with dichlorodimethyl ether in the presence of anhydrous aluminum chloride gives 4-chloro-7-chloromethyl- and 5-chloro-4-chloromethylbenzo-2, 1,3-thiadiazoles respectively. Reductive scission followed by treatment with thionyl chloride converts them to 4-chloro-7-methyl- and 5-chloro-4-methylbenzo-2,1,3-thiadiazoles; Chlorination of the latter gives 4-methyl-5,7-dichlorobenzo-2,1,3-thiadiazole. Replacement of the chlorine in the chloromethyl groups gives 4-chloro-7-hydrosymethyl-,5-chloro-4-hydroxymethyl-, 4-chloro-7-cyanomethyl-,4-chloro-7-carboxymethyl-,5-chloro-4-carboxymethylbenzo-2,1,3-thiadiazoles. Reductive scission of 4-chlorobenzo-2,1,3-thidiazole followed by treatment with sodium selenite gives 4-chlorobenzo-2,1,3-selenadiazole.Part XLIII see [1].     

Conversion of 4-substituted benzo-2,1,3-thiadiazoles to 5-chloro-4,7-dioxobenzo-2,1,3-thiadiazole by action of hydrogen peroxide and hydrochloric acid

Under the influence of hydrogen peroxide and hydrochloric acid in acetonitrile 4-substituted benzo-2,1,3-thiadiazoles form 5-chloro-4,7-dioxobenzo-2,1,3-thiadiazole. 4-Alkoxy- and 4-[(alkoxycarbonyl)methoxy]benzo-2,1,3-thiadiazoles give, in addition, the corresponding 5,7-dichloro derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 114–117, January, 1988.     

Investigation of 2, 1, 3-thia- and 2, 1, 3 selenadiazoles

The nitration of naphtho[1,2-d][2,1,3]thiadiazole under the conditions that are normally used for aromatic compounds gives a mixture of 6- and 9-nitronaphthothiadiazoles, which can be reduced to 6- and 9-amino derivatives, respectively. 6-Hydroxynaphthothiadiazole is obtained from 6-aminonaphthothiadiazole by the Sandmeyer reaction, while 8-hydroxynaphthothiadiazole is converted to the 8-amino derivative under the conditions of the Bucherer reaction. 4-Carboxy-5-(o-carboxyphenyl)-2,1,3-thiadiazole was obtained by the oxidation of naphtho[1,2-d][2,1,3]-thiadiazole with a potassium dichromate-dilute sulfuric acid mixture.See [1] for communication LXVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1496–1502, November, 1972.     

Reactivity of 4-nitro- and 4-nitro-7-halogeno-2,1,3-benzothiadiazoles toward methoxide ion

4-Nitro-2,1,3-benzothiadiazole reacted with sodium methoxide (0.1-1 M) in methanol yielding 2,1,3-benzothiadiazole-4, 7-dione monoxime (syn+anti). Methoxy-dehalogenation of 4-nitro-7-halogeno-derivatives yielded 4-nitro-7-methoxy-2,1,3-benzothadiazole under similar conditions. In both eases transitions attributable to the formation of Meisenheimer complexes were detected.     

Semmler-Wolff aromatization of 4-hydroxyimino-4,5,6,7-tetrahydro-[2,1,3]benzoxadiazole and 4-hydroxyimino-4,5,6,7-tetrahydro[2,1,3]benzoxadiazole 1-oxide and some properties of the obtained amines

The Semmler-Wolff aromatization of 4-hydroxyimino-4,5,6,7-tetrahydro[2,1,3]benzoxadiazole and its 1-oxide derivative in sulfuric acid and in acetic anhydride gave 4-amino[2,1,3]benzoxadiazole and 4-acetamido[2,1,3]benzoxadiazole 1-oxide. Some reactions of the resultant amines were studied.     

Disulfides of the benzo-2,1,3-thiadiazole series

Disulfides of the benzo-2,1,3-thiadiazole series were obtained by reduction of benzo-2,1,3-thiadiazolesulfonyl chlorides (by hydriodic acid or by sulfur dioxide) or by the reaction of benzo-2,1,3-thiadiazolesulfinic acids with hydrogen bromide in acetic acid. Convenient methods for the synthesis of the starting compounds were found, and the fungicidal activity of the disulfides obtained was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1555–1558, November, 1989.     

Full emission color tuning in luminogens constructed from tetraphenylethene, benzo-2,1,3-thiadiazole and thiophene building blocks

Full color luminogens are constructed from tetraphenylethene, benzo-2,1,3-thiadiazole and thiophene building blocks. OLED fabricated using one of the luminogens exhibits orange-red electroluminescence with high luminance and efficiencies of 8330 cd m(-2), 6.1 cd A(-1) and 3.1%, respectively.     

Synthesis of 4(6)-aryloxy- and 4-arylthio-2,1,3-benzoxadiazoles

Reactions of 4,6-dibromo-2,1,3-benzoxadiazole with phenols or arenelthiols lead to 4-aryloxy-6-bromo-2,1,3-benzoxadiazoles or 4-arylthio-6-bromo-2,1,3-benzoxadiazoles, respectively. Isomeric 6-aryloxy-4-bromo-2,1,3-benzoxadiazoles were synthesized by replacement of the fluorine atom in 2,6-dibromo-4-fluoro-1-nitrosobenzene with phenols and treatment of the resulting 4-aryloxy-2,6-dibromo-1-nitrosobenzene with sodium azide.     

Valence electronic structure of benzo-2,1,3-chalcogenadiazoles studied by photoelectron spectroscopy and density functional theory

The He I photoelectron spectra of benzo-2,1,3-thia-, selena-, and telluradiazole were measured, and the observed ionization bands were assigned by comparison with the results of DFT calculations. Whereas the B3LYP exchange-correlation functional provided orbital energies that permitted a preliminary assignment by application of Koopman's theorem, a more-accurate interpretation was established by calculation of the vertical ionization energies with the PW91 functional and analysis of the correlation of energy levels along the homologous series. This strategy clarified earlier disagreements in the assignment of the spectrum of benzo-2,1,3-thiadiazole.