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.     

Synthesis of 4-substituted 3-chloro-1,2,5-thiadiazoles from monosubstituted glyoximes

One-pot synthesis of 3-chloro-1,2,5-thiadiazoles from monosubstituted glyoximes and sulfur monochloride was developed.     

Oxidation of aromatic substrates with hydrogen peroxide and hydrochloric acid

Chloroquinones are prepared conveniently from phenol, naphthols and aromatic amines.     

Efficient palladium-catalyzed C-S cross-coupling reaction of benzo-2,1,3-thiadiazole at C-5-position: A potential class of AChE inhibitors

Functionalization of 2,1,3-benzothiadiazole (BTD) with thiols at C-5 position remains low explored. Moreover, the arylthiol-substitutions at this position are also unexplored and can not be found by a S_N2 or S_N1 reaction. In this sense, herein we present a new palladium-catalyzed methodology for a wide variety of unpublished 5-arylsulfanyl-benzo-2,1,3-thiadiazole derivatives synthesis with moderate to high yields using a low catalytic loading of Pd(L-Pro)₂ as low-coast, and efficient catalyst in low reaction time. Besides, we concluded that the pKa of thiol species has an important role in this catalysis, mainly in the CMD like catalytic cyclo process, which strongly interferes in the reaction yields. Furthermore, arylsulfanyl-benzo-2,1,3-thiadiazoles derivatives have been assessed (in vitro) as potential acetylcholinesterase inhibitors.     

1-Nucleosides of 5-substituted 4-chloro-1,2,3-triazoles

1-Nucleosides of 5-substituted 4-chloro-1,2,3-triazoles were produced by glycosylation of the corresponding triazoles by the method of fusion with tetra-0-acyl-D-ribofuranose in the presence of bis-p-nitrophenyl phosphate. The structure of the compounds obtained and their conformational peculiarities were studied by the methods of mass spectrometry and NMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1556–1564, November, 1984.     

Murexide reaction of caffeine with hydrogen peroxide and hydrochloric acid. II

In continuation of the study on the murexide reaction of caffeine with 3% hydrogen peroxide/hydrochloric acid and then with ammonia giving a purple coloration, we investigated the oxidation reaction of caffeine with 6% hydrogen peroxide/hydrochloric acid to isolate ten reaction products, 3-hydroxy-4,6-dimethyloxazolo[4,5-d]pyrimidine-2,5,7(3H,4H,6H)-trione 1 , 1,3-dimethylalloxan 2 , murexoin 3 , 1,3,7-trimethyl-2,6,8-trioxo-9-hydroxy-1H,3H,7H-xanthine 5 , 1,3,7-trimethyl-2,6,8-trioxo-1H,3H,7H-xanthine 6 , 1,3,7-trimethyl-2,6-dioxo-8-chloro-1H,3H,7H-xanthine 7, 5-(1,3-dimethyl-1,2,3,4,5,6-hexahydro-2,4,6-trioxopyrimidin-5-yl)-aminomethylene-1,3-dimethyl-1,2,3,4,5,6-hexahydro-2,4,6-trioxopyrimidine ammonium salt 9 , 1,3-dimethylpalabanic acid 10 , 1-methyl-2,4,5-trioxoimidazole 11 , 3-hydroxy-5,7-dimethyloxazolo[5,4-d]pyrimidine-2,4,6(3H,5H,7H)-trione 12 and 4,6,8-trimethyl-1,2,4-dioxazino[6,5-d]pyrimidine-3,5,7(4H,6H,8H)-trione 13 . The oxidation reaction using 6% hydrogen peroxide/hydrochloric acid was found to produce a similar purple coloration to that of the murexide reaction despite no subsequent addition of ammonia, indicating the liberation of ammonia by the oxidation of caffeine. Among the above compounds, the purple colored substance murexoin 3 and the yellow colored compound 9 were both ammonium salts, and compound 5 was the red colored substance. In the present investigation, these three compounds were found to contribute to the coloration.     

Direction of glycosylation of 5-substituted 4-chloro-1,2,3-triazoles

The structures of previously obtained nucleosides of 5-substituted 4-chloro-1, 2,3-triazoles were refined by means of high-resolution mass spectrometry and ¹³C NMR spectroscopy. It is shown that fusion of 5-substituted 4-chloro,1,2,3-triazoles with tetra-0-acylribofuranoses in the presence of di(p-nitrophenyl) phosphate leads to the formation of 2-nucleosides of the corresponding triazoles. The signals of the carbon atoms in the ¹³C NMR spectra of the 4,5-di-substituted triazoles and their nucleosides were assigned.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 937–940, July, 1987.     

Studies on the complexes of 4′-substituted benzo-15-crown-5 ligands with sodium picrate and picric acid

Complexes of nine 4'-substituted benzo-15-crown-5 ligands with sodium picrate were prepared. A good linear relationship of the . values from the UV spectra and Hammett [_p - _m] values was observed. Charge transfer complexes of ten 4'-substituted benzo-l5-crown-5 ligands with picric acid were isolated in crystalline form. The color of the complexes depended on the nature of the substituents. All of the complexes were identified by elemental analyses, UV and IR spectra.     

The preparation and characterization of 5-substituted-4-chloro-1,2,3-dithiazolium salts and their conversion into 4-substituted-3-chloro-1,2,5-thiadiazoles

A series of monosubstituted acetonitriles were treated with disulfur dichloride at room temperature in CH2Cl2 to afford 5-substituted-4-chloro-1,2,3-dithiazolium chlorides 1.Where the 5-substituent was not a good leaving group the chloride salts were converted into the corresponding perchlorate salts 2 which were sufficiently stable and soluble to provide both (1)H- and (13)C-NMR and cyclic voltammetry data. Several of the dithiazolium chlorides were converted into their corresponding 4-substituted-3-chloro-1,2,5-thiadiazoles 13 on treatment with aqueous ammonia. Mechanisms for all reactions are proposed.     

Synthesis and properties of 2-substituted 5-chloro-1,3-oxazole-4-carboxamides

Chlorination of 2-aryl-5-benzylsulfanyl-1,3-oxazole-4-carbonitrile in aqueous acetic acid at 50–60°C afforded new 2-aryl-5-chloro-1,3-oxazole-4-carboxamides. The reactivity of the chlorine atom with respect to the N-, O-, and S-nucleophiles was investigated.     

Sorption of gold(iii) from hydrochloric acid solutions by the sorbents based on benzo-15-crown-5

Russian Chemical Bulletin - Regularities of gold sorption by the impregnated type sorbents based on a 1 M solution of benzo-15-crown-5 in nitrobenzene and benzo-15-crown-5 (30%, without diluent)...     

Electrophilic substitution of 5- and 6-substituted benzo-1,4-dioxanes

The compositions of the products of bromination, nitration, and acetylation of 5- and 6-fluoro(chloro, nitro, methoxy, methyl, formyl, and carboxy)benzo-1,4-dioxanes were established. The reactivity indexes and the characteristics of the UV spectra of the starting compounds were calculated by the self-consistent-field (SCF) MO LCAO method within the Pariser-Parr-Pople (PPP) and CNDO/2 CI (complete neglect of differential overlap with configuration interaction) approximations, and the results were compared with the experimental data.Translated from Khimiya Geterotsiklicheskikh Soedinenii,No. 11, pp. 1465–1471, November, 1978.     

Reinvestigation of the action of hydrogen peroxide on ursolic acid acetate

The action of hydrogen peroxide on ursolic acid acetate in boiling acetic acid has been reinvestigated, and the three oxidation products, designated as U_I, U_II and U_III, have been reisolated. The structure of U_I has been revised to 8a and that of U_II has been established as 11a on the basis of spectral and chemical evidence. Additional spectral data are provided in support of the structure of U_III (5a). The stereoelectronic factors responsible for the unusual stability of the epoxide function in U_I towards acid-catalysed rearrangement to the 12-keto-derivative (9a) and the facile conversion of the latter to the enol-acetate (10a), compared to the normal behaviour of the structurally similar compounds, 8b and 9d of the oleanane series, have been rationalised.     

Reactions of 5-diazo-4-nitroimidazole with hydrochloric acid

Reaction of 5-diazo-4-nitroimidazole with concentrated hydrochloric acid leads to 4-chloro-5-diazoimidazole. The same product is formed together with a small quantity of 5-chloro-4-nitroimidazole with 1 N hydrochloric acid, but with 0.1 N hydrochloric acid only chloronitroimidazole was isolated. The results obtained are explained with the aid of quantum chemical calculations.Urals State Technical University-Urals Polytechnical Institute (UPI), Ekaterinburg 620002, Russia; Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 199–202, February, 1999.     

Decomposition of cinnabarinic acid by hydrogen peroxide

The hydrogen peroxide-induced decomposition of cinnabarinic acid 2 has been examined. Two major compounds were found to arise from the decomposition; 3-hydroxyanthranilic acid 1 , and an isomeric mixture of two novel hemiketals.     

Preparation of halomethyl-1,3,4-thiadiazoles. Conversion to 2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole,an important antimicrobial agent

A new route for the synthesis of 2-amino-5-(l-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole ( 1 ) is described. This route was based upon the preparation of 2-amino-5-halomethyl-1,3,4-thiadiazoles by condensation of haloacetic acids with thiosemicarbazide. One of these intermediates, 2-acetamido-5-dichloromethyl-1,3,4-thiadiazole ( 4 ), was hydrolyzed to the corresponding 5-amino-2-carboxaldehyde 6 , which was trapped as its oxime 5 . 5-Acetamido-1,3,4-thiadiazole-2-carbonitrile ( 7 ), formed upon dehydration of 5 , was then converted into 2-amino-5-(2-imidazolyl)-1,3,4-thiadiazole ( 11 ) by a route based on the Pinner amidine synthesis. Methylation and nitration of the imidazole moiety then completed the preparation of 1.