1.2.4- Thiadiazole 1,1-dioxides, 4,5-dihydro

Hydrolysis of amino-alkylamino-l,2,5-thiadiazole 1-oxides 55 with concentrated aqueous HC1 gave the amidines 56 (Equation 4) <2001JME1231>. The hydrolysis reactions of 2-alkyl-4-amino-2,3-dihydro-l, 2,5-thiadiazol-3-one 1,1-dioxides 57 in the range 24-73 °C in buffered aqueous solutions gave the corresponding 2-amino-2-[(iV-alkyl-substituted-sulfamoyl)imino]acetic acid salts 58 (Equation 5) <1998JP0489>. 

Treatment of the 2,5-dihydro-l,2,5-thiadiazole 1,1-dioxide 69 with/>-toluenesulfonic acid monohydrate affords the ring-opened phenylethyl sulfamide 70 (Equation 9) <2004BMC6249>. 

The kinetics of the hydrolysis reactions of 4-amino-2-phenethyl- (354 R = PhCH2CH2) and 4-amino-2-cyclohexyl-2,3-dihydro-3-oxo-l,2,5-thiadiazole 1,1-dioxide (354 R = CeHii) have been investigated in the pH range 1-10 at 24-73 °C. The products are the corresponding new compounds 2-anuno-2-[(A -substituted-sulfamoyl)imino]acetic acid salts (355 R = PhCH2CH2 or CeHn) which hydrolyse further, in a slow reaction, to the sulfamide and oxalic acid derivatives. ... 

The synthesis and preliminary biological activity of substituted 7-alkylseleno-l,4-dihydro[l,6]naphthyridines have been reported <2000DOC218> along with their further synthetic ttansformations <2001RCB122>. There have also been reports of the preparation of selenium-containing fused heterocycles. The C=0 function in benzothiophen-3-ones, 3,4-dihydrothiopyrano[3,2-. ]benzothiophen-4(2//)-ones, and 3,4-dihydro-2//,5//-thiopyrano[2, 3 4,5]thiopyrano[3,2-/ ]ben-zothiophen-4-ones reacts with selenium dioxide and thionyl chloride to give fused 1,2,3-selena and thiadiazoles via their semicarbazones <1999IJB308>. 

Dihydro-1,3,4-thiadiazole 1,1-dioxides (cis and trans) are obtained by the Staudin-ger-Pfenninger reaction of r-butyldiazomethane and sulfur dioxide. Some thiirane is also formed (Scheme 34) (81CB802). 

Azole approach. 3,4-Diamino-l,2,5-thiadiazole reacts with 1,2-dicarbonyl compounds to form pyrazines (747) (76JHC13). From the reaction of 1,2,5-thiadiazole 1,1-oxides such as (748) with o-phenylenediamine, the l,3-dihydro[l,2,5]thiadiazolo[3,4-Z>]quinoxaline 2,2-dioxide (749) is formed. To understand this reaction it is pointed out that the 1,2,5-thiadiazole 1,1-dioxide ring is to be regarded as alicyclic rather than aromatic and is strongly 7r-electron deficient. Substituents with leaving properties in the 3,4-positions are therefore readily displaced as in the reaction of (748) (75JOC2743). 

Thiadiazol 2,2-Dimethyl-5-(3,3,5,5-tetramethyl-thian-l,1-dioxid-4-yliden)-2,5-dihydro-E14a/3, 528 (R2C = C = S +... 

It has been found that some sulfonamides act as carbonic anhydrase (an enzyme that catalyzes the reaction between C02 and water with the formation of H+ and HC03"). The first compound prepared was acetazolamide (2-acetamido-1,3,4-thiadiazole-5-sulfonamide) 48, which increases the urine volume after administration184,185. Other agents like hydrochlorothiazide (6-chloro-3,4-dihydro-2i7-l,2,4-benzothiazine-7-sulfonamide-1,1-dioxide) 49 were developed later and are more effective. They inhibit... 

Diaza-l, 3-butadienes undergo hetero-Diels-Alder cycloaddition with Cgo to afford fused tetrahydropyridazine derivatives 85. The heterodienes are produced in situ upon heating of 2,5-dihydro-l,3,3-thiadiazole-l,l-dioxide 84 (06TL4129). 

Cl 2H18CI4CUN4OS, Thiamine tetrachlorocuprate, 40B, 553 Cl2H18N2O3S, 2,3-Dihydro-2-acetyl-3,3-dimethyl-4 [(lE)-4-methyl-1,3-pentadienyll l,2,5-thiadiazole 1,1-dioxide, 46B, 403 C12H18N4O3S, 2,7-Dimethylthiachromine-8-ethanol dihydrate, 40B, 350 Cl2H19N2O4PS, N-(2,6-Dimethylphenyl)-2-amino-5,6-dihydro-4H-1,3-thiazine phosphate, 45B, 429... 

Thiadiazolo[3,4-6]quinoxaline.—The condensation of 3,4-dimethoxy-l,2,5-thiadiazole 1,1-dioxide with o-phenylenediamine similarly produces 1,3-dihydro-... 

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