Abstract
The course of reaction of aryl and heteroaryl sulfonamides with diphenylcarbonate (DPC) and 4-dimethylaminopyridine (DMAP) was found to depend on the pKa of the sulfonamide used. Aryl sulfonamides with pKa ~ 10 gave 4-dimethylamino-pyridinium arylsulfonyl-carbamoylides, while the more acidic heteroaryl sulfonamides (pKa ~ 8) furnished 4-dimethylaminopyridinium heteroarylsulfonyl carbamates. Both the carbamoylides and carbamate salts reacted with aliphatic and aromatic amines with the formation of appropriate aryl(heteroaryl)sulfonyl ureas, and therefore, can be regarded as safe and stable substitutes of the hazardous and difficult to handle aryl(heteroaryl)sulfonyl isocyanates.
Highlights
Arylsulfonyl ureas constitute a well known class of compounds which exhibit a wide range of biological activities
2-naphthylsulfonamide) with diphenyl carbonate (DPC) in the presence of DMAP proceeded smoothly at room temperature to give appropriate carbamoylides 3a-c in good yields. The reactions of these stable arylsulfonyl isocyanates substitutes carried out in CH3CN with both aliphatic and aromatic amines at elevated temperature afforded the desired arylsulfonyl ureas, which could be separated from the reaction mixtures upon treatment with 1% aqueous HCl
When 2-thienyl and benzothiazol-2-yl-sulphonamides 1d-f were treated with DPC in the presence of DMAP, the pyridinium carbamates 4a-c were obtained as the sole products
Summary
Arylsulfonyl ureas constitute a well known class of compounds which exhibit a wide range of biological activities. The most important include: antidiabetic drugs (e.g., glibenclamide) [1], diuretic drugs (e.g., torasemide) [2], inhibitors of thromboxane synthase and thromboxane A2 receptor antagonists with antithrombotic properties [3,4] and inhibitors of acetohydroxyacid synthase (AHAS). We have described a facile method for the preparation of arylsylfonyl ureas of general formula C (Scheme 1) using 4-dimethylaminopyridinium arylsulfonyl-carbamoylides B, which constitute non-hazardous substitutes of arylsulfonyl isocyanates [12,13]. Carbamoylides B compose of an appropriate arylsulfonyl isocyanate and a DMAP molecule. The stability of these highly polarizable adducts is mainly due to the delocalization of the positive charge on the pyridine ring and the negative charge on the arylsulfonylcarbamoyl moiety. In order to explore the scope of this procedure, an analogous previously not attempted reaction sequence starting from variously substituted phenylsulfonamides, naphthylsulfonamide as well as heteroarylsulfonamides, such as 2-thienyl- and benzothiazol-2-yl-sulfonamide has been attempted
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