Application of sulfuric acid immobilized on silica gel as an efficient and benign catalyst has been explored in the syn-thesis of 2,4,5-Triaryl-1H-imidazoles via condensation reaction of benzil or benzoin, aldehyde and ammonium acetate. The key advantages of this process are high yields, cost effectiveness of catalyst, easy work-up, purification of products by non-chromatographic method and the reusability of the H<sub>2</sub>SO<sub>4</sub>.SiO<sub>2</sub> catalyst
A convenient synthesis of sulfonamides and sulfonyl azides from thiols is described. In situ preparation of sulfonyl chlorides from thiols was accomplished by oxidation with chloramine‐T (=N‐chlorotosylamide=N‐chloro‐4‐methylbenzenesulfonamide), tetrabutylammonium chloride (Bu4NCl), and H2O. The sulfonyl chlorides were then further allowed to react with excess amine or NaN3 in the same pot.
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