Sulfuric Acid Impregnated on Silica Gel (H2SO4/SiO2): A Versatile and Reusable Catalyst for the Synthesis of 1,2,4-Triazolo[5,1-b][1,3]thiazin-7-ones

Abstract

Sulfuric acid adsorbed on silica gel (H₂SO₄/SiO₂) has been found to be a highly efficient and versatile catalyst for the cyclization of 3-(4H-1,2,4-triazol-3-ylsulfanyl)-acrylic acids into 1,2,4- triazolo[5,1-b][1,3]-thiazin-7-ones under solvent-free microwave irradiation and conventional heating. The present methodology offers several advantages such as simple procedure with an easy work-up, short reaction times, high yields and a recyclable, relatively green and eco-friendly catalyst.