Perchloric Acid Impregnated on Silica Gel (HClO₄/SiO₂): A Versatile Catalyst for Michael Addition of Thiols to the Electron‐Deficient Alkenes

Abstract

Abstract Perchloric acid adsorbed on silica gel (HClO 4 /SiO 2 ) has been found to be a highly efficient and versatile catalyst for the Michael addition of thiols to a wide variety of conjugated alkenes such as α,β‐unsaturated ketones, carboxylic esters, nitriles, amides and chalcones in dichloromethane or methanol at room temperature. The reactions are completed within 2–20 min in high yields. Some of the additional advantages are: no aqueous work‐up is necessary, and the catalyst is also reusable. Moreover, the solid product can be obtained without chromatographic separation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)