Sulfuric Acid-Catalyzed Conversion of Alkynes to Ketones in an Ionic Liquid Medium under Mild Reaction Conditions

An efficient and recyclable ionic liquid system containing a small amount of sulfuric acid as the catalyst (0.5−8.0 mol equiv to substrate) has been successfully developed for hydration of various alkynes under mild reaction conditions (40 °C, 0.5 h) to give high yields of ketones (88−100%) as products. The system does not involve heavy metal catalysts or concentrated acids and is simple and easy to prepare and exhibits excellent catalytic activity and isolated yield toward the hydration of alkynes to ketones. The efficiency of the system is attributed to the high chemical activity of protons in the ionic liquid medium.