A green and recyclable CuSO4·5H2O/ionic liquid catalytic system for the CO2-promoted hydration of propargyl alcohols: an efficient assembly of α-hydroxy ketones

α-Hydroxy ketones are important building blocks in biological, pharmaceutical and synthetic chemistry. In this work, diverse α-hydroxy ketones were efficiently constructed through the CO 2 -promoted hydration process of propargyl alcohols, which was catalyzed by a system consisted of economical CuSO 4 ·5H 2 O and a green 1-butyl-3-methylimidazolium acetate ionic liquid. Particularly, this catalytic system exhibited excellent activity under atmospheric CO 2 or even mimetic flue gas (20 vol% of CO 2 ). Moreover, this system employed the lowest metal loading ever reported (0.004–0.25 mol%) meanwhile reached the highest turnover number (11700) for the target hydration reaction. Additionally, this is the first reported Cu catalytic system with reliable recyclability, which could be easily reused at least 6 times with yields higher than 85%.