Novel DABCO Based Ionic Liquids: Green and Efficient Catalysts with Dual Catalytic Roles for Aqueous Knoevenagel Condensation

Abstract

Four novel basic ionic liquids (ILs), based on 1,4-diazobicyclo[2.2.2]octane (DABCO) and 3-chloro-1,2-propanediol, have been introduced as catalysts for Knoevenagel condensation. These catalysts are applicable to a wide range of aromatic/heteroaromatic aldehydes with α-aromatic (heteroaromatic or polyaromatic)-substituted methylene compounds in water at room temperature, and they afford the products in excellent yields within short times. These reactions are operationally simple, and the desired products can be separated directly from the reaction mixture without further purification. A possible reaction mechanism was proposed, and the relevant evidence was given. In addition, the ionic liquids used can be regenerated and recycled several times without significant loss of activity. Furthermore, the novel ILs could be efficiently used in a step of atorvastatin synthesis.