Cholinesulfuric acid drivatives as an efficient catalyst for reaction of aryl aldehydes, cyclic 1,3-diketones and malononitrile

Choline sulfate is a naturally-occurring osmolyte that is synthesized by plants,lichens, algae, fungi, and several bacterial species [1-2]. Cholinesulfuric acid is a biocompatible choline sulfate-based acidic ionic liquid that can be used in organic transformations [3]. Herein we report an efficient and environmentally friendly method for the synthesis of tetrahydrobenzo[b]pyrans as important pharmaceutical compounds has been developed using Cholinesulfuric acid as a cheap and readily available catalyst. A mixture of an aromatic aldehyde, malononitrile and cyclic 1,3-dicarbonyl compounds in the presence of the cholinesulfuric acid ionic liquid in H2O/EtOH resulted in excellent yields of the corresponding products. This new methodology is of interest due to use of aqueous media as a green solvent system, reusability of the acidic ionic liquid catalyst, its short reaction time, high yields and no further purification