An efficient one-pot green synthesis of 4H-benzo[b]pyrans using guanidinium chloride as polyfunctional organocatalyst

A simple, efficient, and high yielding one-pot protocol has been developed for the synthesis of 4H-benzo[b]pyrans scaffolds installing a three-component tandem Knoevenagel-cyclocondensation reaction of an aldehyde, malononitrile and dimedone using guanidinium chloride as polyfunctional organocatalyst under solvent-free conditions in high to excellent yields. Various aromatic aldehydes were utilized in the reaction and, in all situations; the desired product was synthesized successfully. The advantageous features of this methodology are operational simplicity, convenient work-up procedures, shorter reaction time and avoiding the use of toxic solvents and purification of products by non-chromatographic methods. The generality and functional tolerance of this convergent and environmentally benign method is demonstrated.