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 were 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.