An efficient onePot green synthesis of 4HBenzo[b]pyrans using guanidinium chloride as polyfunctional organocatalyst

A simple, efficient, and high yielding onepot protocol has been developed for the synthesis of 4Hbenzo[b]pyrans scaffolds installing a threecomponent tandem Knoevenagelcyclocondensation reaction of an aldehyde, malononitrile and dimedone using guanidinium chloride as polyfunctional organocatalyst under solventfree 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 workup procedures, shorter reaction time and avoiding the use of toxic solvents and purification of products by nonchromatographic methods. The generality and functional tolerance of this convergent and environmentally benign method is demonstrated.