Amberlyst A21 catalyzed one-pot three-component coupling of aldehyde and malononitrile with active methylene compounds such as acetylacetone and ethyl acetoacetate for the synthesis of pharmaceutically important polyfunctionalized 4H-pyrans has been reported. Simple experimental procedure. no chromatographic purification. no hazardous organic solvents. https://hollandscountryclothinges.shop/product-category/binocular-harness/