Mono- and Bis-2-amino-4H-pyrans: Alum Catalyzed Three- or Pseudo Five-Component Reaction of 4-Hydroxycoumarin, Malononitrile and Aldehydes

An efficient method for the three- or pseudo five-component synthesis of mono- and bis-2-amino-4H-pyrans in excellent yields using Alum (KAl(SO4)2.12H2O) as recyclable catalyst is described. The present methodology offers several advantages such as excellent yields, simple procedures, shorter reaction times, milder conditions and the catalysts exhibited remarkable reusable activity.