Novel Mono- and Bis(spiro-2-amino-4H-pyrans): Alum-Catalyzed Reaction of 4-Hydroxycoumarin and Malononitrile with Isatins, Quinones, or Ninhydrin

Some new mono- and bis(spiro-2-amino-4H-pyrans) are synthesized by the multicomponent condensation reaction of 4-hydroxycoumarin and malononitrile with isatins, ninhydrin, 9,10-phenanthrenequinone, or acenaphthenequinone. Alum was found to be a suitable and efficient catalyst for this condensation.