A series of spiro-pyran derivatives have been synthesised by a three-component reaction of ninhydrin or acenaphthenequinone, malononitrile and 1,3-dicarbonyl compounds such as cyclohexane-1,3-dione, dimedone and barbituaric acid in ethanol with NaHCO3as the catalyst. This method has the advantages of easy work-up, mild reaction condition, high yields and it is cheap.
A convenient and efficient synthesis of biologically and pharmacologically important spiropyrans from the condensation of malononitrile, 1,3-dicarbonyl compounds and ninhydrin/acenaphthequinone/isatin has been reported using recyclable heterogeneous polyethylene glycol (PEG)-stabilized Ni nanoparticles in ethylene glycol. This new protocol affords products in high yields and less reaction time.