Graphene oxide nanosheets as metal-free catalysts in the three-component reactions based on aryl glyoxals to generate novel pyranocoumarins

Graphene oxide (GO) was prepared and employed as a novel, recyclable and safe catalyst for the one-pot, three-component condensation of 4-hydroxycoumarin with aryl glyoxals and malononitrile to produce new pyranocoumarins. Catalyst loadings can be as low as 0.005 g to give high yields of the corresponding products. This novel method has many advantages, such as the high product yield and a simple work-up procedure.