Graphene Oxide Incorporated Strontium Nanoparticles as a Highly Efficient and Green Acid Catalyst for One-Pot Synthesis of Tetramethyl-9-aryl-hexahydroxanthenes and 13-Aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraones Under Solvent-Free Conditions

An efficient, inexpensive and recyclable graphene oxide/strontium nanocatalyst was synthesized and applied in a pseudo three-component, one-pot cyclocondensation of aromatic aldehydes and dimedone/lowson to afford the corresponding 3,3,6,6-tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-diones and 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraones in high yields under solvent-free conditions. To the best of our knowledge, there are no literature reports on applying graphene oxide/strontium as a nanocatalyst for xanthene derivatives synthesis. The key potential benefits of the present method are including high yields, short reaction time, easy workup, recyclability of catalyst and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards. The nanocatalyst easily separated from the reaction mixture easily by applying an external magnet and reused at least six times without noticeable degradation in catalytic activity.