Solvent-free, green and efficient synthesis of pyrano[4, 3-b]pyrans by grinding and their biological evaluation as antitumor and antioxidant agents

A facile, green, and efficient method has been developed for the synthesis of pyrano[4, 3-b]pyrans via a one-pot reaction of aromatic aldehydes, malononitrile, and 4-hydroxy-6-methyl-pyran-2-one in the presence of ammonium acetate under solvent-free conditions using grinding method. The experimental simplicity, short reaction time, easy work-up, avoidance of organic solvents, and utilization of an inexpensive and readily available catalyst make this new methodology practical and economically attractive. The antitumor activity of the compounds was tested against human breast cancer cell line MCF-7. Compounds 4l, 4o, and 4p showed good cytotoxic activity comparable with standard drug Doxorubicin. On the other hand, compounds 4q and 4r exhibited potent growth inhibitory activity. Furthermore, the synthesized compounds were screened for in vitro antioxidant activity by DPPH assay. All the compounds assayed showed moderate to good free radical scavenging activity.