Efficient and Expeditious Synthesis of Pyrano‐pyrimidines, Multi‐substituted γ‐Pyrans, and Their Antioxidant Activity

An efficient, expeditious catalytic route for the synthesis of ethyl 6-amino-5-cyano-2-methyl-4-aryl-4H-pyran-3-carboxylates 2 was achieved via a three-component, one-pot reaction of malononitrile, ethyl acetoacetate, and various aromatic aldehydes in water as a solvent at room temperature. The key advantages are excellent yield, reaction time, and inexpensive catalyst. Also, cyclization of 4H-pyrans 2 to the corresponding 4H-pyrano[2,3-d]pyrimidines 3 using silica sulfuric acid in the presence of acetic anhydride was described. Some synthesized compounds exhibited promising antioxidant activities.