Synthesis, structures, electrochemical studies and antioxidant activity of 5-aryl-4-oxo-3,4,5,8-tetrahydropyrido[2,3-d]pyrimidine-7-carboxylic acids

• Ultrasonic and microwave irradiation methodologies has given better yields than conventional methods of synthesis.
• The reaction was regioselective for the formation to one regioisomer.
• The compounds exhibited low free radical scavenging capacity in the DPPH assay.
• The compounds 3a and 3o showed better behavior as antioxidant for the ORAC assay.
• The electrochemical studies found that the oxidations of compounds are irreversible.

The synthesis of 5-aryl-4-oxo-3,4,5,8-tetrahydropyrido[2,3-d]pyrimidine-7-carboxylic acids 3 from the reaction of 6-aminopyrimidines 1 with arylidene derivatives of pyruvic acid 2 under microwave and ultrasound irradiation is described. The orientation of cyclization process was determined by NMR measurements. The methodology provides advantages such as high yields and friendly to the environment without the use of solvents. The antioxidant properties, DPPH free radical scavenging, ORAC, and anodic potential oxidation of the new pyridopyrimidines were studied.

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