A new reaction of 4-arylidene-3-methylisoxazol-5 (4H)-one or 4-arylidene-2-phenyloxazol-5 (4H)-one with 2, 6-diaminopyrimidin-4 (3H)-one is described and a number of new pyrido [2, 3-d] pyrimidine-4, 7-dione derivatives are synthesized. This protocol has the advantages of good yields, broad substrate scope and simple work-up.