An efficient route for the synthesis of a new class of pyrido[2,3-d]pyrimidine derivatives.

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.