Abstract6‐Aminouracil and 6‐aminothiouracil (1a, b) were reacted with benzylidenemalononitrile2ato afford the pyrido[2,3‐d]pyrimidines4a, b. On the other hand, the reaction of1a, bwith benzylidene ethyl cyanoacetate2bresult in a mixture of5a,band/or6a,brespectively. Pyrido[2,3‐d]thiazolo[1,2‐b]pyrimidines8a‐cwere synthesized from the reaction of4bwith α‐halo compounds to give the intermediate derivatives7a‐cfollowed by cyclization