Abstract: | 6-Aminouracil and 6-aminothiouracil ( 1a, b ) were reacted with benzylidenemalononitrile 2a to afford the pyrido2,3-d]pyrimidines 4a, b . On the other hand, the reaction of 1a, b with benzylidene ethyl cyanoacetate 2b result in a mixture of 5a,b and/or 6a,b respectively. Pyrido2,3-d]thiazolo1,2-b]pyrimidines 8a-c were synthesized from the reaction of 4b with α-halo compounds to give the intermediate derivatives 7a-c followed by cyclization using 70% H2SO4. |