Studies on Uracils. 10. A Facile One-Pot Synthesis of Pyrido- and Pyrazolopyrimidines

Article abstract of DOI:10.1021/jo00289a033

The reaction of functionalised uracils bearing amino and hydroxyamino groups at C-6 position (4 and 5) with strongly electrophilic cyano olefins (1,2 and 3) gave rise to pyrido<2,3-d>pyrimidines 7-9 in excellent yields.Hydrazine-substituted uracil 6 gave access to an efficient one-step synthesis of pyrazolo<3,4-d>pyrimidines 10.The capture of an eliminated hydrogen molecule by cyano olefins in the case of their reaction with 4 and 6 was confirmed by the isolation of dihydrocyano olefins.This fact further supported the plausible mechanism for the formation of compounds 7-10 via dihydropyrido<2,3-d>- and dihydropyrazolo<3,4-d>pyrimidine intermediates A and C.