Ring closure reactions of pyrido[2,3-d]pyrimidines to pyrano[2′, 3′:4,5]- and oxazolo[5′,4′:4,5]pyrido[2,3-d]pyrimidines

Article abstract of DOI:10.1002/jhet.5570450517

(Chemical Equation Presented) The cyclocondensation of 5-hydroxy-pyrido[2, 3-d]pyrimidines 1 with malonates gives pyrano[2′,3′:4,5]-pyrido[2,3- d]pyrimidines 2. Nitration of 1 and reduction with zinc in the presence of carboxylic acids/anhydrides gave 2-a