名称:
                                Studies on pyrimidine-annelated heterocycles: synthesis of novel pyrazolo[3′,4′:4,5]pyrido[2,3-d]pyrimidines by intramolecular 1,3-dipolar cycloadditions
                             
                            
                                摘要:
                                Suitably functionalised 1,3-substituted 6-chloro-1,2,3,4-tetrahydro-2,4-dioxopyrimidine-5-carbaldehydes 3a-1 cyclise intramolecularly to yield novel furo- and thieno-[2 '',3 '':4',5']pyrazolo[3',4':4,5]pyrido-[2,3-d]pyrimidines 8a-1 in fair to good yields together with the pyrazolopyrimidines 7 as side products. Remarkably, this synthesis not only left the pyrimidine nucleus unaffected but also gave no dimer formation.