摘要:
The reaction of 5-amino-6-cyano-1,3-dimethyl-7-methylthiopyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione (1c) with dimethyl acetylenedicarboxylate (DMAD) in the presence of potassium carbonate in dimethyl sulfoxide gave tetramethyl 8,9,10,11-tetrahydro-8,10-dimethyl-9,10-dioxo-4H-pyrimido[4',5':5,6]pyrido[2,3,4-cb][1,6]naphthyridine-2,3,5,6-tetracarboxylate (2c). The reaction of other heterocycles bearing amino, cyano, and methylthio groups with DMAD or DEAD under the same reaction conditions gave the corresponding tetracyclic heterocycles containing the fundamental 1,6-naphthyridine ring system.