New and Facile Synthesis of Pyrimidine, Coumarine, Pyrimido[1,6-a]Pyrimidine, 1,2,4-Triazine and Pyrimido[4,5-c] Pyridazine Derivatives

Condensation of cyanoacetylurea 1 with aromatic aldehydes gave the arylidenes 2a-d. Compound 2a cyclised to the pyrimidone 4 by boiling in DMF/Et3N. Compound 1 condensed with 2,4-dihydroybenzaldehyde to give the arylidene 6 .Cyclisation of 6 yield the coumarine 7.Coupling of 1 with aryl diazonium salts gave aryl hydrazones 9a,b. Compound 9a cyclised to 10 . Compound 10 reacted with malononitrile to give pyrimido [1,6-a] pyrimidine 11. Reaction of 9b with triethyl orthoformate and ethyl chloroformate afforded 1,2,4-triazines 13 and 15 respectively. Condensation of 1 with arylhydrazone 16 yielded pyrimido[4,5-c] pyridazine 19.