Chemical behavior of 4,9-dimethoxy-5-oxo-5H-furo[3,2-g]chromene-6-carboxaldehyde towards carbon nucleophilic reagents

The chemical behavior of 6-formylkhellin ( 1 ) was investigated toward a variety of carbon nucleophiles. Treatment of aldehyde 1 with cyanoacetamide, N-benzylcyanoacetamide produced pyridine-3-carboxamides 3 and 4 . Treatment of carboxaldehyde 1 with malononitrile dimer and 1H-benzimidazol-2-ylacetonitrile gave 1,6-naphthyridine 5 and pyrido1,2-a]benzimidazole 6 , respectively. Some novel pyrazolo3,4-b]pyridine 7 , pyrido2,3-d]pyrimidines 8 and 9 were synthesized from the ring opening ring closure reactions of carboxaldehyde 1 with certain heterocyclic enamines. In addition, reaction of carboxaldehyde 1 with certain cyclic enols produced a variety of products. Treatment of carboxaldehyde 1 with 1,3-cyclohexanediones gave xanthene-1,8-diones 19 and 20 . Reaction of carboxaldehyde 1 with 5-methyl-2,4-dihydro-3H-pyrazol-3-one proceeds in 1:2 M ratio producing pyrazolo 4′,3′:5,6]pyrano2,3-c]pyrazole derivative 22 . Carboxaldehyde 1 reacted with certain heterocyclic compounds containing active methylene groups to give the corresponding condensation products 22 - 27 . The synthesized compounds were screened in vitro for their antimicrobial activity and showed high to moderate activities against the tested microorganisms.