Synthetic studies of some varied structural systems of biologically potent polynitrogen heteropolycyclics

1243-1256Four-component one pot cyclocondensation of aromatic aldehydes 1, malononitrile 2, barbituric acid 3 and ammonium acetate in methanol after initial Knoevenagel, subsequent Micheal and final heterocyclisation reactions give substituted and functionalized pyrido[2,3-d]pyrimidine derivatives 4. These pyridopyrimidines on reaction with various active methylene compounds result in the formation of differently functionalized and diversly substituted linear tricyclic pyrimidonaphthyridines 5-7 and 9-10, linear tetracyclic benzo[b]pyrimidonaphthyridines 8 and dipyrimidonaphthyridines 11 as a result of final heterocyclization through either simple cyclocondensation or cyclodehydration, etc. The compounds of system 7/10 and two compounds of system 8 with suitable functionalities on further condensation with formamide, generate the novel angularly fused tetracyclic dipyrimidonaphthyridines 12/14 and ‘ortho and peri’ fused pentacyclic pyrimidonaphthyridinoquinazolines 13 respectively, all hitherto unknown or not reported in literature. Compounds 4 and 5 on condensation with formamide can close the recurring generation of the CN and other reactive functionality on the products resulting in the production of tricyclic pyrido [2,3-d;6,5-d′]dipyrimidine 15 from 4 and two differently fused linear and angular tetracyclic dipyrimidonaphthyridine systems 16 and 17 from 5 similar to the systems 11 and 12/14 respectively. Either of the latter two systems on heterocyclodehydration with boiling formic acid produce same ‘ortho and peri’ fused pentacyclic novel heterocyclic system 1,3,4,6,7,8,9,11-octazabenzo[de]naphthacene 18