The reaction of 7-methyl-1-(morpholin-4-yl)-3-sulfanylidene-2,3,5,6,7,8-hexahydro-2,7-naph thyridine-
4-carbonitrile with hydrazine hydrate gave 1-hydrazinyl-7-methyl-3-sulfanylidene-2,3,5,6,7,8-hexahydro-
2,7-naphthyridine-4-carbonitrile which was used as a key intermediate for the synthesis of new fused naphthyridine-
based heterocyclic systems. The condensation of 1-amino-7-methyl-5-(morpholin-4-yl)-6,7,8,9-
tetra hydrothieno[2,3-c][2,7]naphthyridine-2-carbonitrile with different reagents afforded fused tetra- and
pentacyclic systems. The structure of the newly synthesized compounds was confirmed by elemental analysis
and spectral techniques.