Y. Tominaga et al., Synthesis of polycyclic nitrogen-containing heterocyclic : One pot formation of 1,6-naphthyridine ring system by reaction of amino-cyano-methylthio-heterocycles with dialkyl acetyeledicarboxylates, J HETERO CH, 38(5), 2001, pp. 1135-1141
Reaction of 3-amino-3-methylthio-2-cyanoacrylonitrile (1) with excess dimet
hyl acetylenedicarboxylate(DMAD) in the presence of potassium carbonate in
dimethyl sulfoxide gave a novel tricyclic heterocycle, hexamethyl 1H-1,4,7-
triazaphenalene-2,3,5,6,8,9-hexacarboxylate (5a). When one equivalent of DM
AD was used in this reaction, dimethyl 4-amino-3-eyano-2-methylthiopyridine
-5,6-dicarboxylate (3a), a key intermediate of 5a, was obtained.