One-pot synthesis of 1,6-naphthyridines, pyranopyridines and thiopyranopyridines

A one-step synthesis of [1,6]naphthyridine-2(1H)-thione (3a), pyrano[3,4-b]pyridine-2(1H)-thione (3b), thiopyrano[3,4-b]pyridine-2(1H)-thione (3c) and 6-oxoquinoline-2(1H)-thione (3d) through the reaction of benzylidene-cyanothioacetamide (1) with cyclic ketones 2a-d is described. The reaction of 3a-d with organyl chlorides yielded the 2-alkylthio-3-cyanopyridines 4a-p which upon refluxing in ethanolic sodium ethoxide afforded the thieno[2,3-b]pyridine derivatives 5a-n. Some of the synthesized compounds were screened for the activity against bacteria and fungi. © 2008 Verlag der Zeitschrift für Naturforschung.