Reaction of 3,4-trimethylene-6-amino-5-ethoxycarbonylthiopyrane-2-thione (1) with hydrazine hydrate gave the corresponding o-diaminocyclopentapyridine-2-thione (2). Ring closure of 2 with some reagents, namely, formic acid, aromatic aldehydes, carbon disulphide. phenacyl bromide, ethyl chloroformate, ethyl chloroacetate, nitrosylsulfuric acid, and pyruvic acid gave tricyclic compounds (2-14) by direct or indirect pathways, respectively.