The Synthesis of Cyclopenta[ c ]pyridine (2-Pyrindene) Derivatives

Ethyl 2-(N-morpholinyl)cyclopent-1-ene-1-carboxylate reacted smoothly with cyanothioacetamide to give morpholinium 4-cyano-1-oxo-2,5,6,7-tetrahydro-1H-cyclopentac]pyridine-3-thiolate; the former when treated with N-benzyl-α-chloroacetamide gave either a S-alkyl derivative or cyclopentad]thieno2,3-b]pyridine, depending on the reaction conditions. Under Mannich-type aminomethylation with primary amines and formaldehyde the above thiolate afforded derivatives of the previously unknown heterocyclic system, cyclopentag]pyrido2,1-b]1,3,5]thiadiazine in 81–90% yields.