Some reactions of 3-cyano-4-(p-methoxyphenyl)-5-oxo-5,6,7,8-tetrahydro-quinoline-2(1H)-thione; Synthesis of new tetrahydroquinolines and tetrahydrothieno[2,3-b]quinolines

In this paper, 3-cyano-4-(p-methoxyphenyl)-5-oxo-5,6,7,8-tetrahydroquinoline-2(1H)-thione (2) was prepared and reacted with methyl iodide to give the corresponding 2-methylthio derivative 3. Fusion of compound 2 or 3 with hydrazine hydrate produced the aminopyrazolotetrahydroquinoline-5-hydrazone 4. Reaction of both compounds 2 and 3 with phenylhydrazine or thiosemicarbazide led to the formation of condensation products 6a,b and 9a,b respectively. Reaction of cyanoquinolinethione 2 with some α-halocarbonyl compounds namely; ethyl chloroacetate, chloroacetamide, chloro-N-(p-tolyl)acetamide and phenacyl bromide gave the corresponding alkylated products 10a-d. On treatment of the latter compounds with sodium ethoxide in boiling ethanol, they underwent intramolecular ThorpeZeigler cyclization affording the corresponding tetrahydrothieno[2,3-b] quinolines 11a-d. The elemental analyses and spectroscopic data of all compounds are in agreement with their proposed structures.