Propanal in the Syntheses of Alkyl-substituted 3-Cyano-2-piperidone, 3-Cyano-2,5,6,7-tetrahydropyrindin-2(1H)-one, and 3-Cyanopyridine-2(1H)-thione
Condensation of propanal with cyanothioacetamide and morpholine gave 3-cyano-4-ethyl-5-methyl-6-morpholino-2-piperidone, the structure of which was studied by X-ray analysis. Reaction of propanal with cyanothioacetamides and cycloalkanone enamines gave 3-cyano-4-ethyl-2,5,6,7-tetrahydropyrindin-2(1H)-one and 3-cyano-4-ethyl-5,6-hexamethylenepyridine-2(1H)-thione. The latter was used for the preparation of substituted 2-benzyloxycarbonylmethylthiopyridine and 3-amino-2-benzyloxycarbonylthieno[2,3-b]pyridine.