Abstract
Chemical reactivity of quinoline and isoquinoline skeletons was compared, using 1-cyano-2-methoxy-1, 2-dihydroquinoline (2a), 2-cyano-1-methoxy-1, 2-dihydroisoquinoline (2b), 3-bromo-1-cyano-2, 4-dimethoxy-1, 2, 3, 4-tetrahydroquinoline (3a), and 4-bromo-2-cyano-1, 3-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (3b), in order to know the fundamental chemical characteristics of 2a, b and 3a, b for use as an intermediate for the syntheses of nitrogen-containing heterocyclic compounds. 1) Oxidation of 2a or 2b and 3b afforded 2-one compound or 1-one compounds. 2) Reaction of 2a or 2b with ethanethiol afforded 1 (or 2)-cyano-2 (or 1)-ethylthio-1, 2-dihydroquinoline (2e) or -1, 2-dihydroisoquinoline (2f). Reaction of 3a with ethanethiol gave 4-bromo-2-cyano-1-ethylthio-3-methoxy-1, 2, 3, 4-tetrahydroisoquinoline (3i) but 3b did not react with this reagent. 3) Bromination of 2e and 2f in methanol respectively gave 3a and 3b. 4) Reaction of 2-cyano-3, 4-dibromo-1-methoxy-1, 2, 3, 4-tetrahydroisoquinoline (3c) with ethanethiol or diethylamine afforded 3-bromo-2-cyano-1, 4-diethylthio-1, 2, 3, 4-tetrahydroisoquinoline (3d) or 4-bromo-2-cyano-3-diethylamino-1-methoxy-1, 2, 3, 4-tetrahydroisoquinoline (3g). 5) Alkaline hydrolysis of 3d and 3i produced 1-ethylthioisoquinoline. Acid hydrolysis of 3b, d, g, i resulted in the formation of isoquinolines with the 4-substituent intact. 6) Alkaline hydrolysis of 3b or 3d in alcohol afforded N-iminoethers, while similar reaction in hydrogen peroxide N-carboxamides.
