Studies on nitrogen-containing heterocyclic compounds. XXXI. Synthesis and reactivities of 2-bromobenzo[f]quinoline and its related compounds (author's transl)

Abstract

Application of cyanogen bromide to benzo [f] quinoline (3) in methanol, followed by the application of bromine and sodium carbonate gave 2-bromo-4-cyano-1, 3-dimethyl-1, 2, 3, 4-tetrahydrobenzo [f] quinoline (8a) in a good yield. Hydrolysis of 8 resulted in quantitative formation of 2-bromobenzo [f] quinoline (5), which formed 2-aminobenzo [f]-quinoline (9) by the action of potassium amide in liquid ammonia or 3 by the action of stannous chloride. 2-Bromo-3-cyanobenzo [f] quinoline (15), obtained from 2-bromobenzo-[f] quinoline N-oxide (16) by the application of benzoyl chloride in the presence of potassium cyanide, formed 2-bromo-3-cyanobenzo [f] quinoline (19) by the action of stannous chloride. 19 was also obtained by the application of benzoyl chloride to benzo [f] quinoline N-oxide (17) in the presence of potassium cyanide. 15 was also obtained by debenzoylation of 4-benzoyl-2-bromo-3-cyano-3, 4-dihydrobenzo [f] quinoline (14). Examination of the reactivity of 8a indicated that methanol and water easily added to the N-C≡N group in the presence of a base. Benzo [h] quinoline (4) was similarly derived to 3, x-dibromobenzo [h] quinoline (21) via 3, x-dibromo-1-cyano-2, 4-dimethoxy-1, 2, 3, 4-tetrahydrobenzo [h] quinoline (20) and its hydrolysis. Application of cyanogen bromide to 4, 6-phenanthroline (22) in methanol gave 6-cyano-5-methoxy-5, 6-dihydro-4, 6-phenanthroline (23), and 2-bromo-4, 6-phenanthroline (24) could not be obtained.