On the Oxidation of Bridged 1‐Naphthylamine and Aniline Derivatives – Formation of Substituted Quinoline and Benzo[c,d]indole Derivatives

The bridged aniline or 1-naphthylamine derivatives 8–10 react with nitrous acid in the presence of perchloric acid to give the bridged diphenoquinone diiminium salts 12·2 HClO4, 17·2 HClO4, 19·2 HClO4 and 23. The same products are obtained from these substrates upon their reaction with hydrogen peroxide. Upon treatment of the bridged diphenoquinone diiminium salts 12·2 HClO4 and 23 with base, a disproportionation reaction occurs resulting in the formation of the corresponding benzidine derivatives 13 and 26 and, following a multistep process, the quinoline derivatives 15 and 25 are obtained. Analogously, the 1,2-dihydrobenzo[c,d]indole hydroperchlorate 10·HClO4 is transformed into the bridged benzidine derivative 21 and the bis(benzo[c,d]indol-6-yl) hydroperchlorate 20·HClO4. Furthermore, as a result of an oxidation process initiated by the protonated species of the corresponding indaminium salts, condensation of N,N-dimethyl-4-nitrosoaniline (27) with the bridged aniline or naphthylamine derivatives 8a–8c leads to the N′-(6-quinolyl)-substituted N,N-dimethylbenzoquinone bis(iminium) salts 29a–28c rather than the corresponding indaminium salts 28a–28c.