Synthesis of Dibenzo[c,h][1,6]naphthyridine, [2]Benzopyrano[4,3-c]quinoline and Benzo[i]phenanthridine Analogues of the Quaternary Benzo[c]phenanthridines

All articles of this category Three concise syntheses of the dibenzo[ c , h ][1,6]naphthyridines, [2]benzopyrano[4,3- c ]quinolines and the benzo[ i ]phenanthridines are reported. All methods involve Vilsmeier chemistry, either to generate a 12-methyl-6-oxo-6 H -[2]benzopyrano[4,3- c ]quinolinium salt which after hydrolysis with either ammonia or methanol can ultimately be cyclised to the first two target compounds, whereas the latter can be prepared in one step from 2-(1-pyrrolidino)-3,4-dihydronaphthalene and N -methylformanilide in phosphorus oxychloride. These tetracyclic heteroaromatic ring systems are related to the benzo[ c ]phenanthridines, and form part of our investigations into determining the mechanism of action of this class of compounds as topoisomerase inhibitors. Vilsmeier reaction - quinolines - heterocycles - cyclisations - benzophenanthridines