Intramolecular Ring Formation of Phenyl Azide and Furan Moieties

Thermal decompositions of methyl 5-[2-(2-azidophenyl) ethyl]-2-furoate (3a), methyl 5-[2-(2-azido-4, 5-methylenedioxyphenyl) ethyl]-2-furoate (3b) and methyl 5-[2-(2-azido-4, 5-dimethoxyphenyl) ethyl]-2-furoate (3c) gave methyl pyrrolo [1, 2-a] quinoline-3-carboxylates (10a-c) ; in the case of 3a, the 4, 5-dihydro product 9 was also obtained. Photochemical decompositions of 3a and 3b in ethanol gave methyl 4, 5-dihydro-1-ethoxypyrrolo [1, 2-a]-quinoline-3-carboxylates (15a, b). In contrast, the cyclization product was not detected from 3c under similar conditions. Methyl 5-(2-azido-4, 5-dimethoxybenzyl)-2-furoate (8) gave 7, 8-dimethoxypyrido-[1, 2-a] indole-1, 2-dione (22) on thermolysis, and on photolysis in ethanol, gave methyl 6, 7-dimethoxy-9H-pyrrolo [1, 2-a] indole-3-carboxylate (23), trans-methyl 3-(6, 7-dimethoxy-3-hydroxy-2-quinolyl) acrylate (25) and 22. The pathways of these of these reactions are discussed.