Benzo (f) furo (3,4-c) (2,7) naphthyridines from furo (3,4-b) pyridines

Görlitzer, K.; Bartke, U.

Die Pharmazie 57(12): 804-807


ISSN/ISBN: 0031-7144
PMID: 12561239
Document Number: 6229
The pyridines 5, obtained by dehydrogenation of the 4-(2-nitrophenyl)-1,4-dihydropyridine lactones 4, give the tetracycles 6 and 7 by reduction of the nitro group with zinc/ammonium chloride followed by ring closure. Irradiation of the compounds 4 with UV-A light leads to the 4-(2-nitrosophenyl)pyridines 8. During the reaction of 8 with conc. hydrochloric acid the nitroso group cyclizes with the 5-acyl group yielding the chloro substituted tetracycles 9 and 10. The hydroxamic acids 6 and 9 are deoxygenated by phosphorus trichloride to yield the lactames 11, while O-acetylation with acetic anhydride affords 12. Phosphorus trichloride reduces the N-oxides 7 and 10 to the bases 13. Using the reaction with acetic anhydride the acetates 14 are formed by Boekelheide-transformation. Alcaline saponification of 14 gives the alcohols 15.

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Benzo(f)furo(3,4-c)(2,7)naphthyridines from furo(3,4-b)pyridines