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59. Ring closure reaction of 5-hydroxy-pyrido[2,3-d]pyrimidin-2,4(1H,3H)diones to benzo[b]pyrimido[4,5-h]1,6-naphthyridine-1,3,6-triones
Khattab A., Dang V. Th., Stadlbauer W., J. Prakt. Chem - Chem. Ztg., 338 (1996), 151-156

Abstract: N-Substituted aminouracils react with malonates by cyclocondensation to 5-hydroxy-pyrido[2,3-d]pyrimidine-2,4,7-triones, which give with triethylorthoformate and aniline 6-(phenylaminomethylene)-pyrido[2,3- d]pyrimidine-tetraone. Halogenation of hydroxycompounds (with R2= Me) with phosphorylchloride leads to 5,7-dichloro-pyrido[2,3-d]pyrimidine-2,4-diones by cleavage of the methyl group at N-8, whereas Vilsmeier reaction of hydroxy compounds affords 5-chloro-6-formyl derivatives, which cyclize with arylamines to give benzo[b]pyrimido[4,5-h]1,6-naphthyridines. These compounds could be obtained independently by amination of the tosylates to the 5-arylamino compounds and Vilsmeier formylation to yield benzo[b]pyrimido[4,5-h]1,6-naphthyridines.


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