Ring closure reaction of 5-hydroxy-pyrido[2,3-d]pyrimidine-2,4,7-triones to benzo[b]pyrimido[4,5-h]1,6-naphthyridine-1,3,6-triones

Article abstract of DOI:10.1002/prac.19963380129

N-Substituted aminouracils (1) react with malonates by cyclocondensation to 5-hydroxy-pyrido[2,3-d]pyrimidine-2,4,7-triones (2), which give with triethylorthoformate and aniline 6-(phenylaminomethylene)-pyrido[2,3-d]pyrimidine-tetraone (3). Halogenation of 2a-d (with R² = Me) with phosphorylchloride leads to 5,7-dichloro-pyrido[2,3-d]pyrimidine-2,4-diones (4) by cleavage of the methyl group at N-8, whereas Vilsmeier reaction of 2 affords 5-chloro-6-formyl derivatives (6), which cyclize with arylamines to give benzo[b]pyrimido[4,5-h]1,6-naphthyridines (9). Compounds 9 were obtained independently by animation of the tosylates 5 to the 5-arylamino compounds 8, and Vilsmeier formylation to yield 9. Johann Ambrosius Barth 1996.