| Summary: | A synthesis of hitherto unknown heterocyclic system 1(5)H-1,5-diazacycl[3.3.2]azine-2,4-dione (5) is presented. The cyclocondensation of 2,6-diaminopyridine (1) with maleic anhydride yielded (5-amino-2-oxo-2,3-dihydroimidazo[1,2-a]pyridin-3-yl)acetic acid (2), which was converted to methyl (5-amino-2-oxo-2,3-dihydroimidazo[1,2-a]pyridin-3-yl) acetate hydrochloride (3). The ester (3) upon treatment with sodium carbonate solution underwent intramolecular cyclization to 2a,3-dihydro-1(5)H-1,5-diazacycl[3.3.2]azine-2,4-dione (4), which was oxidized in alkaline condition to provide 5.
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