Purine studies. Part IX. Nucleophilic addition of barbituric acids to purines
Purine (1a) and its 2-amino-(1b), 2-oxo-(2a), 2-thioxo-(2b), 8-methylsulphonyl-(1c), 2-amino-8-methylsulphonyl-(1d), 8-trifluoromethyl-(1e), 2-amino-8-trifluoromethyl-(1f), and 2-oxo-8-trifluoromethyl-(2c) derivatives underwent addition of 2-thiobarbituric acid across the 1,6-double bond to give the 1,6-dihydro-6-(4,6-dioxo-2-thioxohexahydropyrimidin-5-yl)purines (4a–f) and (5a, b, and e). Purine and its 2-oxo-, 2-thioxo-, and 2-oxo-8-trifluoromethyl derivatives also reacted with barbituric acid, to give the corresponding trioxohexahydropyrimidin-5-yl purines (4g) and (5d and c), respectively. U.v. and 1H n.m.r. spectra are reported and discussed.