2,4,5- -pyrimidine trione, 6-Hydroxy

The amidation of one of the ester functions of diethyl malonate by 5-amino-l,3-dimethyluracil requires fusion at 200 C. At that temperature the initial product readily partially cyclizes by intramolecular acylation to yield 8-hydroxy-l,3-dimethylpyrido[3,2-t/]pyrimidine-2,4,6(1 HfH, 5//)-trione (3) 443... 

Pyrimidines 73 with dinucleophiles, such as 2-amino-pyridine, 1,3-dimethylbarbituric acid, 5,5-dimethylcyclohexa-l,3-dione and 4-hydroxy-6-methyl-pyran-2(lH)-one, were carried out in boiling acetic acid formed 4H-pyrido[l,2-fl]pyrimidin-4-one (76), lH-pyrano[2,3-d]pyrimidine-2,4,7(3H)-trione (77), 6H-chromene-2,5-dione (78) and pyrano[4,5-b]pyran-2,5-dione (79) in 30%, 67%, 56% and 73% yields, respectively (Scheme 26). 

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