Dihalogentriphenylphosphoranes in the synthesis of heterocycles, 29. A simple synthesis of pteridin-4-ones, from methyl-3-amino-2-pyrazinecarboxylate and pyrazino[3,1]oxazin-4-ones

Article abstract of DOI:10.1055/s-1994-25487

Methyl 3-amino-2-pyrazinecarboxylate (3) affords the synthetically useful 3-aroylaminopyrazin-2-carboxylates 5a-f with aroyl chlorides, which are converted with dibromotriphenylphosphorane into 2-arylpyrazino[2,3-d][3,1]oxazin-4-ones 6a-f. Nucleophilic attack at the carbonyl function of these oxazinones results in ring cleaved amides which can be recyclized with dibromotriphenylphosphorane to afford 2-arylpteridin-4-ones 7a-f.