N-Aminopyrimidines: The Isomerization of 1-Aminobarbituric Acids to 2-(5-Oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl) Aliphatic Acids

1-Aminobarbituric acid undergoes a facile isomerization in aqueous acid to 2-(5-oxo-4,5-dihydro-l H -l,2,4-triazol-3-yl)acetic acid which in turn can be decarboxylated to give 3-methyl-1 H -1,2,4- triazol-5(4 H )-one. The isomerization reaction is shown to be a general one, adaptable to the synthesis of oxotriazolyl aliphatic acids and their decarboxylated products. A reaction mechanism for the isomerization is proposed.