Pyrimidinecarbamates and Thiolcarbamates Derived from Amino- and Oxopyrimidines. II^1,2

An improvement in the synthesis of ethyl pyrimidinecarbamates

“…With the procedure described by Dyer, et al (3), we were able, unlike the authors, to isolate 4-ethoxycarbonylamino-2,6-dimethylpyrimidine (1) from 4-amino-2,6-dimethylpyrimidine a n d ethyl chloroformate. However, the yield was so low (3% with sodium hydroxide in the cold, 18% by reflux in benzene) that the authors understandably judged the method a failure.…”

“…Other procedures have also been described. The chosen pyrimidine can be reacted with ethyl pyrocarbonate in ethanol (3). We have reproduced the experiment with 4-amino-2,6-dimethylpyrimidine and isolated 1.…”

Synthesis of 2‐Oxo‐2H‐[1,2,4]oxadiazolo‐[2,3‐c]pyrimidine‐5‐carbamates

“…The remaining acylation of 6 to 4 was first attempted with methyl chloroformate in various solvents, but this reaction gave only low yields of product owing to the poor nucleophilicity of the amino function. Dyer & Richmond [3] have demonstrated that aminopyrimidines unreactive towards chloroformates can be converted into the corresponding ethyl carbamates with diethyl pyrocarbonate. We solved the problem in a different manner by forming the anion of 6 with sodium hydride, this ion then reacting with 1-methoxycarbonylimidazole [4], a reagent compatible with the solvent.…”