2-METHOXY-PYRIMIDINES AND 2-(METHYLTHIO)PYRIMIDINES

O-Methylisourea hydrochloride reacts with 2,4-pentanedione and 1,1,1-trifluoro-2,4-pentanedione in boiling ethanol to yield 2-hydroxy-4,6-dimethylpyrimidine hydrochloride and 2-hydroxy-4-methyl-6-(trifluoromethyl)pyrimidine hydrochloride under exchange of the methoxy group. The methoxy group is retained in the synthesis of 2-methoxy-4,6-dimethylpyrimidine and 4-ethyl-2-methoxy-6-methyl-pyrimidine accomplished in an alkaline medium at room temperature. Reaction of S-methylisothiourea sulfate with 2,4-pentanedione and 2,4-hexanedione under the same condition leads to the formation of 4,6-dimethyl-2-(methylthio)pyrimidine and 4-ethyl-6-methyl-2-(methylthio)pyrimidine. In the synthesis of 4,6-diethyl-2-methoxypyrimidine and 4,6-diethyl-2-(methylthio)pyrimidine starting from 3,5-heptaredione, the carbinol amines 5-(2-methyl-1-isoureido)-3-hepten-3, 5-diol and 5-(2-methyl-1-isothioureido)-3-hepten-3,5-diol are isolated as intermediates.