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Salts of 4-hydroxypyrimidine and several 2-substituted 4-hydroxypyrimidines were treated with alkyl halides under a variety of reaction conditions. In cation-solvating media, methylation occurred mainly at N-3. Increased N-l methylation was observed in hydrogen-bonding solvents and solvents of lower dielectric constant. Studies in dimethylf ormamide revealed significant steric influences. When the alkyl halide was varied from methyl to ethyl to isopropyl or when the group on the 2 position was varied from hydrogen to methyl to ethyl, alkylation at oxygen increased at the expense of alkylation at N-3. 2-Trifluoromethyl-4-hydroxypyrimidine in dimethylf ormamide reacted with alkyl halides to give mainly 4-alkoxy-2-trifluoromethylpyrimidines.

Bei der Substitution der 4‐Hydroxy‐pyrimidine (Ia)‐(Id) entstehen nebeneinander die isomeren Substitutionsprodukte (III)‐(V), deren Anteile durch die Reagentien bestimmt und in Relation zu diesen diskutiert werden.