Studies on Pyrimidine Derivatives. XXXVI. Reaction of 6-Substituted 2,4-Dimethylpyrimidines with Benzaldehyde in the Presence of Zinc Chloride

The condensation of 2,4 (2,6)-dimethylpyrimidines (7a-c), but not 6-methoxy-2,4-dimethylpyrimidine (7d), with benzaldehyde in the presence of zinc chloride occurred at the 4 (6)-methyl group predominantly. In contrast, the reaction of 7d under the same conditions gave 6-methoxy-4-methyl-2-styrylpyrimidine (17) as the main product. Similar site-selectivity in the oxidation of the dimethylpyrimidines with selenium dioxide was found.