Further studies of the diazo coupling reactions of pyrimidines

Abstract

6-Arylazo derivatives of the following pyrimidines have been obtained: 2-acetamido-4,5-dihydroxy-, 4-amino-2,5-dihydroxy-, 2,4-diamino-5-hydroxy- and 4-amino-5-hydroxy-2-methyl-pyrimidine. However, some 5-substituted pyrimidines having other electron-releasing groups failed to undergo diazo coupling. 2,4-Dihydroxypyrimidin-5-yl acetate and 2-acetamido-4-hydroxypyrimidin-5-yl acetate lost the 5-acetyl group during the introduction of the arylazo group into the 6-position. However, 2-hydroxy-4,6-dimethylpyrimidin-5-yl acetate undergoes diazo coupling at the 4(6)-methyl substituent without loss of the 5-acetyl group. The mechanisms for these diazo couplings are discussed.