PYRIMIDINES .1. ACYLATION OF 2-AMINO-4-HYDROXYPYRIMIDINES

The formation of O-acyl and O-sulphonyl derivatives of certain 4(6)-hydroxypyrimidines is promoted by the presence of a bulky substituent at the pyrimidine 2-position, and by the use of an acyl or sulphonyl halide having an appreciable steric requirement. 2-Dialkylamino-4-hydroxypyrimidines undergo O-acylation and O-sulphonylation in good yield regardless of the experimental conditions. 2-Alkylamino-, 2-amino-, and 2-acetylamino-4-hydroxypyrimidines undergo O-acylation with pivaloyl chloride and with aroyl halides, and O-sulphonylation with arylsulphonyl halides; attempts to prepare O-acetyl derivatives of these 4(6)-hydroxy-pyrimidines were unsuccessful, as were attempts to prepare O-methanesulphonyl derivatives of 2-amino-4- hydroxypyrimidines. The reaction of 2-dialkylamino-, 2-alkylamino-, 2-amino-, and 2-acetylamino-4-hydroxypyrimidines with phosphorochloridates and phosphorochloridothioates gives O-phosphoryl derivatives.