Ring transformations in reactions of heterocyclic compounds with nucleophiles (VIII). Conversion of pyrimidines into isoxazoles

Abstract

Abstract When pyrimidine, 1‐methylpyrimidinium methosulfate, 1,3‐diethylpyrimidinium tetrafluoroborate or pyrimidine N ‐oxide is reacted with hydroxylamine hydrochloride, isoxazole is formed in a good yield. On reaction of 4,6‐dimethylpyrimidine and its corresponding N ‐oxide with the same reagent 3,5‐dimethylisoxazole is obtained. Similarly, from 6‐methyl‐4‐phenylpyrimidine 1‐oxide 3‐methyl‐5‐phenylisoxazole is formed. It has been found by 15 N‐labelling experiments that the NO moiety of the isoxazole ring originates from the hydroxylamine and not from the magnified image function of the pyrimidine N ‐oxide.