Simple pyrimidines. Part XIV. The formation and reactions of some derivatives of simple pyrimidinesulphonic acids

Abstract

Appropriate pyrimidine-2-thiones react with chlorine in the presence of potassium hydrogen difluoride to give pyrimidine-2-sulphonyl fluoride (2; R = H, X = F) and its 4-methyl, 5-methyl, and 4,6-dimethyl derivatives. Under mild conditions, these react with ammonia to give the corresponding sulphonamides and with amines to give, for example. N(2)-ethyl-4,6-dimethylpyrimidine-2-sulphonamide (2; R = Me, X = NHEt); also the analogous NN-diethyl-sulphonamide, 2-sulphonomorpholide, NN-di-isopropylsulphonamide, and sulphonohydrazide (converted into its N-isopropylidene derivative). Under more vigorous conditions, the whole sulphur-containing group is displaced to yield, for example, 2-hydrazino-, 2-diethylamino-, 2-azido-, and 2-methoxy-4,6-dimethylpyrimidine; also 2-hydrazino- and 2-azido-5-methylpyrimidine. The reaction rate for each sulphonyl fluoride with methoxide ion depends on the number and position of the C-methyl substituents. 4,6-Dimethylpyrimidine-2-thione (1; R = Me) is oxidized by chloramine to a separable mixture of the corresponding sulphenamide (3; R = S·NH₂) and disulphide; and by aqueous permanganate to the potassium sulphonate. This latter improved method also yields potassium 5-methylpyrimidine-2-sulphonate and the isomeric 4-methylpyrimidine-6-sulphonate. Appropriate sulphonates and sulphonamides react with hydrazine to give 2-hydrazino-4,6- and 4-hydrazino-2,6-dimethylpyrimidine (4). U.v. and ¹H n.m.r. spectra were used to confirm structures and to follow reactions.