Pyrimidines. Part III. The reduction of pyrimidines with complex metal hydrides to give 1,6-dihydropyrimidines

Abstract

A number of ethyl 4-substituted-2-methylthiopyrimidine-5-carboxylates in which the 4-substituent is CH:NOH (II), CN (V), Me (VI), Cl (VII), or OH (VIII), and also ethyl 4-acetamido-2-hydroxypyrimidine-5-carboxylate (XLI), were found to be reduced by complex metal hydrides to give 1,6-dihydropyrimidines. The structure of these products was established by ¹H n.m.r. spectoscopy. However, when ethyl4-methyl-2-methylthiopyrimidine-5-carboxylate (VI) was treated with lithium aluminium hydride at a lower temperature (–70°), preferential reduction of the ester group occurred to give the 5-hydroxymethyl derivative (XVII) together with a small amount of 4,5-dimethyl-2-methylthiopyrimidine (XX). Treatment of ethyl 4-hydrazino-2-methylthiopyrimidine-5-carboxylate (IV) and of ethyl 4-methylamino-2-methylthiopyrimidine-5-carboxylate (III) with lithium aluminium hydride readily gave the corresponding 5-hydroxymethyl derivatives.