4-Hydroxy-4-methyl-5-tosylhexahydropyrimidin-2-imines: synthesis and different dehydration pathways

Synthesis of 4-hydroxy-4-methyl-5-tosylhexahydropyrimidin-2-imines by reaction of N-cyano-N′-(1-tosylalk-1-yl)guanidines with enolates of tosylacetone was developed. Base-catalyzed dehydration of the obtained pyrimidines gave the expected 6-methyl-5-tosyl-1,2,3,4-tetrahydropyrimidin-2-imines. However, their acid-catalyzed dehydration led to mixtures of the latter compounds and the products of tosyl group migration, 4-tosylmethyl derivatives. This reaction was strongly influenced by the nature of the solvent. Plausible explanations of the obtained data were given.