2-Imidazolines. Part 2. Pyrolysis of 1-acyl-4,5-diamino-4,5-dihydroimidazoles: a novel pyrimidine synthesis

Abstract

1-Acyl-2-phenyl-(or methyl-)4,5-diamino-4,5-dihydroimidazoles (1), when heated in refluxing xylene, afford 2,4-disubstituted-5,6-diaminopyrimidines in good yield. The relative position of the substituent at C-2 or C-4 of the pyrimidine ring depends on the basicity of the amino-group and the nature of the substituent at C-2 of the imidazole ring. The mechanism of the ring expansion is discussed.