REACTION OF GUANIDINES WITH ALPHA-DIKETONES - SYNTHESES OF "4,5-DISUBSTITUTED-2-AMINOIMIDAZOLES AND 2,6-UNSYMMETRICALLY SUBSTITUTED IMIDAZO[4,5-D]IMIDAZOLES

2-Amino-4, 5-diaryl-4-hydroxy-4H-imidazoles were obtained by the reaction of substituted benzils with guanidine in methanol at room temperature. Catalytic hydrogenation of the 4-hydroxy-4H-imidazoles produced 2-amino-4, 5-diarylimidazoles in excellent yields. In the case of l-phenyl-l, 2-propanedione and butane-2, 3-dione, the intermediate 4-hydroxy-4H-imidazoles could not be isolated and the reaction mixtures were hydrogenated directly to yield the corresponding 2-aminoimidazoles. 1, 1-Dimethylguanidine and benzils also produced the corresponding 4H-imidazoles in excellent yields. These compounds were quantitatively converted to 2-(dimethylamino)-5, 5-diar-ylimidazoiin-4-ones by heating. l-Amidino-3, 5-dimethylpyrazole did not give the corresponding 4H-imidazoles, but produced the 2, 6-unsymmetrically substituted imidazo[4, 5-d]imidazoles. Probable mechanisms for the formation of these products are discussed. © 1979, American Chemical Society. All rights reserved.