5-(4-Chlorophenyl)-<i>N</i>,1-di-<i>o</i>-tolyl-1<i>H</i>-imidazole-2-amine

Abstract

A new 2-amino imidazole derivative, 5-(4-chlorophenyl)-N,1-di-o-tolyl-1H-imidazole-2-amine (3), has been synthesized using a green approach. The reaction was conducted in a ChCl (cholinium chloride)/urea eutectic mixture, which is a nature-inspired and environmentally friendly reaction medium. The proposed reaction mechanism involves the preliminary regioselective alkylation of the Nsp2 of guanidine (2), followed by an intramolecular condensation between the carbonyl moiety and the secondary N′sp3. Finally, a tautomerization/aromatization step furnished the final product (3). Notably, 2-amino imidazole (3) could be isolated in high yield (91%), just by filtration from the DES/water mixture and subsequent crystallization; the remaining ChCl/urea could be recycled, after water removal, for four consecutive reactions without any significant drop in the (3) yield. The product has been fully characterized by 1H, 13C, 2D 1H-13C HSQC, and 2D 1H-13C HMBC NMR; FT-IR spectroscopy; and EI-MS spectrometry.

Keywords

• 2-aminoimidazole
• α-chloroketone
• <i>N</i>,<i>N′</i>-diarylguanidine
• deep eutectic solvent
• solvent recycle
• sustainable synthesis