Synthesis of 2-imidazolines derivatives by microwave irradiation

The synthesis of 2-imidazoline is mainly based on cyclization from nitriles and ethylenediamine with different catalysts.1,2 Our research group has synthesized 1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazoles 1(a-j) and 5-amino-1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazoles 2(a-j) using carbon disulfide under reflux with a long reaction time (methods A and B)3. In the search for new methodologies, we investigated the synthesis of 1(a-j) and 2(a-j). The first step to get 1(a-j) was the aprotic deamination of 3(a-j) with t-butyl nitrite and tetrahydrofuran, under reflux for 2 hours.4 Then, the targets 1(a-j) and 2(a-j) were obtained by microwave irradiation, methods C and D, respectively, with a shorter reaction time and milder reaction conditions. The compounds were characterized by proton and carbon Nuclear Magnetic Resonance (1H and 13C NMR), Mass Spectrometry (MS) and Fourier-transform Infrared (FT-IR).