Toluene (40 mL) and trifluoroacetic acid (650 μL, 8.36 mmol, 10.0 equiv) were added via syringe to a flask charged with ketoguanidine 75 (549 mg, 0.836 mmol, 1 equiv) and the resulting mixture was heated to 75° C. After 16 h, the reaction mixture was allowed to cool to 23° C. and was concentrated under reduced pressure. Water (20 mL) and trifluoroacetic acid (650 μL, 8.36 mmol, 10.0 equiv) were added via syringe to the residue and the resulting mixture was heated to 100° C. After 45 h, the reaction mixture was allowed to cool to 23° C. and was concentrated under reduced pressure to give 2-aminoimidazole 76 (375 mg, 100%) as a brown solid. 1H NMR (500 MHz, CD3OD, 21° C.): δ 6.49 (s, 2H), 2.53 (app-t, J=6.5 Hz, 4H), 1.65 (app-t, J=7.1 Hz, 4H). 13C NMR (125.8 MHz, CD3OD, 21° C.): δ 162.6, 148.8, 128.8, 109.8, 101.4, 28.7, 25.2. FTIR (neat) cm−1: 3179 (br-s), 2361 (w), 1702 (s), 1442 (m), 1205 (s), 1134 (s), 845 (m), 723 (m). HRMS (ESI) (m/z): calc'd for C10H17N6, [M+H]+: 221.1509, found: 221.1512.
