Efficient and environmentally friendly synthesis of 2-amino-imidazole

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Preparation of 2-amino-imidazole-hemisulfate 3:88.74 g O-Methyl-isourea-hemisulfate was weighed into the reaction vessel. Under inert atmosphere (nitrogen) 150 ml deionised water and 109.2 2-amino-acetaldehyde-diethylacetale were added and the reaction mixture was stirred for 4 h at 50°C. TLC control showed complete transformation. The reaction mixture was then cooled to 20°C and 7 ml concentrated sulphuric acid were added (pH 2 and 5). The mixture was heated to 100°C and stirred for 2 h at this temperature. TLC control showed complete transformation. The reaction mixture was cooled to 20°C and slowly dropped over a 1 h period at 0–5°C into 3000 ml ice cold ethanol. The suspension was stirred for an additional hour at 0–5°C. The suspension was filtered off and washed twice with 50 ml ice-cold ethanol. The product was dried at 40°C in a vacuum drying oven. Yield: 84.87 g white crystals (86 %). All spectroscopic and physicochemical data were identical to the values reported in the literature: 1H NMR (400 MHz, D2O): 6.8 (s, 2H). Mass spectrum: ESMS m/z (fragment): 84 (M++1), 83 (M+). IR: (KBr) 3150, 3000, 2750, 1680, 1100.