50-00-0

88965-00-8

124-40-3

106961-33-5

Step (i): Preparation of N,N-dimethyl-1-(6-methyl-2-(p-tolyl)imidazo[1,2-a]pyridin-3-yl)methylamine (8). Under stirring, 6-methyl-2-(4-methylphenyl)imidazo[1,2-a]pyridine (200 g, 0.92 mol) was dissolved in acetic acid (985 mL). The reaction mixture was cooled to 0-5 °C and 40% aqueous dimethylamine (157 g, 1.39 mol) was slowly added followed by paraformaldehyde (36.11 g, 1.20 mol). The reaction mixture was stirred at 50-55°C for 3-4 hours, followed by removal of acetic acid under reduced pressure. Water (1.5 l) was added, the filtrate was filtered through a diatomaceous earth pad and the filtrate was alkalized to pH 8.0-8.5 by dropwise addition of 30% sodium hydroxide solution. filtration afforded an off-white solid, which was washed sequentially with water (500 ml) and hexane (200 ml). The solid was dried to constant weight in an oven to give 230 g of N,N-dimethyl-1-(6-methyl-2-(p-tolyl)imidazo[1,2-a]pyridin-3-yl)methylamine (8) in 91.6% yield and 93.5% purity. Melting point range: 137.9-141.5 °C. IR spectrum (cm^-1): 2944, 2809, 2761, 1502, 1454, 1389, 1018, 829, 799. 1H NMR (400 MHz, CDCl3): δ 2.25 (s, 6H), 2.36 (s, 3H), 2.40 (s, 3H), 3.84 (s, 2H), 7.04 (dd, J = 9.1 Hz, J = 1.6 Hz, 1H), 7.25 (d, J = 7.9 Hz, 2H), 7.52 (d, J = 9.1 Hz, 1H), 7.69 (d, J = 8.0 Hz, 2H), 8.10 (s, 1H). Mass spectrum (m/z): 280.4 (M + H)+.