173530-73-9

Example 3A Synthesis of ethyl 8-hydroxy-2-methylimidazo[1,2-a]pyridine-3-carboxylate: 31.45 g (101.3 mmol) of ethyl 8-(benzyloxy)-2-methylimidazo[1,2-a]pyridine-3-carboxylate was dissolved in 2 L of ethyl acetate and 3.15 g of 10% Pd/C catalyst was added. The mixture was stirred at room temperature and atmospheric pressure for 5 hours in a hydrogen atmosphere. Upon completion of the reaction, the mixture was filtered through diatomaceous earth and the filter cake was washed well with ethyl acetate/methanol (volume ratio not specified). The filtrates were combined and concentrated to dryness under reduced pressure to give 21.94 g ethyl 8-hydroxy-2-methylimidazo[1,2-a]pyridine-3-carboxylate in 98% yield and 99% purity. The product was analyzed by LC-MS (Method 1): retention time (Rt) = 0.61 min, mass spectrum (ESpos): m/z = 221 [M + H]+. 1H NMR (400 MHz, DMSO-d6) δ: 1.36 (t, 3H), 2.60 (s, 3H), 4.36 (q, 2H), 6.78 (d, 1H), 6.98 (t , 1H), 8.73 (d, 1H), 10.60 (br s, 1H).

[1] Patent: US2014/128386, 2014, A1. Location in patent: Paragraph 0994; 0995; 0996; 0997; 0997
[2] Patent: US2017/57954, 2017, A1. Location in patent: Paragraph 0625; 0626; 0627; 0628; 0629
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[4] Patent: US2017/217954, 2017, A1