Synthesis
General procedure for the synthesis of oxazole-5-carboxylic acid from ethyl oxazole-5-carboxylate: an aqueous solution of lithium hydroxide monohydrate (124.5 kg, prepared by dissolving 49.44 kg of lithium hydroxide monohydrate in 319 kg of water, 398 mol) was slowly added to a solution of ethyl oxazole-5-carboxylate (54 kg, 382.7 mol) in water (54 kg), the reaction The temperature was kept below 25°C during the reaction. the reaction mixture was stirred for 6.5 h and then concentrated. Subsequently, an aqueous HCl solution (64.8 kg) was slowly added while keeping the temperature below 25°C. The mixture was cooled to 5°C and maintained for 1 h to promote crystallization. The crystalline product was collected by filtration, washed sequentially with cold water (88 kg) and isopropanol (171 kg) and finally dried under vacuum at 50 °C to give oxazole-5-carboxylic acid (37.88 kg, 87% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 13.68 (br.s, 1H), 8.59 (s, 1H), 7.88 (s, 1H).
References
[1] Patent: WO2016/193255, 2016, A1. Location in patent: Page/Page column 21
[2] Patent: WO2018/29126, 2018, A1. Location in patent: Page/Page column 49
