Synthesis
Example 4: Synthesis of 3-[3-(5-chloro-1H-benzimidazol-2-yl)-azetidin-1-yl]-pyrazine-2-carboxylic acid
Step 1. Preparation of 3-hydroxypyrazine-2-carboxylic acid: 3-aminopyrazine-2-carboxylic acid (6.95 g, 0.05 mol) was dissolved in a mixed solution of water (55 mL) and sulfuric acid (55 mL, 3.75 M) and heated to 50 °C. Sodium nitrite solution (18.5 mL, 0.06 mol) was slowly added to this solution and the reaction mixture was subsequently cooled to 12 °C. During the addition, the reaction temperature was maintained in the range of 10-16 °C for 30 minutes. Afterwards, the mixture was heated to boiling over 30 minutes. After completion of the reaction, it was cooled to room temperature and filtered to collect the yellow solid. The resulting solid was dissolved in dilute sodium bicarbonate solution, acidified with 10% hydrochloric acid to precipitate the carboxylic acid product and collected by filtration. The crude product was purified by recrystallization from water to give a yellow-orange crystalline solid (4.1 g, 58% yield).
References
[1] Synthetic Communications, 2010, vol. 40, # 20, p. 2988 - 2999
[2] Patent: WO2011/143129, 2011, A1. Location in patent: Page/Page column 62
[3] Journal of Heterocyclic Chemistry, 1997, vol. 34, # 1, p. 27 - 32
[4] Patent: WO2013/169907, 2013, A1. Location in patent: Page/Page column 44; 45
[5] MedChemComm, 2015, vol. 6, # 7, p. 1311 - 1317
