N#N.C([O:5][C:6]([C:8]1[N:9]=[C:10]([CH2:13][N:14]2[CH:18]=[C:17]([Br:19])[CH:16]=[N:15]2)[O:11][CH:12]=1)=[O:7])C.[OH-].[Na+]>C1COCC1.Cl>[Br:19][C:17]1[CH:16]=[N:15][N:14]([CH2:13][C:10]2[O:11][CH:12]=[C:8]([C:6]([OH:7])=[O:5])[N:9]=2)[CH:18]=1In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), a solution of 2-(4-bromo-pyrazol-1-ylmethyl)-oxazole-4-carboxylic acid ethyl ester (153 mg, 0.51 mmol) in THF (5.0 mL) was treated at rt with 1N NaOH (2.5 mL, 2.5 mmol) and the reaction mixture was stirred for 1 h at rt. The reaction mixture was poured in 1N HCl and extracted with EA. The org. extracts were dried over MgSO4, filtered, and the solvent was removed under reduced pressure to give the crude 2-(4-bromo-pyrazol-1-ylmethyl)-oxazole-4-carboxylic acid as a pale yellow solid. LC-MS-conditions 02: tR=0.72 min, [M+H]+=271.89.
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