N(C(OC(C)(C)C)=O)=NC(OC(C)(C)C)=O.[CH2:17]([O:19][C:20]([C:22]1[NH:23][N:24]=[C:25]([CH2:27][O:28][C:29]2[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=2)[CH:26]=1)=[O:21])[CH3:18].[Br:35][CH2:36][CH2:37]O.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1>C1COCC1>[CH2:17]([O:19][C:20]([C:22]1[N:23]([CH2:37][CH2:36][Br:35])[N:24]=[C:25]([CH2:27][O:28][C:29]2[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=2)[CH:26]=1)=[O:21])[CH3:18]Di-tert-butyl azodicarboxylate (1.68 g, 7.30 mmol) was added portionwise to a stirred solution of 5-phenoxymethyl-2H-pyrazole-3-carboxylic acid ethyl ester (1.0 g, 4.06 mmol), 2-bromoethanol (0.58 mL, 8.12 mmol) and triphenylphosphine (1.92 g, 7.30 mmol) in THF (24.5 mL) at 0° C. The mixture was stirred at 120° C. for 30 minutes under microwave irradiation and then the solvent was evaporated in vacuo. The crude product was purified by flash column chromatography (silica; DCM). The desired fractions were collected and concentrated in vacuo to yield 2-(2-bromoethyl)-5-phenoxymethyl-2H-pyrazole-3-carboxylic acid ethyl ester (1.08 g, 71% yield) as a yellow oil.
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