[CH2:1]([O:3][C:4]([C:6]1[NH:7][N:8]=[C:9]([OH:11])[CH:10]=1)=[O:5])[CH3:2].C([O-])([O-])=O.[K+].[K+].Br[CH2:19][CH2:20][O:21][CH2:22][CH2:23][O:24][CH3:25].O>C(#N)C>[CH2:1]([O:3][C:4]([C:6]1[NH:7][N:8]=[C:9]([O:11][CH2:19][CH2:20][O:21][CH2:22][CH2:23][O:24][CH3:25])[CH:10]=1)=[O:5])[CH3:2]To a mixture of 3.4 g 5-Hydroxy-2H-pyrazole-3-carboxylic acid ethyl ester and 3 g K2CO3 in 50 ml acetonitrile, 4 g 1-(2-Bromo-ethoxy)-2-methoxy-ethane were added. After stirring for 1 h at RT the reaction was heated to 50° C. for 4 h. Then 50 ml of water were added and the mixture was extracted with DCM (3×100 ml). The combined organic layers were dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified by chromatography on silica eluting with a DCM/MeOH gradient. Yield: 1 g.
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