[NH:1]1[C:5]([C:6]([O:8][CH3:9])=[O:7])=[CH:4][CH:3]=[N:2]1.C(=O)([O-])[O-].[Cs+].[Cs+].I[CH:17]([CH3:19])[CH3:18]>C(#N)C>[CH3:18][CH:17]([N:1]1[C:5]([C:6]([O:8][CH3:9])=[O:7])=[CH:4][CH:3]=[N:2]1)[CH3:19]To a solution of methyl 1H-pyrazole-5-carboxylate (0.6 g) (available from Fluorochem), in acetonitrile (50 ml) was added cesium carbonate (1.55 g) followed by 2-iodopropane (0.476 ml) and the mixture stirred at 20° C. for 18 h. The solvent was removed in vacuo and the residue was partitioned between water (20 ml) and DCM (20 ml) and separated by hydrophobic frit. Purification by chromatography on silica gel (50 g silica), eluting with a gradient of 0-100% ethyl acetate in cyclohexane gave methyl 1-(1-methylethyl)-1H-pyrazole-5-carboxylate (0.24 g) as a colourless oil.
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