[CH3:1][N:2]1[CH:6]=[C:5]([CH2:7][CH2:8][C:9]([O:11][CH3:12])=[O:10])[CH:4]=[N:3]1.[CH:13](OC)=[O:14].CC([O-])(C)C.[K+]>C1COCC1>[CH:13]([CH:8]([CH2:7][C:5]1[CH:4]=[N:3][N:2]([CH3:1])[CH:6]=1)[C:9]([O:11][CH3:12])=[O:10])=[O:14]A solution of methyl 3-(1-methyl-1H-pyrazol-4-yl)propanoate (18.7 g, 111 mmol) and methyl formate (14.02 g, 233 mmol) in dry THF (20 ml) was added dropwise over 2 h to a stirred, ice-cooled suspension of t-BuOK (31.2 g, 278 mmol) in dry THF (160 ml) under argon. The mixture was then allowed to warm to room temperature and stirred for 16 h. The solvents were removed in vacuo, and the residue was dissolved in water (50 ml). The solution was extracted with ethyl acetate (30 ml×2), and the aqueous phase was neutralized with 1M HCl to pH ˜5. The solid was collected. The filtrate was extracted with ethyl acetate (40 ml×2), dried over Na2SO4, filtered and concentrated in vacuo. The solids were combined to give the title compound as a white solid (9.1 g, 39.8% yield). LCMS: rt=1.05 min, [M+H+]=197
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