[CH3:1][C:2]1[CH:6]=[C:5]([CH2:7][C:8]([O:10][CH3:11])=[O:9])[O:4][N:3]=1.[H-].[Na+].Br[CH2:15][CH2:16]Br.C(=O)(O)[O-].[Na+]>CN(C)C=O>[CH3:1][C:2]1[CH:6]=[C:5]([C:7]2([C:8]([O:10][CH3:11])=[O:9])[CH2:16][CH2:15]2)[O:4][N:3]=1
Into a 15 mL round bottom flask was added methyl 2-(3-methylisoxazol-5-yl)acetate (250 mg, 1.61 mmol) dissolved in N,N-dimethylformamide (7 mL) followed by addition of sodium hydride (60% suspension in mineral oil, 322 mg, 8.06 mmol). The mixture was stirred at room temperature for 15 minutes. 1,2-Dibromoethane (417 μL, 4.83 mmol) was added dropwise. The reaction mixture was stirred at room temperature for 18 h. A saturated aqueous solution of sodium bicarbonate was added to the mixture and it was extracted with dichloromethane (3×). The combined organics were washed with brine, dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was dissolved in dichloromethane (1.5 mL) and washed (3×) with an aqueous (10%) lithium chloride solution to remove residues of N,N-dimethylformamide. The organics were dried over sodium sulfate, decanted and concentrated under reduced pressure to afford methyl 1-(3-methylisoxazol-5-yl)cyclopropanecarboxylate MS (ES+) (M+H) 182.0; LCMS retention time: 2.53 minutes (Method L). The material was used for the next step without further purification.
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