[Li+].[I-].[CH2:3]([Mg]Br)[CH2:4][CH2:5][CH2:6][CH3:7].Cl[C:11](=[O:17])[C:12]([O:14][CH2:15][CH3:16])=[O:13]>C1COCC1>[O:17]=[C:11]([CH2:3][CH2:4][CH2:5][CH2:6][CH3:7])[C:12]([O:14][CH2:15][CH3:16])=[O:13]To a suspension of LiI (23.61 g, 176.44 mmol) in THF (200 mL) at rt was slowly added Cu2Br2 (25.30 g, 88.22 mmol). A vigorous exothermic reaction occurred, and the mixture was then cooled to −78° C. Pentylmagnesium bromide (2M, 36.76 mL, 88.22 mmol) was slowly added at −78° C., and followed soon after by ethyl chloro(oxo)acetate (10 g, 73.52 mmol). The resulting solution was stirred 10 minutes at −78° C., then quenched by dropwise addition of water. The mixture was allowed to warm to rt, and then the organic phase was separated, dried (MgSO4), and evaporated. Purification by flash chromatography using 9:1 hexane/EtOAc as eluant gave ethyl 2-oxoheptanoate as a colorless oil (3.0 g, 23%). 1NMR (400 MHz, CDCl3) δ 4.33-4.21 (m, 2 H), 2.82 (m, 2 H), 1.63-1.59 (m, 2 H), 1.63-11.19 (m, p H), 0.9-0.83 (m, 3 H), LC-MS m/z 279.21 (MH+), retention time 2.42 min (method 2).
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