[N+](=[C:3]([C:9](=[O:15])[CH2:10][CH2:11][CH:12]([CH3:14])[CH3:13])[C:4]([O:6][CH2:7][CH3:8])=[O:5])=[N-].Cl>C(Cl)Cl.C([O-])(=O)C.[Rh+3].C([O-])(=O)C.C([O-])(=O)C>[CH3:13][C:12]1([CH3:14])[CH2:11][CH2:10][C:9](=[O:15])[CH:3]1[C:4]([O:6][CH2:7][CH3:8])=[O:5]Rhodium acetate (170 mg) was added to a solution of ethyl 2-diazo-6-methyl-3-oxoheptanoate (0.5 g) in DCM (80 mL). A solution of ethyl 2-diazo-6-methyl-3-oxoheptanoate (7.652 g) in DCM (50 mL) was added in portions. The mixture was stirred at room temperature for 1 hour. 1N HCl (100 mL) was added. The organic phase was separated. The aqueous phase was extracted with DCM (100 mL). The combined DCM solutions were dried (Na2SO4). After filtration and concentration, the crude material was purified with flash chromatography to give ethyl 2,2-dimethyl-5-oxocyclopentanecarboxylate (7.54 g). 1H NMR (CDCl3, 400 MHz) δ (ppm): 4.25-4.09 (m, 2H), 2.52-2.37 (m, 2H), 2.03-1.99 (m, 2H), 1.80-1.67 (m, 1H), 1.33-1.26 (m, 9H).
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