Diethyl Oxalate → Ethyl 3-methyl-2,4-dioxohexanoate

LHMDS solution (35.7 mL, 35.7 mmol, 1M in hexanes) was added to 200 mL of diethyl ether and the mixture was cooled to −78° C. 3-Pentanone (3.8 mL, 35.7 mmol) dissolved in 50 mL of ether was added dropwise, and the resulting mixture was stirred at −78° C. for 1 h. Diethyl oxalate (5.3 mL, 39.3 mmol) was added dropwise, and the cooling bath was removed and the mixture was allowed to come to room temperature. After the mixture was stirred for 16 h, the resulting precipitate was isolated by filtration. The solid was partitioned between CH2Cl2 (150 mL) and 1M hydrochloric acid (100 mL), and the aqueous layer was extracted with additional CH2Cl2. The combined organic layer was dried over MgSO4 and concentrated to give 6.37 g of the title compound. MS: (−) m/z 185.28 (M−1).