[H-].[Na+].[C:3](Cl)(=[O:6])[CH2:4][CH3:5].[OH2:8].S(=O)(=O)(O)O.C[CH2:15][O:16][CH2:17][CH3:18]>>[CH3:15][O:16][C:17]([CH:18]([C:3](=[O:6])[CH2:4][CH3:5])[C:3](=[O:6])[CH2:4][CH3:5])=[O:8]A solution of 6.5 g (50 mmol) of methyl propionyl acetate in 100 mL of ether was treated with 1.19 g (50 mmol) of sodium hydride and the mixture was stirred for 2 hours. The mixture was then cooled to 5° C. and 6.93 g (6.51 mL. 75 mmol) of propionyl chloride was added dropwise over 5 minutes. The reaction mixture was stirred overnight at room temperature and then poured into cold water. This mixture was acidified with sulfuric acid and the product was extracted into ether, washed with water and dried. Evaporation gave the desired product, sufficiently pure for use in the following reaction, in 88% yield. 1H-NMR (CDCl3) δ 1.08 (6H, t, J=7), 2.58 (4H, q, J=7), 3.66 (1H, s), 3.74 (3H, s).
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