C(O[C:4]([O:13]CC)([CH3:12])[CH2:5][CH2:6][C:7]([O:9][CH2:10][CH3:11])=[O:8])C.[CH:16](OCC)=[O:17].[Na].O>C1C=CC=CC=1>[CH:16]([CH:6]([CH2:5][C:4]([CH3:12])=[O:13])[C:7]([O:9][CH2:10][CH3:11])=[O:8])=[O:17]A mixture of 106.3 g (0.489 mol) of ethyl 4,4-diethoxypentanoate and 80 ml (73.6 g, 0.99 mol) of ethyl formate was added dropwise to a vigorously stirred suspension of 12.7 g (0.55 gram atom) of sodium (shavings) in 300 ml of anhydrous benzene at 10-15° C. over 3 h. Stirring was continued for a further 3 h, and the reaction mixture was left to stand overnight. 250 ml of water were added with vigorous stirring, and this was continued for a further 15 min. The water layer was separated off, and the benzene layer was extracted with 70 ml of water. The combined aqueous extracts were acidified to pH 2 and extracted with ethyl acetate (5×50 ml), and the organic extracts were dried over calcium chloride.
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