C[C:2]([CH3:5])([O-:4])C.[Na+].[O:7]1[C:11]2[CH:12]=[CH:13][C:14]([CH:16]=O)=[CH:15][C:10]=2[CH2:9][CH2:8]1.[C:18](O)(=[O:20])[CH3:19].O>C1(C)C=CC=CC=1>[O:7]1[C:11]2[CH:12]=[CH:13][C:14](/[CH:16]=[CH:19]/[C:18]([O:4][CH2:2][CH3:5])=[O:20])=[CH:15][C:10]=2[CH2:9][CH2:8]1To an ice-cooled suspension of sodium t-butoxide (90.4 g, 941 mmols) in toluene (1 L) was added dropwise triethyl phosphonoacetate (211.0 g, 941 mmols) followed by 2,3-dihydrobenzofuran-5-carbaldehyde (115.9 g 782 mmols). The mixture was stirred for 1 hour and then acetic acid (12 g, 200 mmols) and water (604 mL) was added. The separated organic layer was washed with water (525 mL) followed by a saturated aqueous solution of sodium bicarbonate (263 mL) and concentrated under reduced pressure. Methanol (525 mL) and water (525 mL) were added to the residue and the mixture was stirred for 30 minutes. Crystals precipitated were collected by filtration to obtain 161.2 g (yield: 94%) of the title compound.
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