[O:1]1[CH2:5][CH2:4][C:3]2[CH:6]=[C:7]([CH:10]=O)[CH:8]=[CH:9][C:2]1=2.[CH3:12][C:13]([CH3:15])=[O:14].[OH-].[Na+].Cl>C(Cl)Cl.O>[O:1]1[C:2]2[CH:9]=[CH:8][C:7](/[CH:10]=[CH:12]/[C:13](=[O:14])[CH3:15])=[CH:6][C:3]=2[CH2:4][CH2:5]1
2,3-Dihydrobenzo[b]furan-5-carboxaldehyde (Aldrich Chemicals) (2 g, 13.5 mmol), acetone (2.73 ml, 37.1 mmol), water (1.35 ml) and 10% NaOH (aq.) (0.34 ml) were added together and the whole stirred at room temperature for 16 h. The yellow solid was redissolved in approx. 15 ml DCM and 2N HCl added to achieve a solution of pH2. Water (10 ml) was added and the organic layer was extracted with DCM (2×20 ml). The aqueous layers were separated, and re-extracted with DCM (2×15 ml). The combined organics were dried (MgSO4) and concentrated in vacuo to a yellow solid which was purified by column chromatography using 15-30% EtOAc in pentane as eluant to provide the title product (2.13 g, 84%); 1HNMR (400 MHz, CDCl3) δ: 2.3 (s, 3H), 3.2 (t, 2H), 4.6 (t, 2H), 6.5 (d, 1H), 6.75 (d, 1H), 7.3 (d, 1H), 7.4 (s, 1H), 7.45 (d, 1H); LRMS: M+H, 189. (ES+).
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