[C:1]([O-])(=O)[CH3:2].[NH2:5][CH:6]1[CH2:15][C:14]2[C:9](=[C:10]([F:18])[CH:11]=[CH:12][C:13]=2[O:16][CH3:17])[O:8][CH2:7]1.[CH:19](=O)[CH2:20][CH3:21].[Na].[CH3:24]O>O>[CH2:19]([N:5]([CH2:24][CH2:1][CH3:2])[CH:6]1[CH2:15][C:14]2[C:9](=[C:10]([F:18])[CH:11]=[CH:12][C:13]=2[O:16][CH3:17])[O:8][CH2:7]1)[CH2:20][CH3:21]In a round-bottom flask equipped with a magnetic stirrer were placed the crude acetate of 3-amino-8-fluoro-5-methoxychroman (1.18 g; approx. 3.9 mmol) from above, dry methanol (10 mL), propanal (2.8 mL; 39 mmol), glacial acid (pH 3-4) and sodium boronhydride (0.25 g; 3.9 mmol) but with no molecular sieves. The reaction mixture was stirred under nitrogen at room temperature for 1 h. The solution was filtered through Celite and the solvent was evaporated to leave a liquid residue which was diluted with water (25 mL) and extracted with ether (2×100 mL) after adjusting pH to 10-11 with 5M sodium hydroxide. The collected ether phases were dried (K2CO3), filtered and concentrated in vacuo.
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