[OH:1][C:2]1[C:9]([O:10][CH3:11])=[CH:8][C:7]([O:12][CH3:13])=[CH:6][C:3]=1[CH:4]=[O:5].C([O-])([O-])=O.[K+].[K+].[CH2:20]([O:22][CH:23]([O:26][CH2:27][CH3:28])[CH2:24]Br)[CH3:21]>CN(C=O)C>[CH2:20]([O:22][CH:23]([O:26][CH2:27][CH3:28])[CH2:24][O:1][C:2]1[C:9]([O:10][CH3:11])=[CH:8][C:7]([O:12][CH3:13])=[CH:6][C:3]=1[CH:4]=[O:5])[CH3:21]To a stirred suspension containing 2 (1.1 g, 6.0 mmol) and K2CO3 (1.0 g, 7.2 mmol) in DMF (100 mL), bromoacetaldehyde diethyl acetal (0.93 mL, 6.0 mmol) was added dropwise. The mixture was refluxed for 4 h. After cooling, the precipitate was filtered off and the solvent was evaporated in vacuo. The crude residue was adsorbed on silica gel and purified by flash chromatography, eluting with hexane/EtOAc (4:1) to give 3 (1.2 g, 67%) as a clear oil. 1H NMR (500 MHz, CDCl3): δ: 10.50 (1H, s, CHO), 6.88 (1H, d, J4,6=2.9 Hz, H-6), 6.74 (1H, d, J4,6=2.9 Hz, H-4), 4.83 (1H, t, J4,6=5.3 Hz, CH), 4.14 (2H, d, J4,6=5.3 Hz, CH2), 3.88 (3H, s, OMe), 3.83 (3H, s, OMe), 3.77-3.71) (2H, m, CH2CH3), 3.63-3.58 (2H, m, CH2CH3), 1.24 (6H, t, J=7.1 Hz, 2×CH3).
Wird geladen…
