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General Experimental Procedure: To a solution of aldehyde (1 mmol), enolizable ketone (1 mmol) and BiOCl (20 mol%) in dry MeCN (4 mL) MeCOCl (2 mmol) was added and the reaction mixture was stirred at r.t. After completion of the reaction (checked by TLC, Table
[1]
) the mixture was diluted with CH2Cl2 and washed with brine solution (10 mL). The aqueous layer was extracted with CH2Cl2 (3 × 5 mL), the pooled organic layer was then washed subsequently with H2O (1 × 6 mL), NaHCO3 (1 × 6 mL) and finally with H2O (1 × 6 mL). The organic layer was dried over Na2SO4, concentrated and the residue was purified by column filtration on silica gel.
10 All products were characterized by NMR, IR spectroscopy and/or elemental analysis and by comparing the physical data with those in the literature.
[4]
The following spectral data are representative:
Compound 21: White crystals [EtOAc-petroleum ether (60-80 °C)]; mp 130 °C. IR (KBr): 3270, 1675, 1640, 1598, 1570, 1525, 1420, 1365, 1250, 1205, 1170, 1020, 990, 830, 800, 700 cm-1. 1H NMR (300 MHz, CDCl3): δ = 2.00 (s, 3 H), 3.31-3.39 (dd, 1 H, J = 5.95, 16.59 Hz), 3.64-3.71 (dd, 1 H, J = 5.28, 16.57 Hz), 3.84 (s, 3 H), 5.53 (m, 1 H), 6.86 (br s, 1 H), 6.89 (br d, 2 H, J = 8.82 Hz), 7.18-7.34 (m, 5 H), 7.88 (br d, 2 H, J = 8.81 Hz). 13C NMR (75 MHz, CDCl3): δ = 23.37, 42.76, 50.02, 55.46, 113.80, 126.41, 127.30, 128.55, 129.66, 130.45, 141.07, 163.77, 169.49, 197.08. Anal. Calcd for C18H19O3N: C, 72.71; H, 6.44; N, 4.71. Found: C, 72.65; H, 6.82; N, 4.67.
Compound 22: White crystals [EtOAc-petroleum ether (60-80 °C)]; mp 194-195 °C. IR (KBr): 3285, 1685, 1635, 1545, 1525, 1400, 1350, 1310, 1290, 1225, 1200, 755, 735, 700, 690 cm-1. 1H NMR (300 MHz, CDCl3): δ = 3.57-3.64 (dd, 1 H, J = 5.38 Hz, 17.45 Hz), 3.87-3.95 (dd, 1 H, J = 4.94, 17.45 Hz), 5.85 (m, 1 H), 7.44-7.62 (m, 7 H), 7.78 (br d, 1 H, J = 7.8 Hz), 7.84-7.93 (m, 5 H), 8.10 (br d, 1 H, J = 8.11 Hz), 8.28 (s, 1 H). 13C NMR (75 MHz, CDCl3): δ = 42.55, 49.63, 121.39, 122.48, 127.11, 128.16, 128.74, 128.89, 129.64, 131.98, 132.89, 133.67, 134.09, 136.21, 143.47, 166.89, 198.63. Anal. Calcd for C22H18N2O4: C, 70.57; H, 4.84; N, 7.48. Found: C, 70.16; H, 4.96; N, 7.23.