85% |
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To a solution of <strong>[185342-88-5]1,3-dibromo-2,4-dimethoxybenzene</strong> (230) (375 mg, 1.27 mmols) in 10 mL of abs. THF, n-BuLi (1.6 M in hexane, 792 μL, 1.27 mmols) was added slowly at -78 C and the mixture was stirred at this temperature for a further 2 h. Subsequently, at -78 C., a -78 C cold solution of 2-naphthalenehyde (495 mg, 3.17 mmols) in 2 mL of abs. THF was added. The reaction mixture was stirred at the same temperature for 1 h and slowly brought to rt overnight. The reaction mixture was washed successively with 4 mL of water, 4 mL of sat. amMonium chloride solution and 30 mL EtOAc. After stirring for 10 min, the organic layer was separated off and the aqueous phase was extracted three times with in each case 10 mL of EtOAc. The combined organic layers were washed with 15 mL sat. sodium chloride solution and then dried over anhydrous magnesium sulfate. The solvent was completely removed in vacuo and the residue was purified by flash chromatography on silica gel (10% EtOAc/PE). The product (404 mg, 1.08 mmols, 85%) was obtained as a colorless oil. Rf: 0.14 (10% EtOAc/PE). 1H NMR (400 MHz, CDCl3) δ = 7.82 - 7.78 (m, 4H), 7.50 - 7.45 (m, 4H), 6.65 (d, 3J = 8.9 Hz, 1H), 6.44 (s, 1H), 3.74 (s, 3H), 3.63 (s, 3H). 13C NMR (101 MHz, CDCl3) δ = 157.57, 155.50, 141.88, 133.28, 132.91, 132.60, 128.10, 127.87, 127.64, 127.31, 126.05, 125.71, 124.42, 123.71, 109.06, 108.83, 69.34, 61.67, 56.17. ESI-MS: m/z = 354.90, 356.90 [(M-H2O)+H]+. HRMS (ESI): calculated for C19H16O2 79Br: m/z = 355.03282 [M+H]+, found: m/z = 355.03317 [M+H]+. calculated for C19H16O2 81Br: m/z = 357.03077 [M+H]+, found: m/z = 357.03049 [M+H]+. |