A Simple Synthesis of 8-Methoxy-1-tetralone
501
C-2), 2.89–2.92 (m, 1H), 3.06–3.12 (2H at C-4), 3.15–3.18 (m, 1H) (H at C3), 3.76 (s, 3H,
OMe), 6.75 (dd, 1H, J = 8 Hz, J = 3 Hz) (H at C-4ꢀ), 6.85 (d, 1H, J = 3 Hz) (H at C-6ꢀ),
7.45 (d, 1H, J = 8 Hz) (H at C-3ꢀ); 13C NMR (MeOD) δ: 176.18 (C-1), 173.84 (COOH),
159.10 (C-5ꢀ), 138.84 (C-1ꢀ), 133.13 (C-3ꢀ), 116.51 (C-6ꢀ), 114.35 (C-2ꢀ), 113.93 (C-4ꢀ),
54.42 (OMe), 41.32 (C-3), 37.39 (C-2), 34.6 (C-4) .
Anal. Calcd for C12H13BrO5: C, 45.42; H, 4.11. Found : C, 45.65; H, 3.99
3-Carboxy-5-bromo-8-methoxy-1-tetralone (3)
A solution of acid 2 (5 g, 15.8 mmol) in sulfuric acid (50 mL) was stirred for 8 hr at room
temperature and then slowly poured on ice. The precipitated solid was collected, washed
with water and dried to afford ketone 3 (2.72 g, 57%) as a white solid, mp.189–190◦C (from
ethanol) which develops a color upon standing at room temperature for a week; IR (cm−1):
3440, 2925, 1728, 1683, 1589, 1466; MS 299 (M+); 220 (M+1 –Br); 1H NMR (acetone-d6):
δ 2.72–2.78 (m, 2H) (H at C-2), 3.11–3.39 (m, 3H) (H at C-4, C-3), 3.81 (s, 3H, OMe), 7.01
(d, 1H, J = 9 Hz) (H at C-7), 7.74 (d, 1H, J = .9 Hz) (H at C-6); 13C NMR (acetone-d6):
δ 192.62 (C-1), 173.54 (C-11), 159.70 (C-8), 142.48 (C-10), 137.46 (C-6), 123.52 (C-9),
114.03 (C-5), 112.60 (C-7), 55.46 (C-12), 41.42 (C-3), 38.22 (C-4), 32.97 (C-2).
Anal. Calcd for C12H11BrO4 : C, 48.16; H, 3.67. Found: C, 47.88; H, 3.85
5-Bromo-8-methoxy-1-tetralone (4)
To the ketone 3 (2 g, 6.7 mmol) dissolved in a mixture of acetone-water (77:26 mL) was
added silver nitrate (20 mg, 0.128 mmol) and heated under reflux for 5 min. To the resulting
deep yellow solution a solution of sodium persulfate (3.18 g, 13.4 mmol) in water (20 mL)
was added, heated under reflux for 20 min. and then extracted with ether. The organic extract
was washed, dried and evaporated to afford a oil which on chromatographic purification
(eluent hexane:ether 8:2) afforded the bromotetralone 4 (1.31 g,77%) as a colorless oil
whose color changes to pale yellow upon standing at room temperature, IR(cm−1): 2933,
1
1712, 1585,1284; MS (m/z): 255 (M+), 241(M+1 -Me); H NMR: δ 2.05–2.37 (m, 2H)
(H at C-3), 2.53–2.74 (m, 2H) (H at C-2), 3.21–3.33 (m, 2H) (H at C-4), 3.91 (s, 3H,
OMe), 6.72 (d, 1H, J = 8 Hz) (H at C-7), 7.64 (d, 1H, J = 8 Hz) (H at C-6); 13C NMR:
δ 206.46 (C-1), 157.43 (C-8), 155.03 (C-10), 138.60 (C-6), 126.14 (C-9), 111.70 (C-5),
111.21 (C-7), 55.99 (C-11), 42.08 (C-2), 35.35 (C-4), 16.55 (C-3) .
Anal. Calcd for C11H11BrO2 : C, 51.76; H, 4.31. Found: C, 52.03; H, 4.13
8-Methoxy-1-tetralone (5)
A solution of the bromotetralone 4 (1 g, 3.9 mmol) in absolute ethanol (10 mL) was
hydrogenated in presence of Pd-C (10%) at room temperature for 24 hr and atmospheric
pressure. Removal of the catalyst and solvent left an oil which on distillation afforded
the tetralone 5 as a colorless oil (670 mg, 97%) (bp. 141–142◦C/0.10 mmHg) (lit.5 bp.
140◦C/0.9 mmHg) which develops a faint yellow color on standing at room temperature for
a week; IR (cm−1): 1674 (CO); MS (m/z): 176 (M +); 1H NMR: δ 2.01–2.07 (m, 2H) (H at
C-3), 2.61 (t, 2H, J = 6 Hz) (H at C-4), 2.89 (t, 2H, J = 6 Hz) (H at C-2), 3.87 (s, 3H, OMe),
6.78 (d, 1H, J = 8.5 Hz) (H at C-5), 6.82 (d, 1H, J = 8 Hz) (H at C-7), 7.38 (dd, 1H, J = 8