11 General procedure for the benzannulation
of acids 6a-i to give
phenols 7a-i:
Acids 6a-i (50
mmoles)were dissolved in acetic anhydride (48 mL, 0.5 mol). To this
solution, anhyd sodium acetate (8.2 g, 0.1 mol) and hydroquinone
(275 mg, 2.5 mmol) were added in one portion. The obtained heterogeneous
mixture was heated at reflux for 2 h under a nitrogen atmosphere. After
cooling to r.t., the acetic anhydride was removed in vacuo and the
residue was treated with ethyl acetate (200 mL) and water (100 mL).
The organic phase was separated, dried (Na2SO4)
and concentrated under reduced pressure. The residue was purified
by chromatography and crystallisation to give phenols derivatives 7a-i.
12 All new compounds were fully characterised.
Selected analytical data:
6f:
Anal. Calcd for C17H18O6: C, 64.14;
H, 5.70. Found: C, 63.98; H, 5.72. Mp 135-136 °C
(ethyl acetate); 1H NMR (250 MHz, CDCl3) δ 1.30
(3 H, t, J = 7.2 Hz), 3.70 (2
H, s), 3.88 (3 H, s), 3.90 (3 H, s), 4.25 (2 H, q, J = 7.2
Hz), 6.82 (1 H, d, J = 8.5 Hz),
6.95 (1 H, d, J = 1.7 Hz), 7.04
(1 H, s), 7.10 (1 H, dd, J = 8.5,
1.7 Hz); EI-MS m/z 319 (M+ + 1),
318 (M+), 289, 273, 259, 245, 229, 217, 214,
201, 185, 151, 128, 88; FT-IR(nujol): (cm-1)
766, 807, 860, 1036, 1054, 1212, 1247, 1281, 1515, 1594, 1618, 1702,
2187.
6i: Anal. Calcd for C13H12O4S:
C, 59.08; H, 4.58; S, 12.13. Found: C, 59.15; H, 4.60; S, 12.20.
Mp 92 °C (hexane-ethyl acetate); 1H
NMR (250 MHz, CDCl3) δ 1.30 (3 H, t, J = 7.1 Hz), 3.68 (2 H, s),
4.25 (2 H, q, J = 7.1 Hz), 7.02
(1 H, s), 7.14 (1 H, dd, J = 5,
1 Hz), 7.30 (1 H, dd, J = 5,
3 Hz), 7.56 (1 H, dd, J = 3,
1 Hz); EI-MS m/z 264 (M+),
220, 205, 191, 163, 147, 135, 111, 83; FT-IR(nujol): (cm-1)
763, 811, 1041, 1203, 1288, 1421, 1619, 1709, 2195.
7f: Anal. Calcd for C21H22O8:
C, 62.68; H 5.51. Found: C, 62.90; H, 5.55. Mp 109-110 °C
(hexane-ethyl acetate);
1H
NMR (250 MHz, CDCl3) δ 1.39 (3 H, t, J = 7.1 Hz), 2.02 (6 H, s),
3.85 (3 H, s), 3.92 (3 H, s), 4.39 (2 H, q, J = 7.1
Hz), 6.77-6.93 (3 H, m), 7.72 (2 H, s); EI-MS m/z 402 (M+),
360, 343, 318, 303, 273, 244, 214, 199, 183, 157, 131, 115, 95; FT-IR(nujol):
(cm-1) 758, 862, 911, 1030, 1200, 1227,
1258, 1309, 1523, 1586, 1605, 1719, 1770.
7i:
Anal. Calcd for C17H16O6S: C, 58.61;
H 4.63; S, 9.20. Found: C, 58.50; H, 4.65; S, 9.25. Mp 100-101 °C
(hexane-ethyl acetate); 1H NMR (250
MHz, CDCl3) δ 1.38 (3 H, t,
J = 7.1
Hz), 2.08 (6 H, s), 4.38 (2 H, q, J = 7.1
Hz), 7.11 (1 H, dd, J = 4.3,
2 Hz), 7.34-7.39 (2 H, m), 7.72 (2 H, s); EI-MS m/z 348 (M+),
306, 289, 264, 250, 236, 219, 192, 163, 134, 111, 91; FT-IR(nujol):
(cm-1) 756, 868, 1043, 1198, 1208,
1307, 1562, 1719, 1768.
