´
M. Witczak and H. Kwiecien
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aqueous sodium bicarbonate and with water and then dried over MgSO4. The
solvent was evaporated and a crude 2-alkylbenzo[b]furan was distilled under
reduced pressure. The following benzo[b]furans have been obtained:
2-Ethylbenzo[b]furan (2a): bp 54–568C/2 Torr; lit.[21] bp 698C/5 Torr.
2-Butylbenzo[b]furan (2b): bp 80–828C/3 Torr; lit.[13] bp 114–1168C/8
Torr.
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2-Ethyl-5-methoxybenzo[b]furan (2c): bp 112–1148C/6 Torr; H NMR
(400 MHz, CDCl3): d 1.29 (3H, t, J ¼ 7.4 Hz, CH3), 2.75 (2H, J ¼ 7.4 Hz,
CH2), 3.79 (3H, s, OCH3), 6.28 (1H, s, aromatic proton), 6.78–6.74 (1H,
J ¼ 8.5, 2.6 Hz, dd, aromatic protons), 6.94 (1H, d, J ¼ 2.6 Hz, 1H,
aromatic proton), 7.27 (1H, d, J ¼ 8.4 Hz, aromatic proton); GC
(t ¼ 13.23 min); MS, m/z (%) ¼ 176-Mþ (70), 161 (100), 146 (10), 131
(4), 103 (6), 77 (9), 63 (4), 39 (2). Anal. calcd. for C11H12O2 (176.22): C,
74.98; H, 6.86; found: C, 74.82; H, 6.97.
2-Ethyl-5-t-butylbenzo[b]furan (2d): bp 115–1168C/8 Torr; 1H NMR
(400 MHz, CDCl3): d 1.30 (3H, t, J ¼ 7.5 Hz, CH3), 2.75 (2H, q,
J ¼ 7.5 Hz, CH2), 1.36 (9H, s, CH3), 6.32 (1H, d, J ¼ 0.6 Hz, aromatic
proton), 7.25–7.33 (2H, m, aromatic protons), 7.47 (1H, d, J ¼ 1.8 Hz,
aromatic proton); GC (t ¼ 14.12 min); MS m/z (%) ¼ 202-Mþ (36), 187
(100), 171 (7), 159 (9), 131 (16), 115 (8), 91 (7), 72 (6), 57 (7), 41 (2), 39
(2). Anal. calcd. for C14H18O (202.29): C, 83.12; H, 8.97; found: C, 83.02;
H, 9.06.
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4,6-Dimethyl-2-ethylbenzo[b]furan (2e): bp 99–1008C/10 Torr; H NMR
(400 MHz, CDCl3): d 1.30 (3H, t, J ¼ 7.5 Hz, CH3), 2.42 (3H, s, CH3), 2.39
(s, 3H, CH3), 2.76 (2H, q, J ¼ 7.5 Hz, CH2), 6.31 (1H, d, J ¼ 0.7 Hz,
aromatic proton), 7.04 (1H, s, aromatic proton), 7.18 (1H, s, aromatic
proton); GC (t ¼ 12.49 min); MS, m/z (%) ¼ 174-Mþ (50), 159 (100), 144
(5), 128 (8), 115 (12), 91 (6), 72 (2), 51 (2), 39 (2). Anal. calcd. for
C12H14O (174.24): C, 82.72; H, 8.10; found: C, 82.65; H, 8.15.
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6,7-Dimethyl-2-ethylbenzo[b]furan (2f): H NMR (400 MHz, CDCl3): d
1.30 (3H, t, J ¼ 7.5 Hz, CH3), 2.39 (3H, s, CH3), 2.46 (3H, s, CH3), 2.76
(2 h, q, J ¼ 7.5 Hz, CH2), 6.31 (1H, d, J ¼ 0.7 Hz, aromatic proton), 7.18
(1H, s, aromatic proton), 7.48 (1H, s, aromatic proton); GC (t ¼ 13.35 min);
MS, m/z (%) ¼ 174-Mþ (49), 159 (100), 160 (11), 128 (8), 115 (7), 128
(4), 144 (4), 158 (2), 64 (2), 51 (2). Anal. calcd. for C12H14O (174.24): C,
82.72; H, 8.10; found: C, 82.61; H, 8.19.
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5-Methoxy-2-propylbenzo[b]furan (2 g): H NMR (400 MHz, CDCl3): d
1.29 (3H, t, J ¼ 7.4 Hz, CH3), 2.01–1.94 (2H, m, CH2), 2.72 (2H, q,