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with Et2O (2×60 ml), the combined org. phase dried (MgSO4) and evaporated, and the resulting solid
recrystallized from EtOH: 4-hydroxy-3-nitrophenyl benzoate (7.8 g, 76%). Spongy yellow solid. 1H-
NMR (300 MHz, CDCl3): 10.50 (s, 1 H); 8.17 (dd, J=8.4, 1.3, 2 H); 7.99 (d, J=2.7, 1 H); 7.65 (m,
1 H); 7.51 (dd, J=8.4, 7.5, 2 H); 7.47 (dd, J=9.0, 2.7, 1 H); 7.21 (d, J=9.0, 1 H).
2-[4-(Hexyloxy)phenyl]benzoxazol-5-yl Benzoate (6a): By Method A or Method B: 63 or 85% yield,
resp. White solid. 1H-NMR (300 MHz, CDCl3): 8.23 (d, J=7.6, 2 H); 8.16 (d, J=8.8, 2 H); 7.64 (m, 1 H);
7.49–7.56 (m, 4 H); 7.15 (dd, J=8.6, 2.1, 1 H); 7.01 (d, J=9.0, 2 H); 4.03 (t, J=6.4, 2 H); 1.87–1.74 (m,
2 H); 1.63–1.25 (m, 6 H); 0.90 (t, J=6.9, 3 H).
2-(4-Cyanophenyl)benzoxazol-5-yl Benzoate (6b): By Method A or Method B: 43 or 77% yield, resp.
White solid. 1H-NMR (300 MHz, CDCl3): 8.34 (d, J=8.7, 2 H); 8.22 (d, J=7.1, 2 H); 7.81 (d, J=8.7, 2 H);
7.65–7.61 (3 H); 7.52 (m, 2 H); 7.25 (dd, J=8.8, 2.4, 1 H).
2-[4-(Methoxycarbonyl)phenyl]benzoxazol-5-yl Benzoate (6c): By Method B: 89% yield. White
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solid. H-NMR (300 MHz, CDCl3): 8.34–8.17 (m, 6 H); 7.65–7.61 (m, 5 H); 7.55–7.50 (m, 1 H); 3.95
(s, 3 H).
2-[4-(Hexyloxy)phenyl]benzoxazol-5-ol (7a): A soln. of KOH (202 mg) in H2O (5 ml) was added
dropwise to a soln. of 6a (1.5 g, 3.60 mmol) in THF (200 ml) and 96% EtOH (35 ml) at r.t. The mixture
was stirred for 2 h, and a large volume of H2O was added. The resulting mixture was neutralized with
AcOH. The THF was evaporated to precipitate the product, which was filtered off and dried at 458
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for 48 h under vacuum: 7a (965 mg, 86%). H-NMR (300 MHz, CDCl3): 8.12 (d, J=8.6, 2 H); 7.35 (d,
J=8.7, 1 H); 7.16 (d, J=2.4, 1 H); 6.97 (d, J=9.1, 2 H); 6.82 (dd, J=8.7, 2.5, 1 H); 6.08–6.04 (m,
1 H); 4.01 (t, J=6.7, 2 H); 1.78 (m, 2 H); 1.55–1.23 (m, 6 H); 0.89 (t, J=6.8, 3 H).
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4-(5-Hydroxybenzoxazol-2-yl)benzonitrile (7b). As described for 7a, from 6b: 7b (93%). H-NMR
(300 MHz, CDCl3): 8.31 (d, J=8.4, 2 H); 7.79 (d, J=8.0, 2 H); 7.45 (d, J=8.8, 1 H); 7.2 (d, J=2.6,
1 H); 6.92 (dd, J=9.3, 2.5, 1 H); 4.92 (s, 1 H).
4-(5-Hydroxybenzoxazol-2-yl)benzoic Acid (7c). A soln. of KOH (11.88 g) in H2O (40 ml) was added
to a stirred suspension of 6c (4.20 g, 11.28 mmol) in boiling EtOH (125 ml). After 5 min, H2O (450 ml)
was added and the soln. heated under reflux for 30 min and then allowed to cool down to r.t. The mixture
was neutralized with dil. HCl soln., and the solid was filtered off, washed with H2O and recrystallized
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from EtOH: 7c (2.5 g, 87%). White solid. H-NMR (300 MHz, (D6)DMSO): 10.25–9.25 (s, 1 H); 8.24
(d, J=8.4, 2 H); 8.11 (d, J=8.4, 2 H); 7.57 (d, J=9.0, 1 H); 7.13 (d, J=2.4, 1 H); 6.89 (dd, J=9.0, 2.4,
1 H).
2.6. 5-(Hexyloxy)-2-(4-Y-phenyl)benzoxazoles (5HexO-PBO-Y): General Procedure. Hexyl bromide
(0.42 ml, 3.01 mmol) was added dropwise under Ar to a mixture of the corresponding 7 (2.73 mmol) and
K2CO3 (5.46 mmol) in dry dimethylformamide (75 ml). The mixture was heated under reflux for 1 h and
then allowed to cool down to r.t. H2O (120 ml) was added, the mixture extracted with hexane/AcOEt 1:1
(4×100 ml), and the combined org. extract washed with H2O (3×100 ml), dried (MgSO4), filtered
through a pad of silica gel, and evaporated. The crude product was recrystallized from abs. EtOH:
5HexO-PBO-Y, which in some cases was further purified by FC (silica gel, CH2Cl2).
5-(Hexyloxy)-2-[4-(hexyloxy)phenyl]benzoxazole (5HexO-PBO-OHex): 72% yield. White solid. IR
(KBr): 1606. 1H-NMR (300 MHz, CDCl3): 8.12 (d, J=8.8, 2 H); 7.38 (d, J=8.8, 1 H); 7.19 (d, J=2.6, 1
H); 6.98 (d, J=8.8, 2 H); 6.87 (dd, J=8.8, 2.6, 1 H); 4.00 (m, 4 H); 1.80–1.70 (m, 4 H); 1.50–1.21 (m,
12 H); 1.01–0.9 (m, 6 H). 13C-NMR (75 MHz, CDCl3): 163.0; 161.0; 156.0; 145.0; 143.0; 129.0; 119.0;
114.0; 113.0; 110.0; 103.0; 68.8; 68.2; 31.6; 31.5; 29.2; 29.1; 25.74; 25.66; 22.6; 22.5; 14.03; 14.01. Anal.
calc. for C25H33NO3: C 75.91, H 8.41, N 3.54; found: C 76.23, H 8.49, N 3.55.
4-[5-(Hexyloxy)benzoxazol-2-yl]benzonitrile (5HexO-PBO-CN): 170 mg (35%). White solid. IR-
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(nujol): 2223, 1612. H-NMR (300 MHz, CDCl3): 8.29 (d, J=8.5, 2 H); 7.77 (d, J=8.7, 2 H); 7.44 (d,
J=8.9, 1 H); 7.22 (d, J=2.4, 1 H); 6.97 (dd, J=9.0, 2.5, 1 H); 3.98 (t, J=6.5, 2 H); 1.84–1.71 (m, 2 H);
1.49–1.2 (m, 6 H); 0.89 (t, J=7, 3 H). 13C-NMR (75 MHz, CDCl3): 161.5; 157.3; 142.7; 132.6; 131.2;
127.8; 118.2; 115.6; 114.5; 110.9; 103.7; 68.9; 31.6; 29.2; 25.7; 22.6; 14.0. Anal. calc. for C20H20N2O2:
C 74.98, H 6.29, N 8.74; found: C 74.76, H 6.38, N 8.59.
Hexyl 4-[5-(Hexyloxy)-2-yl]benzoatebenzoxazole (5HexO-PBO-COOHex): 76% yield. White solid.
IR (nujol): 1710, 1637. 1H-NMR (300 MHz, CDCl3): 8.27 (d, J=8.2, 2 H); 8.15 (d, J=8.2, 2 H); 7.44 (d,
J=8.8, 1 H); 7.23 (d, J=2.5, 1 H); 6.95 (dd, J=9.0, 2.4, 1 H); 4.33 (t, J=6.6, 2 H); 3.99 (t, J=6.7, 2 H);