486
B. Sreedhar et al.
PAPER
IR (KBr): 2935, 2858, 1592, 1511, 1339, 1260, 1171, 1111, 1042,
1019, 961, 845, 753 cm–1.
with the filtrate for 12 hours. Almost no change in the con-
version of iodobenzene was observed. These studies and
the inactivity of copper(II) nitrate in the O-arylation of 1H NMR (300 MHz, CDCl3): d = 8.25–8.10 (d, J = 8.30 Hz, 2 H),
7.55–7.41 (d, J = 8.30 Hz, 2 H), 3.75 (m, 1 H), 1.95–1.75 (m, 4 H),
phenols clearly proves that the reaction occurs hetero-
1.49–1.41 (m, 6 H).
geneously.
13C NMR (75 MHz, CDCl3): d = 158.9, 129.8, 124.5, 115.1, 35.2,
In conclusion, the described one-pot recyclable Cu/Al-
HTB catalyzed C–O bond approach represents an effi-
cient protocol for the synthesis of a wide variety of diaryl
ethers. This method provides the products in good to ex-
cellent yields in short reaction times compared to the
known procedures and in the absence of ligands and or a
28.5, 23.
MS (EI, 70 eV): m/z (%) = 221 (2) [M+], 141 (8), 139 (3), 124 (8),
109 (7), 84 (5), 81 (28), 67 (45), 55 (100), 41 (92), 40 (6).
Anal Calcd for C12H15NO3: C, 65.14; H, 6.83; N, 6.33. Found: C,
65.41; H, 6.88; N, 6.27.
strong base. Solid-base catalyst, reaction times, and easy
product isolation makes the process attractive for the syn-
1-(Cyclohexyloxy)-4-methoxybenzene (1o)
Pale yellow liquid; yield: 91%.
thesis of ethers. Moreover, the catalyst can be easily sep-
FT-IR (neat): 2922, 2852, 1664, 1378, 1250, 1230, 1172, 1101,
arated by simple filtration and reused for several cycles
with consistent activity.
1072, 961, 894, 723 cm–1.
1H NMR (300 MHz, CDCl3): d = 6.65–6.70 (m, 4 H), 3.78 (s, 3 H),
3.65–3.61 (m, 1 H), 1.99–1.75 (m, 4 H), 1.50–1.41 (m, 6 H).
The catalyst was prepared according to the literature procedure.10
All alcohols and amines were purchased from Aldrich or Fluka and
were used without further purification. ACME silica gel (60–120
mesh) was used for product purification. All solvents and other
chemicals were obtained from commercial sources and purified us-
ing standard methods. Melting points were recorded on a Barnstead
Electrothermal 9200 instrument and are uncorrected. Infrared spec-
tra were recorded on a Thermo Nicolet Nexus 670 FT-IR spectrom-
13C NMR (75 MHz, CDCl3): d = 151.9, 149.8, 114.5, 75.2, 52.5,
34.1, 29.1, 22.3.
MS (EI, 70 eV): m/z (%) = 206 (4) [M+], 191 (16), 167 (22), 149
(75), 124 (14), 111 (14), 97 (31), 81 (62), 69 (100), 47 (9), 44 (4).
Anal Calcd for C13H18O2: C, 75.69; H, 8.80. Found: C, 76.02; H,
8.88.
1
eter as KBr pellets. H and 13C NMR spectra were recorded on a
1-Bromo-4-(4-bromophenoxy)benzene (1p)
Off-white solid; yield: 85%; mp 62 °C
Varian Gemini (200 MHz), a Bruker Avance (300 MHz) or a Varian
Unity (400 MHz) spectrometer using TMS as an internal standard
and CDCl3 as solvent.
IR (KBr): 3087, 2961, 2925, 2854, 1890, 1647, 1579, 1481, 1399,
1250, 1190, 1161, 1098, 1071, 1006, 868, 824, 645, 494 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.25–8.10 (d, J = 8.0 Hz, 4 H),
7.55–7.41 (d, J = 8.0 Hz, 4 H).
13C NMR (75 MHz, CDCl3): d = 155.9, 132.8, 120.5, 116.2.
The spectroscopic data of all known compounds were identical to
those reported in the literature;12–15 the data of all novel compounds
synthesized are given herein.
MS (EI, 70 eV): m/z (%) = 330 (7) [M + 2], 328 (13) [M+], 326 (7)
[M – 2], 221 (6), 219 (6), 183 (5), 168 (12), 139 (12), 122 (42), 105
(59), 85 (65), 83 (100), 43 (93), 41 (44), 40 (19).
Diphenyl Ether (1a); Typical Procedure
A mixture of PhI (1 mmol), PhOH (1.5 mmol), base (2.0 mmol) and
Cu-Al/HTB (100 mg) in DMF (2 mL) was stirred in a 25-mL round-
bottom flask in a pre-heated oil bath at 110 °C. After completion of
the reaction (TLC) the catalyst was filtered through centrifugation
and washed several times with EtOAc to make the catalyst free from
organic matter. The organic solution was washed with brine (30
mL), dried (anhyd Na2SO4), and concentrated under reduced pres-
sure using a rotavapor. The crude product was purified by column
chromatography (silica gel, 60–120, hexane–EtOAc, 90:10) to af-
ford the corresponding diaryl ether.
Anal Calcd for C12H8Br2O: C, 43.94; H, 2.46. Found: C, 44.74; H,
2.49.
1-(4-Bromophenoxy)-4-methoxybenzene (1r)
Off-white solid; yield: 89%; mp 110–112 °C.
IR (KBr): 3108, 3004, 2978, 2843, 1609, 1586, 1447, 1341, 1297,
1237, 1189, 1160, 1105, 1029, 876, 843, 747 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.21–8.10 (d, J = 9.1 Hz, 2 H),
7.10–6.91 (m, 6 H), 3.81 (s, 3 H).
13C NMR (75 MHz, CDCl3): d = 158.5, 153.1, 149.8, 131.3, 118.3,
116.0, 114.7, 55.5.
MS (EI, 70 eV): m/z (%) = 279 (7) [M+], 256 (78), 241 (15), 226
(14), 220 (5), 193 (3), 165 (7), 149 (13), 97 (12), 71 (20), 57 (93),
45 (13), 43 (100).
1-(Benzyloxy)-4-nitrobenzene (1m)
Orange crystalline solid; yield: 93%; mp 185–186 °C.
IR (KBr): 2925, 1917, 1663, 1568, 1474, 1400, 1292, 1207, 1145,
1080, 1000, 843, 715, 647, 542 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.79–7.81 (d, J = 7.6 Hz, 2 H),
7.49–7.31 (m, 7 H), 4.7 (s, 2 H).
13C NMR (75 MHz, CDCl3): d = 169.1, 141.7, 128.1, 121.9, 115.3,
70.7.
Anal Calcd for C13H11BrO2: C, 55.94; H, 3.97. Found: C, 55.74; H,
3.99.
MS (EI, 70 eV): m/z (%) = 221 (4) [M+], 183 (5), 169 (4), 164 (9),
149 (8), 121 (7), 111 (15), 91 (18), 75 (21), 57 (24), 55 (100), 43
(52), 41 (46), 40 (16).
Acknowledgment
R.A. wishes to thank DST (Department of Science and Technology,
India) for financial support under the project GAP-0152 and for
providing a research fellowship.
Anal Calcd for C13H11NO3: C, 68.11; H, 4.84; N, 6.11. Found: C,
67.74; H, 4.79; N, 6.10.
1-(Cyclohexyloxy)-4-nitrobenzene (1n)
Yellow oil; yield: 86%.
Synthesis 2009, No. 3, 483–487 © Thieme Stuttgart · New York