Azobenzene Isomerization
FULL PAPER
spray ionization (ESI). CsI cluster ions were used as internal standard for
high resolution MS measurement.
1189 (m), 1141 (m), 1102 (m), 854 (m). 821 (m), 758 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d=9.03 (d, J=8.4 Hz, 1H), 8.36 (d, J=9.0 Hz, 2H),
8.04 (d, J=9.0 Hz, 2H), 8.03 (d, J=8.4 Hz, 1H), 7.81 (d, J=8.4 Hz, 1H),
7.68 (t, J=7.3 Hz, 1H), 7.56 (t, J=7.3 Hz, 1H), 6.81 (d, J=8.4 Hz, 1H),
4.83 ppm (brs, 2H). 13C NMR (100 MHz, [D6]DMSO): d=157.0, 152.9,
146.2, 137.2, 134.0, 128.5, 125.1, 124.8, 122.9, 122.7, 122.3, 120.9, 117.1,
108.2 ppm; ES-MS: m/z (%): 293 (100, [M+H]+); HR-MS: m/z: calcd
for C16H13N4O2: 293.1039; found: 293.1033 ([M+H]+).
4-(4-Nitrophenylazo)phenylcyclohexylamine (11): Sodium nitrite (0.118 g,
1.71 mmol) was added to a stirred solution of concentrated sulfuric acid
(1 mL). The mixture was heated until the temperature reached 708C and
then cooled to 08C. To this mixture was added a solution of 4-nitroani-
line (0.236 g, 1.71 mmol) dissolved in a mixture of propionic acid/acetic
acid/DMF (0.43 mL:2.14 mL:1.71 mL). The mixture was stirred at 08C
for 2 h. A DMF solution (4.28 mL) of cyclohexylphenylamine (0.15 g,
0.856 mmol) was added to this mixture, which then was stirred at 08C for
1 h, then warmed to room temperature and stirred for 24 h. The product
solution was basified with aqueous ammonium hydroxide (30%) and a
crude dark red solid was obtained after vacuum filtration. The residue
was purified by column chromatography (SiO2, toluene/hexane, 5:1) to
give 11 (0.172 g, 0.53 mmol) in 62% yield. M.p. 146–1478C, Rf =0.28 (tol-
uene/hexane 5:1); IR: n˜ =3392 (m), 2926 (m), 2853 (m), 1599 (s), 1514
Dye 3: A solution of 11 (0.400 g, 1.37 mmol) in EtOH (60 mL) was re-
fluxed with sodium sulfide nonahydrate (0.650 g, 2.72 mmol) for 20 h.
The mixture was poured into water (400 mL). The product was extracted
with ethyl acetate (3ꢁ100 mL), dried over MgSO4 and concentrated by
rotary evaporation. The residue was purified by column chromatography
(SiO2, toluene/ethyl acetate, 6:1) to give 3 (0.322 g, 1.23 mmol) in 90%
yield. M.p. 170–1718C; Rf =0.11 (toluene/ethyl acetate 6:1); IR: n˜ =3432
(w), 3393 (w), 3350 (w), 3313 (w), 3210 (w), 1598 (m), 1571 (m), 1501
(m), 1462 (m), 1398 (m), 1340 (m), 1282 (m), 1255 (m). 1139 (m), 834 (s),
755 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d=9.00 (d, J=8.3 Hz, 1H),
7.86 (d, J=8.7 Hz, 2H), 7.81 (d, J=8.2 Hz, 1H), 7.80 (d, J=8.4 Hz, 1H),
7.65–7.55 (m, 1H), 7.55–7.45 (m, 1H), 6.81 (d, J=8.3 Hz, 1H), 6.80–6.70
(m, 2H), 4.46 (brs, 2H), 3.96 ppm (brs, 2H); 13C NMR (100 MHz,
[D6]DMSO): d=151.0, 147.9, 144.0, 137.2, 132.4, 126.5, 124.1, 122.9,
122.5, 121.5, 113.6, 113.4, 107.3 ppm (only 13 of the 14 expected resonan-
ces were observed); ES-MS: m/z (%): 263 (100, [M+H]+); HR-MS: m/z:
calcd for C16H15N4: 263.1297; found: 263.1308 ([M+H]+,.
1
(s), 1333 (s), 1105 cmÀ1 (m); H NMR (400 MHz, CDCl3): d=8.30 (d, J=
8.9 Hz, 2H), 7.89 (d, J=8.9 Hz, 2H), 7.83 (d, J=8.9 Hz, 2H), 6.61 (d, J=
8.9 Hz, 2H), 4.28 (d, J=7.4 Hz, 1H), 3.45–3.30 (m, 1H), 2.15–2.05 (m,
2H), 1.85–1.75 (m, 2H), 1.75–1.65 (m, 1H), 1.45–1.35 (m, 2H), 1.30–
1.15 ppm (m, 3H); 13C NMR (100 MHz, CDCl3): d=156.8, 151.3, 147.3,
144.3, 126.5, 124.7, 122.6, 112.4, 51.5, 33.1, 25.6, 24.8 ppm; ES-MS: m/z
(%): 325 (100, [M+H]+); HR-MS: m/z: calcd for C18H21N4O2: 325.1665;
found: 325.1670 ([M+H]+.
4-(4-Aminophenylazo)phenylcyclohexylamine (12):
A solution of 11
(0.172 g, 0.53 mmol) in EtOH (20 mL) was refluxed with sodium sulfide
nonahydrate (0.264 g, 1.1 mmol) for 8 h. After the reaction was complete
the mixture was poured into water (80 mL). The product was extracted
with ethyl acetate (3ꢁ30 mL), dried over MgSO4 and concentrated by
rotary evaporation. The residue was purified by column chromatography
(SiO2, toluene/ethyl acetate, 10:1) to give 12 (0.141 g, 0.48 mmol) in 90%
yield. M.p. 145–1468C; Rf =0.23 (toluene/ethyl acetate 10:1); IR: n˜ =
3459 (m), 3373 (m), 3208 (m), 2925 (m), 2848 (m), 1592 (s), 1506 (s),
Acknowledgements
We thank the National Science Foundation (CHE-0615049 to L.I.) and
the University of Maryland (Fellowship to J.W. and GRB semester award
to L.I.) for financial support.
1
1306 (m), 1144 (s), 830 cmÀ1 (s); H NMR (400 MHz, CDCl3): d=7.76 (d,
J=8.7 Hz, 2H), 7.73 (d, J=8.5 Hz, 2H), 6.69 (d, J=8.5 Hz, 2H), 6.61 (d,
J=8.7 Hz, 2H), 3.96 (d, J=7.8 Hz, 1H), 3.89 (d, J=9.2 Hz, 1H), 3.35–
3.25 (m, 1H), 2.10–2.00 (m, 2H), 1.80–1.70 (m, 2H), 1.70–1.60 (m, 1H),
1.45–1.30 (m, 2H), 1.30–1.10 ppm (m, 3H); 13C NMR (100 MHz, CDCl3):
d=149.1, 148.0, 145.8, 144.3, 124.5, 124.0, 114.7, 112.4, 51.3, 33.1, 25.7,
24.8 ppm; ES-MS: m/z (%): 295 (100, [M+H]+); HR-MS: m/z: calcd for
C18H23N4: 295.1923; found: 295.1940 ([M+H]+).
36, 1868–1880; b) S. Masiero, S. Lena, S. Pieraccini, G. P. Spada,
Wahid, R. S. Prosser, A. R. Davidson, G. A. Wooley, J. Am. Chem.
2925–2927; W. A. Sokalski, R. W. Gꢂra, W. Bartkowiak, P. Kobylin-
Dye 2: HCl gas was passed through a solution of 12 (0.118 g, 0.40 mmol)
in anhydrous Et2O (300 mL) for 5 min. The resulting precipitate was sep-
arated from the mother liquor by centrifugation, the supernatant deca-
nted, and the solid dried under high vacuum to give
2 (0.146 g,
0.40 mmol) in 99% yield. M.p. 166–1678C; IR: n˜ =3459 (w), 3390 (w),
3325 (w), 2930 (m), 2848 (m), 1585 (s), 1507 (m), 1304 (s), 1256 (m), 1144
(s), 1082 (m), 831 cmÀ1 (s); 1H NMR (400 MHz, [D6]DMSO): d=7.75–
7.65 (m, 4H), 7.08 (d, J=8.6 Hz, 2H), 6.87 (d, J=8.6 Hz, 2H), 3.35–3.25
(m, 1H), 1.95–1.85 (m, 2H), 1.75–1.65 (m, 2H), 1.60–1.50 (m, 1H), 1.40–
1.05 ppm (m, 5H); 13C NMR (100 MHz, [D6]DMSO): d=149.1, 147.6,
144.8, 143.7, 125.4, 124.5, 119.3, 115.0, 53.1, 32.6, 26.2, 25.2 ppm;. ES-MS:
m/z (%): 295 (100, [M+H]+); HR-MS: m/z: calcd for C18H23N4:
295.1923; found: 295.1931 ([M+H]+).
[4] a) J. Lagona, P. Mukhopadhyay, S. Chakrabarti, L. Isaacs, Angew.
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sky, T. Mori, C. Yang, Y. H. Ko, N. Selvapalam, H. Kim, D. Sobran-
singh, A. E. Kaifer, S. Liu, L. Isaacs, W. Chen, S. Moghaddam, M. K.
632; b) A. Praetorius, D. M. Bailey, T. Schwarzlose, W. M. Nau, Org.
4-(4-Nitrophenylazo)naphthalen-1-amine (13): Sodium nitrite (1.035 g,
15.0 mmol) was added to a stirred solution of concentrated sulfuric acid
(10 mL). The mixture was heated until the temperature reached 708C
and then cooled to 08C. To this mixture was added a solution of 4-nitroa-
niline (2.07 g, 15.0 mmol) dissolved in propionic acid/acetic acid/DMF
(3.5 mL:19 mL:15 mL). The mixture was stirred at 08C for 2 h. A DMF
solution (30 mL) of aminonaphthalene (0.716 g, 5.00 mmol) was added to
this mixture, which then was stirred at 08C for 1 h, then warmed to room
temperature and stirred for 24 h. The solution was basified with aqueous
ammonium hydroxide (30%). The crude dark red solid was obtained by
vacuum filtration. The crude solid was purified by column chromatogra-
phy (SiO2, toluene/ethyl acetate, 10:1) to give 13 (0.789 g, 2.70 mmol) in
54% yield. M.p. 249–2508C; Rf =0.16 (toluene/ethyl acetate 1:25); IR:
n˜ =3424 (w), 3320 (w), 3227 (w), 3220 (w), 1571 (m), 1508 (s), 1321 (s),
Chem. Eur. J. 2009, 15, 11675 – 11680
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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