Synthesis and Property Studies of Cyclotrisazobenzenes
= 7.6 Hz, 1 H), 6.76 (d, 3JHH = 8.3 Hz, 1 H), 6.39 (br. s, 2 H, NH2),
2.01 [s, 3 H, NHC(O)CH3] ppm. 13C NMR (101 MHz, CDCl3): δ
= 168.8, 147.6, 147.2, 142.0, 140.1, 137.7, 135.6, 135.4, 132.9, 132.2,
131.3, 130.1, 122.7, 122.0, 118.8, 117.3 (2 C), 117.3, 116.4,
25.8 ppm. MS (EI, 70 eV): m/z (%) = 438 (11), 436 (11) [M+], 106
(100). C20H17BrN6O (437.29): calcd. C 54.93, H 3.92, N 19.22;
found C 54.95, H 3.91, N 19.20.
purified by flash column chromatography (neutral alox; hexanes/
EtOAc, 5:1) to yield golden brown crystals (151 mg, 51%); m.p.
1
180–182 °C (ref.[9] 169–176 °C). H NMR (400 MHz, CDCl3): δ =
7.72–7.66 (m, 6 H), 7.59–7.53 (m, 6 H) ppm.
3-tert-Butylcyclotrisazobenzene (2b): Triethylamine (0.75 mL,
5.37 mmol, 10.0 equiv.) was added to a solution of 3b (200 mg,
0.54 mmol, 1.00 equiv.) in CH2Cl2 (65 mL). Pb(OAc)4 (541 mg,
1.22 mmol, 2.26 mmol), dissolved in of CH2Cl2 (7 mL), was added
dropwise. After complete addition, the mixture was stirred for
30 min. The solvent was removed under reduced pressure, and the
residue was purified by flash column chromatography (neutral alox;
TBME/hexane, 1:7). A red-brown oil was obtained, which crys-
tallized after a few days to give brown crystals (97.0 mg, 49%); m.p.
Diaminobisazobenzene 3a: A solution of 9a (790 mg, 2.20 mmol,
1.00 equiv.) in ethanol (80 mL) was treated with a solution of KOH
(7.10 g, 0.127 mol, 57.7 equiv.) in ethanol (46 mL) and water
(18 mL). The mixture was heated to 90 °C. After 1 h, the mixture
was poured onto of ice (300 g), extracted with CH2Cl2 (3ϫ 50 mL),
dried with Na2SO4 and concentrated to yield a red oil (660 mg),
which crystallized in the refridgerator overnight (95%); m.p. 94–
96 °C (ref.[10] 96–97 °C). 1H NMR (400 MHz, CDCl3): δ = 7.89
128–132 °C. IR: ν = 2952, 1456, 1360, 825, 758 cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 7.73–7.52 (m, 11 H), 1.43 [s, 9 H,
C(CH3)3] ppm. 13C NMR (101 MHz, CDCl3): δ = 154.4, 147.0,
146.9, 146.8, 146.7, 146.7, 144.4, 130.5, 130.4, 130.4, 130.4, 127.6,
122.8, 122.7, 122.0, 121.8, 121.8, 119.7, 37.6 [C(CH3)3], 31.7
[C(CH3)3] ppm. MS (EI, 70 eV): m/z (%) = 368 (12) [M+], 353
(100). C22H20N6 (368.43): calcd. C 71.72, H 5.47, N 22.81; found
C 71.55, H 5.61, N 22.49.
3
4
(dd, JHH = 8.1, JHH = 1.5 Hz, 2 H), 7.81–7.75 (m, 2 H), 7.52–
3
3
4
7.46 (m, 2 H), 7.21 (ddd, JHH = 8.4, JHH = 7.1 , JHH = 1.6 Hz,
2 H), 6.84 (ddd, 3JHH = 8.2, JHH = 7.1, JHH = 1.2 Hz, 2 H), 6.72
3
4
3
4
(dd, JHH = 8.2, JHH = 1.1 Hz, 2 H), 6.27 (br. s, 4 H, NH2) ppm.
Diamino-tert-butylbisazobenzene 3b: To a solution of 9b (1.23 g,
2.97 mmol, 1.00 equiv.) in ethanol (75 mL) was added KOH
(3.77 g, 67.2 mmol, 22.7 equiv.), dissolved in a mixture of ethanol
(50 mL) and water (20 mL). The reaction mixture was stirred at
100 °C for 2 h. The mixture was allowed to cool to room tempera-
ture and diluted with water. After extraction with CH2Cl2, washing
four times with water and drying with Na2SO4, the solvent was
removed under reduced pressure to yield a red solid (1.13 g, 100%);
3-Bromocyclotrisazobenzene
(2c):
Triethylamine
(1.75 mL,
12.6 mmol, 10.0 equiv.) was added to a stirred solution of 3c
(500 mg, 1.26 mmol, 1.00 equiv.) in CH2Cl2 (150 mL). Pb(OAc)4
(1.27 g, 2.87 mmol, 2.28 equiv.), dissolved in CH2Cl2 (10 mL), was
added dropwise. After stirring for 30 min, the solvent was removed
under reduced pressure. The residue was purified by flash column
chromatography (neutral alox; hexanes/EtOAc, 10:1) to yield the
m.p. 103–105 °C. IR: ν = 3456, 2957, 1614, 1385, 1157, 1139 cm–1.
˜
4
1H NMR (400 MHz, CDCl3): δ = 7.91 (d, JHH = 8.8 Hz, 1 H),
product (208 mg, 42%); m.p. 140–142 °C. IR: ν = 3054, 1757, 1373,
˜
1203, 1009, 690 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.79 (d,
4JHH = 2.0 Hz, 1 H), 7.74–7.52 (m, 10 H) ppm. 13C NMR
(101 MHz, CDCl3): δ = 147.0, 146.74, 142.65, 146.2, 145.9, 145.6,
133.0, 130.7 (2 C), 130.4, 130.3, 124.5, 124.4, 124.0, 123.1, 123.0,
121.4 (2 C) ppm. MS (EI, 70 eV): m/z (%) = 392 (100), 390 (86)
[M+]. C18H11BrN6 (391.22): calcd. C 55.26, H 2.83, N 21.48; found
C 55.34, H 2.87, N 21.25.
3
7.89 (d, JHH = 8.1 Hz, 1 H), 7.80–7.76 (m, 2 H), 7.51–7.46 (m, 2
H), 7.29 (dd, 3JHH = 8.6, JHH = 2.4 Hz, 1 H), 7.24–7.18 (m, 1 H),
4
3
3
6.86–6.81 (m, 1 H), 6.73 (d, JHH = 8.5 Hz, 1 H), 6.71 (d, JHH
=
8.6 Hz, 1 H), 5.95 (br. s, 4 H, NH2), 1.34 [s, 9 H, C(CH3)3] ppm.
13C NMR (101 MHz, CDCl3): δ = 148.5, 148.2, 142.4, 140.6, 140.1,
138.2, 137.9, 132.7, 131.8, 130.8, 130.7, 130.6, 127.1, 124.7, 117.6,
117.5, 117.3, 117.1, 34.4 [C(CH3)3], 31.8 [C(CH3)3] ppm. MS (EI,
70 eV): m/z (%) = 372 (96) [M+], 162 (100). C22H24N6 (372.46):
calcd. C 70.94, H 6.49, N 22.56; found C 70.85, H 6.55, N 22.70.
Supporting Information (see also the footnote on the first page of
this article): Full experimental data for 7, 8a, 13, 14, 15, 16, 17,
1
10a and H and 13C NMR spectra for 2b, 2c, 3b, 3c, 8b, 8c, 9b, 9c,
Diamino-bromobisazobenzene 3c:
A solution of 9c (720 mg,
10a.
1.65 mmol, 1.00 equiv.) in ethanol (40 mL) was prepared and
treated with KOH (2.09 g, 37.2 mmol, 22.5 equiv.), dissolved in eth-
anol (7 mL) and H2O (7 mL). The mixture was heated to 100 °C
for 1 h, and then poured onto of crushed ice (130 g). It was ex-
tracted with CH2Cl2 (3ϫ 100 mL) and dried with Na2SO4. Evapo-
Acknowledgments
We thank the Swiss National Science foundation (SNSF) for finan-
cial support. H. A. W. is indebted to the Fonds der Chemischen
Industrie for a Liebig fellowship. The authors thank Dr. Pavel
Müller for conducting the laser-flash photolysis experiments and
Prof. Dr. André Dreiding for helpful discussions.
ration of the solvent yielded the product (620 mg, 95%); m.p. 118–
1
119 °C. IR: ν = 3438, 1602, 1482, 1393, 1159, 811 cm–1. H NMR
˜
(400 MHz, CDCl3): δ = 7.98 (s, 1 H), 7.87 (d, 3JHH = 8.1 Hz, 1 H),
7.82–7.73 (m, 2 H), 7.56–7.45 (m, 2 H), 7.28 (d, JHH = 8.7 Hz, 1
H), 7.22 (t, JHH = 7.7 Hz, 1 H), 6.84 (t, JHH = 8.7 Hz, 1 H), 6.76
3
3
3
3
3
(d, JHH = 7.2 Hz, 1 H), 6.65 (d, JHH = 8.7 Hz, 1 H), 6.30 (s, 2
H, NH2), 6.08 (s, 2 H, NH2) ppm. 13C NMR (101 MHz, CDCl3):
δ = 148.2, 147.5, 142.2, 141.8, 138.4, 137.9, 134.7, 132.5, 131.1,
130.4, 130.3, 130.2, 118.6, 117.3, 117.2, 116.7, 116.4, 108.8 ppm.
MS (EI, 70 eV): m/z (%) = 396 (31), 394 (33) [M+], 106 (100).
C18H15BrN6 (395.26): calcd. C 54.70, H 3.82, N 21.26; found C
54.58, H 3.80, N 21.05.
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Cyclotrisazobenzene (2a): Triethylamine (1.32 mL, 9.50 mmol,
10.0 equiv.) was added to a solution of 3a (0.30 g, 0.95 mmol,
1.00 equiv.) in CH2Cl2 (100 mL). Pb(OAc)4 (0.96 g, 2.20 mmol,
2.30 equiv.), dissolved in CH2Cl2 (12 mL), was added dropwise. Af-
ter complete addition, the mixture was stirred for 40 min. The sol-
vent was removed under reduced pressure, and the residue was
Eur. J. Org. Chem. 2009, 5647–5652
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