Synthesis of 1,2,3,4-Benzotetrazine 1-Oxides
FULL PAPER
1540, 1360 (NO2), 3340, 3440 (NH2). MS (70 eV): m/z (relative in-
tensities) ϭ 316, 318 (1:1) [Mϩ]. C10H13BrN4O3 (317.14): calcd. C
37.87, H 4.13, Br 25.20, N 17.67; found C 37.92, H 4.12, Br 25.14,
N 17.83.
ν˜ ϭ 1500 cmϪ1 [N(O)ϭN], 2310 (N2ϩ). C12H16BBrF4N4O (398.99):
calcd. C 36.12, H 4.04, N 14.04; found C 35.89, H 4.00, N 14.43.
4,6-Dibromo-2-(tert-butyl-NNO-azoxy)-5-methylphenyldiazonium
Tetrafluoroborate (2e): Light-yellow solid (560 mg, 85 %), m.p.
1
111Ϫ115 °C (decomp.). H NMR ([D6]acetone): δ ϭ 1.51 (s, 9 H,
3,4,6-Tribromo-2-(tert-butyl-NNO-azoxy)aniline
(1n):
NBS
tBu), 2.47 (s, 3 H, CH3), 8.78 (s, 1 H, 3-H) ppm. 13C NMR ([D6]a-
cetone): δ ϭ 20.4 (CH3), 25.5 (CMe3), 62.1 (CMe3), 130.5 (C-3)
ppm. 14N NMR ([D6]acetone): δ ϭ Ϫ60 (∆ν1/2 ϭ 100 Hz, NǞO),
Ϫ156 (∆ν1/2 ϭ 190 Hz, -NϩϵN) ppm. IR (KBr): ν˜ ϭ 1510 cmϪ1
[N(O)ϭN], 2300 (N2ϩ). C11H13BBr2F4N4O (463.86): calcd. C
28.48, H 2.82, N 12.08; found C 28.39, H 2.83, N 12.04.
(200 mg, 1.1 mmol) was added to a solution of 3-bromo-2-(tert-
butyl-NNO-azoxy)aniline (150 mg, 0.55 mmol) in CH2Cl2 (10 mL).
After 3 h stirring at room temperature, the reaction mixture was
worked up as in the previous case to yield 190 mg (80 %) of 1n,
1
m.p. 131Ϫ132 °C. H NMR ([D6]acetone): δ ϭ 1.5 (s, 9 H, tBu),
5.2 (br. s, 2 H, NH2), 8.87 (s, 1 H, 5-H) ppm. 13C NMR ([D6]ace-
tone): δ ϭ 25.8 (CMe3), 61.2 (CMe3), 110.2, 112.0, 118.7, 134.1,
4-Bromo-2-(tert-butyl-NNO-azoxy)phenyldiazonium Tetrafluorobo-
rate (2f):[6] Light brownish solid (470 mg, 89 %), m.p. 130Ϫ135 °C
(decomp.). 1H NMR ([D6]acetone): δ ϭ 1.52 (s, 9 H, tBu), 8.52
(dd, J ϭ 8.8, 2.1 Hz, 1 H, 5-H), 8.87 (d, J ϭ 2.1 Hz, 1 H, 3-H),
136.3 (C-5) ppm. 14N NMR ([D6]acetone): δ ϭ Ϫ54 (∆ν1/2
ϭ
80 Hz, NǞO) ppm. IR (KBr): ν˜ ϭ 1450 cmϪ1 [N(O)ϭN], 3330,
3450 (NH2). MS (70 eV): m/z (relative intensities) ϭ 426, 428, 430,
432, 434 (1:3:5:3:1) [Mϩ]. C10H12Br3N3O (429.93): calcd. C 27.94,
H 2.81, Br 55.76, N 9.77; found C 37.99, H 2.81, Br 55.32, N 9.81.
8.88 (d, J ϭ 8.8 Hz, 1 H, 6-H) ppm. 13C NMR[16aϪ16c] (273 K,
3
[D6]acetone): δ ϭ 25.1 (CMe3), 62.0 (CMe3), 109.7 (C-1, J3-H
ϭ
3
3
9.0, J5-H ϭ 11.8 Hz), 130.2 (C-3, J ϭ 6.0 Hz), 137.4 (C-6), 137.8
(C-5), 138.3 (C-4), 146.7 (C-2) ppm. 14N NMR ([D6]acetone): δ ϭ
Ϫ67 (∆ν1/2 ϭ 100 Hz, NǞO), Ϫ151 (∆ν1/2 ϭ 250 Hz, ϪNϩϵN)
General Procedure for the Diazotization of Anilines 1: A solution of
aniline 1 (1.42 mmol) in dry MeCN (5 mL) was added dropwise at
Ϫ15 °C over a period of 10 min to a stirred suspension of NOBF4
(200 mg, 1.71 mmol) in dry MeCN (15 mL). After an additional
15 min stirring at Ϫ15 °C, the solution was concentrated ca. 90 %
in vacuo at a temperature of 0 °C. Cooled Et2O was added to the
resultant suspension. The precipitate was filtered off and washed
with cooled Et2O and then with pentane and dried in vacuo in an
ice-cooled bath.
ppm. IR (KBr): ν˜
ϭ
1500 cmϪ1 [N(O)ϭN], 2290 (N2ϩ).
C10H12BBrF4N4O (370.94): calcd. C 32.38, H 3.26, N 15.10; found
C 32.45, H 3.30, N 14.99.
4,5-Dibromo-2-(tert-butyl-NNO-azoxy)phenyldiazonium
Tetra-
fluoroborate (2g): Colorless solid (550 mg, 88 %), m.p. 102Ϫ106 °C
1
(decomp.). H NMR ([D6]acetone): δ ϭ 1.51 (s, 9 H, tBu), 8.56 (s,
1 H, 6-H), 8.91 (s, 1 H, 3-H) ppm. 13C NMR[16a] ([D6]acetone):
δ ϭ 25.3 (CMe3), 62.4 (CMe3), 110.5 (C-1), 130.5 (C-5), 131.6 (C-
3), 139.5 (C-6), 141.8 (C-4), 145.3 (C-2) ppm. 14N NMR ([D6]ace-
tone): δ ϭ Ϫ65 (∆ν1/2 ϭ 80 Hz, NǞO), Ϫ155 (∆ν1/2 ϭ 190 Hz,
ϪNϩϵN) ppm. IR (KBr): ν˜ ϭ 1500 cmϪ1 [N(O)ϭN], 2300 (N2ϩ).
C10H11BBr2F4N4O (449.83): calcd. C 26.70, H 2.46, N 12.46; found
C 26.72, H 2.50, N 12.41.
2-(tert-Butyl-NNO-azoxy)phenyldiazonium Tetrafluoroborate (2a):
Colorless solid (390 mg, 94 %), m.p. 141Ϫ145 °C (decomp.). 1H
NMR ([D6]acetone): δ ϭ 1.53 (s, 9 H, tBu), 8.25 (t, J ϭ 8.2 Hz, 1
H, 5-H), 8.52 (t, J ϭ 8.2 Hz, 1 H, 4-H), 8.70 (d, J ϭ 8.2 Hz, 1 H,
3-H), 8.99 (d, J ϭ 8.2 Hz, 1 H, 6-H) ppm. 1H NMR (CD3CN):
δ ϭ 1.53 (s), 8.12 (dt, 5-H), 8.39 (dt, 4-H), 8.59 (dd, 3-H), 8.73 (dd,
6-H) ppm. 13C NMR[16aϪ16e] ([D6]acetone): δ ϭ 25.4 (CH3), 61.9
3
2
3
(CMe3), 110.9 (C-1, J ϭ 9.2, J ϭ 3.8 Hz), 127.1 (C-3, J ϭ 14.0,
6-Bromo-2-(tert-butyl-NNO-azoxy)-4-methylphenyldiazonium
Tetrafluoroborate (2h): Colorless solid (520 mg, 95 %), m.p. 82Ϫ85
3
3
2
3J ϭ 8.2 Hz), 134.8 (C-5, J ϭ 8.2 Hz), 137.1 (C-6, J ϭ 8.7, J ϭ
3.2 Hz), 143.1 (C-4, 3J ϭ 8.2 Hz), 146.7 (br., C-2) ppm. 14N NMR
1
°C (decomp.). H NMR ([D6]acetone): δ ϭ 1.43 (s, 9 H, tBu), 2.72
([D6]acetone): δ ϭ Ϫ66 (∆ν1/2 ϭ 85 Hz, NǞO), Ϫ154 (∆ν1/2
ϭ
(s, 3 H, CH3), 8.05 (d, J ϭ 2 .1 Hz, 1 H, 3-H), 8.88 (d, J ϭ 8.8 Hz,
1 H, 6-H) ppm. 13C NMR[16a] ([D6]acetone): δ ϭ 21.5 (CH3), 25.1
(CMe3), 62.0 (CMe3), 109.7 (C-1), 130.2 (C-3), 137.4 (C-6), 137.8
(C-5), 138.3 (C-4), 146.7 (C-2) ppm. 14N NMR ([D6]acetone): δ ϭ
Ϫ67 (∆ν1/2 ϭ 210 Hz, NǞO), Ϫ151 (∆ν1/2 ϭ 490 Hz, ϪNϩϵN)
240 Hz, -NϩϵN) ppm. 15N NMR/INEPT ([D6]acetone): δ ϭ Ϫ6.9
(ϭN-tBu) ppm. IR (KBr): ν˜ ϭ 1500 cmϪ1 [N(O)ϭN], 2300 (N2ϩ).
C10H13BF4N4O (292.04): calcd. C 41.13, H 4.49, N 19.18; found C
41.21, H 4.53, N 18.79.
ppm. IR (KBr): ν˜
ϭ
1500 cmϪ1 [N(O)ϭN], 2290 (N2ϩ).
4,6-Dibromo-2-(tert-butyl-NNO-azoxy)phenyldiazonium
Tetra-
C11H14BBrF4N4O (384.96): calcd. C 34.32, H 3.67, N 14.55; found
C 34.01, H 3.72, N 14.33.
fluoroborate (2b): Yellow solid (610 mg, 95 %), m.p. 125Ϫ129 °C
(decomp.). 1H NMR ([D6]acetone): δ ϭ 1.52 (s, 9 H, tBu), 8.93 (d,
J ϭ 1.8 Hz, 1 H, 3-H), 8.98 (d, 1 H, 5-H) ppm. 13C NMR[16b]
(273 K, ([D6]acetone): δ ϭ 25.1 (CH3), 62.8 (CMe3), 130.0 (C-3),
141.7 (C-5) ppm. The rest of the signals were unrecordable, due to
the low solubility of the salt. 14N NMR ([D6]acetone): δ ϭ Ϫ69
(∆ν1/2 ϭ 100 Hz, NǞO), Ϫ153 (∆ν1/2 ϭ 250 Hz, -NϩϵN) ppm. IR
(KBr): ν˜ ϭ 1490 cmϪ1 [N(O)ϭN], 2270 (N2ϩ). C10H11BBr2F4N4O
(449.83): calcd. C 26.70, H 2.46, N 12.46; found C 26.53, H 2.52,
N 12.63.
5-Bromo-2-(tert-butyl-NNO-azoxy)phenyldiazonium Tetrafluorobo-
rate (2i): Colorless solid (480 mg, 90 %), m.p. 130Ϫ134 °C (de-
comp.). 1H NMR ([D6]acetone): δ ϭ 1.53 (s, 9 H, tBu), 8.47 (d,
J ϭ 9.2 Hz, 1 H, 3-H), 8.94 (dd, J ϭ 9.2, 1.9 Hz, 1 H, 4-H), 9.31
(d, J ϭ 1.9 Hz, 1 H, 6-H) ppm. 13C NMR[16c] ([D6]acetone): δ ϭ
25.34 (CMe3), 61.5 (CMe3), 134.0 (C-3), 136.9 (C-6), 146.0 (C-4)
ppm. 14N NMR ([D6]acetone): δ ϭ Ϫ65 (∆ν1/2 ϭ 50 Hz, NǞO),
Ϫ150 (∆ν1/2 ϭ 220 Hz, ϪNϩϵN) ppm. IR (KBr): ν˜ ϭ 1500 cmϪ1
[N(O)ϭN], 2280 (N2ϩ). C10H12BBrF4N4O (370.94): calcd. C 32.38,
H 3.26, N 15.10; found C 32.35, H 3.26, N 14.49.
6-Bromo-2-(tert-butyl-NNO-azoxy)-3,4-dimethylphenyldiazonium
Tetrafluoroborate (2d): Yellow solid (340 mg, 60 %), m.p. 120Ϫ122
°C (decomp.). 1H NMR ([D6]acetone): δ ϭ 1.54 (s, 9 H, tBu), 2.49
4,6-Dibromo-2-(isopropyl-NNO-azoxy)phenyldiazonium
Tetra-
(s, 3 H, CH3), 2.73 (s, 3 H, CH3), 8.40 (s, 1 H, 5-H) ppm. 13C fluoroborate (2v): Colorless solid (690 mg, 92 %), m.p. 179Ϫ182 °C
1
NMR[16a] ([D6]acetone): δ ϭ 16.6 (CH3), 22.6 (CH3), 25.7 (CMe3), (decomp.). H NMR ([D6]acetone): δ ϭ 1.37 (d, J ϭ 6.6 Hz, 6 H,
62.9 (CMe3), 126.0 (C-3), 130.3 (C-6), 137.6 (C-5), 143.5 (C-4),
CH3), 4.45 (h, J ϭ 6.6 Hz, 1 H, CH), 8.93 (d, J ϭ 1.6 Hz, 1 H, 3-
H), 8.95 (d, J ϭ 1.6 Hz, 1 H, 5-H) ppm. 13C NMR[16a] ([D6]ace-
tone): δ ϭ 19.3 (CH3), 54.8 (CH), 112.9 (C-1), 129.7 (C-3), 131.0
148.1 (C-2) ppm. 14N NMR ([D6]acetone): δ ϭ Ϫ64 (∆ν1/2
ϭ
90 Hz, NǞO), Ϫ154 (∆ν1/2 ϭ 170 Hz, -NϩϵN) ppm. IR (KBr):
Eur. J. Org. Chem. 2002, 3435Ϫ3446
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