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PAPER
systems, Toronto, Canada) equipped with an ion-spray ionization
source.
lowed to stand in an ice bath for 30 min with occasional stirring. The
reddish precipitate that had formed was collected by filtration,
washed with cold H2O, and dried. The precipitate was purified by
crystallization from EtOAc; this gave the azo dyes 3, 7 and 10.
4-Nitro-m-xylene-d9 (5)
HNO3 (4.66 mL) and H2SO4 (1 mL) were added to m-xylene-d10 (4;
2 mL, 16 mmol), and the reaction mixture was stirred at r.t. When
the reaction was completed (after ca. 5 h), a soln of sat. aq NaHCO3
(3 mL) was added and the mixture was extracted with Et2O (3 × 10
mL). The organic extract was dried (Na2SO4), the solvent was re-
moved, and the residue was distilled under vacuum.
Sudan I
1H NMR (300 MHz, CDCl3): d = 16.24 (s, 1 H, OH), 8.54 (d,
J = 8.31 Hz, 1 H, H*), 7.80–7.20 (m, 9 H, H* + H**), 6.85 (d,
J = 9.44 Hz, 1 H, H*); H* = naphthol protons; H** = phenylazo
protons.
Yield: 1.74 mL (75%); colorless liquid; bp 113 °C/15 Torr.
Sudan I-d5 (3)
Yield: 95%; red crystals; mp 134–133 °C.
2,4-Dimethylaniline-d9 (6)
Concd HCl (1.51 mL) was added in three portions to a mixture of 4-
nitro-m-xylene-d9 (5; 1.51 g, 9.4 mmol) and granular Sn (2.3 g), vig-
orously stirred after each addition. EtOH (ca. 7.5 mL) was added
until 5 was completely solubilized. The reaction mixture was kept
in a water bath at 70 °C for 1 h, then cooled to r.t. and treated with
a 20% NaOH soln (4 mL) until the tin hydroxide precipitate was sol-
ubilized. The crude mixture was extracted with Et2O (3 × 10 mL),
dried (Na2SO4), and evaporated to dryness, and the residue was pu-
rified by vacuum distillation (120 °C/1 Torr); this afforded 6.
1H NMR (300 MHz, CDCl3): d = 16.27 (s, 1 H, OH), 8.52 (d,
J = 8.25 Hz, 1 H, H*), 7.79–7.06 (m, 6 H, H*), 6.84 (d, J = 9.62 Hz,
1 H, H*); H* = naphthol protons.
ESI-HRMS: m/z [M + H]+ calcd for C16H8D5N2O+: 254.1342;
found: 254.1354; 5.42% d4, 94.58% d5.
Sudan II
1H NMR (300 MHz, CDCl3): d = 16.59 (s, 1 H, OH), 8.58 (d,
J = 8.25 Hz, 1 H, H*), 7.94 (d, J = 8.25 Hz, 1 H, H**), 7.77–7.09
(m, 6 H, H* + H**), 6.90 (d, J = 9.17 Hz, 1 H, H*), 2.50 (s, 3 H,
CH3), 2.35 (s, 3 H, CH3); H* = naphthol protons; H** = dimeth-
ylphenylazo protons.
Yield: 1.15 g (94%); colorless liquid.
Diazoaminobenzene-d10 (8)
Aniline-d5 (1; 1 mL, 10 mmol) was added to a soln of H2O (5 mL)
and concd HCl (1.33 mL). The reaction mixture was vigorously
shaken and put in an ice bath (0–5 °C). A soln of NaNO2 (0.346 g,
5 mmol) in H2O (3 mL) was then slowly added, while the bath tem-
perature was maintained at 0–5 °C. The soln was allowed to stand
with frequent shaking for 15 min, and then NaOAc (1.4 g, 17 mmol)
in H2O (3 mL) was added over 5 min. A yellow precipitate of com-
pound 8 formed instantaneously, and was filtered on a Buchner fun-
nel, washed with a little cold H2O, and dried.
Sudan II-d9 (7)
Yield: 85%; red crystals; mp 162–161 °C.
1H NMR (300 MHz, CDCl3): d = 16.58 (s, 1 H, OH), 8.54 (d,
J = 8.24 Hz, 1 H, H*), 7.75–7.30 (m, 4 H, H*), 6.89 (d, J = 9.63 Hz,
1 H, H*); H* = naphthol protons;
ESI-HRMS: m/z [M + H]+ calcd for C18H8D9N2O+: 286.1906;
found: 286.1925; 1.95% d6, 7.31% d7, 25.37% d8, 65.37% d9.
Sudan III
Yield: 1.88 g (91%).
1H NMR (300 MHz, CDCl3): d = 16.36 (s, 1 H, OH), 8.51 (d,
J = 8.25 Hz, 1 H, H*), 8.10–7.35 (m, 13 H, H* + H**), 6.79 (d,
J = 9.62 Hz, 1 H, H*); H* = naphthol protons; H** = diphenylazo
protons.
4-(Phenylazo)aniline-d9 (9)
Diazoaminobenzene-d10 (8; 0.200 g, 0.96 mmol) was dissolved in
aniline-d5 (0.534 mL, 0.576 g) and then aniline-d5HCl (0.096 g) was
added. The mixture was warmed at 40–45 °C for 1 h. Then it was
left to stand for 30 min, and a soln of glacial AcOH, diluted with an
equal volume of H2O, was added until an orange precipitate was ob-
served. The mixture was allowed to stand for 15 min, and then it
was filtered on a Buchner funnel, washed with a little cold H2O, and
dried.
Sudan III-d9 (10)
Yield: 95%; red crystals; mp 208–207 °C.
1H NMR (300 MHz, CDCl3) 16.35 (s, 1 H, OH), 8.50 (d, J = 8.71
Hz, 1 H, H*), 7.72–7.35 (m, 6 H, H*), 6.78 (d, J = 9.62 Hz, 1 H,
H*); H* = naphthol protons.
ESI-HRMS: m/z [M + H]+ calcd for C22H8D9N4O+: 362.1967;
found: 362.1978; 6.78% d8, 93.22% d9.
Yield: 0.161 g (81%).
1,3-Di-o-tolyltriazene (23)
Compound 23 was prepared from o-toluidine (22) by the same pro-
cedure as that used for the preparation of 8.
Azo Compounds 18–21 and 25 by Coupling of Amines 14–17
and 24 and b-Naphthol-d7; General Procedure
Compounds 18–21 and 25 were prepared by coupling of amines 14–
17 and 24 with b-naphthol-d7 by the same procedure as that used for
the preparation of 3, 7, and 10 by the coupling of deuteroamines
with b-naphthol.
Yield: 72%; yellow precipitate.
2-Methyl-4-(o-tolylazo)aniline (24)
Compound 24 was prepared from 23 by the same procedure as that
used for the preparation of 9.
Sudan I-d6 (18)
Yield: 98%; red crystals; mp 132.5–132 °C.
Yield: 71%; orange precipitate.
1H NMR (300 MHz, CDCl3): d = 16.23 (s, 1 H, OH), 7.80–7.15 (m,
5 H, H**); H** = phenylazo protons.
Azo Compounds 3, 7, and 10 by Coupling of Deuteroamines 1,
6, and 9 and b-Naphthol (2); General Procedure
A cooled soln of NaNO2 (11 mmol) in H2O (4 mL) was added drop-
wise to a soln containing the appropriate deuterated amine 1, 6, or 9
(11 mmol) in concd HCl (3.25 mL) and H2O (3 mL), kept at 0–5 °C.
The bath temperature of the diazonium salt soln thus formed was
raised to 10 °C, and a mixture of b-naphthol (2; 11 mmol) in 10%
aq NaOH (9.15 mL) was slowly added. The reaction mixture was al-
ESI-HRMS: m/z [M + H]+ calcd for C16H7D6N2O+: 255.1404;
found: 255.1388; 7.05% d5, 92.95% d6.
Sudan II-d6 (19)
Yield: 81%; red crystals; mp 161–160 °C.
Synthesis 2008, No. 3, 459–463 © Thieme Stuttgart · New York