6698
N. Hirai et al. / Tetrahedron 62 (2006) 6695–6699
(
(
37%) in preference to 2,6-dimethylbenzoic acid (10b)
13%) (Eq. 2).
in 90% yield. The X-ray analysis of THICA indicates that
three OH groups are situated at the same plane.
1
TBTA: H NMR d 7.52 (m, 2H), 7.42 (m, 3H), 5.1 (s, 2H);
C NMR d 144.83, 133.47, 129.52, 129.04, 128.35,
THICA (1 mol%)
Co(OAc)2 (0.5 mol%)
Mn(OAc)2 (0.5 mol%)
1
3
COOH
COOH
78.482; IR (KBr) 1740s, 1401s, 1197m, 1001s, 750s,
696s cm
+
O2
+
ꢂ1
AcOH, 100 °C, 1 h
.
(
1 atm)
9
10a (37%)
10b (13%)
1
13
THICA: H NMR d 11.03 (s, 3H); C NMR d 146.65; IR
(KBr) 3539s, 3166s, 2827s, 1720s, 1433s, 1211m, 1010s,
701s cm
ð2Þ
ꢂ1
ꢀ
.
In the oxidation of 9 at 100 C, no di and tricarboxylic acids
were formed. The preferential formation of 10a over 10b
indicates that the steric effect of the methyl group is a more
important factor than the electron-donating effect.
3.3. Procedure for oxidation of substituted toluenes
under dioxygen atmosphere
An acetic acid solution (5 mL) of substrate (3 mmol),
THICA, Co(OAc) (0.5 mol %) was placed in a 50-mL
In conclusion, we have carried out the first systematic study
on the aerobic oxidation of trimethylbenzenes and devel-
oped an efficient halogen-free route to 1,2,4-benzenetricar-
boxylic acid 4, which is an important polymer material,
using THICA as a key catalyst.
2
pear-shaped flask with a balloon filled with O . The mixture
2
ꢀ
was stirred at 100 C for 6 h. After the reaction, the solvent
was removed under reduced pressure, and the products
were purified by column chromatography on silica gel to
give the corresponding oxygenated products. The products
were identified through comparison of the isolated products
with authentic samples.
3. Experimental
3
.1. General procedure
Acknowledgements
Starting materials and catalysts were purchased from com-
mercial sources and used without further treatment. Yields
were estimated from the peak areas based on the internal
standard technique by using GC. GC analysis was performed
with a flame ionization detector using a 0.2 mmꢁ30 m
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Areas ‘Advanced Molecular
Transformations of Carbon Resources’ from the Ministry
of Education, Culture, Sports, Science, and Technology,
Japan.
1
13
capillary column (OV-17). H and C NMR spectra were
measured at 270 and 400 MHz, respectively, in chloro-
form-d with Me Si as the internal standard. Infrared (IR)
4
spectra were measured using NaCl or KBr pellets. GC–MS
were obtained at ionization energy of 70 eV. All products
were identified by comparison of the isolated products with
authentic samples.
References and notes
1. (a) Ockerbloom, N. E. Hydrocarbon Process. 1972, 51, 114; (b)
Partenheimer, W. Catal. Today 1995, 23, 69; (c) Pershall,
G. W.; Ittel, S. D. Homogeneous Catalysis, 2nd ed; Wiley:
New York, NY, 1992; (d) Suresh, A. K.; Sharma, M. M.;
Sridhar, T. Ind. Eng. Chem. Res. 2000, 39, 3958; (e)
Weissermel, K.; Arpe, H.-J. Industrial Organic Chemistry,
4th ed; Wiley-VCH: Weinhelm, 2003.
2. (a) Bergwerksverband. Hydrocarbon Process. 1971, 50, 214;
(b) Handrick, K; Benning, A; George, D; Curland, E. GB
Patent 1,149,321, 1969.
3. Tanaka, T; Hataya, M; Tanaka, K. EP Patent 83,224, 1983.
4. (a) Ichikawa, I. U.S. Patent 3,299,125, 1967; (b) Partenheimer,
W. J. Mol. Catal. A: Chem. 2003, 206, 105 and 131; (c)
Partenheimer, W; Schammel, W. P. U.S. Patent 4,786,753,
1988; (d) Reeve, A. C. U.S. Patent 5,107,020, 1992.
5. (a) Ishii, Y.; Sakaguchi, S. Oxidation Methods; B a¨ ckvall,
J.-E., Ed.; Wiley-VCH: Weinhelm, 2003; Chapter 5; (b)
Ishii, Y.; Sakaguchi, S.; Iwahama, T. Adv. Synth. Catal.
2001, 343, 393.
0
00
3
(
.2. Preparation of N,N ,N -trihydroxyisocyanuric acid
THICA)
1
0
THICA was prepared by a modified literature procedure.
0
1
,1 -Carbonyldiimidazole (165 mmol) was added to a
pyridine (250 mL) solution of O-benzylhydroxylamine
(
room temperature, and the temperature was raised to 60 C
150 mmol) under Ar. The mixture was stirred for 1 h at
ꢀ
ꢀ
was removed under reduced pressure until the mixture was
for 6 h, and 90 C for 5 h. After the reaction, the solvent
100 g. Water (500 mL) was added slowly to the mixture to
give a white precipitate. The precipitate was filtered and
washed with water (50 mL), AcOH (40 mL), and n-hexane
(40 mL). The solid was recrystallized from AcOH (80 mL)
and AcOEt (70 mL) and dried under vacuum to give
tribenzyloxy-1,3,5-triaine-2,4,6(1H,3H,5H)-trione (TBTA)
(
5.1 g) in 23% yield.
6
. (a) Hirai, N.; Sawatari, N.; Nakamura, N.; Sakaguchi, S.; Ishii,
Y. J. Org. Chem. 2003, 68, 6587; (b) Hirai, N.; Kagayama, T.;
Tatsukawa, Y.; Sakaguchi, S.; Ishii, Y. Tetrahedron Lett. 2004,
45, 8277.
TBTA (5 mmol) in 100 mL of dioxane was hydrogenated on
0 wt % Pd/C (0.5 g) under normal pressure of hydrogen at
1
room temperature overnight. After removal of the catalyst by
filtration, the filtrate was evaporated under reduced pressure
to afford THICA, which was recrystallized from acetone,
7. In the previous papers, we have shown that the NHPI catalyst
decomposed gradually to inert phthalimide and phthalic