316 Bull. Chem. Soc. Jpn., 75, No. 2 (2002)
Oxidation of Phenols with Polymer Catalysts
the products was detected in the wet precipitate by GC. Fresh 1-
hexanol (2 mL), tridecane, and 1a (272 mg, 2 mmol) were added
to the residue without the pretreatment, and the reaction was re-
peated similarly (Table 2).
yloxymethyl-6-methylphenol (3d): MS m/z 322 (M+), 222, 137.
2,6-Dimethoxy-4-(methoxymethyl)phenol (3e): MS m/z 198
(M+), 167; IR (neat) 3143 cm−1; 1H NMR (CDCl3) δ 3.38 (3H, s),
3.89 (6H, s), 4.38 (2H, s) 5.56 (1H, s), 6.58 (2H, s); 13C NMR
(CDCl3) δ 56.2, 57.9, 75.0, 104.5, 129.6, 134.2, 147.0. Anal. Cal-
cd for C10H14O4: C, 60.59; H, 7.12%. Found: C, 60.60; H, 7.12%.
Hexyl 4-hydroxy-3,5-dimethylbenzoate (4a): MS m/z 250 (M+),
General Procedure for the Oxidation of 2,3,6-Trimeth-
ylphenol and Related Compounds 6. CuCl2•2H2O and pyri-
dine were dissolved in an appropriate solvent (2 mL) containing
mesitylene as an internal standard, and the stirring was continued
for a while at room temperature under O2 (1 atm). The phenol 6a
(272 mg, 2 mmol) was added to the homogeneous green solution
and the mixture was stirred under the conditions indicated in Table
5 with monitoring by GC. In the reaction using PVPy under pres-
surized O2 (Table 6), a centrifuge glass tube equipped with a Te-
flon-covered magnetic stirring bar was charged with CuCl2•2H2O
(68 mg, 0.4 mmol), PVPy (45 mg, 2% cross-linked, 0.4 mmol of
Py unit), mesitylene and DMSO (2 mL). The mixture was stirred
for 5 h at 60 °C under O2 (1 atm) to afford green precipitate in the
colorless solution. After addition of the phenol 6 (2 mmol) to the
mixture, a rubber septum with a glass needle was fitted to the tube,
which was placed in a stainless autoclave. The autoclave was
closed and pressurized to 10 atm with O2. The mixture was heated
at 60 °C for 24 h with stirring. After cooling and venting of the re-
sidual gas, the autoclave was opened and the mixture was ana-
lyzed by GC. The products were isolated by column chromato-
graphy, if necessary.
Recycle of CuCl2–PVPy Catalyst in the Oxidation of 2,3,6-
Trimethylphenol (6a). A mixture of CuCl2•2H2O (68 mg, 0.4
mmol), PVPy (66 mg, 25% cross-linked, 0.4 mmol of Py unit) and
mesitylene in DMSO-benzene (1/3, 2 mL) was stirred for 5 h at 60
°C under O2 (1 atm). The phenol 6a (272 mg, 2 mmol) was added
to the mixture, and the reaction was carried out at 80 °C for 24 h
under pressurized O2 (10 atm) in a similar manner to that de-
scribed above. The precipitated catalyst was recovered by decan-
tation and used directly in the next reaction with the same quanti-
ties of the substrate 6a and solvent (Table 5).
1
165, 150, 120; IR (neat) 3433, 1689 cm−1; H NMR (CDCl3) δ
0.90 (3H, t, J = 6.9 Hz), 1.31–1.45 (6H, m), 1.75 (2H, tt, J = 7.4
and 6.9 Hz), 2.28 (6H, s), 4.27 (2H, t, J = 6.9 Hz), 5.25 (1H, s),
7.70 (2H, s); 13C NMR (CDCl3) δ 14.0, 15.7, 22.5, 25.7, 28.7,
31.5, 64.8, 122.2, 122.8, 130.4, 156.4, 166.8. Anal. Calcd for
C15H22O3: C, 71.97; H, 8.86%. Found: C, 72.34; H, 8.66%. Hex-
yl 3-t-butyl-4-hydroxy-5-methylbenzoate (4b): MS m/z 292 (M+),
277, 208, 193. Hexyl 4-hydroxy-3-methyl-5-phenylbenzoate (4c):
MS m/z 312 (M+), 228, 211. Hexyl 3-hexyloxy-4-hydroxy-5-me-
thylbenzoate (4d): MS m/z 336 (M+), 252, 235, 168, 151.
3,3ꢀ,5,5ꢀ-Tetramethylbiphenyl-4,4ꢀ-diol (5a) and (8b): MS m/z 242
1
(M+), 121; IR (neat) 3461 cm−1; H NMR (DMSO-d6) δ 2.07
(12H, s), 6.67 (4H, s), 7.97 (2H, s); 13C NMR (DMSO-d6) δ 16.9,
124.3, 128.6, 132.8, 151.4. 2,3,5-Trimethyl-1,4-benzoquinone
(7a): [935-92-2]; MS m/z 150 (M+), 123, 107; 1H NMR (CDCl3) δ
2.01 (3H, s), 2.04 (6H, two s), 6.56 (1H, s); 13C NMR (CDCl3) δ
12.0, 12.3, 15.8, 133.0, 140.7, 140.8, 145.3, 187.4, 187.8. 2,6-
Dimethyl-1,4-benzoquinone (7b): [527-61-7]; MS m/z 136 (M+),
120. 2-t-Butyl-6-methyl-1,4-benzoquinone (7c): [25543-57-1];
MS m/z 178 (M+), 163, 150, 135. 2,6-Di-t-butyl-1,4-benzoquino-
ne (7d): [719-22-2]; MS m/z 220 (M+), 163; IR (Nujol) 1659,
1
1601 cm−1; H NMR (CDCl3) δ 1.25 (18H, s), 6.48 (2H, s); 13C
NMR (CDCl3) δ 29.4, 35.6, 130.2, 157.9, 187.8, 189.1.
2,2ꢀ,3,3ꢀ,5,5ꢀ-Hexamethylbiphenyl-4,4ꢀ-diol (8a): MS m/z 270
1
(M+), 239, 224, 135; H NMR (CDCl3) δ 1.93 (6H, s), 2.22 (6H,
s), 2.23 (6H, s), 4.58 (2H, s), 6.56 (2H, s); 13C NMR (CDCl3) δ
12.2, 15.8, 16.9, 119.4, 121.6, 129.3, 133.8, 134.7, 150.7. 3,3ꢀ-Di-
t-butyl-5,5ꢀ-dimethylbiphenyl-4,4ꢀ-diol (8c): MS m/z 326 (M+),
311, 283. 3,3ꢀ,5,5ꢀ-Tetra-t-butyldiphenoquinone (8d): mp 125–
Identification of Products and Determination of Their
Yields. All products were identified by GC and GC-MS, and ad-
ditionally by IR, NMR, and microanalyses for the isolated ones,
since most of them are commercially available or known com-
pounds. Their yields were determined by GC using an internal
standard such as tridecane and mesitylene. 4-Hydroxy-3,5-dime-
thylbenzaldehyde (2a): [2233-18-3]; MS m/z 150 (M+), 121. 3-t-
Butyl-4-hydroxy-5-methylbenzaldehyde (2b): MS m/z 192 (M+),
1
126 °C; MS m/z 408 (M+), 393, 351; H NMR (CDCl3) δ 1.35
(36H, s), 7.69 (4H, s); 13C NMR (CDCl3) δ 29.6, 36.0, 126.0,
136.2, 150.5, 180.5. HRMS calcd for C28H40O2 (M+) 408.3025,
found 408.3014.
We are grateful to Dr. Yasushi Sato, Daicel Chemical Indus-
tries, for a generous gift of PPy, PBPy, and PVBPy.
1
177, 149; IR (neat) 3179, 1666 cm−1; H NMR (CDCl3) δ 1.42
(9H, s), 2.31 (3H, s), 5.73 (1H, s), 7.57 (1H, s), 7.71 (1H, s), 9.83
(1H, s). Anal. Calcd for C12H16O2: C, 74.96; H, 8.39%. Found:
C, 74.85; H, 8.48%. 4-Hydroxy-3-methyl-5-phenylbenzaldehyde
(2c): MS m/z 212 (M+), 183, 153. 3-Hexyloxy-4-hydroxy-5-me-
thylbenzaldehyde (2d): MS m/z 236 (M+), 152. 4-Hydroxy-3,5-
dimethoxybenzaldehyde (2e): [134-96-3]; mp 110–112 °C; MS m/
z 182 (M+), 167; IR (Nujol) 3255, 1670 cm−1; 1H NMR (CDCl3) δ
3.96 (6H, s), 6.16 (1H, s), 7.15 (2H, s), 9.82 (1H, s); 13C NMR
(CDCl3) δ 59.4, 106.7, 128.3, 140.8, 147.3, 190.7. Anal. Calcd
for C9H10O4: C, 59.34; H, 5.53%. Found: C, 59.33; H, 5.50%. 4-
(Hexyloxymethyl)-2,6-dimethylphenol (3a): [134778-31-7]; MS
m/z 236 (M+), 135, 121; IR (neat) 3398 cm−1; 1H NMR (CDCl3) δ
0.7–0.9 (3H, m), 1.2–1.8 (8H, m), 2.17 (6H, s), 3.43 (2H, t, J =
7.0 Hz), 4.33 (2H, s), 4.84 (1H, s), 6.91 (2H, s). Anal. Calcd for
C15H24O2: C, 76.22; H, 10.24%. Found: C, 76.12; H, 10.27%. 2-
t-Butyl-4-hexyloxymethyl-6-methylphenol (3b): MS m/z 278
(M+), 191; IR (neat) 3224 cm−1. 5-Hexyloxymethyl-3-methylbi-
phenyl-2-ol (3c): MS m/z 298 (M+), 214, 168. 2-Hexyloxy-4-hex-
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