A green process for oxidation of p-nitrotoluene catalyzed by metalloporphyrins under mild conditions

Article abstract of DOI:10.1021/op060056z

A novel synthetic technology of p-nitrobenzoic acid has been investigated with dioxygen by using metalloporphyrins RTPP-M^IIICl (M = Fe, Co, Mn) as biomimetic catalysts. Oxidation of p-nitrotoluene to p-nitrobenzoic acid under 2.0 MPa of O₂ in the presence of a microamount of metalloporphyrins (RTPP-M^IIICl) at 55 °C was achieved with the highest (up to 90.4%) yield. Further research results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of metalloporphyrins. For the metalloporphyrins with the same center metal ions, the greater the electron-withdrawing degree of groups in the porphyrin ring, the higher the catalytic activities of the metalloporphyrins. The catalytic activities for metalloporphyrins with different center metal ions followed the order RTPPMn ^IIICl > RTPP Fe ^IIICl > RTPP Co ^IIICl.

Full text of DOI:10.1021/op060056z

Organic Process Research & Development 2006, 10, 757−761
A Green Process for Oxidation of p-Nitrotoluene Catalyzed by Metalloporphyrins
under Mild Conditions
Lanzhi Wang,† Yuanbin She,*,† Rugang Zhong,† Hongbing Ji,‡ Yanhui Zhang,† and Xufeng Song†
Institute of Green Chemistry and Fine Chemicals, Beijing UniVersity of Technology, Beijing 100022, P. R. China, and
School of Chemical and Energy Engineering, South China UniVersity of Technology, Guangzhou 510640, P. R. China
Scheme 1
Abstract:
A novel synthetic technology of p-nitrobenzoic acid has been
investigated with dioxygen by using metalloporphyrins RTPP-
MIIICl (M ) Fe, Co, Mn) as biomimetic catalysts. Oxidation of
p-nitrotoluene to p-nitrobenzoic acid under 2.0 MPa of O2 in
the presence of a microamount of metalloporphyrins (RTPP-
MIIICl) at 55 °C was achieved with the highest (up to 90.4%)
yield. Further research results show that the catalytic activities
were relative to the nature of the substituted groups and the
central metal ions of metalloporphyrins. For the metallopor-
phyrins with the same center metal ions, the greater the
electron-withdrawing degree of groups in the porphyrin ring,
the higher the catalytic activities of the metalloporphyrins. The
catalytic activities for metalloporphyrins with different center
metal ions followed the order RTPPMn IIICl >RTPP Fe IIICl >
RTPP Co IIICl.
Our team also reported a one-pot oxidation of cyclohexane
to adipic acid catalyzed by Fe-porphyrin in the presence of
molecular oxygen without any additives with a yield of
21.4%, which was a promising process for production.8 In
this paper, with metallotetraphenylporphyrin chloride com-
plexes (RTPPMIIICl) as biomimetic catalysts for preparation
of p-nitrobenzoic acid from oxidation p-nitrotoluene, the
highest (90.4%) yield of p-nitrobenzoic acid was obtained.
The effect of substituted groups and central metal ions on
catalytic activities of metalloporphyrins was further inves-
tigated, and so far, this research work has not been reported
yet.
Introduction
p-Nitrobenzoic acid, an important intermediate of phar-
maceutical and organic synthesis, was conventionally manu-
factured through the oxidation of p-nitrotoluene using cobalt
bromide and manganese salt as catalysts.1 In one of our
previous works, the oxidation of p-nitrotoluene with metal
phthalocyanines as catalysts in an alkali-methanol solution
had been reported, in which a rather high yield (ca. 88.8%)
of p-nitrobenzoic acid was achieved.2
In the past two decades, the biomimetic catalysis of
metalloporphyrins under mild conditions has increasingly
attracted considerable attention.3-5 More processes involved
in the catalysis of metalloporphyrins under mild conditions
had been developed.6,7 The selection of O2 as the oxygen
source in alkane and alkene oxidations catalyzed by metal-
loporphyrins has raised great prospects in the oxidation of
hydrocarbons.
Results and Discussions
Catalytic Activities of Metalloporphyrins. The struc-
tures of different metalloporphyrin catalysts and the dioxygen
oxidation of p-nitrotoluene to the p-nitrobenzoic acid cata-
lyzed by these metalloporphyrins were shown in Scheme 1.
The oxidation of p-nitrotoluene catalyzed by Fe, Co, and
Mn porphyrins was investigated in a NaOH-methanol
solution under 2.0 MPa of dioxygen at 55 °C for 12 h, and
the results were shown in Table 1 and Figure 1.
Note: There will be a potential hazard of explosion when
using methanol in a pure oxygen environment, although the
explosion limit range of methanol (6.0-36.5 vol %) is
relatively narrower and its flash point (9 °C) is relatively
higher than those of hydrocarbon solvents (<0 °C). When
considering safety, much attention and careful design must
be given in industrial practice. So the reaction temperature
or O2 pressure should be selected as low as possible. To
solve the above problems, the technologies for preparing
p-nitrobenzoic acid using ethanol-water at 60% (v/v) instead
of methanol as solutions and using air instead of dioxygen
are being investigated by our group, and the research work
will be reported soon.
* Corresponding author: Prof. Yuanbin She. E-mail: sheyb@bjut.edu.cn.
Telephone and Fax: +86-10-67392695.
† Beijing University of Technology.
‡ South China University of Technology.
(1) Partenheimer, W. Catal. Today 1995, 23, 69-158.
(2) Song, X. F.; She, Y. B.; Ji, H. B.; Zhang, Y. H. Organic Process Research
& DeVelopment, 2005, 9 (3), 297-301.
(3) Meunier, B. Chem. ReV. 1992, 9 (6), 1411-1456.
(4) Groves, J. T.; Bonchio, M.; Carofiglio, T.; Shalyaev, K. J. Am. Chem. Soc.
1996, 118, 8961-8962.
(5) Zhang, R.; Horner, J. H.; Newcomb, M. J. Am. Chem. Soc. 2005, 127 (18),
6573-6582.
(6) Maldotti, A.; Bartocci, C.; Varani, G.; Molinari, A. Inorg. Chem. 1996, 35,
1126-1131.
(7) Haber, J.; Matachowski, L.; Pamin, K.; Poltowicz, J. J. Mol. Catal. A: Chem.
2003, 198, 215-221.
(8) Yuan, Y.; Ji, H. B.; Chen, Y. X.; Han, Y.; Song, X. F.; She, Y. B.; Zhong,
R. G. Org. Process Res. DeV. 2004, 8, 418-420.
10.1021/op060056z CCC: $33.50 © 2006 American Chemical Society
Published on Web 05/27/2006
Vol. 10, No. 4, 2006 / Organic Process Research & Development
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757

Figure 1. Comparative catalytic activities of metalloporphyrins with different structures.
Table 1. Results of oxidation of p-nitrotoluene catalyzed by
different isolated yields of p-nitrobenzoic acid. For example,
for TPPFeCl with different ortho- substituents from o-NO2
to o-OH, yields changed from 85.3% to 73.3%; and for
TPPFeCl with different para- substituents from p-NO2 to
p-OH, yields changed from 84.4% to 73.2%. Furthermore,
the catalytic activities with different substituents from o/p-
NO2 to o/p-OH followed the order T(o/p-NO2)PPFeCl > T(o/
p-Cl)PPFeCl > TPPFeCl > T(o/p-OCH3)PPFeCl > T(o/p-
OH)PPFeCl. It is obvious that these iron-porphyrin catalysts
with an electron-withdrawing group such as o/p-NO2 exhibit
higher yields than those with an electron-donating group such
as o/p-OH. A similar result was reported by Guo et al.; that
is, the existence of electron-withdrawing groups could also
accelerate the reaction rate of cyclohexane hydroxylation with
the metalloporphyrin catalysts.10 The reasons might be that
the electronic density of Fe ions in metalloporphyrins
decreased with the increase of the electron-withdrawing
degree of substituents from o/p-OH to o/p-NO2, thus leading
to the enhancement of the Fe(III)/Fe(II) reduction potential, and
Fe(III) could be easily reduced to Fe(II), and the all catalytic
cycle of metalloporphyrins could be easily fulfilled.11
Furthermore, Fe porphyrins with ortho-position electron-
withdrawing substituents, such as T(o- NO2)PPFeCl and T(o-
Cl)PPFeCl, exhibited higher yields of p-nitrobenzoic acid
than those with para-position electron-withdrawing substit-
uents such as T(p- NO2)PPFeCl and T(p-Cl)PPFeCl. It is
well-known that self-aggregation of metalloporphyrins could
easily occur and the existence of steric hindrance could well
prevent self-aggregation.12 Comparing Fe porphyrins having
ortho- substituents with those having para- substituents, it
was clear that the steric hindrance for ortho- substituents
was greater, and corresponding catalytic activities were
higher.
Fe, Co, and Mn porphyrinsa
yields of p-nitrobenzoic acidb (%)
entry
catalyst
Fe
Co
Mn
1
2
3
4
5
6
7
8
9
T(o-OH)PPMCl
(R1 ) OH, R2 ) H)
T(p-OH)PPMCl
(R1 ) H, R2 ) OH)
T(o-OCH3)PPMCl
(R1 ) OCH3, R2 ) H)
T(p-OCH3)PPMCl
(R1 ) H, R2 ) OCH3)
TPPMCl
(R1 ) H, R2 ) H)
T(o-Cl)PPMCl
(R1 ) Cl, R2 ) H)
T(p-Cl)PPMCl
(R1 ) H, R2 ) Cl)
T(o-NO2)PPMCl
(R1 ) NO2, R2 ) H)
T(p-NO2)PPMCl
(R1 ) H, R2 ) NO2)
73.3
73.2
75.8
73.7
78.8
82.5
82.3
85.3
84.4
72.3
71.6
74.8
72.3
76.7
78.6
75.9
80.5
77.1
74.8
73.4
75.6
73.8
78.9
86.4
82.6
90.4
84.8
a
Reaction conditions: p-nitrotoluene (20 mmol); catalysts (1.24 × 10-3 mol
%, based on the initial amount of p-nitrotoluene); methanol (50 mL); NaOH
(120 mmol); oxygen pressure (2.0 MPa); at 55 °C for 12 h. b The all yields of
p-nitrobenzoic acid were the isolated yield.
The results of Table 1 and Figure 1 showed that all the
metalloporphyrin catalysts presented excellent activities for
the oxidation of p-nitrotoluene to p-nitrobenzoic acid with
the isolated yield of product being more than 71.6%. The
yields were much higher than the results obtained from
Chandalia and coauthors, who used another type of biomi-
metic catalyst, i.e., cobalt phthalocyanine catalyst and
reported their best yield at less than 40%.9 Moreover, the
yields were comparable to the results with metal phthalo-
cyanines previously reported by our team, with the highest
Similarly cobalt porphyrins were also efficient active
catalysts for the oxidation of unactivated p-nitrotoluene. For
example, the chloro-cobalt tetra-(o-nitrophenyl)porphyrin
T(o-NO2)PPCoCl could catalyze the oxidation of p-nitro-
toluene smoothly under the same reaction conditions, with
a yield of p-nitrobenzoic acid of 80.5%. A similar relation-
ship between substituents of the phenyl groups and catalytic
activities could also be obtained as shown in Figure 1b.
Inspired by the high yields from Fe and Co porphyrins,
Mn was tried in catalyzing the oxidation of p-nitrotoluene
2
yield reaching up to 88.8%.
From Table 1 and Figure 1, we could find that the
structure of metalloporphyrins also affected their catalytic
performance to some extent, i.e., the catalytic activities of
metalloporphyrins in the oxidation of p-nitrotoluene to
p-nitrobenzoic acid not only change with the variety of metal
atom ions in metalloporphyrins but also change with the
variety of peripheral substituents on the porphyrin ring in
the same pattern of metalloporphyrins. For the chloro-iron
tetraphenylporphyrin (RTPPFeCl) catalyst, the different
substituents in the phenyl ring of porphyrin ligands exhibited
(10) Guo, C. C.; Song, J. X.; Chen, X. B.; Jiang, G. F. J. Mol. Catal. 2000, 157,
31-40.
(11) Lyons, J. E.; Ellis, P. E.; Myers, H. K. J. Catal. 1995, 155, 59-73.
(12) Guo, C. C.; Liu, X. Q.; Liu, Y.; Liu, Q.; Chu, M. F.; Zhang, X. B. J. Mol.
Catal. A: Chem. 2003, 192, 289-294.
(9) Chandalia, S. B.; Mukhopadhyay, S.; Org. Process Res. DeV. 1999, 3, 109-
113.
758
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Vol. 10, No. 4, 2006 / Organic Process Research & Development

Scheme 2
Experimental Section
Materials and Instruments. Pyrrole was redistilled
before use. Other reagents such as p-nitrotoluene purchased
from Aldrich were of high purity and used without further
purification.
UV-vis spectra were recorded on a Brucker HITACHI
U-3100. Infrared spectra were recorded on a Brucker
VERTEX 70. A THERMOQUEST Flash EA 1112 elemental
analysis meter was used.
Syntheses of Biomimetic meso-Phenyl Substitute Met-
allotetraphenylporphyrin. The substituted tetraphenylpor-
phyrins (RTPPH2) were synthesized by the direct conden-
sation of pyrrole with the substituted benzaldehydes according
to the documented procedures.15
Chloro-iron Tetraphenylporphyrin (RTPPFeCl). T(o-
NO2)PPFeCl. 200 mg (0.25 mmol) of T(o-NO2)PPH2 were
dissolved in 100 mL of glacial acetic acid. The solution was
heated to reflux with magnetic stirring. Upon dissolution of
T(o-NO2)PPH2, 300 mg (1.50 mmol) of FeCl2‚4H2O were
added in three portions within 30 min. When thin-layer
chromatography (alumina) indicated no free base porphyrin
at this point, using methylene chloride as eluant, 50 mL of
HOAc were removed from the solution. The solution was
cooled to 70 °C, and 40 mL of 6 M HCl were added to it.
The solid appeared in the solution and then was filtrated and
washed with 3 M HCl until the filtrate no longer appeared
green. The resulting solid was vacuum-dried and afforded
above 91.9% yield of T(o-NO2)PPFeCl. Mp > 300 °C. Anal.
Calcd for C44H24N8O8ClFe: C, 59.78; H, 2.74; N, 12.68.
under the same reaction conditions. In this case, the result
of chloro-manganese tetra-(o-nitrophenyl)porphyrin T(o-
NO2)PPMnCl was shown in Scheme 2.
In this oxidation, the chloro-manganese tetra-(o-nitrophen-
yl)porphyrin T(o-NO2)PPMnCl presented a yield of 90.4%
for p-nitrobenzoic acid in the presence of molecular oxygen,
which was the highest yield reported presently. A similar
relationship of chloro-manganese porphyrin complexes could
also be found as shown in Figure 1c.
The results of Table 1 also showed that tetra-(o-nitro-
phenyl) porphyrins with Fe, Co, and Mn central metal ions
gave different yields such as 85.3%, 80.5%, and 90.4%; that
is, the order Mn > Fe > Co could be observed. Haber13
also reported a similar sequence when performing the
oxidation of cyclohexane. The most active catalyst was a
manganese tetra-(o-nitrophenyl) porphyrin with the highest
yield (90.4%) of p-nitrobenzoic acid.
The three possible O2 oxidation paths were fully described
in our former work with metal phthalocyanines as catalysts.2
The catalytic mechanism of metalloporphyrins was reported
by Lyons for the oxidation of isobutene and propane using
halogenated porphyrin chromium, manganese, and iron
complexes as catalysts.11 During the reaction process, a high
valence manganese-oxygen cation radical as an active
intermediate was reported to be more stable than the high
Found: C, 59.35; H, 2.64; N, 12.61. UV-vis(CH2Cl2) λmax
:
422.0 nm (Soret band), 509.6 nm, 579.0 nm (Q-band). IR:
999.8 cm-1 (δFe-N), 367 cm-1 (νFe-Cl).
T(o-Cl)PPFeCl. The solution of T(o-ClTPP) 200 mg
(0.26 mmol) in dimethylformamide(100 mL) was heated to
reflux with magnetic stirring. 300 mg (1.50 mmol) of FeCl2‚
4H2O were added in three portions within 30 min. When
thin-layer chromatography (alumina) indicated no free base
porphyrin, the reaction mixture was cooled to 70 °C, and
40 mL of 6 M HCl were added to it. The solid appeared in
the solution and then was filtrated and washed with 3 M
HCl until the filtrate no longer appeared green. The resulting
solid was vacuum-dried and afforded above 94.7% yield of
T(o-Cl)PPFeCl. Mp > 300 °C. Anal. Calcd for C44H24N4-
Cl5Fe: C, 62.78; H, 2.87; N, 6.66. Found: C, 62.44; H, 3.16;
N, 7.01. UV-vis(CH2Cl2) λmax: 418.5 nm (Soret band),
505.4 nm, 576.0 nm (Q-band). IR: 998.3 cm-1 (δFe-N), 369.6
cm-1 (νFe-Cl).
T(o-OCH3)TPPFeCl was prepared using the same pro-
cedure as that described for T(o-Cl)PPFeCl, and the final
solid was recrystallized from methylene chloride to yield
91.5%. Mp > 300 °C. Anal. Calcd for C48H36N4ClFeO4: C,
69.96; H, 4.40; N, 6.80. Found: C, 69.36; H, 4.73; N, 6.78.
UV-vis(CH2Cl2) λmax: 418.9 nm (Soret band), 512.9 nm,
668.9 nm (Q-band). IR: 997.8 cm-1 (δFe-N), 360.4 cm-1
(νFe-Cl).
14
valence iron-oxygen cation radical, making the reaction
easily performed. For Co, the lower stability of trivalent Co
might attribute to the lower catalytic activity. This might
explain the order Mn > Fe > Co towards the oxidation of
p-nitrotoluene.
Conclusions
Metalloporphyrins were more active catalysts than metal
phthalocyanines for the oxidation of p-nitrotoluene to p-
nitrobenzoic acid. The nature of the porphyrin rings and the
central metal ions had a remarkable effect on the activities
of metalloporphyrins. Metalloporphyrins with electron-
withdrawing groups located in the ortho-position of a phenyl
ring were more efficient catalysts than those with electron-
donating groups located in the para-position of a phenyl ring
while using the same center metal ions; that is, catalytic
activities of metalloporphyrins were in the order T(o/p-
NO2)PPMCl > T(o/p-Cl)PPMCl > TPPMCl > T(o/p-
OCH3)PPMCl > T(o/p-OH)PPMCl. The catalytic activities
of metalloporphyrins with different center metal ions were
in the order RTPPMn IIICl >RTPP Fe IIICl > RTPP Co IIICl.
(13) Haber, J.; Matachowski, L.; Pamin, K.; Poltowicz, J. J. Mol. Catal. 2000,
162, 105-109.
(14) Guo, C. C.; Huang, G.; Li, Z. P.; Song, J. X. J. Mol. Catal. 2001, 170,
43-49.
(15) Adler, A. D.; Longo, F. R.; Finarelli, J. D.; Goldmacher, J.; Assour, J.;
Korsakoff, L. J. Org. Chem. 1967, 32 (2), 476-476.
Vol. 10, No. 4, 2006 / Organic Process Research & Development
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759

T(o-OH)TPPFeCl was prepared using the same proce-
dure as that described for T(o-Cl)PPFeCl, and the final solid
was recrystallized from methanol to yield 61.5%. Mp > 300
°C. UV-vis(CH2Cl2): λmax: 415.6 nm (Soret band), 523.2
nm, 578.6 nm (Q-band). IR: 998.8 cm-1 (δFe-N), 361.4 cm-1
(νFe-Cl).
TPPFeCl was prepared using the same procedure as that
described for T(o-Cl)PPFeCl and recrystallized from CH2-
Cl2/methanol, and the yield was up to 97.4%. Mp > 300
°C. Anal. Calcd for C44H28N4ClFe: C, 75.07; H, 4.01; N,
7.96. Found: C, 74.29; H, 4.07; N, 7.92. UV-vis(CH2Cl2):
base porphyrin, using dimethylformamide as eluant, 30 mL
of dimethylformamide were removed from the solution. The
solution was cooled to 70 °C, and 40 mL of 6 M HCl were
added to it. The solid appeared in the solution and then was
filtrated and washed 3 times with 3 M HCl. The resulting
solid was vacuum-dried and afforded above 94.9% yield of
T(o-NO2)PPMnCl. UV-vis(CH2Cl2) λmax: 471.0 nm (Soret
band), 508.8 nm, 563.2 nm (Q-band). IR: 1009.3 cm-1
(δMn-N), 322 cm-1 (νMn-Cl).
T(o-Cl)PPMnCl. 200 mg (0.26 mmol) of T(o-Cl)PPH2
were dissolved in 50 mL of dimethylformamide. The solution
was heated to reflux with magnetic stirring. Upon dissolution
of T(o-Cl)PPH2, 300 mg (1.50 mmol) of MnCl2‚4H2O were
added in three portions within 30 min. When thin-layer
chromatography (alumina) indicated no free base porphyrin,
using methylene chloride as eluant, the solution was cooled
to 70 °C, and 40 mL of 6 M HCl were added to it. The solid
appeared in the solution and then was filtrated and washed
3 times with 3 M HCl. The resulting solid was vacuum-
dried and afforded above 94.9% yield of T(o-Cl)PPMnCl.
UV-vis(CH2Cl2) λmax: 478.0 nm (Soret band), 583.6 nm,
620.0 nm (Q-band). IR: 1008.5 cm-1 (δMn-N), 322 cm-1
(νMn-Cl).
λ
max: 418.8 nm (Soret band), 507.2 nm, 572.4 nm (Q-band).
IR: 999.6 cm-1 (δFe-N), 378.9 cm-1 (νFe-Cl).
T(p-NO2)PPFeCl: 200 mg (0.25 mmol) of T(p-NO2)PPH2
were dissolved in 100 mL of propionic acid. The solution
was heated to reflux with magnetic stirring. Upon dissolution
of the T(p-NO2)PPH2, 300 mg (1.50 mmol) of FeCl2‚4H2O
were added in three portions within 30 min. When thin-layer
chromatography (alumina) indicated no free base porphyrin,
50 mL of propionic acid was removed from the solution.
The solution was cooled to 70 °C, and 40 mL of 6 M HCl
were added to it. The solid appeared in the solution and then
was filtrated and washed with 3 M HCl until the filtrate no
longer appeared green. The resulting solid was vacuum-dried
and afforded above 92% yield of T(p-NO2)PPFeCl. Mp >
300 °C. Anal. Calcd for C44H24N8O8ClFe: C, 59.78; H, 2.74;
N, 12.68. Found: C, 59.35; H, 2.74; N, 12.68. UV-vis-
(CH2Cl2) λmax: 422.0 nm (Soret band), 514.4 nm, 583.0 nm
(Q-band). IR: 998.8 cm-1 (δFe-N), 368 cm-1 (νFe-Cl).
T(p-Cl)PPFeCl was prepared using the same procedure
as described for T(o-Cl)PPFeCl and recrystallized from CH2-
Cl2/methanol. The yield was up to 99.4%. Mp > 300 °C.
Anal. Calcd for C44H24N4Cl5Fe: C, 62.78; H, 2.87; N, 7.04.
TPPMnCl was prepared using the same procedure as that
described for T(o-Cl)PPMnCl and recrystallized from CH2-
Cl2/methanol. The yield was up to 88.5%. UV-vis(CH2Cl2)
λ
max: 477.0 nm (Soret band), 534.0 nm, 583.3 nm (Q-band).
IR: 1008.0 cm-1 (δMn-N), 320 cm-1 (νMn-Cl).
T(o-OCH3)PPMnCl was prepared using the same pro-
cedure as that described for T(o-Cl)PPMnCl and recrystal-
lized from CH2Cl2, in a yield of 90%. UV-vis(CH2Cl2)
λ
max: 477.5 nm (Soret band), 513.3 nm, 583.0 nm (Q-band).
IR: 1007.0 cm-1 (δMn-N), 321 cm-1 (νMn-Cl).
Found: C, 62.32; H, 3.31; N, 6.66. UV-vis(CH2Cl2) λmax
420.5 nm (Soret band), 509.4 nm, 573.0 nm (Q-band). IR:
998.6 cm-1 (δFe-N), 359.1 cm-1 (νFe-Cl).
:
T(o-OH)PPMnCl was prepared using the same procedure
as that described for T(o-Cl)PPMnCl and recrystallized from
methanol, in a yield of 90%. UV-vis(CH2Cl2): λmax: 472.0
nm (Soret band), 530.3 nm, 583.0 nm (Q-band). IR: 1007.0
cm-1 (δMn-N), 317 cm-1 (νMn-Cl).
T(p-OCH3)PPFeCl was prepared using the same proce-
dure as that described for T(o-Cl)PPFeCl, and the resulting
solid was washed twice with water (50 mL) and then
recrystallized from CH2Cl2/methanol, in a yield of 95.2%.
Mp > 300 °C. Anal. Calcd for C48H36N4ClFeO4: C, 69.96;
H, 4.40; N, 6.80. Found: C, 69.30; H, 4.68; N, 6.86. UV-
vis(CH2Cl2) λmax: 421.5 nm (Soret band), 509.4 nm, 571.0
nm (Q-band). IR: 997.9 cm-1 (δFe-N), 359.7 cm-1 (νFe-Cl).
T(p-OH)PPFeCl was prepared using the same procedure
as that described for T(o-Cl)PPFeCl and then recrystallized
from methanol, in a yield of 91.6%. Mp > 300 °C. Anal.
Calcd for C44H28N4ClFeO4: C, 68.74; H, 3.60; N, 7.29.
T(p-NO2)PPMnCl was prepared using the same proce-
dure as that described for T(o-Cl)PPMnCl and recrystallized
from DMF, in a yield of 91.0%. UV-vis(CH2Cl2) λmax
:
477.8 nm (Soret band), 528.6 nm, 583.6 nm (Q-band). IR:
1008 cm-1 (δMn-N), 323 cm-1 (νMn-Cl).
T(p-Cl)PPMnCl was prepared using the same procedure
as that described for T(o-Cl)PPMnCl and recrystallized from
methanol, in a yield of 99.5%. UV-vis(CH2Cl2) λmax: 477.6
nm (Soret band), 532.0 nm, 585.6 nm (Q-band). IR: 1007.9
cm-1 (δMn-N), 320 cm-1 (νMn-Cl).
Found: C, 67.29; H, 3.95; N, 7.21. UV-vis(CH2Cl2) λmax
418.3 nm (Soret band), 503.2 nm, 575.8 nm (Q-band). IR:
998.4 cm-1 (δFe-N), 339.7 cm-1 (νFe-Cl).
Chloro-manganese Tetraphenylporphyrin (RTPP-
MnCl). T(o-NO2)PPMnCl. 200 mg (0.25 mmol) of T(o-
NO2)PPH2 were dissolved in 50 mL of dimethylformamide.
The solution was heated to reflux with magnetic stirring.
Upon dissolution of T(o-NO2)PPH2, 300 mg (1.50 mmol)
of MnCl2‚4H2O were added in three portions within 30 min.
When thin-layer chromatography (alumina) indicated no free
:
T(p-OCH3)PPMnCl was prepared using the same pro-
cedure as that described for T(o-Cl)PPMnCl and recrystal-
lized from methanol, in a yield of 97.5%. UV-vis(CH2-
Cl2): λmax: 479.2 nm (Soret band), 535.2 nm, 589.6 nm (Q-
band). IR: 1005.1 cm-1 (δMn-N), 322 cm-1 (νMn-Cl).
T(p-OH)PPMnCl was prepared using the same procedure
as that described for T(o-Cl)PPMnCl and recrystallized from
methanol, in a yield of 81.9%. UV-vis (CH2Cl2) λmax: 471.0
nm (Soret band), 535.2 nm, 584.6 nm (Q-band). IR: 1007.9
cm-1 (δMn-N), 321 cm-1 (νMn-Cl).
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Vol. 10, No. 4, 2006 / Organic Process Research & Development

Chloro-cobalt Tetraphenylporphyrin (RTPPCoCl). T-
(o-NO2)PPCoCl. 200 mg (0.25mol) of T(o-NO2)PPH2 were
dissolved in 100 mL of propionic acid. The solution was
heated to reflux with magnetic stirring. Upon dissolution of
T(o-NO2)PPH2, 300 mg (1.20 mmol) of Co(OAc)‚4H2O were
added in three portions within 30 min. When thin-layer
chromatography (alumina) indicated no free base porphyrin
using benzene/ligroin as eluant, 50 mL of propionic acid were
removed from the solution. The solution was cooled to 70
°C, and 40 mL of 6 M HCl were added to it. The solid
appeared in the solution and then was filtrated and washed
with 3 M HCl until the filtrate no longer appeared red. The
resulting solid was recrystallized from DMF and then
vacuum-dried, and affording above 85% yield of T(o-
NO2)PPCoCl. UV-vis(CH2Cl2) λmax: 414.3 nm (Soret band),
535.1 nm, 565.2 nm (Q-band). IR: 1000.8 cm-1 (δCo-N),
307 cm-1 (νCo-Cl).
T(p-Cl)PPCoCl was prepared using the same procedure
as that described for T(o-Cl)PPCoCl and recrystallized from
CH2Cl2/methanol, in a yield of 98.9%. UV-vis(CH2Cl2)
λ
max: 410.0 nm (Soret band), 529.0 nm, 653.0 nm (Q-band).
IR: 1000.6 cm-1 (δCo-N), 320 cm-1 (νCo-Cl).
T(p-OCH3)PPCoCl was prepared using the same pro-
cedure as that described for T(o-Cl)PPCoCl and recrystallized
from CH2Cl2/methanol, in a yield of 98.3%. UV-vis(CH2-
Cl2) λmax: 414.0 nm (Soret band), 530.0 nm (Q-band). IR:
1001.2 cm-1 (δCo-N), 321 cm-1 (νCo-Cl).
T(p-OH)PPCoCl was prepared using the same procedure
as described for T(o-Cl)PPCoCl and recrystallized from
methanol, in a yield of 87.3%. UV-vis(CH2Cl2) λmax: 410.0
nm (Soret band), 546.0 nm, 603.0 nm (Q-band). IR: 1000.1
cm-1 (δCo-N), 323 cm-1 (νCo-Cl).
The above results showed that the synthetic complexes
were metalloporphyrins as expected.
T(o-Cl)PPCoCl was prepared using the same procedure
as that described for T(o-NO2)PPCoCl, and only the reaction
solvent was DMF instead of propanoic acid. The resulting
solid recrystallized from methanol, in a yield of 99.7%. UV-
vis(CH2Cl2) λmax: 419.0 nm (Soret band), 541.4 nm, 559.0
nm (Q-band). IR: 1005.0 cm-1 (δCo-N), 317 cm-1 (νCo-Cl).
TPPCoCl was prepared using the same procedure as that
described for T(o-Cl)PPCoCl and recrystallized from CH2-
Dioxygen Oxidation of p-Nitrotoluene with Substitute
Metallotetraphenylporphyrin. The catalytic oxidation of
p-nitrotoluene to p-nitrobenzoic acid was carried out using
molecular oxygen as an oxidant. For these experiments, a
solution of p-nitrotoluene and catalyst in methanol was sealed
into a 200 mL stainless steel autoclave equipped with a
baffled magnetic stirrer. The reactor was pressurized at 2.0
MPa of oxygen and heated to reaction temperature for 12 h.
Then, the reactor was cooled to room temperature, and the
gas was slowly vented. p-Nitrobenzoic acid was obtained
via dissolving the reaction mixture with water, filtration,
extraction with benzene, acidifying the water phase with
concentrated HCl, filtration, and drying.
Cl2/methanol, in a yield of 99.0%. UV-vis (CH2Cl2) λmax
:
405.5 nm (Soret band), 544.3 nm, 571.3 nm (Q-band). IR:
1004.0 cm-1 (δCo-N), 301 cm-1 (νCo-Cl).
T(o-OCH3)PPCoCl was prepared using the same pro-
cedure as that described for T(o-Cl)PPCoCl and recrystallized
from CH2Cl2/methanol, in a yield of 98%. UV-vis(CH2-
Cl2) λmax: 411.5 nm (Soret band), 523.6 nm, 562.3 nm (Q-
band). IR: 1000.0 cm-1 (δCo-N), 306 cm-1 (νCo-Cl).
T(o-OH)PPCoCl was prepared using the same procedure
as that described for T(o-Cl)PPCoCl and recrystallized from
methanol, in a yield of 98%. UV-vis(CH2Cl2) λmax: 406.5
nm (Soret band), 530.6 nm, 562.3 nm (Q-band). IR: 1001.0
cm-1 (δCo-N), 310 cm-1 (νCo-Cl).
Acknowledgment
We are indebted to the Project of the National Natural
Science Foundation of China (No. 20576005), the Key
Project of the National Natural Science Foundation of China
(No. 20436010), and the Key Project of Beijing Natural
Science Foundation of China (No. 2061001) for financial
support of this work.
T(p-NO2)PPCoCl was prepared using the same procedure
as that described for T(o-NO2)PPCoCl and recrystallized
from DMF, in a yield of 63.0%. UV-vis(CH2Cl2) λmax
:
Received for review March 12, 2006.
OP060056Z
414.0 nm (Soret band), 553.0 nm (Q-band). IR: 1003.3 cm-1
(δCo-N), 320 cm-1 (νCo-Cl).
Vol. 10, No. 4, 2006 / Organic Process Research & Development
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