A Convenient, Efficient, and Environmentally Benign Method for Preparing Nitroanilines

Article abstract of DOI:10.1246/cl.2003.1142

An efficient method for the catalytic monoreduction of aromatic dinitro compounds to nitroanilines is reported. In the presence of selenium catalyst, the dinitroaromatic compounds are selectively reduced by CO/H₂O to the corresponding nitroanilines under atmospheric pressure. The mono-reduction occurs in high selectivity regardless of the substitution groups on the aromatic ring without affecting other reducible functional groups.

Full text of DOI:10.1246/cl.2003.1142

1
142
Chemistry Letters Vol.32, No.12 (2003)
A Convenient, Efficient, and Environmentally Benign Method for Preparing Nitroanilines
Xiao-zhi Liu and Shi-wei Lu
National Engineering Research Center for Catalysis, Dalian Institute of Chemical Physics, The Chinese Academy of Sciences,
Dalian, Liaoning, 116011, P. R. China
(Received September 9, 2003; CL-030840)
An efficient method for the catalytic monoreduction of aro-
Table 1. The selenium-catalyzed monoreduction of dinitroben-
a
matic dinitro compounds to nitroanilines is reported. In the pres-
ence of selenium catalyst, the dinitroaromatic compounds are se-
lectively reduced by CO/H2O to the corresponding nitroanilines
under atmospheric pressure. The mono-reduction occurs in high
selectivity regardless of the substitution groups on the aromatic
ring without affecting other reducible functional groups.
zene derivatives to the corresponding nitroanilines
c
d
Run Substrate Product Reaction Con. Sel.
Time/min /% /%
NO2
NO2
1
65
55
100 87.7
100 96.4
b
NO2
NH2
2
3
Nitroanilines are of significant industrial importance, be-
cause they are widely used as intermediates for dyes, pharma-
ceuticals, and agrochemicals. The monoreduction of aromatic
dinitro compounds is one of the most common methods to pre-
pare the corresponding nitroanilines. Most often, hydrogen sul-
60
100 78.4
O2N
O2N
NO2
O2N
O2N
NH2
NO2
NH2
4
325
50
84
92
1
2
CF3
CF3
fide or variations of this reagent (Zinn reduction) and iron
are used in industry, but large amounts of waste is produced. Re-
cently, some homogeneous as well as heterogeneous catalytic
systems in combination with different hydrogen donors have
been employed for monoreduction of dinitroaromatic com-
O2N
NO2
O2N
NH2
5
6
7
120
100
140
100
CN
CN
3
pounds.
CO/H2O as a hydrogen source for the reduction of aromatic
nitro compounds to the corresponding amines is of great indus-
trial potential, especially when a cheap catalytic system can be
O2
N
NO2
O2N
NH2
100 79.0
100 83.7
NH2
NH2
NO2
NO2
4
employed. In 1980, Sonoda et al. reported the selenium-cata-
NO2
NH2
lyzed reduction of some aromatic nitro compounds to the corre-
sponding amines by using CO/H2O under high pressure in the
presence of triethylamine (Et3N). But the high pressure of CO
makes it difficult to apply in industry. When they extended their
catalytic system to dinitro-compounds, they could not obtain the
NH2
NH2
a
Reaction conditions: substrate, 10 mmol; selenium, 0.4mmol;
DMF, 40 mL; H2O, 2 mL; NaAc, 5 mmol; CO, bubble; 95 C.
DMF, 60 mL. Conversion. Selectivity.
ꢀ
b
c
d
5
corresponding monoreduction products.
the reaction was complete under atmospheric pressure, all m-di-
nitrobenzene derivatives examined can be reduced to the corre-
sponding nitroanilines with good selectivities and no ureas were
detected. However, o- and p-dinitrobenzenes, in which the two
nitro groups resonate with each other, cannot be reduced under
our conditions. This indicates that the electron deficiency of
the nitro groups prevents the reduction, as can be assumed from
the fact that the reduction of the 1,3-dinitro-5-trifluoromethyl-
benzene is slow (Run 4). Perhaps because of the ortho-effect,
more hindered nitro group was selectively reduced (Run 7). In
addition to the mono reduction products, small amounts of dia-
O N
2
O N
2
Cat.Se/NaAc
NO2 + 3CO + H O
2
o
NH + 3CO
2
2
95 C/DMF
X
X
(
1)
Now we for the first time report the selenium-catalyzed
monoreduction of dinitroaromatic compounds with carbon mon-
oxide and water using sodium acetate (NaAc) as a base in di-
methylformamide (DMF) under atmospheric pressure to give
the corresponding nitroanilines (Eq 1). Besides the advantages
of efficiency and convenience, the catalytic system possesses
the character of phase transfer catalysis: namely, this system
can be used for homogeneous catalytic reduction of dinitroben-
zenes, using CO/H2O as the reducing agent, and exhibits high
conversion and selectivity as well as excellent catalyst stability.
After the reaction, the catalyst and base can be easily filtered and
reused just like heterogeneous catalysts. Therefore, the catalytic
system possesses the advantages of both homogeneous and het-
erogeneous catalysts.
5
mines were also produced. The syntheses of the diamines and
arylureas under high pressure condition have been reported pre-
6
viously. In particular, o-aminonitrobenzene prefers the forma-
tion of benzimidazolon derivatives. In contrast, the carbonyla-
tion was difficult and the reduction of m-nitroaniline was slow
7
8
under our conditions, so the selectivity of amines was high
and the reduction of m-dinitrobenzene derivatives stopped at
the monoreduction stage. Although the reaction of nitriles with
Se/CO/H2O in the presence of Et3N is known to provide the
m-Dinitrobenzene and five substituted dinitrobenenes were
investigated and the results are summarized in Table 1. Although
9
corresponding selenoamides, such conversion was not observed
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.12 (2003)
1143
Table 2. The influence of solvents and bases on the reduction of
a
catalyst was precipitated and recovered. As shown in Table 3,
the catalytic activity of the recovered catalysts was practically
the same as that of the fresh catalyst, indicating the excellent sta-
bility of the catalyst.
m-dinitrobenzene
f
Run
Solvent
Base
Reaction
e
Yield
/%
Time /min
A typical reaction procedure is described as follows:
1
2
3
DMF
DMSO
1,4-Dioxane
NaAc
NaAc
NaAc No reaction
65
120
87.7
73.9
–
The reduction was carried out in a 100-mL-three-necked
flask fitted with a gas inlet tube, a condensator and a magnetic
stirring bar. Substrates, water, selenium powder, anhydrous
NaAc, and the solvent were placed in the three-necked flask.
CO was introduced into the flask and the mixture was heated
to the given temperature. When the reaction was complete, the
mixture was cooled to room temperature and CO bubbling was
stopped. Then air was introduced into the reaction mixture to
precipitate selenium. After filtration of selenium, evaporation
of the solvent and purification by column chromatography on
silica gel, led to the corresponding nitroanilines. The structures
of the products were assigned by a comparison of their mp.,
4
Toluene
NaAc No reaction
1,2-Diethoxy-ethane NaAc No reaction
–
b
5
6
7
8
9
–
c
c
c
c
DMF
DMF
DMF
DMF
DMF
DMF
NaAc
Et3N
Na2CO3
DBUd
NaOH
–
80
300
240
90
210
540
90.6
56.5
71.7
55.0
60.1
95.0
c
1
1
0
1
c
a
Reaction conditions: dinitrobenzene 10 mmol, base 5 mmol,
solvent 40 mL, H2O 2 mL, CO bubble, 95 C.
ꢀ
b
ꢀ
1
13
92 C.
5 C. 1,8-Diazabicyclo[5.4.0]undec-7-ene. The time
H and C NMR spectra with those of the authentic compounds.
c
ꢀ
d
e
8
when the conversion of m-dinitrobenzene reached to 100%.
Isolated yield is based on m-dinitrobenzene.
The recovered selenium by filtration can be reused.
In summary, we have developed the selenium-catalyzed
monoreduction process of dinitroaromatic compounds with
CO/H2O using sodium acetate as a base under atmospheric pres-
sure, which gives the corresponding nitroanilines. During the re-
duction, other reducible functional groups such as cyano group
remain unchanged.
f
in our reactions. The sensitive functional groups, e.g., cyano,
cannot be reduced at all (Table 1, Run 5).
Why is the nitro groups reduced so well by CO/H2O under
the mild conditions ? We think the selection of solvent is of great
importance on this reduction. The effects of solvents on the re-
action are shown in Table 2. As can be seen from these data, po-
lar aprotic solvents are essential. In the experiments, with the
blowing of carbon monoxide, we can see that selenium can dis-
solve quickly in the polar aprotic solvents (such as DMF) even in
the absence of bases. This process is impossible in less polar sol-
vents. In the presence of Et3N, the process is slow in the nonpo-
lar solvents. This indicates that the polar aprotic solvents are fa-
vorable for the formation of carbonyl selenide and promote the
References and Notes
1
S. Hashimoto and H. Fujii, Kagaku to Kogyo (Osaka), 55, 88
(1981).
2
3
D. S. Wulfman and C. F. Cooper, Synthesis, 1978, 924.
Some reviews: a) M. Hudlicky, ‘‘Reductions in Organic
Chemistry,’’ Ellis Horwood Limited, England (1984). b) R.
S. Downing, P. J. Kunkeler, and H. van Bekkum, Catal.
Today, 37, 121 (1997). Some reports: c) O. Terpko and R.
F. Heck, J. Org. Chem., 45, 4993 (1980). d) G. Theodoridis,
U.S. Patent 5,105,012 (1992). e) E. S. Lazer, J. S. Anderson,
J. E. Kijek, and K. C. Brown, Synth. Commun., 12, 691
(1982). f) S. A. Shevelev, A. Kh. Shakhnes, B. I. Ugrak,
and S. S. Vorob’ev, Synth. Commun., 31, 2557 (2001).
nucleophilic attack of water to generate selane (H2Se), which
À
(
or its anion, i.e., HSe ) is regarded as the active intermediate
4
in Se/CO/H2O reducing system.
Table 3. The recycling of catalyst for the mono-reduction of m-
a
4T. Miyata, K. Kondo, S. Murai, T. Hirashima, and N.
Sonoda, Angew. Chem., Int. Ed. Engl., 19, 1008 (1980).
dinitrobenzen
Selectivityb
/%
5
6
T. Miyata, T. Mizuno, I. Nishiguchi, N. Kanbe, and N.
Sonoda, Kagaku to Kogyo (Osaka), 70, 374(1996).
Catalyst
Reaction Time
/
Conversion
/%
min
Some reports about the synthesis of arylureas under high
pressure conditions: a) K. Kondo, N. Sonoda, and S.
Tsutsumi, J. Chem. Soc., Chem. Commun., 1972, 307. b) S.
Zhang and Y. Zhen, Tianranqi Huagong, 17, 27 (1992). c)
J. He and S. Zhang, Tianranqi Huagong, 19, 26 (1994). d)
Y. Yang and S. Lu, Tetrahedron Lett., 40, 4845 (1999).
X. Yan and S. Lu, Huaxue Tongbao, 3, 187 (2002).
Fresh
Recycle 1
Recycle 2
a
65
70
65
100
100
100
87.7
90.6
88.4
Reaction conditions: m-dinitrobenzene, 10 mmol; selenium,
0.4mmol; DMF, 40 mL; H 2O, 2 mL; NaAc, 5 mmol; CO,
bubble; 95 C. Based on m-nitroaniline.
ꢀ
b
7
8
Reaction conditions: m-nitroaniline, 10 mmol; selenium,
0.4mmol; DMF, 40 mL; H 2O, 2 mL; NaAc, 5 mmol; CO,
The bases accelerate the reduction but they are not essential.
Even without bases the reaction can proceed slowly (Table 2,
Run 11). NaAc is suitable for this reduction. Organic bases,
which are favorable for carbonylation and reduction under high
pressure, are not effective for this reaction under atmospheric
pressure (Table 2, Runs 7 and 9).
ꢀ
bubble; 95 C, 5 h. The conversion of m-nitroaniline is
53%, the selectivity of benzene-1,3-diamine is 100%.
a) A. Ogawa, J. Miyake, Y. Karasaki, S. Murai, and N.
Sonoda, J. Org. Chem., 50, 384(1985). b) A. Ogawa, J.
Miyake, Y. Karasaki, S. Murai, and N. Sonoda, Bull. Chem.
Soc. Jpn., 58, 1448 (1985).
9
At the end of catalytic reduction of m-dinitrobenzene, the
Published on the web (Advance View) November 17, 2003; DOI 10.1246/cl.2003.1142