One-pot syntheses of amides from N-acylation of nitroarenes with esters mediated by samarium diiodide

Article abstract of DOI:10.1081/SCC-200026659

Mediated by samarium diiodide, various amides were prepared directly from nitroarenes and esters under mild conditions in a one-pot procedure.

Full text of DOI:10.1081/SCC-200026659

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One‐Pot Syntheses of
Amides from N‐Acylation
of Nitroarenes with Esters
Mediated by Samarium
Diiodide
Xiaoxia Wang a , Hongyun Guo b , Guanqun Xie a &
Yongmin Zhang c
a College of Chemistry and Life Sciences , Zhejiang
Normal University , Jinhua, 321004, P.R. China
b College of Chemical Engineering and Materials ,
Zhejiang University of Technology , Hangzhou, P.R.
China
c Department of Chemistry , Zhejiang University
(Campus Xixi) , Hangzhou, P.R. China
Published online: 06 Jan 2011.
To cite this article: Xiaoxia Wang , Hongyun Guo , Guanqun Xie & Yongmin Zhang
(2004) One‐Pot Syntheses of Amides from N‐Acylation of Nitroarenes with Esters
Mediated by Samarium Diiodide, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 34:16, 3001-3008,
DOI: 10.1081/SCC-200026659
To link to this article: http://dx.doi.org/10.1081/SCC-200026659
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 16, pp. 3001–3008, 2004
One-Pot Syntheses of Amides from
N-Acylation of Nitroarenes with Esters
Mediated by Samarium Diiodide
2
1
Xiaoxia Wang,1, Hongyun Guo, Guanqun Xie,
*
and Yongmin Zhang3
1College of Chemistry and Life Sciences, Zhejiang Normal University,
Jinhua, P.R. China
2College of Chemical Engineering and Materials, Zhejiang University of
Technology, Hangzhou, P.R. China
3Department of Chemistry, Zhejiang University (Campus Xixi),
Hangzhou, P.R. China
ABSTRACT
Mediated by samarium diiodide, various amides were prepared directly
from nitroarenes and esters under mild conditions in a one-pot procedure.
Key Words: Samarium diiodide; One-pot syntheses; Amides;
N-Acylation; Nitroarenes; Esters.
*
Correspondence: Xiaoxia Wang, College of Chemistry and Life Sciences, Zhejiang
Normal University, Jinhua 321004, P.R. China; E-mail: wxxia75@sohu.com.
3001
DOI: 10.1081/SCC-200026659
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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Wang et al.
INTRODUCTION
The preparation of amides from nitro compounds usually involves two
separate steps: (1) the reduction of nitro compounds to amines; (2) the acyl-
ation of the corresponding amines with an acylating agent. Though various
reducing agents can be used for the reduction of nitro compounds to amines
and a number of acylating reagents are available for the acylation of
amines, the preparation of amides from nitro compounds and acylating
agent in a one-pot procedure is scarcely reported. Several reductive N-acyl-
ation systems such as PtCl2(PPh3)2/tin(IV)chloride/CO/carboxylic acid
have been used for this one-pot transformation;[1] however, usually high temp-
erature or long reaction time was required. Very recently, the one-pot reduc-
tive conversion of nitroarenes to N-arylacetamides mediated by indium in the
presence of acetic anhydride and acetic acid was reported.[2] Despite the
operational simplicity and mild reaction conditions, the method seems
limited for the preparation of acetamides.
Samarium diiodide was reported to reduce nitroalkanes and aromatic nitro
compounds easily affording the corresponding amines in the presence of
proton source such as MeOH.[3a,b] The amines were even acylated sub-
sequently with benzoyl chloride to afford amides as reported,[3b] but direct
synthesis of amides in one pot promoted by samarium diiodide was not
investigated.
It was reported that nitro groups attached to aromatic rings can be reduced
by samarium diiodide in the absence of proton source to afford a living nitro-
gen anion,[3c] which is active than amines and is hopeful to be easily acylated
with esters. The consideration promoted us to investigate the possibility of a
one-pot transformation of the nitroarenes into amides by reductive acylation
of nitro compounds with samarium diiodide in the presence of esters. In the
present paper, we wish to report our encouraging results that provide an effi-
cient and novel one-pot synthesis of various amides from nitroarenes and
esters under mild conditions.
Since ordinary esters are inert towards samarium diiodide in the absence
of other additives,[4] the nitro compounds and esters can be added to the
samarium diiodide–THF solution simultaneously. The reaction can be com-
pleted within 30 min at room temperature under neutral conditions (not any
extra catalysts such as bases are needed for the acylation process, Sch. 1).
Scheme 1.

Syntheses of Amides from Nitroarenes with Esters
3003
Scheme 2.
The reaction is so neat that the corresponding amides were obtained in excel-
lent yields.
To explore the scope of the reaction, 1,4-g-butyrolactone was attempted as
the acylating agent. It was found that the expected ring opening of the lactone
took place smoothly to afford the g-hydroxy amides in good yields (Sch. 2).
a,b-Unsaturated esters were reported not to undergo any reaction or the
reduction of double bond took place slowly under the action of samarium diio-
dide.[5] Therefore, tentative experiment was carried out with nitro compounds
and a,b-unsaturated esters being added at the same time to the SmI2–THF solu-
tion. However, mixtures of several by-products could be detected on the TLC
analysis though no attempts were made to isolate them. In contrast to that
described above, when a,b-unsaturated esters were added after the reduction
of the nitro compounds was complete (all the samarium diiodie having been
consumed out), as shown in Sch. 3, the corresponding a,b-unsaturated
amides were obtained almost exclusively. It should be noted that 1,4-
Michael addition product was not obtained under the reaction conditions.
Finally, double acylation of the resulting nitrogen anion was investigated.
When butyl o-phthalates was used as the acylating agent, the expected diacyl-
ation occurs and the corresponding N-tolylphthalimide was obtained not with-
standing the yield was relatively lower (Table 1, entry 12). Attempts to realize
the reductive diacylation of nitrobezene with 2 eq. of esters resulted the
expected N-acetyl-N-phenyl acetamide only in 35% yield (Table 1, entry 13).
All the amides synthesized by this method are listed in Table 1.
In conclusion, mediated by samarium diiodide, the one-pot syntheses of
several types of amides from nitroarenes and esters were realized successfully.
The reaction undergoes smoothly at room temperature and under neutral
conditions. In combination with the high yields, the simplified procedure and
the ready access to the starting materials, the present method may be attractive
for the preparation of amides.
Scheme 3.

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Wang et al.
Table 1. Syntheses of amides from nitroarenes and esters mediated by samarium
diiodide.
Entry Nitroarenes
1
Esters
Products
Yieldsa (%)
89
2
3
92
95
93
90
85
90
82
92
87
92
45
35b
4
5
6
7
8
9
10
11
12
13
aIsolated yields.
bA2.2 eq. of ethyl acetate was used for diacylation.

Syntheses of Amides from Nitroarenes with Esters
EXPERIMENTAL
3005
Tetrahydrofuran was distilled from sodium–benzophenone immediately
prior to use. All reactions were conducted under a nitrogen atmosphere.
1
Melting points are uncorrected. H NMR spectra were recorded on a Bruker
400 MHz instrument as CDCl3 solutions using TMS as internal standard.
Chemical shifts (d) are reported in ppm and coupling constant J is given in
Hz. IR spectra were recorded using KBr disks with a Bruker Vector-22 infra-
red spectrometer. Elemental analyses were performed on an EA-1110
instrument.
General Procedure for the Reductive Acylation of Nitroarenes
with Samarium Diiodide and Esters
A mixture of nitroarenes (1 mmol) and esters (ordinary esters or lac-
tones) (1.1 mmol) in anhydrous THF (3 mL) was added by syringe to the solu-
tion of 6 mmol SmI2 in dry THF (30 mL) at room temperature under nitrogen
atmosphere. After completion of the reaction (about 30 min, monitored by
TLC), 0.1 N of hydrochloric acid (3 mL) was added followed by extraction
with ether (3 ꢀ 20 mL). The combined extracts were washed with saturated
brine (15 mL) and dried over anhydrous sodium sulfate. Removal of the
solvent under reduced pressure gave a residue, which was purified by
preparative TLC on silica gel using ethyl acetate : cyclohexane (1 : 4) as
eluent.
When a,b-unsaturated esters were used as substrates, the nitroarene
(1 mmol) in 2 mL of dry THF was added first by syringe to the solution of
6 mmol SmI2 in dry THF (30 mL) at room temperature under nitrogen atmos-
phere. After the disappearance of the characteristic blue color of samarium
diiodide (within 10 min), the a,b-unsaturated esters (1.1 mmol) in 2 mL of
dry THF was then added to realize the N-acylation. The subsequent treatment
process is just the same as that described above.
Compound 1a. M.p.: 115–1178C (lit.[6] 115–1168C). nmax (KBr)/
cm21: 3296, 3195, 3137, 3060, 3021, 1657. dH (CDCl3): 8.48 (1H, s),
7.29–7.54 (5H, m), 1.95 (3H, s).
Compound 1b. M.p.: 157–1598C (lit.[6] 1588C). nmax (KBr)/cm21
:
3550, 3476, 3413, 3309, 3066, 2918, 1647. dH (CDCl3): 7.87–7.89 (2H, d,
J 8.0 Hz), 7.76 (1H, s), 7.50–7.56 (5H, m), 7.18–7.20 (2H, d, J 8.0 Hz),
2.35 (3H, s).
Compound 1c. M.p.: 190–1928C (lit.[6] 192–1938C). nmax (KBr)/
cm21: 3545, 3478, 3350, 3013, 2923, 1653. dH (CDCl3): 7.86–7.89 (2H,
m), 7.82 (1H, s), 7.49–7.62 (5H, m), 7.34–7.36 (2H, m).

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Wang et al.
Compound 2a. M.p.: 59–628C (lit.[7] 60–638C). nmax (KBr)/cm21: 3430,
3155, 2927, 2852, 1667, 1599. dH (CDCl3): 8.42 (1H, s), 7.05–7.50 (5H, m),
3.59–3.70 (2H, m), 2.78 (1H, br, s), 2.44 (2H, t, J 6.8 Hz), 1.87–1.89 (2H, m).
Compound 2b. M.p.: 98–1008C. nmax (KBr)/cm21: 3329, 2960, 2933,
2864, 1673. dH (CDCl3): 7.59 (1H, s), 7.35 (2H, d, J 8.0 Hz), 7.09 (2H, d, J
8.0 Hz), 3.73 (2H, t, J 5.6 Hz), 2.73 (1H, br, s), 2.49 (2H, t, J 6.8 Hz), 2.29
(3H, s), 1.91–1.96 (2H, m). 13C NMR (100 MHz, CDCl3): 171.8, 135.2,
134.0, 129.5, 120.1, 62.2, 34.7, 28.0, 20.9. m/z (%): 193 (Mþ, 8.54), 107
(100), 106 (46.87). Anal. Calcd. for C11H15NO2: C, 68.37; H, 7.82; N, 7.25.
Found C, 68.43; H, 7.85; N, 7.22%.
Compound 2c. M.p.: 73–748C. nmax (KBr)/cm21: 3278, 3071, 2944,
2879, 1653. dH (CDCl3): 7.69–7.73 (1H, m), 7.42 (1H, s), 7.06–7.34 (3H,
m), 3.75–3.77 (2H, m), 2.80 (1H, br, s), 2.57 (2H, t, J 6.8 Hz), 2.25 (3H, s),
1.96–1.98 (2H, m). 13C NMR (100 MHz, CDCl3): 173.2, 135.5, 130.5,
126.7, 125.5, 123.6, 62.1, 34.5, 28.1, 17.8. m/z (%): 193 (Mþ, 11.46), 107
(100), 106 (39.18). Anal. Calcd. for C11H15NO2: C, 68.37; H, 7.82; N, 7.25.
Found C, 68.42; H, 7.79; N, 7.28%.
Compound 2d. Viscous oil. nmax (KBr)/cm21: 3340, 2923, 2853, 1650. dH
(CDCl3): 7.60 (1H, s), 7.18–7.36 (4H, m), 3.75 (2H, t, J 5.6 Hz), 2.78 (1H, br, s),
2.52 (2H, t, J 6.8 Hz), 2.34 (3H, s), 1.90–2.00 (2H, m). 13C NMR (100MHz,
CDCl3): 172.8, 140.5, 138.0, 130.3, 125.7, 122.5, 116.6, 62.0, 34.2, 28.1, 19.0.
m/z (%): 193 (Mþ, 8.12), 107 (100), 106 (48.18). Anal. Calcd. for
C11H15NO2: C, 68.37; H, 7.82; N, 7.25. Found C, 68.47; H, 7.86; N, 7.21%.
Compound 2e. M.p.: 107–1098C. nmax (KBr)/cm21: 3282, 3181, 3123,
3073, 2956, 2926, 2883, 1664. dH (CDCl3): 7.64 (1H, s), 7.46 (2H, d, J 8.8 Hz),
7.27 (2H, d, J 8.8 Hz), 3.77 (2H, t, J 6.0 Hz), 2.54 (2H, t, J 6.8 Hz), 2.31 (1H,
br, s), 1.95–2.05 (2H, m). 13C NMR (100 MHz, CDCl3): 172.3, 139.1, 129.0,
121.0, 62.3, 34.8, 27.7. m/z (%): 215 (Mþ, 3.07), 213 (9.58), 129 (32.03), 127
(100). Anal. Calcd. for C10H12ClNO2: C, 56.21; H, 5.66; N, 6.56. Found C,
56.12; H, 5.63; N, 6.54%.
Compound 3a. M.p.: 99–1028C (lit.[8] 1048C). nmax (KBr)/cm21: 3253,
3128, 2924, 1660, 1614. dH (CDCl3): 8.08 (1H, s), 7.30–7.57 (5H, m),
6.27–6.46 (2H, m), 5.69 (1H, d, J 11.2 Hz).
Compound 3b. M.p.: 151–1538C (lit.[9] 154–1568C). nmax (KBr)/cm21
:
3261, 3104, 2920, 1637. dH (CDCl3): 7.89 (1H, d, J 15.6Hz), 734–7.56 (11H,
m), 6.65 (1H, d, J15.6Hz).
Compound 3c: M.p.: 114–1168C (lit.[9] 1148C). nmax (KBr)/cm21: 3265,
3145, 2919, 1660, 1625. dH (CDCl3): 7.76 (1H, d, J 15.6Hz), 737–7.54 (8H,
m), 724–7.27 (1H, m), 6.95 (1H, s), 6.57 (1H, d, J 15.6Hz), 2.36 (3H, s).
Compound 4a. M.p.: 200–2028C (lit.[10] 201–2028C). nmax (KBr)/
cm21: 3042, 2917, 1715. dH (CDCl3): 7.95–7.97 (2H, m), 7.78–7.81 (2H,
m), 7.27–7.32 (4H, m), 2.42 (3H, s).

Syntheses of Amides from Nitroarenes with Esters
3007
Compound 4b. M.p.: 36–388C (lit.[11] 388C). nmax (KBr)/cm21: 2923,
2854, 1634. dH (CDCl3): 7.07–7.45 (5H, m), 2.06 (6H, s).
ACKNOWLEDGMENT
We are grateful to the Education Foundation of Zhejiang Province
(Project No. 20020851) and the Doctors’ Foundation of Zhejiang Normal
University for financial support.
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Received in Japan January 19, 2004