A New Simple and Efficient Synthesis of N-Aryl Phthalimides in Ionic Liquid [bmim][PF6]

Article abstract of DOI:10.1081/SCC-120025187

The room temperature ionic liquid [bmim][PF₆], namely 1-butyl-3-methyl-imidazolium hexafluorophosphate, is used as an alternative solvent to classic solvents for the synthesis of a series of N-aryl phthalimides in good to excellent yields.

Full text of DOI:10.1081/SCC-120025187

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A New Simple and Efficient Synthesis of N-Aryl
Phthalimides in Ionic Liquid [bmim][PF6]
Mei-Yun Zhou a , Yi-Qun Li Ph.D. a & Xin-Ming Xu a
a Department of Chemistry , Jinan University , Guangzhou, P.R. China
Published online: 16 Aug 2006.
To cite this article: Mei-Yun Zhou , Yi-Qun Li Ph.D. & Xin-Ming Xu (2003) A New Simple and Efficient Synthesis of N-Aryl
Phthalimides in Ionic Liquid [bmim][PF6], Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 33:21, 3777-3780, DOI: 10.1081/SCC-120025187
To link to this article: http://dx.doi.org/10.1081/SCC-120025187
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 21, pp. 3777–3780, 2003
A New Simple and Efficient Synthesis of N-Aryl
Phthalimides in Ionic Liquid [bmim][PF6]
*
Mei-Yun Zhou, Yi-Qun Li, and Xin-Ming Xu
Department of Chemistry, Jinan University,
Guangzhou, P.R. China
ABSTRACT
The room temperature ionic liquid [bmim][PF6], namely 1-butyl-3-
methyl-imidazolium hexafluorophosphate, is used as an alternative
solvent to classic solvents for the synthesis of a series of N-aryl
phthalimides in good to excellent yields.
Key Words: N-Aryl phthalimides; Ionic liquid; Synthesis.
Imide derivatives are an important class of substrates for
biological and chemical applications.[1] Accordingly, the synthesis of
these derivatives has developed remarkably in recent years. Well
known methods are: dehydrative condensation of an anhydride and
*Correspondence: Yi-Qun Li, Associate Professor, Ph.D., Assistant head of de-
partment, Department of Chemistry, Jinan University, 601 Huangpu Dadaoxl,
Guangzhou 510632, P.R. China; Fax: 86-20-85221697; E-mail: tlyq@ jnu.edu.cn.
3777
DOI: 10.1081/SCC-120025187
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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3778
Zhou, Li, and Xu
amine catalyzed conc. H2SO4 in acetic anhydride at refluxing.[2] Direct
N-alkylation of phthaloyl dichloride with azide in the presence of PPh3 in
[3]
CH2Cl2 and N-alkylation of imides using of alcohol promoted by
PPh3 and DIAP in THF[4] etc. These methods have not been entirely
satisfactory owing to such drawbacks as using of organic solvents. It is
necessary to develop an alterative solvent for the synthesis of imides
under mild and environmentally benign conditions.
Recently, ionic liquids have gained increasing interest in organic
synthesis. This is mainly because their negligible vapor pressure, easy of
handling and potential for recycling, circumvents many of the problems
associated with volatile organic solvents. With the continuing depletion of
natural resources and growing environmental awareness in the
practices of both the chemical industry and academia, the replacement
of deleterious molecular solvents with environmentally more benign has
emerged. Examples of their application in organic reactions have been
summarized in a number of recent review articles.[5]
In this article we describe a new and efficient synthetic approach to
N-aryl phthalimides from phthalic anhydride and aromatic amines in
ionic liquids, [bmim][PF6] (Sch. 1). The ionic liquids used here not only
overcome many of the problems brought from volatile organic solvents,
but also be recovered for reuse.
In summary, the synthetic approach reported here is an attractive
addition to the existing methodologies since the procedure is simple, the
yields are excellent, the product purification is convenient, and the ionic
liquids can be reused and moreover it is benign to the environment.
EXPERIMENTAL
Melting points were uncorrected. Infrared spectra were recorded
using KBr pellets on a Bruker Equinox 66 spectrometer. All chemicals
used were of commercial grade without further purification. The ionic
liquids, [bmim][PF6] used here is prepared according to the literature.[6]
O
O
C
[bmim][PF6]
C
C
NAr
O
H2N-Ar
2
+
C
O
O
1
3
Scheme 1.

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N-Aryl Phthalimides in Ionic Liquid
3779
Table 1. The N-aryl phthalic anhydride with aromatic amines in ionic liquids
a
[bmim]PF6 .
Ar
(1)
Reaction
time (h)
M.p.
(ꢀC)
Lit. mp
(ꢀC)
Yieldsb
(%)
Entry
3a
3b
3c
3d
3e
3f
C6H5
8
8
8
8
8
8
8
206–208
155–156
203–204
264–266
192–194
202–204
182–184
206[7]
155–156[8]
204[8]
264–266[8]
194–195[8]
203–204[8]
184–185[8]
93
92
97
91
90
90
94
o-MeOC6H4
p-MeC6H4
p-NO2C6H4
p-ClC6H4
p-BrC6H4
a-C10H7
3g
aAll of these compounds were confirmed by IR and compared with authentic
samples.
bIsolated yields.
General Procedure
To a 25 mL round-bottomed flask, a mixture of phthalic anhydride
(1, 7.5 mmol) and an aromatic amine (5.0 mmol) in [bmim][PF6] (2 mL)
was added and stirred for 8 h at 80ꢀC as indicated in Table 1. On com-
pletion of the reaction as monitored by TLC, EtOH (95%, 5 mL) was
added to the reaction mixture and was heated to reflux for 10 min
to extract the ionic liquid. After cooling, the product was filtered
off and washed with EtOH for several times to afford the pure N-aryl
phthalimide as a white solid. The ionic liquid can be reused for the next
run prior removing the ethanol and drying in vacuum. The melting points
and IR of compound 3a–g agreed well with the reported data.[7,8]
ACKNOWLEDGMENT
The Project Sponsored by the National Nature Science Foundation
of China (20272018), the Scientific Research Foundation for the
Returned Overseas Chinese Scholars, State Education Ministry of
China and the Nature Science Foundation of Guangdong Province
(974021, 021166).
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3780
Zhou, Li, and Xu
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Received in Japan March 17, 2003