A Novel Method for Synthesis of 1, 3-Dialkylimidazole-2-Selenones in Water

Article abstract of DOI:10.1080/10426507.2013.865124

A novel method for the synthesis of 1, 3-dialkylimidazole-2-selenones is described. The reaction of 1, 3-dialkylimidazolium salts with selenium using Na₂CO₃ as a base in water under refluxing conditions afforded 1, 3-dialkylimidazole-2-selenones in yields up to 95%.

Full text of DOI:10.1080/10426507.2013.865124

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Phosphorus, Sulfur, and Silicon and the
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A Novel Method for Synthesis of 1, 3-
Dialkylimidazole-2-Selenones in Water
Fengshou Tiana, Yahong Chena, Peng Lib & Shiwei Lub
a Department of Chemistry, Zhoukou Normal University, Zhoukou
Henan, 466001, P. R. China
b Dalian Institute of Chemical Physics, Chinese Academy of Sciences,
457 Zhongshan Road, Dalian, Liaoning, 116023, P. R. China
Accepted author version posted online: 13 Mar 2014.Published
online: 21 Aug 2014.
To cite this article: Fengshou Tian, Yahong Chen, Peng Li & Shiwei Lu (2014) A Novel Method for
Synthesis of 1, 3-Dialkylimidazole-2-Selenones in Water, Phosphorus, Sulfur, and Silicon and the
Related Elements, 189:9, 1391-1395, DOI: 10.1080/10426507.2013.865124
To link to this article: http://dx.doi.org/10.1080/10426507.2013.865124
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Phosphorus, Sulfur, and Silicon, 189:1391–1395, 2014
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2013.865124
A NOVEL METHOD FOR SYNTHESIS OF 1,
3-DIALKYLIMIDAZOLE-2-SELENONES IN WATER
Fengshou Tian,1,* Yahong Chen,1 Peng Li,2 and Shiwei Lu2
1Department of Chemistry, Zhoukou Normal University, Zhoukou Henan 466001,
P. R. China
2Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457
Zhongshan Road, Dalian, Liaoning, 116023, P. R. China
GRAPHICAL ABSTRACT
Abstract A novel method for the synthesis of 1, 3-dialkylimidazole-2-selenones is described.
The reaction of 1, 3-dialkylimidazolium salts with selenium using Na2CO3 as a base in water
under refluxing conditions afforded 1, 3-dialkylimidazole-2-selenones in yields up to 95%.
Keywords 1, 3-Dialkylimidazolium salts; 1, 3-dialkylimidazole-2-selenones; Selenium; Water
INTRODUCTION
The chemistry of N-heterocyclic carbenes and their metal complexes1,2 is of consid-
erable current interest duo to their applications in homogeneous catalysis3 and medicinal
chemistry.4 Among them, 1, 3-dialkylimidazole-2-selenones are a type of chalcogen deriva-
tive of N-heterocyclic carbenes, and they are useful precursors for the synthesis of various
N,Se-containing heterocycles.5 1, 3-dialkylimidazole-2-selenones had been synthesized by
reacting the corresponding iodide salts with selenium powder in methanol in the presence of
potassium carbonate.6 1, 3-dialkylimidazolium salts reacted with selenium in strong bases
such as KH or NaH to give the corresponding 1, 3-dialkylimidazole-2-selenones.7 In addi-
tion, 1, 3-dialkylimidazolium salts also reacted with Na2Se2 in the presence of potassium
tert-butoxide to afford the target products at room temperature in dry THF.8 Both Roy9
and Guziec10 reported that treatment of imidazole with BuLi and selenium power also gave
1, 3-dialkylimidazole-2-selenones under Schlenk conditions. However, most of the known
methods for the preparation of imidazole-2-selenones suffer from disadvantages such as
Received 17 August 2013; accepted 6 November 2013.
Address correspondence to Fengshou Tian, Department of Chemistry, Zhoukou Normal University, Zhoukou,
Henan, 466001, P. R. China. E-mail: fengshoutian@163.com
1391

1392
F. TIAN ET AL.
the use of strong bases and harsh reaction conditions, long reaction time, low yields, or
complicated manipulations.
RESULTS AND DISCUSSION
In the course of our ongoing studies on organic selenium chemistry,11 we found
the 1, 3-dialkylimidazole-2-selenones catalyzed carbonylation of organic amines and
ethanolamine using carbon monoxide as oxidant agents to give ureas and 2-oxazolidinone.12
Keeping these results in mind, we investigated reactions of 1, 3-dialkylimidazolium salts
with selenium in the presence of Na2CO3 in water under refluxing conditions and sur-
prisingly found these reactions easily led to 1, 3-dialkylimidazole-2-selenones. Herein, we
report a novel method for the synthesis of 1, 3-dialkylimidazole-2-selenones in the presence
of Na2CO3 (Scheme 1).
Scheme 1
1-butyl-3-methylimidazolium chloride was treated with an equivalent of selenium
in the presence of two equivalents of sodium carbonate in H2O under refluxing condition
for 4 h to give 1-butyl-3-methylimidazole-2-selenone (1b) in 92% (entry 1 in Table 1).
We investigated the effect of different bases under similar conditions and found Na2CO3
is the best additive reagent for this reaction (entries 1–6 in Table 1). In addition, when
two equivalents of Na2CO3 were used, the reaction yield was the highest (entries7–10 in
Table 1).
Reactions of other 1, 3-dialkylimidazolium salts were also investigated and the re-
sults are summarized in Table 2. From Table 2, we can see that 1, 3-dialkylimidazolium
Table 1 Effect of different bases to the reaction in water
Entrya
Base
The ratio of amount of base and substrate
Yieldb
1
2
3
4
5
6
7
8
9
10
Na2CO3
K2CO3
NaOAc
Et3N
NaHCO3
KHCO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
2:1
2:1
2:1
2:1
2:1
2:1
1:1
1.5:1
1.5:1
2:1
92
91
trace
<3
7
9
45
81
90c
92
aReaction conditions: 1-butyl-3-methylimidazolidine chloride 5 mmol; Se, 5 mmol; H2O, 5 mL; Base 10 mmol;
Refluxing, 4 h; bIsolated yields. cRefluxing, 6 h.

SYNTHESIS OF 1, 3-DIALKYLIMIDAZOLE-2-SELENONES
1393
Table 2 Synthesis of 1, 3-dialkylimidazole-2-selenones in water
Entrya
R
X
Cmpd
Yield (%)b
1
2
3
4
5
6
7
8
9
10
n-Butyl
n-Butyl
n-Butyl
n-Propyl
Cl
I
1b
1b
1b
2b
3b
4b
5b
6b
7b
8b
9212
8612
7412
818b
808b
9512
93c
BF4
Br
Br
Br
Br
Cl
Br
I
Ethyl
n-Hexadecyl
2-Bromobenzyl
3-Chlorobenzyl
Iso-propyl
Methyl
90c
428b
478b
aReaction conditions: 1, 3-dialkylimidazolium salts, 5 mmol; Se, 5 mmol; H2O, 5 mL; Na2CO3, 10 mmol; 4 h.
bIsolated yields. cNovel products.
chlorides, bromides, and tetrafluoroborate can react with selenium easily to give the cor-
responding 1, 3-dialkylimidazole-2-selenones in water under refluxing conditions (entries
1–8 in Table 2). The effect of steric hindrance on the 3-position of the imidazole rings
did not significantly influence the yields of the products (entries 6–8 in Table 2). When 1-
isopropyl-3-methylimidazolium bromide and 1, 3-dimethylimidazolium iodide were used
as the substrate, the yields of selenation reactions were reduced rapidly to 42% and 47%
(entries 9–10 in Table 2).
In analogy with the mechanism proposed for the reaction of 1, 3-dialkylimidazolium
salts and Se,7 the possible mechanism for the reaction is shown in Figure 1. The for-
mation of 1-butyl-3-methylimidazole-2-selenone (1b) may involve a two-step pathways:
(1) deprotonation of 1-butyl-3-methylimidazolium chloride (1a) by Na2CO3 to give the
N-heterocyclic carbene intermediate C in water and (2) reaction of intermediate C with
selenium to produce 1-butyl-3-methylimidazole-2-selenone (1b).
In summary, in our work, we have found a new method for the synthesis of 1,
3-dialkylimidazole-2-selenones from 1, 3-dialkylimidazolium salts and selenium in the
presence of Na2CO3 in H2O under refluxing conditions.
Figure 1 Proposed pathway to 1, 3-dialkylimidazole-2-selenone (1b).

1394
F. TIAN ET AL.
Experimental Procedure for the Synthesis of 1,
3-Dialkylimidazole-2-Selenones
In a 50-mL, two-necked flask, 1-butyl-3-methylimidazolium chloride (5 mmol), sele-
nium (5 mmol), Na2CO3 (10 mmol), H2O (5 mL), and a magnetic stirring bar were placed.
Then, the reaction mixture was vigorous stirring under refluxing condition for 4 h. After the
reaction was complete, and the resultant mixture was filtered, and the solvent evaporated
under reduced pressure. Further purification by recrystallization or column chromatogra-
phy on silica gel gave the pure product. All the products were characterized by NMR and
HRMS. Detailed characterization of the previously known compounds from Table 2 are
presented in the Supplemental Materials.
Data of Novel Products
1-(2-bromobenzyl)-3-methyl-1H-imidazole-2(3H)-selenone 5b: Mp.110–
112◦C, 1H NMR (400 MHz, CDCl3): δ3.72 (s, 3H, N-CH3), 5.46 (s, 2H, N-CH2), 6.82
(br, J = 2.4Hz, 1H, CH), 6.90 (br, J = 2.4Hz, 1H, CH), 7.19 (m, 2H, 2 × Ar-H), 7.27
(d, J = 4.4 Hz, 2H, 2 × Ar-H), 7.58 (d, J = 7.6Hz, Ar-H). 13C NMR (100 MHz, CDCl3):
δ14.09,22.51, 26.53, 29.13, 29.68, 30.96, 31.75, 37.05, 49.98, 118.64, 119.71, 155.33
(C Se). HRMS for C11H11N2BrSe: (m/z) calcd 329.9271; found. 329.9279 [M]+.
1-(3-chlorobenzyl)-3-methyl-1H-imidazole-2(3H)-selenone
6b: Mp.97–
98◦C, 1H NMR (400 MHz, CDCl3): δ3.70 (s, 3H, N-CH3), 5.34 (s, 2H, N-CH2), 6.66
(s, 1H, CH), 6.96 (s, 1H, CH), 7.22–7.27 (m, 3H, 3 × Ar-H), 7.30 (s, 1H, Ar-H). 13C
NMR (100 MHz, CDCl3): δ30.77, 37.11, 52.15, 118.43, 120.40, 126.15, 127.85, 128.14,
129.97, 134.29, 137.44, 156.26(C Se). HRMS for C11H11N2ClSe: (m/z) calcd 285.9776;
found. 285.9753 [M]+.
FUNDING
We are grateful to the Natural Science Foundation of Henan Province (No.
142102310365 and No. 132300410176) and the Doctor Start-up Foundation of Zhoukou
Normal University (No. zksybscx201204) for financial support.
SUPPLEMENTAL MATERIAL
Supplementary data for this article can be accessed on the publisher’s website,
www.tandfonline.com/gpss
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