A simple and effective approach to the synthesis of alkynyl selenides from terminal alkynes

Article abstract of DOI:10.1016/j.cclet.2012.06.036

Alkynyl selenides were prepared under very mild conditions by reacting terminal alkynes with respective diorganic diselenides in the presence of potassium t-butoxide. The advantages of this protocol include the use of readily available substrates and reag

Full text of DOI:10.1016/j.cclet.2012.06.036

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Chinese Chemical Letters 23 (2012) 1035–1038
www.elsevier.com/locate/cclet
A simple and effective approach to the synthesis of alkynyl
selenides from terminal alkynes
*
Barahman Movassagh , Mozhgan Navidi
Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran, Iran
Received 16 May 2012
Available online 18 July 2012
Abstract
Alkynyl selenides were prepared under very mild conditions by reacting terminal alkynes with respective diorganic diselenides
in the presence of potassium t-butoxide. The advantages of this protocol include the use of readily available substrates and reagent
and good yield of the products.
# 2012 Barahman Movassagh. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Alkynyl selenides; Diorganic diselenides; Potassium t-butoxide; Terminal alkynes; Phenyl acetylene
The impact of organoselenium chemistry on modern organic synthesis is undisputable [1]. Over the last three
decades many researchers have investigated important chemical transformations that were efficiently achieved using
organoselenium reagents. The chemistry of organoselenium compounds has been of growing interest because of their
involvement as key intermediates in organic synthesis and use as a food supplement [2].
Organoselenium compounds have also pivotal role in the synthesis of a large number of biological compounds (e.g.
selenopeptides, selenoamino acids, selenocarbohydrates). These compounds are also promising pharmacological
agents in view of their antioxidant, antitumor, antimicrobial, and antiviral properties [3].
Among various organoselenium compounds, alkynyl selenides play an important role in organic synthesis by
serving as crucial synthons in the transformations of a wide range of functional groups with a high degree of selectivity
[4,5]. Alkynyl selenides can be transformed into substituted olefins by chlorocarbonylation, hydrosulfonation,
hydrohalogenation, hydrostannylation, hydrozirconation, and hydroboration reactions [6]. In addition, they can act as
excellent Diels-Alder dienophiles [7] and as inhibitors of oxidative enzymes such as d-aminolevulinate dehydratase
[8]. Very recently, a new palladium-catalyzed reaction of alkynyl selenides with acetylenedicarboxylates leading to
alkynylvinyl selenides and multisubstituted aryl selenides, via an intermolecular [2 + 2 + 2] cycloaddition reaction
have been developed [9]. Consequently, a number of methodologies have been developed for the synthesis of these
compounds [4b]. In general, the methods for the preparation of alkynyl selenides include (a) metal-assisted cross-
coupling with either Mg or Cu salts [6a,10,11], (b) reaction of alkynyl organometallics with organoselenenyl halide
(RSeX) or diorgano diselenides (RSeSeR) [12], (c) intramolecular Wittig reaction of a-acyl-a-seleno phosphoranes
[13], (d) seleno functionalization of alkynes [14], (e) reaction of (potentially explosive) bromoalkynes with selenolates
* Corresponding author.
E-mail address: bmovass1178@yahoo.com (B. Movassagh).
1001-8417/$ – see front matter # 2012 Barahman Movassagh. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.06.036

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B. Movassagh, M. Navidi / Chinese Chemical Letters 23 (2012) 1035–1038
or diselenides [12c,15], and (f) coupling of terminal acetylenes to phenylselenenyl bromide in the presence of
CsOHÁH2O [16]. As a drawback, most of these synthetic protocols elaborated upon above suffer from various
disadvantages such as long reaction times, low temperatures, use of air and moisture sensitive and expensive reagents,
and the use of hazardous and toxic reagents or organic solvents. Taking into account these constraints, we were
motivated to investigate the development of a mild, more convenient, and efficient reaction condition for the synthesis
of alkynyl selenides which circumvented these common impediments. In a recent report, Xu et al. [17] prepared
alkynyl selenides from the reaction of diselenides with terminal alkynes catalyzed by CsOH.
1. Experimental
Melting points were recorded on a Buchi B-540 apparatus and are uncorrected. IR spectra were recorded on an
ABB FTLA 2000 instrument. NMR spectra were recorded with either a Bruker AQS-300 spectrometer with nominal
frequency of 300 MHz for proton or 75 MHz for carbon, respectively in CDCl3 using TMS as an internal standard.
1.1. General procedure
A mixture of terminal alkyne (1.0 mmol), t-BuOK (0.134 g, 1.2 mmol), and DMF (1 mL) was placed in a test tube.
The reaction mixture was magnetically stirred at 25 8C for about 15 min; then diselenide (0.5 mmol) was added at
once to the above mixture, and stirring was continued at that temperature for the appropriate time (Table 1) in air
atmosphere. The progress of the reaction was monitored by TLC. After completion of the reaction, the solution was
filtered and the solvent was evaporated under reduced pressure, EtOAc (8 mL) was added, and the mixture washed
with H2O (3 Â 6 mL). The organic layer was dried (Na2SO4), and concentrated. The resulting crude product was
purified by preparative TLC (Silica, eluent, n-hexane:EtOAc = 9:1) to afford the desired product. All compounds are
known, and were identified by comparison of their spectral data with those reported in the literature. Selected data: 4-
chlorophenyl-4-tolylethynyl selenide (3d): Yellow crystals; mp: 49–51 8C; IR (KBr, cmÀ1): 2161; 1H NMR
(300 MHz, CDCl3): d 7.52 (d, 2H, J = 8.6 Hz), 7.41 (d, 2H, J = 7.9 Hz), 7.30 (d, 2H, J = 8.6 Hz), 7.16 (d, 2H,
J = 7.9 Hz), 2.37 (s, 3H); 13C NMR (75 MHz, CDCl3): d 139.1, 134.6, 132.2, 131.8, 130.2, 129.6, 129.2, 127.1, 103.6,
67.5, 21.6. Phenyl-1-hexynyl selenide (3i): Light yellow oil; IR (neat, cmÀ1): 2177; 1H NMR (300 MHz, CDCl3): d
7.59–7.54 (m, 2H), 7.33–7.24 (m, 3H), 2.30 (t, 2H, J = 7.0 Hz), 1.48 (quin, 2H, J = 7.5 Hz), 1.26 (sext, 2H,
J = 7.2 Hz), 0.83 (t, 3H, J = 7.3 Hz); 13C NMR (75 MHz, CDCl3): d 136.3, 132.8, 132.6, 129.2, 104.7, 57.3, 39.6, 31.1,
21.9, 13.8.
2. Results and discussion
In this letter, we present our contribution to the field by developing a mild protocol for the synthesis of alkynyl
selenides via the reaction of terminal alkynes with various diselenides at room temperature in an aerial atmosphere in
Table 1
Alkynyl selenide formation in the presence of t-BuOK.
Entry
R1
R2
Product
Time (min)
Yielda,b (%)
1
2
Ph
Ph
3a
3b
3c
3d
3e
3f
10
15
45
40
15
25
60
50
70
120
82 [15b]
66 [15b]
70 [12e]
65 [12e]
64 [20]
Ph
4-MeC6H4
4-ClC6H4
4-ClC6H4
4-MeC6H4
4-MeC6H4
Ph
3
Ph
4
4-MeC6H4
4-MeC6H4
4-ClC6H4
4-ClC6H4
4-BrC6H4
n-C4H9
n-C6H13
5
6
60 [11a]
61 [15b]
58 [11c]
47 [14]
7
3g
3h
3i
8
Ph
9
Ph
10
Ph
3j
53 [21]
a
Isolated yields.
b
References for the known compounds.

B. Movassagh, M. Navidi / Chinese Chemical Letters 23 (2012) 1035–1038
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Scheme 1.
the presence of potassium t-butoxide as a base. The alkoxide-promoted addition of terminal alkynes to ketones [18]
and aziridines [19] has been reported in recent years.
The experiments were initially conducted with phenylacetylene and diphenyl diselenide, as a model reaction, at
various molar ratios, solvents, and temperatures under an aerial atmosphere. The best molar ratios of phenylacetylene:
diphenyl diselenide: potassium t-butoxide was found to be 1:0.5:1.2. Regarding the influence of the solvent and
temperature, better results were achieved using dry DMF at 25 8C, which furnished the desired selenoalkyne, after
purification, in 82% yield after 10 min. To demonstrate the efficiency of this reaction, we explored the generality of our
method, extending the conditions to other alkynes and different diselenides (Scheme 1) and the results are summarized
in Table 1.
As clear from the table, the reactions proceeded to provide moderate to good yield of alkynyl selenides (3) with
varied substrates within a short time (10–70 min). We found that this method is applicable for aromatic as well as
aliphatic alkynes and different diaryl diselenides. Reaction of aliphatic alkynes, 1-hexyne and 1-octyne, with diphenyl
diselenide (entries 9 and 10, Table 1) took long times (70 and 120 min, respectively) giving the products (3i and 3j)
with 47 and 53% yields respectively. The structures of all the products were established from their analytical and
1
spectral (IR, H and 13C NMR) properties. It is noteworthy that solid potassium t-butoxide is inexpensive and
commercially available.
To conclude, we have developed a simple, general, mild and efficient procedure for the synthesis of alkynyl
selenides in good yields using readily available substrates and reagents. Our method has the advantages of operational
simplicity, mild reaction conditions, fast reaction rates, and simple reaction work-up.
Acknowledgment
The authors thank the K.N. Toosi University of Technology Research Council for financial assistance.
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