Cryptand-22 as an efficient ligand for the copper-catalyzed cross-coupling reaction of diorgano dichalcogenides with terminal alkynes leading to the synthesis of alkynyl chalcogenides

Article abstract of DOI:10.1016/j.tetlet.2014.01.088

A general and efficient method for the cross-coupling reaction of diorgano dichalcogenides with terminal alkynes using copper iodide/cryptand-22 (CuI/C22) has been developed. This protocol gave alkynyl chalcogenides in moderate to excellent yields in the

Full text of DOI:10.1016/j.tetlet.2014.01.088

Tetrahedron Letters 55 (2014) 1613–1615
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Cryptand-22 as an efficient ligand for the copper-catalyzed
cross-coupling reaction of diorgano dichalcogenides with terminal
alkynes leading to the synthesis of alkynyl chalcogenides
⇑
Elmira Mohammadi, Barahman Movassagh
Department of Chemistry, K.N. Toosi University of Technology, PO Box 16315-1618, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A general and efficient method for the cross-coupling reaction of diorgano dichalcogenides with terminal
alkynes using copper iodide/cryptand-22 (CuI/C22) has been developed. This protocol gave alkynyl chalc-
ogenides in moderate to excellent yields in the presence of K3PO4 as the base under aerobic conditions.
Ó 2014 Elsevier Ltd. All rights reserved.
Received 16 October 2013
Revised 11 January 2014
Accepted 21 January 2014
Available online 29 January 2014
Keywords:
Cross-coupling
Catalysis
Dichalcogenides
Alkynyl chalcogenides
Terminal alkynes
Organoselenium compounds have received significant attention
from the chemical community, because of their chemo-, regio-, and
stereoselective reactions,1 and their potential biological activities,
such as antiviral, antihypertensive, anti-oxidant, antitumor, anti-
microbial, and anticancer.2 In addition, many chiral and achiral
organoselenium compounds act as catalysts in organic synthesis.3
Among organoselenium compounds, alkynyl derivatives of sele-
nium have emerged as versatile building blocks for many organic
transformations.4 Alkynyl selenides, can be considered as potent
dienophiles in Diels–Alder reactions.5 Also, they are useful precur-
sors in nucleophilic additions6 and for the preparation of selenium
salts.7 Additionally, they are employed in the formation of
functionalized olefins by hydroamination,8 hydrosulfonation,9
hydrozirconation,10 hydrohalogenation,11 hydroboration,12 and
hydrostannylation.13 Selenocarboxylic esters, which are mild and
efficient acyl transfer agents, can also be prepared from alkynyl
selenides.14 Furthermore, alkynyl sulfides have been employed in
cross-coupling,15 and cycloaddition16 reactions, as well as in the
preparation of self-assembled monolayers in the production of
composite materials.17
diselenides,20 or selenocyanates;21 (ii) selenodecarboxylation of
either arylpropiolic or cinnamic acids by hypervalent iodine spe-
cies such as iodosylbenzene (IB) and iodosobenzene diacetate
(IBDA);22 (iii) the reaction of alkynyl bromides with a nucleophilic
source of selenium;23 (iv) elimination of nitrogen by cleavage of
selenodiazoles in the presence of an alkylating agent;24 and (v)
coupling of terminal alkynes with diorganyl diselenides in the
presence of a base.25 In some cases, the described procedures need
long reaction times, harsh reaction conditions, excess amounts of
alkynes or require toxic metals, strictly anhydrous conditions, high
temperatures, and careful handling of selenium compounds. Thus,
the development of efficient and highly active metal-based cata-
lysts for the synthesis of this class of compounds has received
increasing attention.
The effectiveness of copper-based catalysts in the organosele-
nium field,26 especially in the preparation of alkynyl selenides
prompted us to design a new catalytic system for the synthesis
of alkynyl selenides. In this regard, and according to our previous
studies,27 we explored commercially available bidentate cryptand
compounds, which contain a molecular cavity, as appropriate
ligands for stabilizing copper(I) iodide in reactions under an air
atmosphere. The complex of copper(I) iodide with 1,4,10,13-tetra-
oxa-7,16-diazacyclooctadecane (KryptofixÒ 22 or cryptand-22)
was first reported by Mühle and Sheldrick,28 and has been
prepared by an easier method in our laboratory.27 This catalytic
system is an air-stable solid powder and remains as such for at
least two months with no change in its activity. We thought that
The most common methodologies developed for the prepara-
tion of alkynyl selenides involve: (i) the reaction of metal
alkynylides with elemental selenium,18 or an appropriate electro-
philic selenium agent, such as an arylselenium halide,19 diaryl
⇑
Corresponding author. Tel.: +98 21 8802 5459; fax: +98 21 2285 3650.
E-mail address: bmovass1178@yahoo.com (B. Movassagh).
http://dx.doi.org/10.1016/j.tetlet.2014.01.088
0040-4039/Ó 2014 Elsevier Ltd. All rights reserved.

1614
E. Mohammadi, B. Movassagh / Tetrahedron Letters 55 (2014) 1613–1615
Table 2
the flexible macrocyclic and chelating effect of such an N- and
O-containing ligand may assist the stabilization of the reactive
copper intermediates. Herein, we report a mild, efficient, and inex-
pensive synthetic route for the preparation of acetylenic chalcoge-
nides using a CuI/cryptand-22 (CuI/C22) complex that suppresses
Cu(I)-mediated homocoupling,27 even under aerobic conditions.
Our preliminary studies were directed toward finding general
sets of reaction conditions that could be applied to a wide variety
of dichalcogenides and terminal alkynes. In order to optimize the
reaction conditions, the coupling reaction between diphenyl disel-
enide (1a) (1.0 equiv), phenylacetylene (2a) (2.0 equiv), and a base
(2.0 equiv) was employed as a model reaction in air (Table 1).
The reaction rates were found to be strongly dependent on the
base, solvent, temperature, and copper concentration employed.
Different inorganic and organic bases were screened. The yield of
the cross-coupling products was reduced when organic bases such
as triethylamine or N,N-diisopropylethylamine (DIPEA) were em-
ployed at room temperature (Table 1, entries 4 and 5). Moreover,
a considerable increase in product formation was observed in the
presence of an inorganic base such as K3PO4 in DMSO (Table 1, en-
try 3). Raising the reaction temperature from 25 °C to higher tem-
peratures (55 and 70 °C) had a substantial positive effect on the
product yields (Table 1, entries 6 and 7). Also, other solvents
including DMF, CHCl3, and even solventless conditions were also
surveyed under similar reaction conditions, but compared to
DMSO, all gave inferior results (Table 1, entries 10–12). Next, dif-
ferent copper concentrations (0.5, 1 and 1.5 mol %) were investi-
gated (Table 1, entries 7–9); among them, 1 mol % of the catalyst
was found to be the best (Table 1, entry 7). Therefore, it was
decided to use K3PO4 as the base, DMSO as the solvent, and
1 mol % of the catalyst at 70 °C as the optimum conditions in fur-
ther studies.29 To find out if the in situ formation of CuI/C22 in
the reaction vessel would drive the reaction, the process was also
conducted under the same reaction conditions, by adding a mix-
ture of diphenyl diselenide and phenylacetylene in dry DMSO, to
a test-tube containing CuI (1 mol %), cryptand-22 (1 mol %), and
K3PO4; stirring the reaction mixture for 24 h produced the corre-
sponding product in 33% yield.
Cross-coupling of dichalcogenides with terminal alkynes using CuI-C22a
CuI-C22 (1 mol%)
R1
H
R1
Y R2
+
R2YYR2
Y=Se, S, Te
DMSO, K3PO4
air, 70 o
C
1
3
2
Entry
R1
R2
Ph
4-ClC6H4
PhCH2
Y
Product
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
9
Ph
Ph
Ph
Ph
C4H9
C6H13
CH2OH
CH2OTHP
Ph
C4H9
C6H13
Ph
Se
Se
Se
Se
Se
Se
Se
Se
S
3a
3b
3c
3d
3e
3f
3g
3h
3i
0.2
1
2
0.6
3
3
5
8
6
96
87
52
78
81
79
81
62
74
31
28
71
4-MeOC6H4
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
10
11
12
S
S
Te
3j
3k
3l
24
24
5
a
Reaction conditions: diorgano dichalcogenide (1 equiv), alkyne (2 equiv), K3PO4
(2 equiv), DMSO (2 mL), air atmosphere.
b
Isolated yield.
To survey the generality of the catalytic protocol, we studied
the reaction using various dichalcogenides coupled with terminal
alkynes under the optimized conditions. The results are summa-
rized in Table 2. The reactions proceeded smoothly to provide good
to excellent yields of alkynyl selenides with various substrates
(Table 2, entries 1–8). We found that this method was applicable
to aromatic as well as aliphatic alkynes and diselenides. As shown
in Table 2, reactions of aromatic terminal alkynes proceeded at rel-
atively higher rates compared with those of aliphatic alkynes,
which can be explained due to facile deprotonation of aromatic ter-
minal alkynes versus aliphatic examples. The reaction was almost
equally facile with both electron-donating and electron-withdraw-
ing substituents on the diselenides (Table 2, entries 2 and 4). An
important feature associated with this protocol is the tolerance
of different functional groups, such as alcohols (Table 2, entry 7).
To extend the scope of this method, the cross-coupling of diphe-
nyl-disulfide and -ditelluride with terminal alkynes was evaluated
under the optimized conditions (Table 2, entries 9–12). The corre-
sponding products were obtained in lower yields (28–74%) and in
longer reaction times (5–24 h) than those of their diselenide
counterparts.
Finally, we compared the catalytic performance of our catalyst
with other catalytic systems reported in the literature for the
cross-coupling of diphenyl diselenide with phenylacetylene
(Table 3). Table 3 clearly demonstrates the advantages of the pres-
ent methodology over the other reported protocols, in terms of the
product yield and reaction time.
In conclusion, we have presented an efficient and simple proto-
col for the cross-coupling of diorgano dichalcogenides with termi-
nal alkynes catalyzed by the air-stable CuI-C22 complex, affording
the corresponding alkynyl chalcogenides. The present method has
Table 1
Optimization of the reaction conditionsa
CuI-C22
Ph
Se Ph
3a
PhSeSePh
Ph
+
base, solvent
20 min
1a
2a
H
N
O
O
O
I
O
Cu
N
H
CuI-C22
Entry
Base
Temp (°C)
Solvent
Catalyst (mol %)
Yieldb (%)
1
2
3
4
5
6
7
8
K2CO3
Cs2CO3
K3PO4
Et3N
25
25
25
25
25
55
70
70
70
70
70
70
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
1
1
1
1
1
1
1
0.5
1.5
1
1
1
78
82
87
49
36
91
96
81
95
62
12
–
Table 3
Comparison of different catalytic systems with the present work
DIPEAc
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
Entry Catalyst
Conditions
Time (h) Yielda,b (%)
1
CuI/
Mg, DMF, 120 °C
48
8323b
imidazole
InCl3
Cu/Al2O3
CuI
CuO NPs
CuI
2
3
4
5
6
7
Cs2CO3, DMSO, 80 °C 12
9119b
9
Zn dust, THF, reflux
K2CO3, 30 °C, DMSO
K2CO3, DMSO, 80 °C
DMF, rt
8
9223a
10
11
12
20
14
2
9726e
CHCl3
neat
8026f
6826d
a
Reaction conditions: diphenyl diselenide (1 equiv), phenylacetylene (2 equiv),
CuI-C22
K3PO4, DMSO, 70 °C
0.2
96 [Present work]
base (2 equiv), solvent (2 mL), 20 min, air atmosphere.
a
b
Isolated yield.
Reference.
Isolated yield.
N,N-Diisopropylethylamine.
b
c

E. Mohammadi, B. Movassagh / Tetrahedron Letters 55 (2014) 1613–1615
1615
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29. General procedure for the preparation of alkynyl cholcogenides: A test-tube was
charged with diorgano dichalcogenide (0.5 mmol), terminal alkyne (1.0 mmol),
CuI-C22 (4.5 mg, 1 mol %), K3PO4 (1.0 mmol), and dry DMSO (1 mL). The
mixture was then stirred at 70 °C under aerobic conditions. The progress of the
reaction was monitored by TLC. When the reaction was complete, the mixture
was poured into H2O (15 mL) and extracted with EtOAc (2 Â 15 mL). The
combined organic layers were dried over MgSO4, filtered and concentrated in
vacuo to give the crude product, which was purified by preparative thin-layer
chromatography (silica gel, n-hexane/EtOAc = 9:1) to afford the desired pure
product.