Copper(I) selenophene-2-carboxylate (CuSC) promoted C–S cross-coupling reaction of thiols with aryl iodides

Article abstract of DOI:10.1080/17415993.2018.1519566

We reported the synthesis of copper (I)-selenophene-2-carboxylate (CuSC) and application as new catalyst in the cross-coupling reactions of thiols with aryl iodide to afford the corresponding unsymmetrical thioethers. The optimized reaction conditions were applied to thiols and aryl iodides having a wide range of functional groups, including electron rich and electron poor substrates. The chemoselectivity of the reaction with 4-iodobromobenzene and 2-aminothiophenol derivatives was briefly examined through the competitive iodine versus bromine and thiol versus nitrogen cross-coupling.

Full text of DOI:10.1080/17415993.2018.1519566

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Copper(I) selenophene-2-carboxylate (CuSC)
promoted C–S cross-coupling reaction of thiols
with aryl iodides
Olga Soares do Rêgo Barros, Francielle Rodrigues Silva & Vanessa Loren
Nunes
To cite this article: Olga Soares do Rêgo Barros, Francielle Rodrigues Silva & Vanessa Loren
Nunes (2018): Copper(I) selenophene-2-carboxylate (CuSC) promoted C–S cross-coupling reaction
of thiols with aryl iodides, Journal of Sulfur Chemistry, DOI: 10.1080/17415993.2018.1519566
To link to this article: https://doi.org/10.1080/17415993.2018.1519566
View supplementary material
Published online: 10 Sep 2018.
Submit your article to this journal
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gsrp20

JOURNAL OF SULFUR CHEMISTRY
https://doi.org/10.1080/17415993.2018.1519566
Copper(I) selenophene-2-carboxylate (CuSC) promoted C–S
cross-coupling reaction of thiols with aryl iodides
Olga Soares do Rêgo Barros , Francielle Rodrigues Silva and Vanessa Loren Nunes
Instituto de Química, Universidade Federal de Goiás, Goiânia, Goiás, Brasil
ABSTRACT
ARTICLE HISTORY
Received 7 June 2018
Accepted 30 August 2018
We reported the synthesis of copper (I)-selenophene-2-carboxylate
(CuSC) and application as new catalyst in the cross-coupling reac-
tions of thiols with aryl iodide to afford the corresponding unsym-
metrical thioethers. The optimized reaction conditions were applied
to thiols and aryl iodides having a wide range of functional
groups, including electron rich and electron poor substrates. The
chemoselectivity of the reaction with 4-iodobromobenzene and
2-aminothiophenol derivatives was briefly examined through the
competitive iodine versus bromine and thiol versus nitrogen cross-
coupling.
KEYWORDS
Unsymmetrical thioethers;
copper(I) carboxylate;
crosscoupling;
chemoselectivity;
regioselectivity
1. Introduction
Transition-metal-catalyzed cross-coupling reactions are powerful synthetic methods for
the construction of new carbon–carbon and carbon-heteroatom bonds [1–3]. During the
last three decades, palladium catalyzed cross-coupling reactions between C(sp2)-centers
have been extensively used for selective construction of structural units found in natural
products, pharmaceuticals and electrical conductors [4–6,7] (for aryl halides and thiols
cross-coupling, see [8,9], and references there in [10,11]). This reaction is generally co-
catalyzed by copper salts, and the use of an amine as base and a phosphine as a ligand are
typically employed [12–15]. Recent advances in cross-coupling reactions, including the
use of metals other than palladium and a copper-free protocol have also been reported
[16,17]. In this context, copper-catalyzed coupling systems have been developed because
CONTACT Olga Soares do Rêgo Barros
olga_barros@ufg.br
Instituto de Química, Universidade Federal de
Goiás, Campus Samambaia, 74001-970 Goiânia, Goiás, Brasil
Supplemental data for this article can be accessed here. https://doi.org/10.1080/17415993.2018.1519566
© 2018 Informa UK Limited, trading as Taylor & Francis Group

2
O. S. D. R. BARROS ET AL.
Scheme 1. Copper cross-coupling reactions of aryl iodides 1 with thiols 2 using selenophene-2-
carboxylic acid as a ligand.
of the great interest in the increase of coupling substrates that are economic, more eas-
ily accessible, and reactive even under mild conditions [5,18]. Of the variety of reactions
that fall into this category, copper salts have been used as promoter agents in cross cou-
pling reactions, carbon-heteroatom bond formation (carbon–nitrogen, carbon–oxygen,
carbon–sulfur, carbon–selenium) and intramolecular cyclization processes [19,20]. How-
ever, due to the cost of catalysts, the use of equimolar amounts and the use of high
temperature, there has been an increasing attention to the development of such transfor-
mation by using ligands. In this sense, several classes of ligands such as diamine [21–25],
amino acids [26–31], 1,10-phenanthrolines [32–36], diols [37] have proven to be effective
and promising alternatives to give the cross-coupling products in good yields under mild
conditions. Recently, heterocyclic-2-carboxylic acids, such as piconilic acid [38] and pyr-
role 2-carboxylic acid [39], have been efficiently used as ligands in copper cross-coupling
reactions. Alternatively, the use of boronic acids and copper as a catalyst, under ligand free
was described for the synthesis of unsymmetrical thioethers [40–42]. Keeping in mind
that selenium-containing ligands have a high propensity to bridge metal centers [43] and
that the use of selenophene derivatives as a ligand in copper cross-coupling reactions is
unknown, we searched the preparation of unsymmetrical thioethers 3 via copper cross-
coupling reactions of thiols 1 with aryl iodides 2 using selenophene-2-carboxylic acid as
ligand (Scheme 1).
2. Results and discussion
Our initial experiments focused on studying the efficiency of selenophene-2-carboxylic
acid as a ligand under the influence of different copper salts. For this purpose, iodoben-
zene 1a and 4-methylbenzenethiol 2a were used as standard substrates. Thus, a mixture of
iodobenzene 1a (0.5 mmol) and 4-methylbenzenethiol 2a (0.6 mmol) was treated with a
variety of copper catalysts in DMSO as a solvent, using K3PO4 as a base in the presence of
selenophene-2-carboxylic acid as ligand (Table 1) A comparison of the effectiveness of cop-
per salts showed that all of them gave the cross-coupling products in good yields (Table 1,
entries 1–8). It is interesting that copper compounds in various oxidation states are cat-
alytically active and presumably are transformed into the same active catalyst under the
reaction conditions [21,44]. Although Cu2O was the most efficient, giving the product in
77% yield (Table 1, entry 2), it is important to note that replacement of selenophene-2-
carboxylic acid by thiophene-2-carboxylic acid as a ligand led to inferior results (Table 1,
entry 8). Furthermore, in the absence of the selenophene-2-carboxylic acid, the product
was obtained in low yield (Table 1, entry 1).
This result was considered satisfactory compared to those obtained by other
heterocyclic-2-carboxylic acids reported in the literature [45]. However, in order to make

JOURNAL OF SULFUR CHEMISTRY
3
Table 1. Copper sources examined for cross-coupling reaction of iodobenzene 1a with
4-methylbenzenethiol 2a.
Entry
Copper catalyst (5%)
Yield, 3 (%)a
1b
Cu2O
Cu2O
CuI
52
77
69
68
65
70
70
20
2
3
4
CuCl
5
CuBr
6
Cu(OAc)2
CuSO4
Cu2O
7
8c
aReaction conditions: 1a (0.5 mmol), 2a (0.6 mmol), [CuX] (5 mol%), ligand (10 mol%), K3PO4 (1.2 mmol), DMSO (3 mL), Ar,
110°C, 24 h.
bIn the absence of ligand.
cAs a ligand thiophene-2-carboxylic acid (10 mol%).
Scheme 2. Synthesis of copper(I)-senelenophene-2-carboxylate I.
the reaction more efficient and easier to handle, we decided to prepare the catalyst I from
the reaction of selenophene-2-carboxylic acid and Cu2O (Scheme 2). This catalyst I is a
single-site catalyst and is intrinsically more active and selective. Additionally, the free lig-
and in the reactional medium can hamper the isolation and purification of the desired
products, i.e. they can make it difficult to remove the desired product [46].
In this way, the reaction of selenophene-2-carboxylic acid with Cu2O in toluene under
reflux gave an air stable yellowish-brown color powder that was used for further cross-
coupling reactions. The cross-coupling of iodobenzene 1a and 4-methylbenzenethiol 2a
was initially examined under the influence of the catalyst previously prepared. The reaction
was first performed with some screened parameters, such as solvents, molar ratios of the
reagents and base, which could affect the cross-coupling reaction (Table 2).
The results shown in Table 2 indicated that the cross-coupling of iodobenzene 1a and
4-methylbenzenethiol 2a gave the desired thioether 3a in better yields, when the reaction
was carried out using copper(I)-selenophene-2-carboxylate I (5 mol%), DMSO (3 mL),
iodobenzene 1a (0.5 mmol), 4-methylthiophenol 2a (0.6 mmol) and K3PO4 (2 mmol) at
110°C for 24 h. In order to compare the reactivity and catalytic efficiency in promot-
ing cross-coupling reactions of CuSC with copper (I) thiophene-2-carboxylate (CuTC),

4
O. S. D. R. BARROS ET AL.
Table 2. Screening optimal condition for the copper (I)-selenophene-2-carboxylate catalyzed coupling
of iodobenzene 1a and 4-methylbenzenethiol 2a.
Entry
Solvent
Base
I (%)
1
2
Yield 3 (%)a,b
1
2
3
4
5
6
7
DMSO
DMF
2.0
2.0
2.0
1.0
1.2
2.0
2.0
20
20
20
20
5
1.0
1.0
1.0
1.0
0.5
0.5
0.5
0.5
0.5
0.5
1.0
0.6
0.6
0.6
90
86
H2O
NR
92
DMSO
DMSO
DMSO
DMSO
70
5
90
–
NR
aReaction conditions: solvent (3 mL), K3PO4 (mmol), I (mmol%) 1a (mmol), 2a (mmol), temperature (110°C), 24 h.
bYields (%) for isolated product.
an isostructural analogous to CuSC, the coupling reaction of iodobenzene 1a and 4-
methylthiophenol 2a in the presence of CuTC was performed under the optimized reaction
conditions depicted in entry 1 of Table 2. The expected reaction product 3a was obtained
in only 20% yield. To the best of our knowledge, there are few reports that CuTC [47,48]
promoted cross coupling in catalytic quantities of less than 30 mol%. A recent protocol,
for the CuTC promoted C–S bond formation between 2-(piperazine)-pyrimidine iodides
with aryl thiols [48], the diaryl sulfides containing the piperazine ring were obtained using
quantities 40 mol% of this copper salt. In most of the instances reported, CuTC was used as
a co-catalyst or in equimolecular amounts for the C–N and C–C bond coupling processes
[14,49,50]. On the basis of above results, this methodology was applied to a variety of aryl
iodides 1 and thiols 2 in order to test the tolerance of functional groups as well as their
effects on the conversion.
These results are shown in Table 3.
The analyses of these experiments showed that the catalytic process was not signifi-
cantly influenced by electronic effects of the substituent in the aromatic rings in the aryl
iodide or aryl thiols, because neutral, electron-donating or electron-withdrawing groups
provided thioethers 3 in similar yields. For example, reactions of aryl iodides and aryl thi-
ols with neutral, donating, and electron-withdrawing group, bonded to the C(sp2) lead to
desired unsymmetrical diaryl thioethers in high yields 78–100% (Table 3, 3a–3g). In the
same way, the reaction of aryl iodides with a neutral, electron-donating and withdrawing
group was slightly influenced by electronic effects of the substituent in the aromatic rings
giving 80–85% yields (Table 3, 3j–3l). It is notable that the coupling proceeded well even
with a sterically hindered substitute such as methyl or amino at the ortho position (Table 3,
3b and 3g). A heteroaryl thiol (pyridine-2-thiol) also underwent coupling with a good yield
of 80% (Table 3, 3f).
The coupling reaction is also very chemo selective when a variety of other potentially
reactive groups were present in the substrates. For example, aryl iodides coupled with

JOURNAL OF SULFUR CHEMISTRY
5
Table 3. Scope and generality of the Copper (I)-Selenophene-2-carboxylate catalyzed carbon–sulfur
coupling reaction of aryl iodides 1 with thiols 2.
thiophenol without affecting the bromo or chloro group in the aryl thiol ring (Table 3,
3d and 3k). Finally, we observed that with the coupling of alkyl thiols with aryl iodides the
reaction gave a 70–98% yields (Table 3, 3h–3i).
2.1. Mechanistic considerations
On the basis of these observations and similar findings reported in the literature [21–25],
we propose that the mechanism for this catalytic process proceeds by oxidative addition
followed by reductive elimination. Thus, the results obtained in the present study are con-
sistent with the mechanism in which a four coordinated Cu (III) intermediate is involved.
Scheme 3 shows a plausible mechanism for this process.
3. Conclusion
In summary, we have developed a simple, efficient and general methodology for copper-
catalyzed carbon–sulfur coupling reactions of aryl, alkyl, and heterocyclic thiols in a

6
O. S. D. R. BARROS ET AL.
Scheme 3. Proposed mechanism for the catalytic process.
homogeneous catalysis using a low quantity of the catalyst. This method shows excellent
functional-group compatibility and high selectivity in the presence of multiple potentially
reactive groups at moderate temperatures. Because of these issues, we believe that this new
copper catalyst could find wide application in carbon-heteroatom coupling reactions as
well as carbon–nitrogen, carbon–oxygen and carbon–selenium.
4. Experimental section
4.1. Materials and methods
All reagents and solvents used were previously purified and dried in agreement with the
literature [51]. THF was distilled from sodium/benzophenone under nitrogen immedi-
ately before use. Butyllithium was titrated using 1,10-phenanthroline as indicator prior
to use. Nitrogen gas used in the reactions was deoxygenated and dried. All operations
were carried out in flame-dried glassware. Column chromatography separations were per-
formed with Aldrich Chemical Co. silica gel 60 (0.063–0.200 mm, 70–230 mesh) or silica
gel (0.035–0.075 mm, pore diameter ca. 6 nm). The chemicals were obtained from com-
1
mercial sources. All new compounds have been characterized by H and 13C NMR, IR
spectroscopy and elemental analysis.1H and 13C NMR spectra were obtained on a Bruker
Avance III 500 (500 MHz, 1H; 125 MHz, 13C) Spectrometer. All spectra were taken in
CDCl3 and the chemical shifts are given in ppm with respect to tetramethylsilane (TMS)
used as an internal standard. Near IR spectra were obtained on a Perkin Elmer Pre-
cisely Spectrum 400 FT-IR/FT-FIR Spectrometer. Elemental analyses were performed on
a Thermo scientific Flash 2000 Organic Elemental Analyzer. The IUPAC names were
obtained using the software ChemDraw, version 8.0.
4.2. Procedure for the preparation of copper(I)-selenophene-2-carboxylate
A similar procedure to that of the preparation of copper(I) thiophene-2-carboxylate
(CuTC) [46]. A Schlenk tube was charged with selenophene-2-carboxylic acid (0.94 g,
5.5 mmol), Cu2O (0.19 g, 1.3 mmol) and toluene (5 mL) and the mixture stirred at reflux

JOURNAL OF SULFUR CHEMISTRY
7
for 12 h under dry argon to afford a brown suspension that was cooled to ambient tem-
perature. The product was collected on a fritted-glass funnel under a stream of argon. The
solid was then washed with methanol to remove the excess of acid, and then with ether
until the eluent was colorless, and finally with hexanes. The solid was dried under vac-
uum affording the copper(I)-selenophene-2-carboxylate. The product was obtained as a
tan, air stable powder (0.210 g, 72%). IR (KBr): 3057, 1564, 1433, 1383 cm−1. Anal. Calc.
For C5H3O2CuSe: C: 25.28, H: 1.27. Found: C: 24.5, H: 1.3.
4.2.1. General procedure for the preparation of aryl sulfides 3
In a Schlenk tube a mixture of I (6 mg, 0.025 mmol), iodobenzene 1a (101 mg, 0.5 mmol),
4-methylbenzenethiol 2a (75 mg, 0.6 mmol) and K3PO4 (422 mg, 2.0 mmol) was sus-
pended in DMSO (3 mL) and stirred at 110°C under an argon atmosphere for 24 h. After
this, the reaction mixture was filtrated with DCM (10 mL), quenched with 5 mL of a
(NH4Cl) solution and extracted with EtOAc (3 × 10 mL). The organic layer was dried with
(Na2SO4). The solvent was evaporated under reduced pressure, and the crude mixture was
purified by silica gel column chromatography eluting with hexane.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico.
ORCID
Olga Soares do Rêgo Barros http://orcid.org/0000-0002-1096-5282
References
[1] Yamaguchi J, Yamaguchi AD, Itami K. C–H bond functionalization: emerging synthetic
tools for the synthesis of natural products and pharmaceuticals. Angew Chem Int Ed.
2012;51:8960–9009.
[2] Li CJ. Cross-dehydrogenative coupling (CDC): exploring C–C bond formations beyond func-
tional group transformations. Acc Chem Res. 2009;42:335–344.
[3] Bolm C, Legros J, Le Paih J, et al. Iron-catalyzed reactions in organic synthesis. Chem Rev.
2004;104:6217–6254.
[4] Hartwig JF. Transition metal catalyzed synthesis of arylamines and aryl ethers from aryl halides
and triflates: scope and mechanism. Angew Chem Int Ed. 1998;37:2047–2067.
[5] Beletskaya IP, Cheprakov AV. Copper in cross-coupling reactions: the post-Ullmann chemistry.
Coord Chem Rev. 2004;248:2337–2364.
[6] Corbet JP, Mignani G. Selected patented cross-coupling reaction technologies. Chem Rev.
2006;106:2651–2710.
[7] Johannesson P, Lindeberg GA, Johanson GV, et al. Vinyl sulfide cyclized analogues of
angiotensin II with high affinity and full agonist activity at the AT1 receptor. J Med Chem.
2002;45:1767–1777.
[8] Masanori K, Toshimi O, Masahiro T, et al. Palladium-catalyzed reaction of stannyl sulfide with
aryl bromide. Preparation of aryl sulfide. Bull Chem Soc Jpn. 1985;58:3657–3658.
[9] Murata M, Buchwald SL. A general and efficient method for the palladium-catalyzed cross-
coupling of thiols and secondary phosphines. Tetrahedron. 2004;60:7397–7403.

8
O. S. D. R. BARROS ET AL.
[10] Fernández-Rodríguez MA, Shen Q, Hartwig JF. A general and long-lived catalyst for the
palladium-catalyzed coupling of aryl halides with thiols. J Am Chem Soc. 2006;128:2180–2181.
[11] Itoh T, Mase T. A general palladium-catalyzed coupling of aryl bromides/triflates and thiols.
Org Lett. 2004;6:4587–4590.
[12] J T. Palladium reagents and catalysts. New perspectives for the 21st century. Chichester: Wiley;
2004.
[13] Negishi E, de Meijre A. Organopalladium chemistry for organic synthesis. New York: Wiley;
2002.
[14] Innitzer A. Copper(I) thiophene-2-carboxylate(CuTC). Synlett. 2005;15:2405–2406.
[15] Selander N, Szabó KJ. Catalysis by palladium pincer complexes. Chem Rev. 2011;111:2048–
2076.
[16] Siemsen P, Livingston RCF, Diederich F. Acetylenic coupling: A powerful tool in molecular
construction. Angew Chem Int Ed. 2000;39:2632–2657.
[17] Soheili A, Albaneze-Wlker J, Murry JA, et al. Efficient and general protocol for the copper-free
Sonogashira coupling of aryl bromides at room temperature. Org Lett. 2003;5:4191–4194.
[18] Ley SV, Thomas AW. Modern synthetic methods for copper-mediated C(aryl)-O, C(aryl)-N,
and C(aryl)-S bond formation. Angew Chem Int Ed. 2003;42:5400–5449.
[19] Kunz K, Lui N. Process chemistry and copper catalysis, in copper-mediated cross-coupling
reactions. Hoboken (NJ): Wiley; 2013.
[20] Hirano K, Miura M. Recent advances in copper-mediated direct biaryl coupling. Chem Lett.
2015;44:868–873.
[21] Klapars A, Huang X, Buchwald SL. A general and efficient copper catalyst for the amidation of
aryl halides. J Am Chem Soc. 2002;124:7421–7428.
[22] Buchwald SL, Blackmond DG, Strieter ER. The role of chelating diamine ligands in the Gold-
berg reaction: a kinetic study on the copper-catalyzed amidation of aryl iodides. J Am Chem
Soc. 2005;127:4120–4121.
[23] Strieter ER, Bhayana B, Buchwald SL. Mechanistic studies on the copper-catalyzed N-arylation
of amides. J Am Chem Soc. 2009;131:78–88.
[24] Surry DS, Buchwald S. Diamine ligands in copper-catalyzed reactions. Chem Sci. 2010;1:13–31.
[25] Chen CW, Chen YL, Reddy DM, et al. Cui/oxalic diamide-catalyzed cross-coupling of thiols
with aryl bromides and chlorides. Chem Eur J. 2017;23:10087–10091.
[26] Zhang H, Cai Q, Ma D. Amino acid promoted CuI-catalyzed C–N bond formation between
aryl halides and amines or N-containing heterocycles. J Org Chem. 2005;70:5164–5173.
[27] Ma D, Cai Q. L-proline promoted Ullmann-type coupling reactions of aryl iodides with indoles,
pyrroles, imidazoles or pyrazoles. Synlett. 2004;1:128–130.
[28] Alcalde E, Dinares I, Rodríguez S, et al. Synthetic approaches to sterically hindered N-
arylimidazoles through copper-catalyzed coupling reactions. Eur J Org Chem. 2005;2005:
1637–1643.
[29] Lv X, Wang Z, Bao W. Cui catalyzed C-N bond forming reactions between aryl/heteroaryl
bromides and imidazoles in [Bmim] BF4. Tetrahedron. 2006;62:4756–4761.
[30] Sreedhar B, Shiva Kumar KB, Srinivas P, et al. Cui/l-histidine catalyzed N-arylation of hetero-
cycles. J Mol Catal A Chem. 2007;265:183–185.
[31] Huang Y-Z, Gao J, Ma H, et al. Ninhydrin: An efficient ligand for the Cu-catalyzed N-arylation
of nitrogen-containing heterocycles with aryl halides. Tetrahedron Lett. 2008;49:948–951.
[32] Tye JW, Weng Z, Johns AA, et al. Copper complexes of anionic nitrogen ligands in the
amidation and imidation of aryl halides. J Am Chem Soc. 2008;130:9971–9983.
[33] Tye JW, Weng Z, Giri R, et al. Copper(I) phenoxide complexes in the etherification of aryl
halides. Angew Chem Int Ed. 2010;49:2185–2189.
[34] Giri R, Hartwig JF. Cu(I) amido complexes in the Ullmann reaction. Reactions of Cu(I)-
amido complexes with iodoarenes with and without autocatalysis by CuI. J Am Chem Soc.
2010;132:15860–15863.
[35] Ogiwara Y, Maeda H, Sakai N. Copper-catalyzed production of diaryl sulfides using aryl
iodides and a disilathiane. Synlett. 2018;29:655–657.

JOURNAL OF SULFUR CHEMISTRY
9
[36] Wang M, Wei J, Fana Q, et al. Cu(II)-catalyzed sulfide construction: both aryl groups
utilization of intermolecular and intramolecular diaryliodonium salt. Chem Commun.
2017;53:2918–2921.
[37] Zhang SL, Liu L, Fu Y, et al. Theoretical study on copper(I)-catalyzed cross-coupling between
aryl halides and amides. Organometallics. 2007;26:4546–4554.
[38] Buchwald SL, Maiti D. Cu-catalyzed arylation of phenols: synthesis of sterically hindered and
heteroaryl diaryl ethers. J Org Chem. 2010;75:1791–1794.
[39] Altman RA, Anderson KW, Buchwald SL. Pyrrole-2-carboxylic acid as a ligand for the Cu-
catalyzed reactions of primary anilines with aryl halides. J Org Chem. 2008;73:5167–5169.
[40] Saba S, Botteselle GV, Godoi M, et al. Copper-catalyzed synthesis of unsymmetrical dior-
ganyl chalcogenides (Te/Se/S) from boronic acids under solvent-free conditions. Molecules.
2017;22:1367–1381.
[41] Shanmugapriya J, Rajaguru K, Muthusubramanian S, et al. Copper(II)-catalyzed C–S cross-
coupling with thiazolidine-2-thiones and boronic acids: synthesis of azole sulfides. Eur J Org
Chem. 2016;11:1963–1967.
[42] Rostami A, Rostami A, Ghaderi A, et al. Copper-catalyzed C-S bond formation via the cleavage
of C-O bonds in the presence of S8 as the sulfur source. Synthesis (Mass). 2017;49:5025–5038.
[43] Kimani MM, Watts D, Graham LA, et al. Dinuclear copper(I) complexes with N-heterocyclic
thione and selone ligands: synthesis, characterization, and electrochemical studies. Dalton
Trans. 2015;44:16313–16324.
[44] Weston PE, Adkins H. Catalysis with copper in the Hullmann reaction. J Am Chem Soc.
1928;50:859–866.
[45] Sujatha A, Thomas AM, Thankachan AP, Anilkumar G. Recent advances in copper catalyzed
C-S cross-coupling reactions. Arkivoc. 2015; I:–28.
[46] Al-Amin M, Honma T, Hoshiya N, et al. Ligand-free Buchwald–Hartwig aromatic aminations
of aryl halides catalyzed by low-leaching and highly recyclable sulfur-modified gold-supported
palladium material. Adv Synth Catal. 2012;354:1061–1068.
[47] Gandeepan P, Mo J, Ackermann L. Photo-induced copper-catalyzed C-H chalcogenation of
azoles at room temperature. Chem Commun. 2017;53:5906–5909.
[48] Shrestha L, Patel HJ, Kang Y, et al. Copper mediated coupling of 2-(piperazine)-
pyrimidine iodides with aryl thiols using Cu(I)thiophene-2-carboxylate. Tetrahedron Lett.
2017;58:4525–4531.
[49] Wei K-J, Quan Z-J, Zhang Z, et al. Copper(I)-promoted C–N cross-coupling of N-heterocyclic
compounds with 1,2-di(pyrimidin-2-yl) disulfides. Synlett. 2016;27:1743–1747.
[50] Allred GD, Liebeskind LS. Copper-mediated cross-coupling of organostannanes with organic
iodides at or below room temperature. J Am Chem Soc. 1996;118:2748–2749.
[51] Armarego WLF, Chai C. Purification of laboratory chemicals. 6th ed. Burlington: Butterworth-
Heinemann; 2009.