Microwave-assisted one-pot synthesis of symmetrical diselenides, ditellurides and disulfides from organoyl iodides and elemental chalcogen catalyzed by CuO nanoparticles

Article abstract of DOI:10.1016/j.molcata.2012.09.003

In this study CuO nanoparticles were applied as a catalyst for CSe, CTe, and CS bond formation. The reaction was performed with organoyl iodides and elemental selenium, tellurium or sulfur under microwave irradiation in the presence of a base and solvent at 80 °C. This novel protocol allowed the synthesis of a variety of diselenides, ditellurides and disulfides in good to excellent yields in a very short reaction time.

Full text of DOI:10.1016/j.molcata.2012.09.003

Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Microwave-assisted one-pot synthesis of symmetrical diselenides, ditellurides
and disulfides from organoyl iodides and elemental chalcogen catalyzed
by CuO nanoparticles
Giancarlo V. Bottesellea, Marcelo Godoia, Fabio Z. Galettoa, Luana Bettanina, Devender Singhb,
Oscar E.D. Rodriguesb, Antonio L. Bragaa,∗
a Departamento de Química, Universidade Federal de Santa Catarina, 88040-970, Florianópolis, SC, Brazil
b Departamento de Química, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 March 2012
Received in revised form 27 June 2012
Accepted 1 September 2012
Available online 7 September 2012
In this study CuO nanoparticles were applied as a catalyst for C Se, C Te, and C S bond formation.
The reaction was performed with organoyl iodides and elemental selenium, tellurium or sulfur under
microwave irradiation in the presence of a base and solvent at 80 ◦C. This novel protocol allowed the
synthesis of a variety of diselenides, ditellurides and disulfides in good to excellent yields in a very short
reaction time.
© 2012 Elsevier B.V. All rights reserved.
Keywords:
Diselenide
Ditelluride
Disulfide
CuO nanoparticle
Microwave irradiation
1. Introduction
However, most of these methods have drawbacks, such as the
use of strong reducing agents, highly toxic gas, harsh reaction con-
Over the past few decades organochalcogen compounds have
attracted considerable attention due to their importance as
reagents and synthetic intermediates in organic synthesis [1–6].
Several types of these compounds play a crucial role in biology and
biochemistry. For instance, they have been used as antioxidants and
apoptosis inducers, and their role in the degradation of hydroper-
oxides and in the chemoprevention of cancer in a variety of organs
has been exploited [7,8].
Several methods have been described for the synthesis of
diorganoyl diselenides and ditellurides [9–18] which include the
reaction of metal diselenides or ditellurides with organoylhalides
[19–21], the well established reaction of Grignard reagents with
elemental selenium or tellurium, the reduction of selenocyanates
[22–25] and the oxidation of both selenols and selenolates [26,27].
Several methodologies have been described for the synthesis of
diorganoyl disulfides generally obtained by oxidation of thiols
[28–33] or even, according to Taniguchi, from elemental sulfur and
aryl iodides catalyzed by Cu-bpy, aluminum and sodium carbonate
[34].
ditions, low yields, and/or complex manipulations, requiring the
use of an inert atmosphere, besides a long reaction time.
Thus, there is a growing need for new methods that are truly
efficient, high yielding, responsive to mild reaction conditions and
carried out in a short reaction time. Currently, nanostructured
metallic catalysts are commonly used in organic reactions, espe-
cially in coupling reactions [35–38], and generally these catalysts
afford a more effective process and allow a genuine advance in rela-
tion to traditional methodologies. In this new intensive area CuO
has emerged as a powerful and useful catalyst in several transfor-
mations [39–45].
In this context, we have recently reported the synthesis of
organochalcogen compounds employing nano CuO as a catalyst
in several transformations (Scheme 1) [46–49]. These include the
preparation of organoyl diselenides and ditellurides through a
cross-coupling reaction with either selenium or tellurium and
organoyl halides using 10 mol% of catalyst [47]. Despite the effec-
tiveness of this approach, the development of new methodologies
for the synthesis of organoyl dichalcogenides under mild reaction
conditions, open to the air, in a short reaction time and employing
a lower amount of catalyst, is highly desirable.
In this context, besides the advantages associated with the
use of nanocatalysts in organic reactions cited above, microwave
irradiation has also been widely used in organic synthesis
∗
Corresponding author. Tel.: +55 48 37216850; fax: +55 48 37216427.
E-mail address: albraga@qmc.ufsc.br (A.L. Braga).
1381-1169/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2012.09.003

G.V. Botteselle et al. / Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
187
Scheme 1. Synthesis of organochalcogen compounds via nano CuO catalyst.
particularly due to its ability to heat quickly and evenly when
compared with conventional heating [50,51]. Moreover, the use
of microwaves associated with nano catalysts has been reported
for the preparation of different classes of compounds [52]. There-
fore, the combination of microwave irradiation and nanocatalysts
could emerge as a powerful tool for the chalcogen–carbon bond
formation.
ionization voltage of 70 eV). Melting points were measured on a
Microquímica MQ APF-301 hot plate system. Transmission elec-
tron microscopy (TEM) images were recorded in a JEOL JEM-100
electron microscope operating at 100 kV. TEM samples were pre-
pared from one drop catalyst solubilized in acetone, which was
deposited on a 200-mesh Formvar/carbon-coate copper grid, and
excess solution was removed by wicking with filter paper.
Thus, in connection with our ongoing research interest
in organochalcogen chemistry [53–59] we described herein a
microwave-assisted procedure for the synthesis of diselenides,
ditellurides and disulfides employing their respective elemental
chalcogen and organoyl iodides catalyzed by CuO nanopowder in
the presence of a base and in the absence of an inert atmosphere
(Scheme 2).
2.2. General procedure for the microwave-assisted synthesis of
diorganoyl diselenides, ditellurides and disulfides
Elemental chalcogen (Se, Te or S, 1.0 mmol), CuO nanopowder
(5.0 mol%), KOH (2.0 equiv.), organoyl iodide (0.5 mmol) and DMSO
(1 mL) were placed in a specific microwave tube equipped with a
magnetic stir bar. The tube was placed in the microwave cavity
and submitted to irradiation for 7 or 15 min (see Tables 3 and 4)
at 80 ◦C using a maximum power of 100 W. After cooled the reac-
tion system at room temperature the crude product was directly
purified by flash column chromatography without previous work-
up. For example in case of diphenyl diselenide 2a, 20 g of silica gel
(230–400 mesh) was used to packing the column and the reaction
mixture was directly added to the top of column and eluted with n-
hexane. Alternatively, the flash chromatograph can be performed
by a Super flash purification column SF25-40g with a BSR pump
system and eluted with hexane. Flash chromatography was per-
formed by mixing of the crude with silica gel 60 (230–400 mesh)
in a proportion of 1:4 using a SimpliFlash with BSR pump system.
The identity and purity of the products was confirmed by 1H NMR,
13C NMR, GC/MS and the melting points and all of the spectral data
were in perfect agreement with those reported in the literature
[14–16,21,27–29,31,47,60].
2. Experimental
2.1. Materials
All reactions were performed in 10 mL sealed tubes in a com-
mercially available monomode reactor (CEM Discover) with IR
monitoring and a non-invasive pressure transducer. The solvents
were dried by standard methods. CuO nanoparticles (mean particle
size: 33 nm; surface area: 29 m2/g), selenium (powder, 325 mesh;
purity: 99.70%), tellurium (powder, 200 mesh; purity: 99.80%), sul-
fur (powder, 100 mesh; purity: 99.50%) and all other reagents
were purchased from appropriate commercial sources. Flash chro-
matography column was performed using Merck silica gel 60
(230–400 mesh) and flash chromatography by Super flash purifi-
cation column was performed using SF25-40g Sepra Si 50 with a
BSR (Bottomless Solvent Reservoir) pump system. Thin layer chro-
matography (TLC) was performed using Merck silica gel GF254, with
a thickness of 0.25 mm. The NMR spectra were measured in CDCl3
on a Bruker DPX 200 and Bruker Avance 200 spectrometer. 1H
and 13C spectra were recorded at 200 and 50 MHz, respectively,
with tetramethysilane (TMS) as the internal standard. Mass spec-
tra of dichalcogenides were obtained by GC–MS analysis (Shimadzu
GCMS-QP5050A, equipped with a DB-5 capillary column (30 m) and
2.3. Characterization of the products
2.3.1. Diselenides
Diphenyl diselenide (2a): [27,47] yellow solid, mp 59–60 ◦C (lit.
61–62 ◦C), yield: 70%; 1H NMR (CDCl3, 200 MHz) (ı, ppm) 7.61 (m,
4H), 7.25–7.21 (m, 6H); 13C NMR (CDCl3, 50 MHz) (ı, ppm) 131.5,
130.9, 129.1, 127.7; GC–MS: m/z (%) 314 (34), 312 (33), 310 (16),
234 (18), 232 (10), 230 (5), 159 (16), 158 (25), 157 (80), 155 (48),
153 (22), 117 (16), 78 (78), 77 (100), 51 (61), 50 (29).
Bis(4-methylphenyl) diselenide (2b): [27,47] orange solid, mp
42–43 ◦C (lit. 44–45 ◦C), yield: 71%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.49 (d, J = 8.2 Hz, 4H), 7.07 (d, J = 8.2 Hz, 4H), 2.34 (s, 6H);
13C NMR (CDCl3, 50 MHz) (ı, ppm) 139.3, 133.2, 130.5, 127.4, 22.8;
Scheme 2. General synthesis of organoyl diselenides, ditellurides and disulfides.

188
G.V. Botteselle et al. / Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
(m, 2H), 7.93–7.87 (m, 2H), 7.26–7.19 (m, 2H); 13C NMR (CDCl3,
50 MHz) (ı, ppm) 152.4, 149.4, 149.2, 140.1, 124.2; GC–MS: m/z (%)
316 (17), 314 (18), 312 (11), 159 (53), 158 (41), 157 (32), 156 (43),
155 (19), 131 (26), 129 (17), 127 (9), 125 (11), 69 (51), 57 (90), 51
(78), 43 (79), 41 (55).
GC–MS: m/z (%) 344 (6), 342 (15), 340 (21), 338 (12), 336 (4), 182
(23), 173 (9), 171 (23), 169 (31), 167 (16), 91 (100), 77 (7), 65 (23),
57 (15), 44 (15).
Bis(4-methoxyphenyl) diselenide (2c): [27,47] orange solid, mp
48–49 ◦C (lit. 45–47 ◦C), yield: 76%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.53 (d, J = 8.8 Hz, 4H), 6.83 (d, J = 8.8 Hz, 4H), 3.80 (s, 6H);
13C NMR (CDCl3, 50 MHz) (ı, ppm) 160.0, 138.1, 135.4, 114.7, 55.3;
GC–MS: m/z (%) 376 (3), 375 (3), 374 (18), 372 (19), 370 (10), 207
(25), 189 (18), 188 (22), 187 (100), 186 (19), 185 (54), 184 (25), 183
(20), 172 (16), 144 (17), 108 (77), 78 (31), 77 (16), 63 (29), 55 (11),
44 (18).
Bis(3-methoxyphenyl) diselenide (2d): [47] orange solid, mp
191–193 ◦C (lit. 194 ◦C), yield: 94%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.22–7.16 (m, 6H), 6.81–6.75 (m, 2H), 3.76 (s, 6H); 13C NMR
(CDCl3, 50 MHz) (ı, ppm) 159.7, 131.7, 129.8, 123.4, 116.4, 113.7,
55.2; GC–MS: m/z (%) 374 (18), 372 (16), 370 (10), 188 (22), 187
(38), 186 (20), 185 (23), 184 (16), 144 (17), 142 (10), 108 (100), 92
(22), 78 (56), 77 (43), 63 (42), 57 (13), 44 (28).
Dibutyl diselenide (2m): [21] yellow oil, yield: 52%; 1H NMR
(CDCl3, 200 MHz) (ı, ppm) 2.92 (t, J = 7.6 Hz, 4H), 1.72 (qui, J = 7.6 Hz,
4H), 1.43 (sex, J = 7.6 Hz, 4H), 0.93 (t, J = 7.6 Hz, 6H); 13C NMR (CDCl3,
50 MHz) (ı, ppm) 33.7, 30.6, 23.3, 14.2; GC–MS: m/z (%) 276 (3), 274
(2), 272 (8), 270 (5), 268 (2), 220 (2), 218 (8), 216 (8), 214 (5), 212
(2), 162 (3), 160 (3), 159 (2), 158 (2), 135 (4), 95 (2), 57 (100), 55
(16), 41 (45).
2.3.2. Ditellurides
Diphenyl ditelluride (3a): [15,47,60] orange solid, mp 63–65 ◦C
(lit. 64–66 ◦C), yield: 65%; 1H NMR (CDCl3, 200 MHz) (ı, ppm)
7.81–7.76 (m, 4H), 7.24–7.12 (m, 6H); 13C NMR (CDCl3, 50 MHz)
(ı, ppm) 137.6, 129.5, 128.1, 107.9; GC–MS: m/z (%) 414 (4), 412
(7), 410 (7), 408 (8), 284 (7), 282 (7), 207 (24), 205 (19), 203 (11),
154 (22), 153 (4), 78 (23), 77 (100), 57 (11), 51 (52).
Bis(2-methoxyphenyl) diselenide (2e): [47] orange solid, mp
84–85 ◦C (lit. 83–84 ◦C), yield: 85%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.57–7.52 (m, 2H), 7.21–7.16 (m, 2H), 6.91–6.80 (m, 4H), 3.90
(s, 6H); 13C NMR (CDCl3, 50 MHz) (ı, ppm) 156.7, 130.4, 128.1,
121.8, 110.0, 97.5, 55.8; GC–MS m/z (%) 376 (12), 374 (61), 372 (60),
370 (27), 368 (11), 367 (13), 294 (9), 187 (15), 186 (35), 185 (23),
184 (22), 183 (15), 182 (13), 159 (47), 157 (60), 155 (24), 108 (35),
107 (100), 93 (40), 78 (85), 77 (98), 65 (41), 63 (38), 51 (19).
Bis(2,4-dimethoxyphenyl) diselenide (2f): [47] yellow solid, mp
133–135 ◦C, yield: 75%; 1H NMR (CDCl3, 200 MHz) (ı, ppm)
Bis(4-methoxyphenyl) ditelluride (3b): [15,47,60] orange solid,
mp 61–62 ◦C (lit. 58–60 ◦C), yield: 55%; 1H NMR (CDCl3, 200 MHz)
(ı, ppm) 7.66 (d, J = 8.8 Hz, 4H), 6.72 (d, J = 8.8 Hz, 4H), 3.76 (s, 6H);
13C NMR (CDCl3, 50 MHz) (ı, ppm) 160.1, 138.1, 135.4, 114.7, 55.2;
GC–MS: m/z (%) 474 (1), 472 (2), 470 (3), 293 (10), 281 (5), 237 (5),
235 (5), 233 (3), 207 (16), 108 (13), 85 (20), 81 (32), 77 (7), 71 (36),
69 (69), 57 (37), 55 (25), 43 (42), 41 (43).
Bis(2-aminophenyl) ditelluride (3c): [47] reddish solid, yield:
45%; 1H NMR (CDCl3, 200 MHz) (ı, ppm) 7.67–7.63 (m, 2H),
7.18–7.10 (m, 2H), 6.77–6.69 (m, 2H), 6.62–6.55 (m, 2H), 4.20 (s,
4H); 13C NMR (CDCl3, 50 MHz) (ı, ppm) 150.4, 142.5, 131.3, 118.8,
113.4, 94.7.
Bis(4-chlorophenyl) ditelluride (3d): [15,47] orange solid, mp
111–113 ◦C (lit. 114–115 ◦C), yield: 50%; 1H NMR (CDCl3, 200 MHz)
(ı, ppm) 7.66 (d, J = 8.4 Hz, 4H), 7.13 (d, J = 8.4 Hz, 4H); 13C NMR
(CDCl3, 50 MHz) (ı, ppm) 139.3, 139.1, 129.8, 129.4; GC–MS: m/z
(%) 484 (3), 482 (4), 480 (3), 478 (6), 476 (6), 281 (17), 241 (33), 239
(24), 237 (18), 224 (13), 208 (17), 207 (80), 191 (12), 113 (26),112
(32), 111 (49), 97 (23), 96 (17), 91 (11), 85 (42), 77 (28), 71 (49), 57
(71), 55 (31), 44 (100), 43 (71).
Bis(4-nitrophenyl) ditelluride (3e): [16] light orange solid, mp
124–126 ◦C, yield: 67%; 1H NMR (CDCl3, 200 MHz) (ı, ppm) 8.17
(d, J = 9.2 Hz, 4H), 6.92 (d, J = 9.2 Hz, 4H); 13C NMR (CDCl3, 50 MHz)
(ı, ppm) 141.3, 130.2, 126.2, 115.6; GC–MS: m/z (%) 504 (2), 503
(4), 254 (7), 253 (10), 252 (5), 251 (5), 77 (12), 57 (950), 44 (74).
Dibutyl ditelluride (3f): [14] red oil, yield: 51%; 1H NMR (CDCl3,
200 MHz) (ı, ppm) 3.11 (t, J = 7.6 Hz, 4H), 1.76–1.67 (m, 4H),
1.44–1.33 (m, 4H), 0.93 (t, J = 7.4 Hz, 6H); 13C NMR (CDCl3, 50 MHz)
(ı, ppm) 35.1, 23.9, 12.7, 3.6; GC–MS: m/z (%) 374 (2), 372 (4), 370
(5), 368 (3), 366 (2), 316 (3), 314 (4), 312 (3), 260 (3), 258 (5), 256
(4), 254 (2), 113 (3), 99 (4), 85 (13), 71 (19), 57 (100), 43 (21), 41
(48).
7.53–7.49 (m, 2H), 6.46–6.42 (m, 4H), 3.82 (s, 6H), 3.79 (s, 6H); 13
C
NMR (CDCl3, 50 MHz) (ı, ppm) 161.2, 158.5, 133.7, 110.0, 105.6,
98.5, 55.4; GC–MS m/z (%) 436 (1), 433 (1), 428 (2), 302 (9), 300
(21), 298 (7), 296 (3), 219 (10), 217 (45), 215 (25), 213 (6),189 (27),
185 (26), 123 (27), 109 (28), 85 (50), 79 (27), 77 (20), 57 (100),55
(68), 43 (77), 41 (63).
Bis(2-aminophenyl) diselenide (2g): [47] orange solid, mp
82–84 ◦C (lit. 81–83 ◦C), yield: 70%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.54 (dd, J1 = 7.8 Hz, J2 = 1.4 Hz, 2H), 7.19–7.11 (m, 2H), 6.72
(dd, J1 = 7.8 Hz, J2 = 1.4 Hz, 2H), 6.64–6.55 (m, 2H), 4.26 (s, 4H); 13
C
NMR (CDCl3, 50 MHz) (ı, ppm) 148.5, 138.0, 131.1, 118.4, 114.4,
82.8; GC–MS: m/z (%) 346 (1), 257 (11), 255 (37), 253 (17), 252 (5),
251 (5), 184 (23), 183 (17), 181 (14), 174 (34), 173 (16), 172 (100),
170 (84), 169 (29), 168 (29), 149 (52), 83 (74), 77 (29), 65 (52), 57
(89), 55 (50), 44 (48), 43 (87).
Bis(4-chlorophenyl) diselenide (2h): [27,47] orange solid, mp
83–85 ◦C (lit. 85–86 ◦C), yield: 81%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.47 (d, J = 8.6 Hz, 4H), 7.20 (d, J = 8.6 Hz, 4H); 13C NMR (CDCl3,
50 MHz) (ı, ppm) 134.2, 133.2, 129.5, 129.3; GC–MS: m/z (%) 384
(18), 382 (27), 381 (7), 380 (23), 379 (8), 378 (12), 194 (16), 193
(45), 192 (35), 191 (100), 190 (21), 189 (48), 188 (12), 187 (17), 156
(56), 112 (63), 77 (23), 75 (55), 63 (18), 50 (31).
Bis(4-bromoyphenyl) diselenide (2i): [27,47] reddish solid, mp
110–111 ◦C (lit. 108–109 ◦C) yield: 60%; 1H NMR (CDCl3, 200 MHz)
(ı, ppm) 7.47–7.36 (m, 8H); 13C NMR (CDCl3, 50 MHz) (ı, ppm)
134.5, 133.3, 132.5, 132.2; GC–MS: m/z (%) 474 (1), 472 (2), 470
(2), 238 (17), 237 (10), 236 (21), 235 (14), 234 (12), 159 (10), 158
(18), 157 (51), 156 (25), 155 (21), 96 (18), 77 (39), 44 (87).
Bis(4-nitrophenyl) diselenide (2j): [21] light yellow solid, mp
174–176 ◦C (lit. 175–177 ◦C), yield: 83%; 1H NMR (CDCl3, 200 MHz)
(ı, ppm) 8.14 (d, J = 8.6 Hz, 4H), 7.75 (d, J = 8.6 Hz, 4H); 13C NMR
(CDCl3, 50 MHz) (ı, ppm) 133.2, 130.4, 124.6, 124.3; GC–MS: m/z
(%) 406 (2), 405 (1), 404 (1), 326 (17), 324 (58), 322 (40), 320 (11),
281 (15), 232 (26), 231 (18), 230 (15), 229 (12), 207 (71), 184 (36),
156 (26), 152 (100), 151 (38), 139 (46), 117 (22), 113 (20), 99 (21),
85 (64), 77 (11), 76 (30), 71 (71), 57 (99), 50 (47), 44 (90), 43 (85).
2.3.3. Disulfides
Diphenyl disulfide (4a): [28,29,31] white solid, mp 60–61 ◦C (lit.
57–59 ◦C), yield: 67%; 1H NMR (CDCl3, 200 MHz) (ı, ppm) 7.50–7.28
(m, 10H); 13C NMR (CDCl3, 50 MHz) (ı, ppm) 137.0, 129.0, 127.5,
127.1; GC–MS: m/z (%) 220 (9), 219 (13), 218 (95), 186 (5), 185 (25),
154 (23), 111 (5), 110 (12), 109 (100), 77 (10), 65 (44), 51 (13).
Bis(4-methoxyphenyl) disulfide (4b): [29,31] white solid, mp
38–40 ◦C (lit. 41–43 ◦C), yield: 66%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.39 (d, J = 8.8 Hz, 4H), 6.83 (d, J = 8.8 Hz, 4H), 3.80 (s, 3H);
13C NMR (CDCl3, 50 MHz) (ı, ppm) 159.9, 132.6, 128.4, 114.6, 55.3;
GC–MS: m/z (%) 280 (4), 278 (32), 140 (16), 139 (100), 125 (7), 124
(8), 96 (13), 95 (14), 77 (4), 69 (6), 45 (5).
Di(pyridin-3-yl)diselenide (2l): [47] orange solid, yield: 70%; 1
NMR (CDCl3, 200 MHz) (ı, ppm) 8.79–8.75 (m, 2H), 8.53–8.50
H

G.V. Botteselle et al. / Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
189
Table 1
Screening of copper sources in cross-coupling reaction.
Entry
Catalyst
Amount (mol%)
Yielda (%)
1
2
3
4
5
6
7
8
9
CuO nano
CuO nano
CuO nano
CuO nano
CuO nano
CuO
1.0
2.5
5.0
10.0
5.0
5.0
5.0
5.0
–
10
31
71
72
68b
20
35
38
–
CuI
CuFe2O4 nano
–
a
Yield of the isolated product.
Reaction performed in inert atmosphere.
b
Dibutyl disulfide (4f): [28] colorless liquid, yield: 54%; 1H NMR
(CDCl3, 200 MHz) (ı, ppm) 2.88 (t, J = 7.6 Hz, 4H), 1.76–1.67 (m, 4H),
1.51–1.40 (m, 4H), 0.95 (t, J = 7.4 Hz, 6H); 13C NMR (CDCl3, 50 MHz)
(ı, ppm) 39.5, 31.0, 21.6, 13.4; GC–MS: m/z (%) 180 (6), 179 (7), 178
(54), 124 (5), 122 (53), 89 (5), 88 (8), 86 (10), 58 (8), 57 (100), 56
(13), 55 (20), 41 (73).
Bis(2-aminophenyl) disulfide (4c): [29] light yellow solid, mp
95–96 ◦C (lit. 93–94 ◦C), yield: 55%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.19–7.12 (m, 4H), 6.73–6.55 (m, 4H), 4.23 (s, 4H); 13C NMR
(CDCl3, 50 MHz) (ı, ppm) 148.2, 135.9, 131.7, 118.5, 118.3, 115.5;
GC–MS: m/z (%) 250 (2), 248 (11), 207 (12), 127 (6), 126 (10), 185
(100), 124 (52), 97 (25), 93 (30), 81 (25), 80 (58), 77 (3), 65 (14), 53
(16).
Bis(4-chlorophenyl) disulfide (4d): [28,29,31] white solid, mp
73–75 ◦C (lit. 72–74 ◦C), yield: 50%; 1H NMR (CDCl3, 200 MHz) (ı,
ppm) 7.40 (d, J = 8.5 Hz, 4H), 7.27 (d, J = 8.5 Hz, 4H); 13C NMR (CDCl3,
50 MHz) (ı, ppm) 135.1, 133.7, 129.4, 129.3; GC–MS: m/z (%) 288
(25), 286 (33), 145 (34), 144 (25), 143 (100), 109 (18), 110 (71), 99
(17), 75 (14), 73 (13), 63 (24), 43 (17), 32 (27).
Bis(4-nitrophenyl) disulfide (4e): [29] orange solid, mp
167–169 ◦C (lit. 176–178 ◦C), yield: 79%; 1H NMR (CDCl3, 200 MHz)
(ı, ppm) 8.20 (d, J = 8.8 Hz, 4H), 7.62 (d, J = 8.8 Hz, 4H); 13C NMR
(CDCl3, 50 MHz) (ı, ppm) 144.5, 133.2, 126.4, 124.4; GC–MS: m/z
(%) 309 (1), 308 (1), 234 (49), 232 (29), 155 (16), 154 (100), 153
(15), 152 (23), 115 (9), 77 (40), 51 (43), 43 (9).
2.4. Recovering of the catalyst
After the complete cross coupling reaction for preparation of
the diphenyl diselenide, the CuO nanopowder was recovered. The
reaction mixture was treated with water and ethyl acetate and
the CuO nanoparticles were recovered from aqueous solution by
centrifugation.
3. Results and discussion
We initiated our study by screening the effect of the cat-
alyst loading on the reaction system (Table 1). As a standard
Table 2
Search for the best cross-coupling reaction conditions.
Entry
Solvent
Base (2.0 equiv.)
Time (min)
Yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
DMSO
DMF
CH3CN
THF
KOH
KOH
KOH
KOH
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
7.0
5.0
3.0
0.5
7.0
7.0
7.0
71
56
40
–
EtOH
KOH
–
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
NaOH
t-BuOK
K2CO3
Cs2CO3
KOH
KOH
KOH
KOH
KOH
48
55
–
–
70
59
50
Traces
29b
68c
73d
KOH
KOH
a
Yield of the isolated product.
b
c
Reaction performed in the microwave at 50 W.
Reaction performed in the microwave at 150 W.
Reaction performed in the microwave at 150 ◦C.
d

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G.V. Botteselle et al. / Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
Table 3
Synthesis of symmetrical diselenides.a.
Entry
1
R
Product
Time (min)
Yieldb (%)
1a
2a
7
70
1b
2
3
2b
2c
15
15
71
76
1c
1d
4
5
2d
2e
15
15
94
85
1e
1f
6
2f
15
75
1g
7
8
2g
2h
15
7
70
81
1h
1i
9
2i
2j
7
7
60
83
1j
10
1l
11
2l
7
7
70
52
1m
12
2m
a
Reaction conditions: iodide (0.5 mmol), CuO nanoparticles (5.0 mol%), Se0 (1.0 mmol), KOH (1.0 mmol), and DMSO (1.0 mL) were stirred under microwave irradiation
(100 W) at 80 ◦C for 7.0 or 15.0 min.
b
Yield of the isolated product.
protocol for the synthesis iodobenzene 1a (1.0 equiv.), elemental
selenium (2.0 equiv.), KOH (2.0 equiv.) and DMSO were subjected
to microwave irradiation (100 W) for 10 min at 80 ◦C. Initially, 1.0
and 2.5 mol% of CuO nanopowder were employed, affording the
corresponding diselenide 2a in low yields (entries 1 and 2). How-
ever, with the use of 5.0 mol% the yield increased to 71% (entry 3).
When the amount of CuO nanopowder was increased to 10 mol%,
the yield of compound 2a was not significantly modified, affording

G.V. Botteselle et al. / Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
191
Table 4
Synthesis of symmetrical ditellurides and disulfides.a.
Entry
1
R
Y
Product
Yieldb (%)
65
Te
3a
1a
S
4a
3b
67
55
Te
2
3
1c
S
4b
3c
66
Te
45c
1g
S
4c
55
50
Te
3d
4
5
1h
S
4d
3e
50
67
Te
1j
S
4e
3f
79
51
Te
6
1m
S
4f
54
a
Reaction conditions: iodide (0.5 mmol), CuO nanoparticles (5.0 mol%), Te◦ or S◦ (1.0 mmol), KOH (1.0 mmol), and DMSO (1.0 mL) were stirred under microwave irradiation
(100 W) at 80 ◦C for 7.0 min.
b
Yield of the isolated product.
The reaction complete in 15 min using 15 mol% of nano CuO.
c
the desired product in 72% yield (entry 4). Based on these results,
we selected 5.0 mol% of CuO nanopowder as the best amount of
catalyst.
Furthermore, it was observed in this study that the inert atmo-
sphere did not influence the reaction, since we obtained the desired
product in the similar yield compared with an open atmosphere
(entries 3 vs. 5).
As a result, KOH and DMSO were defined as ideal bases and
solvents for this reaction, which suggests that the superbasic
KOH–DMSO system in the presence of elemental chalcogen enables
the preparation of the dichalcogenolate anion [61]. Another factor
that probably contributes for the good results obtained by using
Cu catalyst in DMSO under microwave irradiation conditions is the
phenomenon of “nonequilibrium local heating” [62].
In order to examine the efficiency of the CuO nanopowder, other
catalysts (such as commercial CuO, CuI and nano-CuFe2O4) were
also tested (entries 6–8). However, on using all of these catalysts
a decline in the yield was observed (entries 6–8). It is notable that
in the absence of the catalyst in the reaction the product was not
observed (entry 9).
Having determined the best loading of the catalyst we tested
a series of reaction parameters in order to find the best reaction
conditions, as shown in Table 2. Initially we studied the influence
of the solvent on the reaction system (Table 2, entries 1–5). The use
of DMSO, DMF or CH3CN as the solvent afforded the formation of
the desired product in 71, 56 and 40% yields, respectively (entries
1–3). However, when both THF and EtOH were used the desired
product was not obtained and all starting material was recovered
(entries 4 and 5).
Next, we evaluated the influence of different bases on the
reaction (Table 2, entries 6–9). Sodium hydroxide and potassium
t-butoxide were tested but the yield was lower when compared to
potassium hydroxide (entries 6 and 7). Moreover, when the reac-
tion was carried out in the presence of inorganic carbonate bases,
such as potassium and cesium carbonate, the desired product was
not obtained and all starting material was recovered (entries 8 and
9).
After the optimization of the best solvent and base, other impor-
tant parameters were studied, such as the reaction time, microwave
irradiation (power) and temperature (Table 2, entries 10–16).
When the reaction time was reduced from 10 to 7 min of irradia-
tion no significant decline in the yield was observed (entries 1 and
10). A further decrease in the reaction time to 5 and 3 min afforded
the product in considerably decreased yields of 59 and 50% respec-
tively (entries 11 and 12). Furthermore, the reaction was irradiated
for 0.5 min and only traces of the desired product were achieved
(entry 13).
Focusing on the influence of microwave irradiation, the reac-
tion was irradiated at 50 W of maximum power for 7 min and the
desired product 2a was obtained in only 29% yield (entry 14). On
increasing the power to 150 W no significant difference in the yield
was observed compared to irradiation at 100 W (entries 10 vs. 15).
Finally, the temperature was increased to 150 ◦C and no significant
change in the yield was observed (Table 2, entry 16).
Moreover, we alsoobserveda slightlycontaminationof organoyl
selenides in the crude residue, which probably can be formed via
reductive cleavage of Se Se bond [42,46]. For instance, when p-
toluyl iodine 1b was employed the correspondent selenide was
identified in 2% yield. Therefore, a strict control in the reaction time
was performed to avoid these side reactions. Thus, after complete

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G.V. Botteselle et al. / Journal of Molecular Catalysis A: Chemical 365 (2012) 186–193
employed the respective diselenides 2l and 2m were obtained in
70 and 52% yield, respectively (entries 11 and 12).
Encouraged by these results we extended the methodology to
the synthesis of ditellurides and disulfides as shown in Table 4. A
wide range of substituted aryl iodides containing either donating
or withdrawing groups were employed in order to prepare differ-
ent organoyl dichalcogenides and the desired diaryl ditellurides
3a–d and diaryl disulfides 4a–d were obtained in yields of 45–79%
(Table 4, entries 1–5).
Furthermore, applying the same reaction conditions we also
prepared aliphatic ditellurides and disulfides. For instance, when
iodobutane 1m was used the corresponding ditelluride 3f and
disulfide 4f were synthesized in good yields (entry 6).
Aiming to find out how the copper catalyst is transformed during
the reaction, TEM analysis of the CuO nanopowder was performed
before and after the reaction (Fig. 1). The experimental results sug-
gest that the reaction involves heterogeneous process since the
catalyst could be recovered. However, aggregation of the nanoparti-
cles was observed, which suggest a reduced activity and difficulties
for reuse the catalyst.
4. Conclusions
In summary, we have developed a rapid and efficient method
for the synthesis of diselenides, ditellurides and disulfides from
organoyl iodides and their respective elemental chalcogens,
catalyzed by CuO nanoparticles under microwave irradiation.
Applying this new methodology, the desired products were
obtained in good to excellent yields.
The major advantage of this microwave-assisted protocol is the
reduction in the reaction time and the amount of catalyst CuO
nanoparticles used when compared to our previously reported
results. More interestingly, for the first time, CuO nanoparticles
have been employed as a catalyst for the synthesis of organoyl
disulfides.
We believe that the combination of nanocatalysis and
microwave irradiation described here represents a new direction
in organochalcogen chemistry. Intensive studies remain in progress
in our laboratory.
Fig. 1. TEM images of CuO nanopowder. (a) Fresh CuO nanopowder, (b) CuO
nanopowder after the reaction. CuO was purchased from Sigma–Aldrich (mean
particle size: 33 nm; surface area: 29 m2/g).
Acknowledgment
the reaction time (see Tables 3 and 4) the crude product was cooled
at room temperature and immediately purified by flash chromatog-
raphy without any extraction.
The authors gratefully acknowledge to CNPq, INCT-Catálise,
CAPES and FAPESC for financial support.
Having established the best reaction conditions, we extended
our protocol to the synthesis of a variety of diorganoyl diselenides
2a–m (Table 3).
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