the electronic and steric effects of attached groups in the aryl bro-
mides and in the diselenide moiety. In terms of electronic effects,
the reaction was not very sensitive to this influence, since the
coupling of diphenyl diselenide with neutral, electron donating
and electron withdrawing aryl bromides were efficiently achieved
nologia) for financial support. Devender Singh thanks TWAS-
CNPq for a Ph.D. fellowship.
Notes and references
1
(a) D. L. Klayman, and H. H. G u¨ nter, Organoselenium Compounds:
Their Chemistry and Biology, Wiley-Interscience, New York, 1973;
(
entries 1–5). Comparing the coupling reaction between the aryl
bromide 1c and 1e, the activated one (4-OMe group) 1c showed
a higher yield (entry 3 vs. 5). Despite this, the coupling was
efficient and allowed the formation of diaryl selenides with good
yields. Analyzing Table 4 (entries 3–4 and 8–10), it is possible to
observe that in terms of steric and electronic effects, the reaction
was not strongly influenced by these parameters. As described,
the reaction was not hampered and the diaryl selenides were
obtained in high yields. To extend the scope of our coupling
protocol, alkyl bromides were also employed (entries 6 and 7).
Using our methodology it was possible to prepare alkyl aryl
selenides in reasonable yields, which are difficult to prepare
(
b) J. T. Rotruck, A. L. Pope, H. E. Ganther, A. B. Swanson, D. G.
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9
according to the previous report.
The quest for developing economic and environmental
friendly methods is one of our prime concerns. It prompted us
to evaluate the possibility of reusing the ionic liquid employed in
our reactions. After the work-up, the catalyst CuO nanopowder
was removed from BMIM-BF by filtration and the recovered
4
40
4 For a review on an aryl-chalcogen bond formation, see: Comprehen-
sive Organic Synthesis, ed. B. M. Trost and I. Fleming, Pergamon
Press, Ltd., New York, 1991, Vol. 6.
ionic liquid was used again for the next coupling reactions. This
operation was repeated for more three times without significant
lose of efficiency, as shown in Fig. 2.
5 For selected examples of an aryl-heteroatom bond formation, see:
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(
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4
Fig. 2 Reuse of BMIM-BF .
9
V. P. Reddy, A. V. K. Kokkirala Swapna and K. R. Rao, Org. Lett.,
2
009, 11, 951.
In conclusion, we have developed a clean, eco-friendly,
inexpensive and efficient methodology to obtain diaryl or alkyl
aryl selenides from alkyl or aryl halides with diaryl diselenides
using CuO nanopowder in ionic liquid as a recyclable solvent.
Features of this method include the following: (i) easily accessible
alkylating agents were used; (ii) very small amount of catalyst
used; (iii) use of recyclable solvent.
1
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Acknowledgements
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The authors gratefully acknowledge, CNPq (INCT-Catalise,
INCT-NANOBIOSIMES, Jovem Pesquisador em Nanotec-
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