NJC
Letter
on these results, we envision that these complexes can be
employed as a source of halogens in a variety of reactions.
Acknowledgements
Fig. 8 Formation of bromohydrin from cyclopentene.
Table 2 Allylic bromination of cyclohexene
The authors thank CNPq, FAPESP and CAPES for financial
support. G. Demets also thanks NAPMI for support. Dr C. V.
Stevani is also aknowledged.
Notes and references
1
(a) J. Lagona, P. Mukhopadhyay, S. Chakrabarti and L. Isaacs,
Angew. Chem., Int. Ed., 2005, 44, 4844; (b) G. J. F. Demets,
Quim. Nova, 2007, 30, 1313; (c) L. Isaacs, Chem. Commun.,
2009, 619; (d) G. Hettiarachchi, D. Nguyen, J. Wu, D. Lucas,
D. Ma, L. Isaacs and V. Briken, PLoS One, 2010, 5;
(e) S. Walker, R. Oun, F. J. McInnes and N. J. Wheate, Isr.
J. Chem., 2011, 51, 616; ( f ) A. C. Bhasikuttan, H. Pal and
J. Mohanty, Chem. Commun., 2011, 47, 9959; (g) H. Cong,
Z. Tao, S. F. Xue and Q. J. Zhu, Curr. Org. Chem., 2011, 15, 86;
Entry Reagents and conditions
Product: isolated yield
20: 56% (lit. 60)
1
2
3
4
5
1 equiv. NBS, (PhCO
2
)
2
(5 mol%)
(5 mol%) 17: 65%
0.25 equiv. Br -CB[6], (PhCO )
2
2 2
0.25 equiv. Br
0.25 equiv. Br
0.25 equiv. Br
2
-CB[6], (PhCO (10 mol%) 17: 60%
-CB[6], (PhCO ) (50 mol%) 17: 54%
2
)
2
2
2 2
2
-CB[6], AIBN (50 mol%)
17: 58%
(
h) E. Masson, X. X. Ling, R. Joseph, L. Kyeremeh-Mensah
obtained in a low yield (entry 2). However, bromohydrin 16
and X. Y. Lu, RSC Adv., 2012, 2, 1213.
was obtained in 70% yield changing the solvent to only water
2
3
(a) H. D. Correia and G. J. F. Demets, Electrochem. Commun.,
(entry 3). To confirm the effect of the solvent, the behavior of
2
009, 11, 1928; (b) L. F. S. da Silva, G. J. F. Demets, C. Taviot-
Gueho, F. Leroux and J. B. Valim, Chem. Mater., 2011, 23, 1350;
c) G. C. Bolfarini, M. P. Siqueira-Moura, G. J. F. Demets, P. C.
another substrate was investigated. Indeed, this condition was
also successfully applied to convert cyclopentene (18) into 19
(
(
Fig. 8).
Another important reaction employing NBS is allylic radical
substitution. Using again cyclohexene (15) as the substrate, we
investigated the possibility of replacing NBS by Br –CB[6]
complex to obtain bromocyclohexene 20 (Table 2, entry 1).
Morais and A. C. Tedesco, J. Photochem. Photobiol., B, 2012, 115, 1.
F. C. Kupper, M. C. Feiters, B. Olofsson, T. Kaiho, S. Yanagida,
M. B. Zimmermann, L. J. Carpenter, G. W. Luther III, Z. Lu,
M. Jonsson and L. Kloo, Angew. Chem., Int. Ed., 2011, 50, 11598.
H. S. El-Sheshtawy, B. S. Bassil, K. I. Assaf, U. Kortz and
W. M. Nau, J. Am. Chem. Soc., 2012, 134, 19935.
2
1
0
4
5
Nevertheless, only trans-1,2-dibromocyclohexene (17) was
obtained (entry 2). The amount of the radical initiator was
increased, but a similar result was obtained (entries 3 and 4).
(a) L. F. Silva Jr. and S. A. P. Quintiliano, Tetrahedron Lett.,
2
009, 50, 2256; (b) K. R. K. K. Reddy, G. B. Longato, J. E. de
Carvalho, A. L. T. G. Ruiz and L. F. Silva Jr., Molecules, 2012,
7, 9621; (c) K. R. K. K. Reddy and L. F. Silva Jr., J. Braz.
AIBN was tested instead of (PhCO ) , giving again 17 (entry 5).
2
2
In summary, only electrophilic addition of bromine to cyclohexene
was observed. Probably, the radical initiator reacts with the CB part
of the complex and the radical chain does not occur.
1
Chem. Soc., 2013, 24, 1414.
R. Varala, S. Nuvula and S. R. Adapa, J. Org. Chem., 2006,
6
7
71, 8283.
R. S. Bhosale, S. V. Bhosale, T. Y. Wang and P. K. Zubaidha,
Tetrahedron Lett., 2004, 45, 7187.
Conclusions
In conclusion, an efficient protocol for the preparation of
iodine and bromine inclusion compounds was developed.
A brown powder consisting of I –CB[6]Á4H O and an orange
8 B. Das, P. Thirupathi, I. Mahender and K. R. Reddy, J. Mol.
Catal. A: Chem., 2006, 247, 182.
9 M. A. Pasha and V. P. Jayashankara, Bioorg. Med. Chem. Lett.,
2007, 17, 621.
2
2
one of (Br ) –CB[6]Á10H O were employed in several different
2
4
2
reactions. I –CB[6] can be used in catalytic reactions giving 10 B. S. Furniss, A. J. Hannaford, P. W. G. Smith and A. R.
2
yields comparable to those reported in the literature. Br
2
–CB[6]
Tatchell, Vogel’s Textbook of Practical Organic Chemistry,
was effectively applied in electrophilic bromination of benzene
Longman Group, London, 5th edn, 1989.
and in the formation of bromohydrin. However, the radical sub- 11 B. Das, K. Venkateswarlu, K. Damodar and K. Suneel,
stitution at cyclohexene could not be performed. Overall, based J. Mol. Catal. A: Chem., 2007, 269, 17.
2
264 | New J. Chem., 2014, 38, 2262--2264
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