E. J. Lenardão et al. / Tetrahedron Letters 50 (2009) 5215–5217
5217
the selenonium ionic liquid a similar yield was obtained just after
h (entries 6 and 9, respectively). With the aim to increase the
yield of the reaction and to eliminate the use of volatile solvent,
we decide to evaluate the use of [bmim]BF instead acetonitrile
as solvent. Unfortunately, no increasing in yields or reaction accel-
eration were observed, even when a smaller amount of [bmim]BF
aromatic and aliphatic aldehydes in good yields. The reaction time
was reduced when the selenonium salt was used.
2
4
Acknowledgements
4
This project is funded by CNPq, FAPERGS and CAPES.
(5 mol %) was used to minimize the competition for the DABCO
Table 1, entries 1–5). Thus, for example, the adduct 3a was ob-
(
tained in 63% after 24 h using 0.5 mL (100 mol %) of [bmim]BF
as solvent in the presence of DABCO and [pbe]SeBF (entry 3). This
result is similar to the observed when [bmim]BF was used alone,
showing that this high polar medium inhibits the selenonium salt
action (entry 4). A mixture of [bmim]BF and acetonitrile as solvent
4
References and notes
4
4
a
1.
(a) Basavaiah, D.; Jaganmohan, R.; Satyanarayana, T. Chem. Rev. 2003, 103, 811;
b) Basavaiah, D.; Rao, P. D.; Hyma, R. S. Tetrahedron 1996, 52, 8001; (c)
Declerck, V.; Martinez, J.; Lamaty, F. Chem. Rev. 2009, 109, 1.
4
(
4
2. (a) Krishna, P. R.; Manjuvani, A.; Kannan, V.; Sharma, G. V. M. Tetrahedron Lett.
2004, 45, 1183; (b) Yu, C.; Liu, B.; Hu, L. J. Org. Chem. 2001, 66, 5413.
was also tested, but 3a was obtained in modest yields, even after
3
.
.
(a) Basavaiah, D.; Rao, A. J.; Krishnamacharyulu, M. Arkivoc 2002, 7, 136; (b)
Emme, I.; Fulford, S. Y. J. Org. Chem. 2003, 68, 692; (c) Kawamura, M.;
Kobayashi, S. Tetrahedron Lett. 1999, 40, 1539; (d) Aggarwal, V. K.; Mereu, A.;
Tarver, G. J.; McCague, R. J. Org. Chem. 1998, 63, 7183; (e) Aggarwal, V. K.; Dean,
D. K.; Mereu, A.; Williams, R. J. Org. Chem. 2002, 67, 510.
(a) Rosa, J. N.; Afonso, C. A. M.; Santos, A. G. Tetrahedron 2001, 57, 4189; (b)
Chandrasekhar, S.; Narsihmulu, C.; Saritha, B.; Sultana, S. S. Tetrahedron Lett.
2004, 45, 5865; (c) Garre, S.; Parker, E.; Ni, B.; Headley, A. D. Org. Biomol. Chem.
several hours of stirring (entry 7). Because some BH reactions were
1
carried out with good results under solvent-free conditions, we
also tested the solvent-free reaction of 1a and 2a using our new io-
nic liquid, [pbeSe]BF
4
, but 3a was obtained only in 21% yield after
4
2
4 h (entry 8). The use of other solvents, such as dichloromethane,
was not satisfactory (entry 13).
2
008, 6, 3041; (d) Kim, E. J.; Ko, S. Y. HeIv. Chim. Acta 2003, 86, 894; (e) Gong, H.;
Cai, C.-Q.; Yang, N.-F.; Yang, L.-W.; Zhang, J.; Fan, Q.-H. J. Mol. Catal. A: Chem.
006, 249, 236; (f) Zhao, S.-H.; Zhang, H.-R.; Feng, L.-H.; Chen, Z.-B. J. Mol. Catal.
The chalcogeno-Baylis–Hillman is a variant of the BH reaction
9
using organyl chalcogenides as base and a Lewis acid as catalyst.
2
Thus, we decide to test [pbeSe]BF
4
(5 mol %) as acid catalyst in
A: Chem. 2006, 258, 251; (g) Mi, X.; Luo, S.; Xu, H.; Zhang, L.; Cheng, J.-P.
Tetrahedron 2006, 62, 2537; (h) Mi, X.; Luo, S.; Cheng, J.-P. J. Org. Chem. 2005, 70,
the presence of 1 equiv of diphenyl selenide or diphenyl diselenide
as soft Lewis bases for the reaction of 1a with 2a. The reaction mix-
ture was stirred at room temperature for several hours and no ad-
duct 3a was formed, even heating at 60 °C or using a larger amount
of the selenonium salt.
2
338; (i) Kumar, A.; Pawar, S. S. J. Mol. Catal. A: Chem. 2004, 211, 43; (j) Hsu, J.-
C.; Yen, Y.-H.; Chu, Y.-H. Tetrahedron Lett. 2004, 45, 4673; (k) Porto, R. S.;
Amarante, G. W.; Cavallaro, M.; Poppi, R. J.; Coelho, F. Tetrahedron Lett. 2009, 50,
1
184; (l) Aggarwal, V. K.; Emme, I.; Mereu, A. Chem. Commun. 2002, 1612.
(a) Zhao, S.; Zhao, E.; Shen, P.; Zhao, M.; Sun, J. Ultrason. Sonochem. 2008, 15,
55; (b) Coelho, F.; Almeida, W. P.; Veronese, D.; Mateus, C. R.; Lopes, E. C. S.;
5
.
.
9
The rate enhancement caused by acidic [pbeSe]BF
4
can be cred-
Rossi, R. C.; Silveira, G. P. C.; Pavan, C. H. Tetrahedron 2002, 58, 7437; (c) Souza,
R. O. M. A.; Souza, A. L. F.; Fernández, T. L.; Silva, A. C.; Pereira, V. L. P.; Esteves,
P. M.; Vasconcellos, M. L. A. A.; Antunes, O. A. C. Lett. Org. Chem. 2008, 5, 379.
Oishi, T.; Oguri, H.; Hirama, M. Tetrahedron: Asymmetry 1995, 6, 1241.
ited to the stabilization of the zwitterionic intermediate formed by
the DABCO attack to the electron-poor alkene, similarly to de-
6
3
d
3c
scribed by Aggarwal and Kobayashi for metal salts (Fig. 1).
The scope of our methodology was successfully expanded to
others aromatic and aliphatic aldehydes and alkenes, with the best
yields obtained when aromatic aldehydes were used (Table 2). The
present selenonium-promoted BH-reaction was also applicable to
acrylonitrile 2b (Table 2, entries 5–8), affording the respective ad-
ducts 3e–h in good yields and shorter reaction times, comparing
with those obtained with methyl acrylate 2a (entries 1–4). These
results are similar to those described in the literature using DAB-
7. (a) Lenardão, E. J.; Mendes, S. R.; Ferreira, P. C.; Perin, G.; Silveira, C. C.; Jacob, R.
G. Tetrahedron Lett. 2006, 47, 7439; (b) Lenardão, E. J.; Borges, E. L.; Mendes, S.
R.; Perin, G.; Jacob, R. G. Tetrahedron Lett. 2009, 49, 1919; (c) Silveira, C. C.; Cella,
R.; Braga, A. L.; Jacob, R. G.; Lenardão, E. J.; Perin, G. Tetrahedron 2005, 61, 7712;
(
d) Silveira, C. C.; Perin, G.; Braga, A. L. J. Chem. Res. (S) 1994, 492.
8. General procedure for the Baylis–Hillman reaction: To
benzaldehyde (1a, 0.265 g; 2.5 mmol) and methyl acrylate (2a, 0.215 g;
.5 mmol) in acetonitrile (128
L; 2.5 mmol; 100 mol %) were added DABCO
0.28 g; 2.5 mmol) and [pbeSe]BF
solution was stirred at room temperature for 24 h (followed by TLC). The crude
product was purified by column chromatography over silica gel (SiO ) eluting
with ethyl acetate/hexanes (2:8), yielding the product 3a (0.37 g, 77%) as a
a
mixture of
2
(
l
7a
4
(0.041 g, 0.125 mmol; 5 mol %) and the
2
1
,10
CO.
When methyl vinyl ketone 2c and cyclohexenone 2d were
colourless oil. 1H NMR (200 MHz, CDCl
) d (ppm) 3.10 (br s, 1H); 3.68 (s, 3H);
5.53 (s, 1H); 5.84 (s, 1H); 6.31 (s, 1H); 7.28–7.36 (m, 5H).
(a) Rao, J. S.; Brière, J.-F.; Metzner, P.; Basavaiah, D. Tetrahedron Lett. 2006, 47,
553; (b) Kataoka, T.; Iwama, T.; Tsujiyama, S.-I.; Iwamura, T.; Watanabe, S.-I.
Tetrahedron 1998, 54, 11813.
3
5b
used, it was also possible to obtain the respective BH-adducts.
However, the yields of 3i–k were only reasonable (Table 2, entries
9.
3
9
–11).
In conclusion, [pbeSe]BF
for the BH-reaction of several electron-deficient alkenes with
4
was found to be a new acid catalyst
10. (a) Basavaiah, D.; Gowriswari, V. V. L. Synth. Commun. 1987, 17, 587; (b) Amri,
H.; Villieras, J. Tetrahedron Lett. 1986, 27, 4307.