T. Blasco et al. / Journal of Catalysis 275 (2010) 78–83
83
the mixture was recoþrded at the end of the reaction, and the signals
ciana, and Fundación Areces. I. Lezcano-González acknowledges
Universidad Politécnica de Valencia (UPV) for a FPI-UPV fellowship.
of PO2Fꢁ in ½C4m2imꢀ PFꢁ were observed, indicating the hydrolysis
2
6
of the anion and consequently the formation of HF. The 11B NMR
signal of boric acid which could indicate the hydrolysis of BF3 is
References
not observed in either of the two ionic liquids, ½C4m2imꢀþPFꢁ and
6
½C4mimꢀþBFꢁ. These results suggest that the higher activity
[1] S. Lee, Chem. Commun. (2006) 1049.
[2] G. Machado, J.D. Scholten, T. da Vargas, S.R. Teixeira, L.H. Ronchi, J. Dupont, Int.
J. Nanotechnol. 4 (2007) 541;
M. Armand, F. Endres, D.R. MacFarlane, H. Ohno, B. Scrosati, Nat. Mater. 8
(2009) 621;
X. Han, D.W. Armstrong, Acc. Chem. Res. 40 (2007) 1079.
[3] T. Welton, Coord. Chem. Rev. 248 (2004) 2459;
V.I. Parvulescu, C. Hardacre, Chem. Rev. 107 (2007) 2615.
[4] N.V. Plechkova, K.R. Seddon, Chem. Soc. Rev. 37 (2008) 123.
[5] S. Chowdhury, R.S. Mohan, J.L. Scott, Tetrahedron 63 (2007) 2363.
[6] K.R. Seddon, A. Stark, M.-J. Torres, Pure Appl. Chem. 72 (2000) 2275.
[7] B. Wu, W. Liu, Y. Zhang, H. Wang, Chem. Eur. J. 15 (2009) 1804.
[8] H. Weingärtner, Angew. Chem. Int. Ed. 47 (2008) 654.
[9] J. Dupont, J. Braz. Chem. Soc. 15 (2004) 241;
C. Chiappe, Monach. Chem. 138 (2007) 1035.
[10] H. Sato, Catal. Rev. Sci. Eng. 39 (1997) 395.
[11] G. Dalhoff, J.P.M. Niederer, W.F. Hölderich, Catal. Rev. 43 (2001) 381.
[12] A. Corma, J. Catal. 216 (2003) 298.
[13] P. Botella, A. Corma, S. Iborra, R. Montón, I. Rodríguez, V. Costa, J. Catal. 250
(2007) 161.
4
achieved in the ½C4m2imꢀþPFꢁ IL is due to the presence of HF. It
6
is worth noting that the addition of BF3 into the reaction mixture
of cyclododecanone oxime in ½C4m2imꢀþPFꢁ induces a sharp mod-
6
ification in the reactivity of the ionic liquid with water, enabling
the hydrolysis of the hexafluorophosphate anion. This is a proof
of the complex chemistry of ionic liquids since their properties
and reactivity can dramatically change when they are mixed with
other substances, even at the level of ppm.
What we believe can be of interest is the fact that a very low
concentration of HF in the ionic liquid is able to perform the Beck-
mann rearrangement of cyclododecanone oxime, which is now
being carried out using large amounts of oleum. It must be re-
marked that while an alternative heterogeneous catalytic process
to the one that uses H2SO4 or oleum has been found for the Beck-
[14] M.A. Camblor, A. Corma, H. García, V. Semmer-Herlédan, S. Valencia, J. Catal.
177 (1998) 267.
[15] C. Ngamcharussrivichai, P. Wu, T. Tatsumi, J. Catal. 235 (2005) 139.
[16] H. Ichihashi, M. Kitamura, Catal. Today 73 (2002) 23;
Y. Yzumi, H. Ichihashi, Y. Shimazu, M. Kitamura, H. Sato, Bull. Chem. Soc. Jpn.
80 (2007) 1280.
[17] J. Peng, Y. Deng, Tetrahedron Lett. 42 (2001) 403.
[18] R.X. Ren, L.D. Zueva, W. Ou, Tetrahedron Lett. 42 (2001) 8441.
[19] K. Elango, R. Sriram, G. Anantharaman, Tetrahedron Lett. 48 (2007) 9059.
[20] S. Guo, Y. Deng, Catal. Commun. 6 (2005) 225.
[21] X. Liu, L. Xiao, H. Wu, Z. Li, J. Chen, C. Xia, Catal. Commun. 10 (2009) 424.
[22] X. Liu, L. Xiao, H. Wu, J. Chen, C. Xia, Helv. Chim. Acta 92 (2009) 1014.
[23] A. Zicmanis, S. Katkevica, P. Mekss, Catal. Commun. 10 (2009) 614.
[24] Z. Du, Z. Li, Y. Gu, J. Zhang, Y. Deng, J. Mol. Catal. A: Chem. 237 (2005) 80.
[25] J. Gui, Y. Deng, Z. Hu, Z. Sun, Tetrahedron Lett. 45 (2004) 2681.
[26] S. Guo, Z. Du, S. Zhang, D. Li, Z. Li, Y. Deng, Green Chem. 8 (2006) 296.
[27] V. Fabos, D. Lantos, A. Bodor, A.-M. Bálint, L.T. Mikca, O.E. Sielcken, A. Cuiper, I.
Horváth, ChemSusChem 1 (2008) 189.
[28] L. Vogel, A Text Book of Practical Organic Chemistry, Longman, London, 1971.
[29] A.B. Fernández, M. Boronat, T. Blasco, A. Corma, Angew. Chem. Int. Ed. 44
(2005) 2370.
[30] A.B. Fernández, I. Lezcano-Gonzalez, M. Boronat, T. Blasco, A. Corma, J. Catal.
249 (2007) 116.
[31] V.R. Reddy Marthala, Y. Jiang, J. Huang, W. Wang, R. Gläser, M. Hunger, J. Am.
Chem. Soc. 128 (2006) 14812.
[32] V.R. Reddy Marthala, S. Rabl, J. Huang, S.A.S. Rezai, B. Thomas, M. Hunger, J.
Catal. 257 (2008) 134.
mann rearrangement of cyclohexanone oxime to
producing Nylon-6, there is not, today, any alternative to H2SO4 for
manufacturing -laurolactam used for the production of Nylon-12.
e-caprolactam for
x
The results presented here prove that just the residual water pres-
ent in dry ionic liquids can hydrolyze PFꢁ6 of ½C4mimꢀþPFꢁ and
6
½C4mpyrꢀþPFꢁ ILs producing HF, and the presence of HF at the level
6
of ppm is already able to catalyze the Beckmann rearrangement of
cyclododecanone oxime to
x-laurolactam with good activity and
selectivity. The advantage of using an ionic liquid as a source of
HF is that avoids the use of this acid diluted with water which de-
creases the lactam selectivity, or the use of relatively larger
amounts of BF3. If one takes into account that the reactants are
not perfectly dry and that in some cases [34] small amounts of
water are also added deliberately, a process involving the active li-
quid acids described above could be considered [35].
The results obtained in the present work also show that atten-
tion must be paid when using ILs for organic reaction that can be
catalyzed by HF. In those cases, where anion hydrolysis can occur
and HF could be formed, one should be aware of that for catalyst
activity.
[33] R. Fernández-Galán, B.R. Manzano, A. Otero, M. Lafranchi, M.A. Pellinghelli,
Inorg. Chem. 33 (1994) 2309.
[34] T.H. Huang, A.J. Silvestri, S. Yurchak, US 260/683.44, 1975 (to Mobil Oil
Corporation).
Acknowledgments
[35] R. Monton, S. Iborra, A. Corma, V. Costa, Span 2257202, 2006 (to UBE
Corporation).
We thank the Spanish CICYT (Project MAT2006-14274-C02-01)
for financial support; Prometeo Project from the Generalitat Valen-