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dimethylformamide (0.4 mL), furfural (0.2 mmol) and DBU (0.6
mmol). In the vial was bubbled argon, then the vial was closed
and le at room temperature for 20 h. To regenerate the hybrid
catalysts, a HCl solution (0.4 mmol of HCl 37%) was added. The
crude mixture was ltered to recover the catalysts and the cata-
lysts were washed with methanol, dried under vacuum and
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1
reused in the next reaction. The conversion was checked by H-
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8
R. Ye, J. Zhao, B. B. Wickemeyer, F. Dean Toste and
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4
. Conclusions
N-heterocyclic carbene (NHC) pre-catalyst has been anchored
on different inorganic supports with hierarchical porosity, in
9 M. Hartmann, A. Gonche Machoke and W. Schwieger, Chem.
Soc. Rev., 2016, 45, 3313–3330.
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inorganic hybrid catalysts. The hierarchical inorganic supports
Ram ´ı rez, Angew. Chem., Int. Ed., 2015, 54, 1591–1594.
have been synthesized following two different procedures: HP- 11 X.-Y. Yang, L.-H. Chen, Y. Li, J. C. Rooke, C. Sanchez and
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able base, the self-coupling reaction of furfural. Good catalytic 15 M. N. Hopkinson, C. Richter, C. M. Schedler and F. Glorius,
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nevertheless the superior performances observed for NHC/HP- 16 D. Enders, O. Niemeier and A. Henseler, Chem. Rev., 2007,
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the top-down method used to synthesize HP-HZSM-5 induced 2009, 253, 862–892.
the formation of a high fraction of silanols and high mesopores 18 K. V. S. Ranganath, S. Onitsuka, A. Kiran Kumar and
volumes that are less affected by the presence of the organic J. Inanaga, Catal. Sci. Technol., 2013, 3, 2161–2181.
NHC inside the channels. Moreover, the concomitant presence 19 Z. Zhou, Q. Meng, A. Seifert, A. Wagener, Y. Sun, S. Ernst and
of the Brønsted acid sites in the inorganic framework that are
W. Thiel, Microporous Mesoporous Mater., 2009, 121, 145–
not affected by the presence of the organic base together with
151.
the anchored basic NHC functionality makes these systems 20 R. Zhong, A. C. Lindhorst, F. J. Groche and F. E. K u¨ hn, Chem.
extremely interesting as bifunctional hybrids to catalyze tandem
reactions.
Rev., 2017, 117, 1970–2058.
21 L. Benhamou, E. Chardon, G. Lavigne, S. Bellemin-Laponnaz
and V. C ´e sar, Chem. Rev., 2011, 111, 2705–2733.
2
2
2 L. Wang and E. Y.-X. Chen, ACS Catal., 2015, 5, 6907–6917.
3 B. Boddenberg, V. R. Rani and R. Grosse, Langmuir, 2004, 20,
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Conflicts of interest
There are no conicts to declare.
2
4 M. Thommes, S. Mitchell and J. Pe ´r ez-Ram ´ı rez, J. Phys.
Chem. C, 2012, C116, 18816–18823.
5 M. Thommes and K. A. Cychosz, Adsorption, 2014, 20, 233–
250.
Acknowledgements
2
The project leading to these results has received funding from
the European Union's Horizon 2020 research and innovation 26 G. Paul, C. Bisio, I. Braschi, M. Cossi, G. Gatti, E. Gianotti
pro-gram under grant agreement N. 720783—MULTI2HYCAT. and L. Marchese, Chem. Soc. Rev., 2018, 47, 5684–5739.
L. Guarnieri is kindly acknowledged for experimental 27 M. E. Potter, M. E. Cholerton, J. Kezina, R. Bounds,
contribution.
M. Carravetta, M. Manzoli, E. Gianotti, M. Lefenfeld and
R. Raja, ACS Catal., 2014, 4, 4161–4169.
2
8 S. I. Lee and H. Chon, J. Chem. Soc., Faraday Trans., 1993, 93,
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