Green Chemistry
Paper
the validity of this procedure has been verified by using pure
maleic acid in a control experiment.
Conclusions
A new oxidation method has been explored to catalytically
convert renewable furfural to maleic anhydride using
H5PV2Mo10O40 and Cu(CF3SO3)2 as catalysts in liquid phase.
Notably, a highly value-added synthetic intermediate with bio-
logical importance, 5-acetoxyl-2(5H)-furfuran, was also produced
as a minor product. This method offers an alternative route
to maleic anhydride synthesis, which is not competitive with
food of human beings. Detailed mechanistic studies revealed
that, in the dominant oxidation pathway, the reaction is
initiated by hydrogen abstraction from the 5-position of fur-
fural, and then maleic anhydride and 5-acetoxyl-2(5H)-fura-
none are formed in parallel. These results have provided novel
insights to understand the oxidation mechanisms of furan
sketch based biomass, which thus benefits the design of selec-
tive oxidation catalysts and control of their reactivity in
biomass valorizations.
Isolation and characterization of 5-acetoxyl-2(5H)-furanone
After 14 h reaction of the above described furfural oxidation,
the autoclave was cooled to room temperature and depressur-
ized to atmosphere pressure. The insoluble mass was filtered,
and then acetonitrile was removed by rotary evaporator under
vacuum. The resultant mixture was diluted with 2 mL water,
and excess NaHCO3 (2 g) was added to neutralize acetic acid
and maleic anhydride. Next, the aqueous mixtures were
extracted with dichloromethane (3 × 2 mL). The combined
organic layers were concentrated under reduced pressure, and
the oily residue was further purified by silica gel chromato-
graphy with hexane–ethyl acetate 1 : 1 as eluent to obtain
yellow oil as the product (0.18 mmol, 7.5% yield). 1H NMR
(300 MHz, CDCl3, 25 °C, TMS) δ = 2.14 (s, CH3), 6.29 (dd, J =
0.8 Hz, 1.6 Hz, CH), 6.96 (s, CH), 7.32 ppm (dd, J = 1.2 Hz,
5.6 Hz, CH); 13C NMR (75 MHz, CDCl3, 25 °C, TMS): δ = 20.58,
93.79, 125.13, 149.80, 168.88, 169.65 ppm.
Acknowledgements
Control experiment using 5-acetoxyl-2(5H)-furanone as
substrate
The funds from NSFC (no. 21273086) and the Project of
Chutian Scholar foundation, Hubei province are deeply
H5PV2Mo10O40·xH2O (34.8 mg, 0.02 mmol) and Cu(CF3SO3)2 appreciated. The product identifications by GC-MS and NMR
(7.4 mg, 0.02 mmol) were dissolved in 2 mL acetonitrile and were performed in Analytical and Testing Center, Huazhong
1.3 mL acetic acid in a glass tube, and then 5-acetoxyl-2(5H)- University of Science and Technology.
furanone (341 mg, 2.4 mmol) was added to the solution. The
glass tube was placed into a 50 mL stainless steel autoclave.
Then, the autoclave was charged with 20 atm of oxygen. The
reaction solution was magnetically stirred at 383 K in an oil
Notes and references
bath for 14 h. Next, analysis procedures were conducted,
which were similar to those conducted for furfural oxidation.
1 (a) C. H. Christensen, J. Rass-Hansen, C. C. Marsden,
E. Taarning and K. Egeblad, ChemSusChem, 2008, 1, 283–
289; (b) D. R. Dodds and R. A. Gross, Science, 2007, 318,
1250–1251; (c) B. Kamm, Angew. Chem., Int. Ed., 2007, 46,
5056–5058; (d) N. Dimitratos, J. A. Lopez-Sanchez and
G. J. Hutchings, Top. Catal., 2009, 52, 258–268;
(e) J. N. Chheda, G. W. Huber and J. A. Dumesic, Angew.
Chem., Int. Ed., 2007, 46, 7164–7183; (f) P. Gallezot, Green
Chem., 2007, 9, 295–302; (g) J. J. Bozell and G. R. Petersen,
Green Chem., 2010, 12, 539–554.
2 (a) L. Wang, H. Wang, F. Liu, A. Zheng, J. Zhang, Q. Sun,
J. P. Lewis, L. Zhu, X. Meng and F.-S. Xiao, ChemSusChem,
2014, 7, 402–406; (b) Y. Kwon, E. de Jong,
S. Raoufmoghaddam and M. T. M. Koper, ChemSusChem,
2013, 6, 1659–1667; (c) Z. Du, J. Ma, F. Wang, J. Liu and
J. Xu, Green Chem., 2011, 13, 554–557; (d) N. Yan, C. Zhao,
C. Luo, P. J. Dyson, H. Liu and Y. Kou, J. Am. Chem. Soc.,
2006, 128, 8714–8715; (e) C. Luo, S. Wang and H. Liu,
Angew. Chem., Int. Ed., 2007, 119, 7780–7783.
Control experiment using 2(5H)-furanone as substrate
H5PV2Mo10O40·xH2O (34.8 mg, 0.02 mmol) and Cu(CF3SO3)2
(7.4 mg, 0.02 mmol) were dissolved in 2 mL acetonitrile and
1.3 mL acetic acid in a glass tube, and then 2(5H)-furanone
(202 mg, 2.4 mmol) was added into the solution. The glass
tube was placed into a 50 mL stainless steel autoclave. Then,
the autoclave was charged with 20 atm of oxygen. The reaction
solution was magnetically stirred at 383 K in an oil bath for
14 h. Next, analysis procedures were conducted similar to
those for furfural oxidation.
Control experiment using furan as substrate
H5PV2Mo10O40·xH2O (34.8 mg, 0.02 mmol) and Cu(CF3SO3)2
(7.4 mg, 0.02 mmol) were dissolved in 2 mL acetonitrile and
1.3 mL acetic acid in a glass tube, and then furan (163 mg,
2.4 mmol) was added to the solution. The glass tube was
placed into a 50 mL stainless steel autoclave. Then, the auto-
clave was charged with 20 atm of oxygen. The reaction solution
was magnetically stirred at 383 K in an oil bath for 14 h. Next,
analysis procedures were conducted, which were similar to
those conducted for furfural oxidation.
3 (a) W. Xu, Q. Xia, Y. Zhang, Y. Guo, Y. Wang and G. Lu,
ChemSusChem, 2011, 4, 1758–1761; (b) W. Xu, H. Wang,
X. Liu, J. Ren, Y. Wang and G. Lu, Chem. Commun., 2011,
47, 3924–3926; (c) J. C. Serrano-Ruiz, R. Luque and
A. Sepulveda-Escribano, Chem. Soc. Rev., 2011, 40, 5266–
5281; (d) S. Liu, Y. Amada, M. Tamura, Y. Nakagawa and
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