Green Chemistry
Paper
case of HMF oxidation where high yields of either DFF or
FDCA can be obtained, depending on the contact time.
Additionally, less stable alcohols like lactic acid or prenols
could be smoothly oxidized, due to the moderate conditions of
only 55 °C and 5 bar O2.
Overall, the reported system offers a promising alternative
to state-of-the-art stoichiometric oxidants or transition metal
catalysts for the environmentally benign and economical oxi-
dation of alcohols.
W. T. Fu, O. Roubeau, P. Gamez and J. Reedijk,
Eur. J. Inorg. Chem., 2007, 4197; J. Luo, C. Pardin,
W. D. Lubell and X. X. Zhu, Chem. Commun., 2007, 2136;
M. Lei, R. J. Hu and Y. G. Wang, Tetrahedron, 2006, 62,
8928; J. M. Vatele, Synlett, 2006, 2055; W. Qian, E. Jin,
W. Bao and Y. Zhang, Tetrahedron, 2006, 62, 556; K. Kloth,
M. Brünjes, E. Kunst, T. Jöge, F. Gallier, A. Adibekian and
A. Kirschning, Adv. Synth. Catal., 2005, 347, 1423;
O. Holczknecht, M. Cavazzini, S. Quici, I. Shepperson and
G. Pozzi, Adv. Synth. Catal., 2005, 347, 677; M. Brünjes,
G. Sourkouni-Argirusi and A. Kirschnig, Adv. Synth. Catal.,
2
2
003, 345, 635; C. Tanyeli and A. Gümüs, Tetrahedron,
003, 44, 1639; T. Fey, H. Fischer, S. Bachmann, K. Albert
Experimental section
The continuous flow reactor (Teflon®, internal diameter
and C. Bolm, J. Org. Chem., 2001, 66, 8154; A. Dijksman,
I. W. C. E. Arends and R. A. Sheldon, Synlett, 2001, 102;
A. Dijksman, I. W. C. E. Arends and R. A. Sheldon, Chem.
Commun., 2000, 271; S. S. Wang, Z. Popovic, H. H. Wu and
Y. Liu, ChemCatChem, 2011, 3, 1208; C. Zhu, L. Ji and
Y. Wei, Catal. Commun., 2010, 11, 1017; N. Jiang and
A. J. Ragauskas, Tetrahedron Lett., 2005, 46, 3323; X. E. Wu,
L. Ma and M. X. Ding, Synlett, 2005, 607.
1
.65 mm) was packed with a commercially available TEMPO
catalyst attached to a silica support (Sigma-Aldrich, 0.7 mmol
−
1
g
6
active sites; particle size 0.16–0.24 mm, void fraction of
5%) and connected to an HPLC pump and an O mass flow
2
controller. When the oil bath reached the desired temperature
the packed bed was put inside the oil bath and the reaction
was started. For all benzyl alcohol oxidation experiments a
−
1
liquid flow rate of 0.4 mL min and a gas flow rate of 5 mL
8 I. Hermans, E. S. Spier, U. Neuenschwander, N. Turrà and
A. Baiker, Top. Catal., 2009, 52, 1162.
−
1
min was chosen. For other contact times the ratio of liquid
to gas flow-rate was kept constant. For the rest of the substrates
9 N. Tamura, T. Aoyama, T. Takido and M. Kodomari, Synlett,
2012, 1397; J. M. Hoover, J. E. Steves and S. Stahl, Nat.
Protocols, 2012, 6, 1161; Z. Hu and F. M. Kerton, Appl.
Catal., A, 2012, 413–414, 332; J. Zhu, P. C. Wang and M. Lu,
RSC Adv., 2012, 2, 8265; L. Wang, J. Li, Y. Lv, G. Zhao and
S. Gao, Appl. Organomet. Chem., 2011, 26, 37; J. M. Hoover
and S. Stahl, J. Am. Chem. Soc., 2011, 133, 16901; Q. Wang,
Y. Zhang, G. Zheng, Z. Tian and G. Yang, Catal. Commun.,
2011, 14, 92; M. N. Kopylovich, K. T. Mahmudov,
M. Haukka, P. J. Figiel, A. Mizar, J. A. L. da Silva and
A. J. L. Pombeiro, Eur. J. Inorg. Chem., 2011, 4175; Y. Jing,
J. Jiang, B. Yan, S. Lu, J. Jiao, H. Xue, G. Yang and
G. Zheng, Adv. Synth. Catal., 2011, 353, 1146; S. Ma, J. Liu,
S. Li, B. Chen, J. Cheng, J. Kuang, Y. Liu, B. Wan, Y. Wang,
J. Ye, Q. Yu, W. Yuan and S. Yu, Adv. Synth. Catal., 2011,
−1
a liquid flow rate of 0.1 mL min and a gas flow rate of
1
1
.3 mL min− was chosen. Segmented flow could be visually
verified in the transparent Teflon® tubes (see the ESI†). Liquid
hold ups in order to determine contact times were calculated
2
1
with the correlation of Larachi et al. (see the ESI†). The
pressure was set to 5 bar with a back pressure regulator and
the reaction was run for 30 min before taking the first sample.
The gas phase effluent of the reactor could be monitored with
IR spectroscopy. The liquid products were quantified against a
biphenyl internal standard using gas chromatography
(HP-FFAP column, a flame ionization detector).
Notes and references
353, 1005; A. Dhakshinamoorthy, M. Alvaro and H. Garcia,
1
2
F. Cavani and J. H. Teles, ChemSusChem, 2009, 2, 508.
G. Franz and J. H. Sheldon, Oxidation, Ullmann’s Encyclo-
pedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2000.
C. Aellig, C. Girard and I. Hermans, Angew. Chem., Int. Ed.,
ACS Catal., 2011, 1, 48; N. Mase, T. Mizumori and
Y. Tatemoto, Chem. Commun., 2011, 47, 2086; W. Yin,
C. Chu, Q. Lu, J. Tao, X. Liang and R. Liu, Adv. Synth.
Catal., 2010, 352, 113; A. K. Tucker-Schwartz and
R. L. Garell, Chem.–Eur. J., 2010, 16, 12718; P. J. Figiel,
A. Sibaouih, J. U. Ahmad, M. Nieger, M. T. Räisänen,
M. Leskelä and T. Repo, Adv. Synth. Catal., 2009, 351, 2625;
L. Lin, J. Liuyan and W. Yunyang, Catal. Commun., 2007, 9,
1379; P. J. Figiel, M. Leskelä and T. Repo, Adv. Synth. Catal.,
2007, 349, 1173; G. Yang, J. Ma, W. Wang, J. Zhao, X. Lin,
L. Zhou and X. Gao, Catal. Lett., 2006, 112, 83; M. Benaglia,
A. Puglisi, O. Holczknecht, S. Quici and G. Pozzi, Tetra-
hedron, 2005, 61, 12058; N. Wang, R. Liu, J. Chen and
X. Liang, Chem. Commun., 2005, 5322; R. A. Miller and
R. S. Hoerner, Org. Lett., 2002, 5, 285; A. Cecchetto,
F. Fontana, F. Minisci and F. Recupero, Tetrahedron
Lett., 2001, 42, 6651; A. Dijksman, A. Marino-Gonzalez,
3
4
5
6
7
2
011, 50, 12355.
C. Aellig, U. Neuenschwander and I. Hermans, Chem-
CatChem, 2012, 4, 525.
C. Aellig, D. Scholz and I. Hermans, ChemSusChem, 2012,
9
, 1732.
Y. Ma, C. Loyns, P. Price and V. Chechik, Org. Biomol.
Chem., 2011, 9, 5573.
Y. Suzuki, M. Iinuma, K. Moriyama and H. Togo, Synlett,
2
012, 1250; Y. Wang, X. Song, S. Shao, H. Zhong and F. Lin,
RSC Adv., 2012, 2, 7693; A. Fall, M. Sene, M. Gaye,
G. Gómez and Y. Fall, Tetrahedron Lett., 2010, 51, 4501;
X. Q. Li and C. Zhang, Synthesis, 2009, 1163; J. S. Uber,
Y. Vogels, D. van den Helder, I. Mutikainen, U. Turpeinen,
This journal is © The Royal Society of Chemistry 2013
Green Chem., 2013, 15, 1975–1980 | 1979