Rose Bengal immobilized on wool as an efficiently "green" sensitizer for photooxygenation reactions

Article abstract of DOI:10.1246/cl.2012.1500

A new type of supported photosensitizer derived from renewable wool and Rose Bengal is described. The novel sensitizer could efficiently promote the photooxygenation of furan derivatives to the corresponding 5-hydroxy-2-(5H)- furanone in excellent yields, via singlet oxygen, using visible light as the energy source. The sensitizer could be easily recovered from the reaction mixture by a simple filtration. It is discovered that the recovered sensitizer can be reused four times.

Full text of DOI:10.1246/cl.2012.1500

doi:10.1246/cl.2012.1500
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Published on the web November 10, 2012
Rose Bengal Immobilized on Wool as an Efficiently “Green” Sensitizer
for Photooxygenation Reactions
Zhang Yan,* Wang Wei, He Xun, and Sang Anguo
School of Materials Science and Engineering, Beijing Institute of Fashion Technology,
No. A2, East Yinghua Street, Chaoyang, Beijing 100029, P. R. China
(
Received July 18, 2012; CL-120765; E-mail: clyzhy@bift.edu.cn)
A new type of supported photosensitizer derived from
Sensitizer, O2
renewable wool and Rose Bengal is described. The novel
sensitizer could efficiently promote the photooxygenation of
furan derivatives to the corresponding 5-hydroxy-2-(5H)-
furanone in excellent yields, via singlet oxygen, using visible
light as the energy source. The sensitizer could be easily
recovered from the reaction mixture by a simple filtration. It is
discovered that the recovered sensitizer can be reused four times.
R
hv, Solvent
O
HO
O
O
2
1
a, R = CHO
1b, R = COOH
Sensitizer: RB-wool solid sensitizer =
Environmentally friendly synthesis of organic compounds
is currently required for sustainable development. One way to
develop green or sustainable organic synthesis is to utilize
energy coming from nonrenewable sources like petroleum as
little as possible. Another way is to develop processes with low
1
E-factor (weight of by-product per unit weight of desired
Figure 1. Synthesis of butenolide 2 from photooxygenation of
furan derivatives.
product). Use of heterogeneous catalysts could result in waste
minimization, simple and safe operation, and convenient work
up. Thus, it is one important strategy to develop sustainable
organic synthesis. Photocatalytic approaches are gaining in-
creasing acceptance because light is used to trigger the reaction
processes and, hence, allow the possibility to carry out oxidation
in a more controllable manner than conventional thermal
methods. The common approch involves dye-sensitized photo-
excitation of ground-state triplet oxygen to produce excited-state
type of Rose Bengal sensitizer supported by wool, which was
prepared by a general dyeing procedure. It can promote the
photochemical synthesis of 5-hydroxy-2-(5H)-furanone (bute-
nolide, 2) from furan derivatives (Figure 1) in excellent yields,
by using solar light as a unique energy source and molecular
oxygen as oxidant. This approach is undoubtedly environ-
mentally friendly.
1
2
singlet oxygen ( O ) using sensitizers such as Methylene Blue,
Wool fabric was pretreated and dyed with Rose Bengal by a
conventional dyeing method (see Supporting Information for
2
Rose Bengal, porphyrins, and fullerenes.5 Highly reactive
3
4
1
14
singlet oxygen ( O2) generated photochemically can be
detailed dyeing conditions). The dye uptake (i.e., the Rose
quenched either physically or by a chemical reaction. Furan
and its derivatives are among the most reactive substrates for
singlet oxygen leading to 5-hydroxy-2-(5H)-furanone which is
Bengal content in the solid wool sensitizer) was approximately
99%, which was calculated from the UV­vis spectra (see
Supporting Information). Then the dyed wool was subjected to
6
14
a key constituent of the potent analgesic and anti-inflammatory
agent manoalide and many other natural and unnatural products
of biomedical importance.7 The most popular methods for
preparing 5-hydroxy-2-(5H)-furanone compounds have been
reported in many cases.6 But one of the drawbacks of using a
photosensitizer is that it needs to be removed from the reaction
mixture once the oxidation is finished. The typical way to
remove the sensitizer is chromatographic separation. And the
sensitizer cannot be recycled. It is possible to attach a photo-
sensitizer to a solid support, allowing it to be removed from the
reaction mixture by means of simple filtration or centrifugation.
One of the most employed photocatalysts of this type is Rose
the fastness test according to standard methods (see Supporting
1
4
Information). The washing and light fastness exhibit to be 3­4
grade. The results show that dyed wool exhibits good fastness
properties.
,8
In order to clarify the mechanism of adsorption of Rose
Bengal to the wool fabrics, the adsorption behaviors were
observed by SEM-EDX (S4800 Field-Emission Scanning
Electron Microscope, Figure 2). Elemental analysis of the Rose
Bengal which was absorbed in wool showed the presence of
chlorine and iodine elements (Figure 2b). These images show
that RB compound is bound to the surfaces of the wool.
We further analyzed the difference between the wool and
RB­wool system by means of infrared spectroscopy (IR). IR
9
Bengal (RB) covalently linked to a series of polymers or other
1
0
¹1
supports. However, to date, the utilization of the soluble
sensitizer (Rose Bengal disodium salt) is preferred in synthesis
of 5-hydroxy-2-(5H)-furanone. On the basis of our investiga-
spectroscopy of RB shows characteric absorption at 1334 cm
¹1
due to ­Cl and 951 cm due to ­I, which was not observed in IR
spectra of the wool. However, clear absorption at 1338 and
953 cm could be observed for the RB­wool system (see
Supporting Information). This result indicated that the func-
tional groups of ­Cl and ­I were present on the surface of wool.
11
¹1
tions of the photooxygenation of endocyclic enol ethers, we
recently became interested in the photooxgenation reaction using
environmentally friendly solid sensitizer. We report herein a new
1
4
Chem. Lett. 2012, 41, 1500­1502
© 2012 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

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Table 1. Photooxygenation of 1a and 1b sensitized by RB­
wool system
a
c
b
d
Reaction
time/h
Substrate
Yield/%
1
1
a
b
10
12
71
68
Table 2. Solvent effect for photooxygenation of 2-furfural (1a)
with RB­wool system as the sensitizer
Reaction
time/h
Entry
Solvent
Conv/%
Yield/%
1
2
3
4
5
MeCN
CHCl3
Acetone
Benzene
Hexane
8
8
8
8
8
83
81
55
40
11
68
72
46
22
7
Figure 2. SEM-EDX spectras: a. SEM photograph of the
surface of the wool, Bar indicates 20 μm. b. Results of elemental
analysis in SEM-EDX of the surface of the wool [cursor in 1.557
(23 cts)], C carbon, O oxygen, S sulfur. c. SEM photograph
of the surface of the RB­wool system, Bar indicates 20 μm.
d. Results of elemental analysis in SEM-EDX of the surface of
the RB­wool system [cursor in 3.592 (20 cts)], C carbon, O
oxygen, S sulfur, Cl chlorine, I iodine.
Table 3. Recycling of sensitizer in photooxygenation of 1a
Cycle
Time/h
Yield/%
Degradation/%
1
2
3
4
8.5
9.5
10
67
54
50
49
19
43
75
96
As reported,6 RB as a sensitizer could promote the
photooxygenation of 2-furfural or other furan derivatives to
11.5
5-hydroxy-2-(5H)-furanone. We would like to explore wool-
supported RB’s activity of promoting photooxygenation of furan
derivatives. The RB­wool system was washed repeatedly with
CH CN until the final filtrate was colorless before use. The
procedure is as follows: To a solution of 2-furfural (1a, 200 mg,
The recyclability of the photosensitizer in the photooxyge-
nation of 2-furfural (1a) was also investigated. The results for
this study are summarized in Table 3.
3
2.04 mmol) in CH3CN (30 mL) was added RB­wool sensitizer
(
150 mg, 1% mol of substrate on the basis of RB). The resultant
For the photooxygenation of 2-furfural (1a), which required
a longer reaction time, the RB­wool system could be repeatedly
used a fourth time also. In the fifth run, no complete conversion
was obtained due to the severe photobleaching of sensitizer.
In fact, after 4 cycles of these reactions, the sensitizer was
dissolved in 30 mL NaClO solution (3%). As shown by
absorption spectroscopy of the solutions, about 96% of RB­
wool sensitizer was photobleached for 1a. These results
indicated that the RB­wool system has a relatively higher
photostability than RB and, therefore, serves as a better
sensitizer for the photooxygenation reactions.
mixture contained in a Pyrex vessel was vigorously stirred at
room temperature under O2 and irradiated with a medium-
pressure mercury lamp through a UV-cutoff filter. GC analysis
indicated complete oxidation of 1a after 10 h. Removal of the
sensitizer by filtration of the reaction mixture and removal of the
solvent under vacuum gave the crude product of 2 which could
be further purified by flash chromatography to afford pure
compound 2 (145 mg, 71%). Absorption spectra of the filtered
reaction solution after photolysis indicated that no RB is leached
into the reaction solution.
1
2
Apart from the substrate 1a, the photooxygenation reactions
of 1b was also studied. The reactions were carried out as
described for the photooxygenation 1a. 1b could be smoothly
converted into the expected products in decent yields (Table 1).
In each case, the products of the reaction using the wool­RB
system were compared with those obtained by using Rose
In summary, the utilization of RB­wool as an efficiently
“green” sensitizer for photooxygenation of furan derivatives 1a
and 1b to butenolides 2 in excellent yields has been demon-
strated. The sensitizer was prepared by a general dyeing
procedure. It could be recovered simply by filtration and reused
four times. It represents a practical alternative to soluble RB for
relatively high photostability, recyclability, sensitizing activity,
and sustainable development. Further work is in progress to
explore applications of RB­wool sensitizer in photooxygenation
of other typical compounds in our laboratory.
6
a,6b,6d,6e
Bengal dye.
Some solvents were screened. The results are summarized in
Table 2. The reported yields and conversion were determined by
GC analysis.
As shown in this table, this reaction is sensitive to solvent
polarity which is consistent with the general rules of solvent
Financial supports from the National Natural Science
Foundation of China (Grant No. 51003002), the Project of
Beijing Key Laboratory of Clothing Material R & D and
Assessment (Grant No. 2010ZK-06), and the Training Pro-
gramme Foundation for the Excellent Talents by the Organ-
ization Department of Beijing (Grant No. 2010D005001000004)
effect on the photooxygenation.13 CHCl is the most preferable
3
solvent, which leads to 81% conversion with a higher yield
(
Entry 2). Although a good yield was also obtained with acetone
as solvent, the relatively low conversion was a problem
Entry 3).
(
Chem. Lett. 2012, 41, 1500­1502
© 2012 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

1
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are acknowledged. We thank Dr. Wang BaiHua of BIFT for
providing the wool.
38, 3878. e) G. C. M. Lee, E. T. Syage, D. A. Harcourt, J. M.
Holmes, M. E. Garst, J. Org. Chem. 1991, 56, 7007.
C. Navarro, A. Moreno, A. G. Csákÿ, J. Org. Chem. 2009,
74, 466; S.-R. Sheng, L. Xu, X.-L. Zhang, X.-L. Liu, M.-H.
Wei, J. Comb. Chem. 2006, 8, 805; G. H. Hakimelahi, N.-W.
Mei, A. A. Moosavi-Movahedi, H. Davari, S. Hakimelahi,
K.-Y. King, J. R. Hwu, Y.-S. Wen, J. Med. Chem. 2001, 44,
1749; P. Esser, B. Pohlmann, H.-D. Scharf, Angew. Chem.,
Int. Ed. Engl. 1994, 33, 2009.
J. A. Navio, J. F. Mota, M. A. P. Adrian, M. G. Gomez,
J. Photochem. Photobiol., A 1990, 52, 91; P. Kumar, R. K.
Pandey, Green Chem. 2000, 2, 29; J. Boukouvalas, N.
Lachance, Synlett 1998, 31.
L. Moczek, M. Nowakowska, Biomacromolecules 2007, 8,
433; D. Drozd, K. Szczubiałka, M. Nowakowska, J. Photo-
chem. Photobiol., A 2010, 215, 223; D. Gryglik, J. S. Miller,
S. Ledakowicz, Sol. Energy 2004, 77, 615; A. A. Frimer,
M. Afri, S. D. Baumel, P. Gilinsky-Sharon, Z. Rosenthal,
H. E. Gottlieb, J. Org. Chem. 2000, 65, 1807; R. Alcántara,
L. Canoira, P. G. Joao, J. G. Rodriguez, I. Vázquez,
J. Photochem. Photobiol., A 2000, 133, 27; J. Paczkowski,
D. C. Neckers, Macromolecules 1985, 18, 1245; J.
Paczkowski, D. C. Neckers, Macromolecules 1985, 18,
2412; J. Paczkowski, D. C. Neckers, J. Photochem. 1986,
35, 283; E. C. Blossey, D. C. Neckers, A. L. Thayer, A. P.
Schaap, J. Am. Chem. Soc. 1973, 95, 5820.
7
References and Notes
1
2
R. A. Sheldon, Chem. Ind. (London) 1997, 12.
S. Horsa, K. Perez, J. Miksovska, J. Photochem. Photobiol.,
A 2011, 221, 84; C. Marisa, D. S. Ilaria, R. Marotta, A.
Roberto, C. Vincenzo, J. Photochem. Photobiol., A 2010,
210, 69; J. Kühni, J.-L. Debieux, P. Belser, Synthesis 2007,
1421; F. Cermola, M. R. Iesce, G. Buonerba, J. Org. Chem.
2005, 70, 6503; J. C. Niles, J. S. Wishnok, S. R.
8
9
Tannenbaum, Org. Lett. 2001, 3, 963; H.-R. Li, L.-Z. Wu,
C.-H. Tung, J. Am. Chem. Soc. 2000, 122, 2446; F. C.
Goodspeed, B. L. Scott, J. G. Burr, J. Phys. Chem. 1965, 69,
1
149.
D. Noutsias, A. Kouridaki, G. Vassilikogiannakis, Org. Lett.
011, 13, 1166; A. Posadaz, A. Biasutti, C. Casale, J. Sanz,
F. Amat-Guerri, N. A. García, Photochem. Photobiol.
004, 80, 132; N. Sofikiti, M. Tofi, T. Montagnon, G.
3
2
2
Vassilikogiannakis, M. Stratakis, Org. Lett. 2005, 7, 2357;
O. Shimizu, J. Watanabe, S. Naito, Y. Shibata, J. Phys.
Chem. A 2006, 110, 1735; A. Natarajan, L. S. Kaanumalle,
S. Jockusch, C. L. D. Gibb, B. C. Gibb, N. J. Turro, V.
Ramamurthy, J. Am. Chem. Soc. 2007, 129, 4132.
4
S. M. A. Pinto, Â. C. B. Neves, M. J. F. Calvete, A. R.
Abreu, M. T. S. Rosado, T. Costa, H. D. Burrows, M. M.
Pereira, J. Photochem. Photobiol., A 2012, 242, 59; P. K.
Frederiksen, S. P. McIlroy, C. B. Nielsen, L. Nikolajsen, E.
Skovsen, M. Jørgensen, K. V. Mikkelsen, P. R. Ogilby,
J. Am. Chem. Soc. 2005, 127, 255; C. Schweitzer, Z.
Mehrdad, A. Noll, E.-W. Grabner, R. Schmidt, J. Phys.
Chem. A 2003, 107, 2192; I. Erden, J. Song, W. Cao, Org.
Lett. 2000, 2, 1383; S. G. DiMagno, P. H. Dussault, J. A.
Schultz, J. Am. Chem. Soc. 1996, 118, 5312.
10 H. Koizumi, Y. Kimata, Y. Shiraishi, T. Hirai, Chem.
Commun. 2007, 1846; M. Nowakowska, M. Kepczyński, M.
Dabrowska, Macromol. Chem. Phys. 2001, 202, 1679; F.
Prat, C. S. Foote, Photochem. Photobiol. 1998, 67, 626; W.
Lin, M. C. Garnett, S. S. Davis, E. Schacht, P. Ferruti, L.
Illum, J. Controlled Release 2001, 71, 117.
11 Y. Zhang, Z.-H. Zeng, Y.-Y. Liu, X.-X. Cheng, X.-S. Wang,
B.-W. Zhang, Chem. Lett. 2005, 34, 368.
1
5
6
B. Talukdar, Y. Takaguchi, Y. Yanagimoto, S. Tsuboi, M.
Ichihara, K. Ohta, Bull. Chem. Soc. Jpn. 2006, 79, 1983;
A. W. Jensen, C. Daniels, J. Org. Chem. 2003, 68, 207; M.
Ohno, N. Koide, H. Sato, S. Eguchi, Tetrahedron 1997, 53,
12 Mp: 48.0­50.7 °C. H NMR (300 MHz, CDCl3): ¤ 6.23 (1H,
sb), 6.25 (1H, d, J = 5.1 Hz), 7.30 (1H, dd, J = 5.1 Hz,
+
+
1.5 Hz); MS(EI): m/z 55 [(C3H3O) , 100%], 72 [(C3H4O2) ,
40%], 100 [(C4H4O3) , 15%].
+
9
075.
13 K. Gollnick, K. Knutzen-Mies, J. Org. Chem. 1991, 56,
a) M. I. Burguete, R. Gavara, F. Galindo, S. V. Luis,
Tetrahedron Lett. 2010, 51, 3360. b) Y. Morita, H.
Tokuyama, T. Fukuyama, Org. Lett. 2005, 7, 4337. c) P.
Magnus, P. M. Cairns, S. K. Chung, Tetrahedron Lett. 1985,
4017.
14 Supporting Information is available electronically on the
CSJ-Journal Web site, http://www.csj.jp/journals/chem-lett/
index.html.
2
6, 1963. d) I. L. Doerr, R. E. Willette, J. Org. Chem. 1973,
Chem. Lett. 2012, 41, 1500­1502
© 2012 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/