Oxidation of benzoins with ferric (III) nitrate supported on aluminum silicate

Article abstract of DOI:10.1080/15533171003629089

The preparation of benzils by oxidation of corresponding benzoins using ferric (III) nitrate nonahydrate supported on aluminum silicate reagent under heterogeneous conditions and reflux in yields between 82-95% is described. The main advantage of this oxidation is that the reaction time is much shorter as compared to the other reported ferric (III) nitrate nonahydrate based reagents, and it is an extension of application for the ferric (III) nitrate nonahydrate supported on aluminum silicate reagent as well.

Full text of DOI:10.1080/15533171003629089

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:157–159, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533171003629089
Oxidation of Benzoins with Ferric (III) Nitrate Supported
on Aluminum Silicate
Ji-Dong Lou,1 Yi-Chun Ma,1 Negin Vatanian,2 Qiang Wang,2 and Changhe Zhang3
1College of Life Sciences, China Jiliang University, Hangzhou, Zhejiang, China
2Sirnaomics, Inc., Gaithersburg, MD, USA
3Instituto de Biologia Experimental e Tecnologia, Universidade Nova de Lisboa, Oeiras, Portugal
ture is magnetically stirred. A solution of benzoin (212 mg,
1 mmol) in dichloromethane (3 mL) is added, and after 2 h
at reflux the solid is filtered and washed with dichloromethane
(3 × 5 mL). The combined filtrates are evaporated to give crude
product, which is purified by preparative TLC with hexane:ethyl
acetate (7:3) to afford 202 mg (95%) benzil.
The preparation of benzils by oxidation of corresponding ben-
zoins using ferric (III) nitrate nonahydrate supported on aluminum
silicate reagent under heterogeneous conditions and reflux in yields
between 82–95% is described. The main advantage of this oxidation
is that the reaction time is much shorter as compared to the other
reported ferric (III) nitrate nonahydrate based reagents, and it is
an extension of application for the ferric (III) nitrate nonahydrate
supported on aluminum silicate reagent as well.
Oxidation of Benzoin to Benzil
1H NMR (300 MHz, CDCl3): δ (ppm) 7.9-7.8 (4H, m, 2 ×
Ar-H); 7.6-7.4 (6H, m, 2 × Ar-H). FT-IR (KBr): 1680 (C=O),
1595 (C=C).
Keywords benzils, benzoins, ferric (III) nitrate, oxidation, supported
reagent
Oxidation of 4,4ꢀ-Dimethylbenzoin to
INTRODUCTION
4,4ꢀ-Dimethylbenzil
The preparation of benzils by way of oxidation of benzoins
is one of the important reactions in organic synthesis, which has
received a great deal of attention due to the practical applica-
tions of the benzils, such as photosensitive agents and synthetic
agents, in organic and pharmaceutical chemistry.[1] Of this oxi-
dation reaction, several oxidants have been employed, especially
ferric (III) nitrate nonahydrate based reagents for instance, ferric
nitrate–clay,[2] ferric nitrate–silica,[3] ferric nitrate-graphite,[4]
ferric nitrate-kieselguhr,[5] etc., which reagents have received
good results. Although a diversity of ferric (III) nitrate nonahy-
drate based reagents is available, developments of convenient,
selective, and mild procedures are still an important objective of
current relevance. Consequently, introduction of new methods
or reagents is still fraught with experiment challenges, especially
in search of versatile and selective reagents.
1H NMR (300 MHz, CDCl3): δ (ppm) 7.6 (4H, d, J = 9Hz,
2 × Ar-H); 7.2 (4H, d, J = 9Hz, 2 × Ar-H); 2.4 (6H, s, 2 ×
CH3). FT-IR (KBr): 1680 (C=O), 1600 (C=C).
Oxidation of 4,4ꢀ-Dimethoxybenzoin to
4,4ꢀ-Dimethoxybenzil
1H NMR (300 MHz, CDCl3): δ (ppm) 7.6 (4H, d, J = 9Hz,
2 × Ar-H); 6.9 (4H, d, J = 9Hz, 2 × Ar-H); 3.8 (6H, s, 2 ×
OCH3). FT-IR (KBr): 1675 (C=O), 1600 (C=C).
Oxidation of 4,4ꢀ-Dichlorobenzoin of 4,4ꢀ-Dichlorobenzl
1H NMR (300 MHz, CDCl3): δ (ppm) 7.6 (4H, d, J = 9Hz,
2 × Ar-H); 7.1 (4H, d, J = 9Hz, 2 × Ar-H). FT-IR (KBr): 1680
(C=O), 1595 (C=C).
EXPERIMENTAL
Oxidation of 2,2ꢀ-Furoin to 2,2ꢀ-Furil
Oxidation of Benzoin to Benzil: Typical Procedure
The Fe(NO3)3- aluminum silicate reagent[6] (2.2 g) is placed
in a flask together with dichloromethane (50 mL) and the mix-
1H NMR (300 MHz, CDCl3): δ (ppm) 7.6-7.5 (2H, m, 2 ×
HCO); 7.2-7.1 (2H, m, 2 × CH); 6.5-6.4 (2H, m, 2 × CH).
FT-IR (KBr): 1670 (C=O).
Received 23 September 2009; accepted 17 January 2010.
Address correspondence to Ji-Dong Lou, College of Life Sciences,
China Jiliang University, Hangzhou, Zhejiang 310018, China. E-mail:
lou@cjlu.edu.cn
RESULTS AND DISCUSSION
To the best of our knowledge, ferric nitrate nonahydrate
[Fe(NO3)3·9H2O] based reagents are, probably, the good choice
157

158
J.-D. LOU ET AL.
environmentally benign methods or reagents for this process.
OH
O
Fe(NO3)3 - Aluminum silicate
CH2Cl2, Reflux
Ar2
Ar2
In addition, the solid supported reagents are widely used
to carry out a range of reactions with the benefits of short re-
action time, high conversion, and selectivity. In most cases,
solid supported reagents have been found superior to the
non-supported reagents. In continuation of our more recent
study on the oxidation of alcohols with a new ferric (III) ni-
trate nonahydrate supported on aluminum silicate reagent,[6]
we now report here using this reagent for selective oxida-
tion of benzoins (1) into corresponding benzils (2) under het-
erogeneous conditions with reflux in high yields (Scheme 1),
which is an extension of application for the ferric (III) nitrate
nonahydrate supported on aluminum silicate reagent as well.
The mechanism of the present oxidation that we consider is the
same as those described previously in the literature.[7]
In the present reaction, a 1 to 1.2 molar ratio of the substrate
to the oxidant is employed, and all the reactions are completed
within 2 hours with high yields. The progress of the reaction
is monitored with TLC, and the product is purified by prepara-
tive TLC. Compared with some of the other existing ferric (III)
nitrate nonahydrate supported reagents for the oxidation of ben-
zoins cited above, the main advantage of the present method is
that the solid reagent is more stable as well as the reaction time
of the present oxidation is comparatively shorter. The oxidized
products are all known compounds and identified by spectro-
scopic comparison with authentic samples. Our results are listed
in Table 1.
Ar1
Ar1
O
O
(1)
(2)
Ar1
Ar2
H3C
H3CO
Cl
H C
3
H CO
3
Cl
O
O
SCH. 1.
for the selective oxidation of benzoins that have the advantages
of being commercially available, inexpensive, and relatively
non-toxic. However, it is still notable to develop an easy and
TABLE 1
Oxidation of benzoins with ferric (III) nitrate supported on aluminum silicate reagent
m.p. (◦C)
Substrate
Producta
Reaction time (h)
2
Yieldb (%)
95
Found
Reported[8]
95
93–94
2
2
2
2
86
82
90
90
102–104
104–105
131–133
197–199
162
130–132
196–197
160–161
aAll the products are known compounds and were identified by comparison of their melting points with the literature values as well as by 1H
NMR and IR.
bYields of isolated pure products.

OXIDATION OF BENZOINS
159
CONCLUSION
3. Paul, A. M., Khandekar, A. C., and Shenoy, M. A. Silica supported ferric
nitrate nonahydrate: selective oxidation of benzoins under mild conditions.
Synth. Commun. 2003, 33(15), 2581–2584.
4. Lou, J. D., Piao, M. H., Li, F., and Li, L. Selective oxidation of benzoins to
benzils with ferric (III) nitrate supported on graphite reagent. Synth. React.
Inorg. Metal Org. Nano-Metal Chem., 2007, 37, 553–555.
5. Wang, G. Q., Zhang, C., Vatanian, N., and Lou, J. D. Oxi-
dation of benzoins with ferric (III) nitrate supported on kiesel-
guhr. Synth. React. Inorg. Metal Org. Nano-Metal Chem., 2008, 38,
481–483.
6. Lou, J. D., Huang, L. H., Marrogi, A. J., Li, F., Li, L., and Gao, C. Selective
oxidation of alcohols with a new reagent: Iron (III) nitrate supported on
aluminum silicate, Synth. Commun. 2008, 38(3), 428–433.
7. Cornelis, A., Laszlo, P. Clay-supported copper and iron nitrates:
novel multi-purpose reagents for organic synthesis. Synthesis 1985,
909–918.
8. Khandekar, A. C., Paul, A. M., and Khadilkar, B. M. Silica supported
manganese dioxide: An efficient reagent for oxidation of benzoins. Synth.
Commun. 2002, 32(19), 2931–2936.
In conclusion, in this paper a preparation of benzils by oxi-
dation of corresponding benzoins using ferric (III) nitrate non-
ahydrate supported on aluminum silicate reagent under hetero-
geneous conditions and reflux in high yields is described. The
main advantage of this oxidation is that the reaction time is much
shorter as compared to the other reported ferric (III) nitrate non-
ahydrate based reagents, and it is an extension of application
for the ferric (III) nitrate nonahydrate supported on aluminum
silicate reagent as well.
REFERENCES
1. Matsushita Electric Industrial Co. Ltd. Photohardenable resin compositions.
Jpn. Kokai Tokkyo Koho 1981, 8198203 (Chem. Abstr. 1981,95, 188163u).
2. Bessermann, M., Cornelis, A., and Laszlo, P. Oxidation of benzoins by ferric
nitrate adsorbed on clay. C. R. Acad. Sci. Ser. C, 1984, 299(8), 427–428.

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