Rapid oxidation of 1,2-diols, α-hydroxyketones and some alcohols using N-bromosuccinimide in ionic liquid

Full text of DOI:10.1080/00304948.2013.786585

This article was downloaded by: [University Of Pittsburgh]
On: 10 July 2013, At: 13:43
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Organic Preparations and Procedures
International: The New Journal for
Organic Synthesis
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/uopp20
Rapid Oxidation of 1,2-Diols, α-
Hydroxyketones and Some Alcohols using
N-Bromosuccinimide in Ionic Liquid
Jitender M. Khurana a , Ankita Chaudhary a & Sanjay Kumar a
a Department of Chemistry , University of Delhi , Delhi , 110007 ,
India
Published online: 16 May 2013.
To cite this article: Jitender M. Khurana , Ankita Chaudhary & Sanjay Kumar (2013) Rapid Oxidation
of 1,2-Diols, α-Hydroxyketones and Some Alcohols using N-Bromosuccinimide in Ionic Liquid, Organic
Preparations and Procedures International: The New Journal for Organic Synthesis, 45:3, 241-245,
DOI: 10.1080/00304948.2013.786585
To link to this article: http://dx.doi.org/10.1080/00304948.2013.786585
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Organic Preparations and Procedures International, 45:241–245, 2013
Copyright © Taylor & Francis Group, LLC
ISSN: 0030-4948 print / 1945-5453 online
DOI: 10.1080/00304948.2013.786585
Rapid Oxidation of 1,2-Diols, α-Hydroxyketones
and Some Alcohols using N-Bromosuccinimide
in Ionic Liquid
Jitender M. Khurana, Ankita Chaudhary, and Sanjay Kumar
Department of Chemistry, University of Delhi, Delhi-110007, India
Oxidation of 1,2-diols, α-hydroxyketones and alcohols to carbonyl compounds is of
great importance in organic synthesis1 and can be achieved with an array of reagents
such as chromium(VI)-based reagents,2 hypervalent iodine reagents,3 and DABCO/Br2,4
DMSO/N2H4.H2O/I2/H2O/CH3CN.5 The oxidation of α-hydroxyketones to 1,2-diketones
has also been reported by a variety of reagents including pyridinium chlorochromate,6 am-
monium chlorochromate,7 iodine,8 Fe(NO3)2.9H2O9 and Fe(NO3)3/4-OH-TEMPO.10 The
conversion of 1,2-diols to 1,2-diketones has been performed with 4-MeO-TEMPO,11 (4-
AcNH-TEMPO)-OTs-TsOH,12 CrO3-NH4Cl,13 NBS-CCl4-Py,14 NBS-Al2O3.15 The oxida-
tion of alcohols has also been reported by NBS/2,6-lutidine in 1-butyl-3-methylimidazolium
tetrafluoroborate ([bmim]BF4).16 This method involves the use of stoichiometric amount
of base and suffers from narrow substrate generality and is limited to benzylic alcohols.
Ionic liquids have emerged as efficient alternatives to conventional solvents, owing to their
favorable properties, such as good solvating capability, wide liquid range, negligible vapor
pressure, tunable polarity, high thermal stability, and ease of recyclability.17–19 We now
report the oxidation of a variety of 1,2-diols, α-hydroxyketones and alcohols using NBS
(N-bromosuccinimide) in different ionic liquids in the absence of any catalyst.
The appropriate reaction conditions were optimized by initially investigating the ox-
idation of hydrobenzoin (1a) with NBS in different ionic liquids and by changing the
substrate:NBS ratio. The reaction using 1:2 molar ratio of substrate:NBS in [bmim]BF4
gave the best results with respect to reaction time (2.5 h) and yield (92%) at 70◦C. The
yield of benzil was low in other ionic liquids such as [bmim]PF6, [bmim]Br and [bmim]Cl.
It was further observed that although the reaction of hydrobenzoin was complete using 1:1
molar ratio (substrate:NBS), it yielded a mixture of benzoin and benzyl (51:35% yields
respectively); however, increasing the molar ratio of 1a: NBS to 1:3 had no marked effect on
the yield or time of the reaction. Subsequently, oxidation of different hydrobenzoins, naph-
thoins and aliphatic 1,2-diols was carried out under the optimized reaction conditions. All
reactions were rapid, clean and no side-products from ring bromination or α-bromination,
Received November 11, 2011; in final form December 31, 2012.
Address correspondence to Jitender M. Khurana, Department of Chemistry, University of Delhi,
Delhi-110007, India. E-mail: jmkhurana1@yahoo.co.in
241

242
Khurana et al.
were detected.
NBS, [bmim]BF4
70 oC
(1)
R
C
O
C
O
R'
R
CH CH R'
OH OH
1
2
b) R = R' = 4-ClC6H4
e) R = R' = 3-BrC6H4
h)R = R' = 1-Naphthyl
c) R = R' = 2-ClC6H4
f) R = R' = 4-MeC6H4
a) R = R' = C6H5
d) R = R' = 4-BrC6H4
g) R = R' = 4-MeOC6H4
i) R-R' =
CH2
4
j) R = C8H17, R' = C7H14COOH
The application of NBS as an oxidant for the oxidation of α-hydroxyketones in
[bmim]BF4 was also investigated. A variety of α-hydroxyketones underwent clean oxi-
dation to corresponding 1,2-diketones by using 1:2 molar ratio of substrate:NBS (Table 1,
Entries 11–14) (Eq. 2). Reaction using 1:1 molar ratio of benzoin to NBS, resulted in an
incomplete reaction and gave 2a in low yield (51%).
NBS, [bmim]BF4
(2)
R
C
O
C
O
R
R
CH
OH
C
O
R
70 oC
2, 4
3
a) R = C6H5
d) R = n- C3H7
b) R = 4-ClC6H4
c) R = 4-MeC6H4
We also studied the oxidation of alcohols with NBS in [bmim]BF4 (Eq. 3). Primary and
secondary benzylic and allylic alcohols underwent oxidation to the corresponding aldehydes
and ketones (Table 1, Entries 15–28) using 1:2 molar ratio of substrate to NBS. Aliphatic
alcohols also gave the corresponding aldehydes (Table 1, Entries 29–31), which did not
undergo further oxidation to carboxylic acids. It was surprising that secondary aliphatic
alcohols gave the corresponding alkyl bromide on reaction with NBS in [bmim]BF4 (Table
1, Entries 32–35) rather than the carbonyl compound.
NBS, [bmim]BF4
R
CH R'
Br
R
CH R'
OH
R
C
O
R'
(3)
or
70 oC
7
5
6
a) R-R' = 9-Fluorenyl
b) R = R' = C6H5
c) R = C6H5, R' = 4-ClC6H4
f) R = C6H5, R' = CH3
d) R = C6H5, R' = 4-BrC6H4 e) R = R' = 4-ClC6H4
g) R = 4-BrC6H4, R' = CH3
j) R = 4-MeC6H4, R' = CH3
h) R = 4-ClC6H4, R' = CH3
i) R = 4-O2NC6H4, R' = CH3
k) R = 4-MeOC6H4, R' = CH3 l) R = Cinnamyl, R' = H
m) R = 9-Anthryl, R' = H
p) R = n- C6H13, R' = H
s) R = C6H13, R' = CH3
n) R = 1-Naphthyl, R' = H
q) R = C7H15, R' = H
o) R = Ph(CH3)CH, R' = H
r) R-R' =
u) R = C2H5, R' = C2H5
CH2
5
t) R = C3H7, R' = C3H7
The reaction of hydrobenzoins was also attempted with N-chlorosuccinimide and N-
iodosuccinimide in [bmim]BF4. Although, in both cases, the reaction of hydrobenzoin was
complete after 4–5 h and benzil was isolated, the reactions of substituted hydrobenzoins

Rapid Oxidation of 1,2-Diols, α-Hydroxyketones
243
Table 1
Oxidation of 1,2-Diols, α-Hydroxyketones and Alcohols with NBS in [bmim]BF4 at 70◦C
Entry
Substrate
Product
Yield (%)
mp (◦C)
lit. Mp (◦C)
Time (h)
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
1g
1h
1i
2a
2b
2c
2d
2e
2f
2g
2h
2i
92
88
86
82
81
88
87
90
85
70
90
90
85
80
93
92
84
87
90
83
82
82
86
78
85
80
65
60
82
85
80
85
82
77
75
92–94
92–9413
198–19913
128–13013
224–22613
120–12213
103–10413
121–12213
192–19420
34–3821
82–8322
92–9413
198–19913
103–10413
—
2.5
2
2
2
2
2
2
2
2.5
2.5
1.5
1
1.5
2.5
1
1
1
1
1
2
1
1
2
1.5
1.5
1
2
2
2
2
2
2
2
2
2
199–200
131–133
225–226
118–120
102–103
122–123
187–189
32–33
83–85
90–92
199–200
102–103
Liquid
82–84
46–48
74–76
78–80
142–144
Liquid
48–51
Liquid
76–80
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
1j
2j
3a
3b
3c
3d
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
5q
5r
5s
2a
2b
2c
4a
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
6q
7r
7s
7t
80–8323
47–4924
75–7725
79–8026
144–14527
—
48–5228
—
76–7829
—
Liquid
38–41
38–3930
—
Liquid
102–104
Liquid
Liquid
Liquid
Liquid
Liquid
Liquid
Liquid
Liquid
100–10531
—
—
—
—
—
—
—
—
5t
5u
7u
were incomplete and yielded mixtures of benzoins and benzils. In the case of aliphatic
1,2-diols, namely, trans-1,2-cyclohexanediol and 9,10-dihydroxystearic acid, no oxidation
took place even after 24 h and starting materials were recovered.
In conclusion, the oxidation of 1,2-diols, α-hydroxyketones and alcohols by NBS in
[bmim]BF4 is a facile and clean synthetic protocol. The ionic liquid can be recycled three
times.

244
Khurana et al.
Experimental Section
Melting points were determined on a Tropical Labequip apparatus and are uncorrected. IR
1
spectra were recorded on Perkin-Elmer FT–IR SPECTRUM-2000 and H NMR spectra
were obtained on a Hitachi FT-NMR model R-600 (60 MHz) with TMS as internal standard.
All the products are known and were identified by co-TLC with authentic samples and by
mp. (wherever applicable), IR and 1H NMR spectra. The ionic liquids used were synthesized
according to the procedure reported in the literature.32,33
General Procedure
In a typical experiment, a mixture of hydrobenzoin (0.21 g, 1 mmol), N-bromosuccinimide
(0.35 g, 2 mmol) and [bmim]BF4 (5 mmol) with a stir bar were placed in a 50 ml RB flask
fitted with a calcium chloride guard tube. The reaction mixture was stirred magnetically
in an oil bath maintained at 70◦C for the appropriate time (Table 1). After completion of
reaction (TLC using petroleum ether:ethyl acetate), the reaction mixture was cooled to
room temperature and diethyl ether (3 × 10 ml) was added to it. The combined ethereal
layer was washed with water (4 × 10 ml) and then dried over anhyd. Na2SO4, concentrated
on a rotary evaporator to give a yellow solid, which was identified as benzil (0.19 g, 92%)
by mp., IR and 1H NMR spectra.
The above reaction was repeated to determine the recyclability of the ionic liquid. On
completion of reaction, as monitored by TLC, the reaction mixture was cooled to room
temperature. The product obtained was extracted in diethyl ether, leaving behind the ionic
liquid and the by-product of NBS i.e. succinimide as residue. The residue was diluted with
ethyl acetate and the insoluble succinimide, was removed by filtration. Ethyl acetate was
evaporated under reduce pressure to give ionic liquid which was dried before use at 80◦C
under vacuum for 30 min. The recovered ionic liquid could be used for oxidation up to
three runs without any appreciable loss of efficiency by adding 2 equiv. of NBS for each
run.
Acknowledgments
AC and SK thank CSIR, New Delhi, India for the grant of Senior Research Fellowships.
References
1. T. V. Lee, In “Comprehensive Organic Synthesis”, B. M. Trost, I. Fleming, and S. V. Ley, Vol. 7,
p. 291, Pergamon: Oxford, 1991.
2. A. H. Haines, In “Methods of Oxidation of Organic Compounds”, p. 17, Academic Press: London,
1988.
3. D. B. Dess and J. C. Martin, J. Org. Chem., 48, 4155 (1983).
4. M. M. Heravi, F. Derikvand, M. G. Zadeh and B. Neumuller, Tetrahedron Lett., 46, 6243 (2005).
5. P. Gogoi, G. K. Sarmah and D. Konwar, J. Org. Chem., 69, 5153 (2004).
6. A. K. Mitra, A. De and N. Karchaudhuri, J. Chem. Res. (S), 246 (1999).

Rapid Oxidation of 1,2-Diols, α-Hydroxyketones
245
7. G. S. Zhang, Q. Z. Shi, M. F. Chen and K. Cai, Synth. Commun., 27, 953 (1997).
8. B. B. Corson and R. W. McAllister, J. Am. Chem. Soc., 51, 2822 (1929).
9. Y. W. Zhao and Y. L. Wang, J. Chem. Res., 70 (2001).
10. W. Xinliang and L. Xinmia, Chin. J. Catal., 29, 935 (2008); Chem. Abstr., 150, 329516 (2008).
11. P. L. Anelli, S. Banfi, F. Montanari and S. Quici, J. Org. Chem., 54, 2970 (1989).
12. M. G. Banwell, V. S. Bridges, J. R. Dupuche, S. L. Richards and J. M. Walter, J. Org. Chem., 59,
6338 (1994).
13. J. T. Li and X. L. Sun, Lett. Org. Chem., 3, 842 (2006); Chem. Abstr., 148, 78708 (2006).
14. J. M. Khurana and B. M. Kandpal, Tetrahedron Lett., 44, 4909 (2003).
15. J. M. Khurana and R. Arora, ARKIVOC, 211 (2008).
16. J. L. Lee, J. Y. Lee and J. M. Lee, Synth. Commun., 35, 1911 (2005).
17. V. I. Parvulescu and C. Hardacre, Chem. Rev., 107, 2615 (2007).
18. H. Olivier-Bourbigou, L. Magna and D. Morvan, Appl. Catal. A, 373, 1 (2010).
19. S. Chowdhury, R. S. Mohan and J. L. Scott, Tetrahedron, 63, 2363 (2007).
20. N. S. Nudelman and P. Outumuro, J. Org. Chem., 47, 4347 (1982).
21. G. L. Cantrell and R. Filler, J. Fluorine Chem., 27, 35 (1985).
22. K. L. Rinehart, S. I. Goldberg, C. L. Tarimaun and T. P. Culbertson, J. Am. Chem. Soc., 83, 225
(1961).
23. T. B. Patrick, G. L. Cantrell, and S. M. Inga, J. Org. Chem., 45, 1409 (1980).
24. F. F. Blicke and E. L. Schumann, J. Am. Chem. Soc., 76, 1226 (1954).
25. I. Mohammadpoor-Baltork, H. R. Memarian and K. Bahrami, Kiumars, Monatsh. Chem., 135,
411 (2004).
26. J.-Y. Chen, S. J. Chen, Y. J. Tang, C. Y. Mou and F. Y. Tsai, J. Mol. Catal. A: Chem., 307, 88
(2009).
27. C. S. Marvel and V. Nichols, J. Org. Chem., 6, 296 (1941).
28. H. Sharghi, M. Jokar, D. Mahboubeh, M. Mohammad and R. Khalifeh, Adv. Synth. Catal., 352,
3031 (2010).
29. M. Cai, G. Zheng and G. Ding, Green Chem., 11, 1687 (2009).
30. P. D. Gardner, J. Am. Chem. Soc., 76, 4550 (1954).
31. M. Maddani and K. R. Prabhu, Tetrahedron Lett., 49, 4526 (2008).
32. S. Park and R. J. Kazlauskas, J. Org. Chem., 66, 8395 (2001).
33. P. Bohnote, A. P. Dias, N. Papageorgiou, K. Kalyanasundaram and M. Gratzel, Inorg. Chem., 35,
1168 (1996).