A H2O2/HBr system-several directions but one choice: oxidation-bromination of secondary alcohols into mono- or dibromo ketones

Article abstract of DOI:10.1039/c8ra04885a

In this work we found that a H₂O₂-HBr(aq) system allows synthesis of α-monobromo ketones and α,α′-dibromo ketones from aliphatic and secondary benzylic alcohols with yields up to 91%. It is possible to selectively direct the process toward the formation of mono- or dibromo ketones by varying the amount of hydrogen peroxide and hydrobromic acid. The convenience of application, simple equipment, multifaceted reactivity, and compliance with green chemistry principles make the application of the H₂O₂-HBr(aq) system very attractive in laboratories and industry. The proposed oxidation-bromination process is selective in spite of known properties of ketones to be oxidized by the Baeyer-Villiger reaction or peroxidated with the formation of compounds with the O-O moiety in the presence of hydrogen peroxide and Bronsted acids.

Full text of DOI:10.1039/c8ra04885a

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A H2O2/HBr system – several directions but one
choice: oxidation–bromination of secondary
alcohols into mono- or dibromo ketones†
Cite this: RSC Adv., 2018, 8, 28632
Gennady I. Nikishin, Nadezhda I. Kapustina, Liubov L. Sokova, Oleg V. Bityukov
*
and Alexander O. Terent'ev
In this work we found that a H2O2–HBr(aq) system allows synthesis of a-monobromo ketones and a,a0-
dibromo ketones from aliphatic and secondary benzylic alcohols with yields up to 91%. It is possible to
selectively direct the process toward the formation of mono- or dibromo ketones by varying the amount
of hydrogen peroxide and hydrobromic acid. The convenience of application, simple equipment,
multifaceted reactivity, and compliance with green chemistry principles make the application of the
H2O2–HBr(aq) system very attractive in laboratories and industry. The proposed oxidation–bromination
process is selective in spite of known properties of ketones to be oxidized by the Baeyer–Villiger
reaction or peroxidated with the formation of compounds with the O–O moiety in the presence of
hydrogen peroxide and Bronsted acids.
Received 7th June 2018
Accepted 6th August 2018
DOI: 10.1039/c8ra04885a
rsc.li/rsc-advances
Bromo ketones are involved in organic chemistry as multi-
purpose reagents.36,37 They can be easily transformed into
Introduction
unsaturated ketones and ketones containing functional
groups.38,39 Favorskii rearrangement of a-bromo ketones leads
to the formation of esters.40 a,a0-Dibromo ketones are the
precursors of 1,2-dialkyl cyclopropenones,41,42 and divinyl
A wide variety of methods for the oxidation of secondary alco-
hols into ketones is regularly replenished with new oxidants
and oxidizing systems. Hydrogen peroxide attracts increased
attention as a cheap and environment-friendly oxidant. For the
oxidation of secondary alcohols with H2O2, catalysts of different
chemical nature were used: Br2,1 HBr,1–6 NaBr,7,8 BiBr3,9 FeBr3,10
MgBr2/[bmim] BF4,11 Mn(III) complex,12 Co(II) complex,13 Zn
polyoxometalate,14 Na2WO4/PTC,15–18 [bmim]4[W10O23] in ionic
liquids,19 W/phosphate,20 Keggin complexes,21,22 Al/W-poly-
oxoanions,23 W/Sc/P-salt.24
The H2O2–HBr(aq) system is known in organic chemistry for
its application in the following processes: oxidation of
secondary and primary alcohols to ketones1–4 and esters,1,25
respectively, bromination of olens,26,27 acetylenes,27 ketones,4,28
arenes26,27,29,30 and heterocyclic compounds.31 This oxidation–
bromination system is characterized by the use of inexpensive
reagents, low environmental impact and the absence of organic
wastes, which makes it a good alternative to existing oxidation
and bromination methods.32 The H2O2–HBr(aq) system is also
of interest for more extensive practical application.33 In our
previous studies, this system was applied for the homo- and
cross-condensation of alcohols into esters,34 the bromination of
alkyl phenyl ketones into the aromatic ring and side-chain
position.35
N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences, 47
Leninsky prosp., Moscow 119991, Russian Federation. E-mail: terentev@ioc.ac.ru
† Electronic supplementary information (ESI) available: Detailed experimental
procedures and characterization of new compounds. See DOI: 10.1039/c8ra04885a
Scheme 1 Oxidation-halogenation with H2O2–HBr(aq) system.
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salt1–8 and H2O2/Br2.1 There is only one report of the oxidation of
secondary alcohols into a-bromo ketones, but a,a0-dibromo
ketones were not obtained (Scheme 1).4
This paper describes dibromo- and monobromo ketones
synthesis by one-pot oxidation–bromination of secondary
alcohols with H2O2–HBr(aq) (Scheme 1). The process is more
experimentally simple, low-cost, and complies with green
chemistry standards unlike the sole method proposed for the
similar transformation, which is based on the oxidation–
bromination of secondary alcohols with Ce(IV)/LiBr system.45
Change of hydrogen peroxide and hydrobromic acid amount
can selectively direct the reaction routes towards the formation
of mono- or dibromo ketones.
Scheme 2 Oxidation–bromination of secondary alcohols 1a–h with
the formation of a-bromoketones 2a–h or a,a0-dibromo ketones
3a–g.
It is important to note that in the reaction conditions we
didn't detect the formation of traditional Baeyer–Villiger oxida-
tion products46–48 or expected peroxides,49–61 which are products
of a reaction between C-atom of carbonyl group and hydrogen
peroxide. Possible explanation of these reactions failure can be
based on the higher rate of ketone bromination in competition
with peroxidation and (or) following transformations. Steric
hindrance in mono- and dibrominated ketones prevents the
attack of hydrogen peroxide on the electrophilic carbon atom of
the carbonyl group. To the best of our knowledge the only one
example of a-brominated ketone peroxidation exists: 3-bromo-
2,2-dihydroperoxy-1,7,7-trimethyl-bicyclo[2.2.1]heptane was ob-
tained with H2O2–AlCl3 ꢀ 6H2O system.62
Scheme
3 Oxidation–bromination of secondary alcohols 4a–e
bearing only one a-CH2 group near the carbonyl group with the
formation of a-bromoketones 5a–e or a,a-dibromo ketones 6a,b,d,e.
ketones,43 the latter ones are starting reagents for the synthesis
of cyclopentenones by Nazarov reaction.40 H2O2–HBr(aq) system
was used for the oxidative bromination of styrenes,5 ketones4,28
and oximes44 into bromo ketones. It is especially noteworthy
that bromo ketones were not detected in the reactions with
various substrates including alcohols under the action bromine
containing systems: H2O2/HBr or hydrobromic acid sodium
Results and discussion
The starting substrates for the oxidation–bromination were
symmetrical 1a–e, 1h and unsymmetrical aliphatic alcohols 1f-g
and benzylic alcohols 4a–e (Schemes 2 and 3).
Table 1 Oxidation and oxidation–bromination of 1a with the H2O2–HBr(aq) systema
Molar ratio: mole HBr
and H2O2/mole 1a
Yield, %
Entry
HBr
H2O2
Solvent
s, h
2a
3a
7a
1
2
3
4
5
6
7
8
1.2
1.2
1.4
2
2.5
2.5
2.5
6
5
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN (50% aq.)
H2O
CH3CN
CH3CN
MeOH
6
6
6
6
6
6
6
10
6
6
6
38
80
76
60
14
38
Trace
Trace
40
Trace
Trace
13
35
44
43
80
90
—
55
Trace
—
Trace
33
Trace
—
—
52
47
20
10
10
10
10
10
15
15
10
10
10
9
10
11
1.2
1.2
1.2
THF
DCE
31
71
—
—
a
General procedure: to a solution of alcohol 1a (1 mmol, 88.2 mg) and HBr (48% aq., 1.2–6 mmol, 0.136–0.679 ml) in 1 ml of a solvent at 65–70 ꢁC
(for entry 9 and 10, 60 ꢁC) and vigorous stirring a solution of H2O2 (35% aq., 10–15 mmol, 0.860–1.290 ml) was added portionwise (0.2–0.3 ml)
during 0.6–10 h. Yields were determined by GC analysis.
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Depending on the experimental conditions and the structure H2O2 and 1.2 equivalents of HBr (entry 2). 5-Fold molar excess
of the alcohol 1a–h, it is possible to change the direction of the of H2O2 is insufficient for selective preparation of 2a. An
reaction, towards the formation of either a-bromo ketones 2a–h increase of the HBr amount from 1.2 to 2.5 equivalents (entries
(molar ratio of 1a–h : HBr : H2O2 ¼ 1 : 1.2 : 10) or a,a0-dibromo 3–5) resulted in a decrease in the selectivity of products 2a, 3a,
ketones 3a–g (molar ratio of 1a–h : HBr : H2O2 ¼ 1 : 6 : 15) and 7a formation. When water was used as the solvent (entry 5),
(Scheme 2).
a-Bromo ketones 5a–e (molar ratio of 4a–e : HBr : H2O2
1 : 1.2 : 10) and a,a-dibromo ketones 6a,b,d,e (molar ratio of achieved with a 15-fold molar excess of H2O2 (entries 7, 8). An
4a–e : HBr : H2O2 ¼ 1 : 6:15) can be selectively prepared in the increase of the HBr amount up to 6 equivalents and the reaction
oxidation–bromination reactions with starting alcohols 4a–e time up to 10 hours (entry 8) afforded the product 3a with the
bearing only one a-CH2 group near the carbonyl group maximum yield (90%). In the best conditions for 2a preparation
a mixture of monobromo ketones 2a and dibromo ketones 3a
was also formed. The best yield of dibromo ketone 3a was
¼
(Scheme 3).
The inuence of the experimental conditions on the selec- leads to the synthesis of 2a and 7a mixtures (entries 9–11).
tivity of oxidation–bromination and on the yield of a-bromo Results of the optimization (Table 1) demonstrate that the
(entry 2), using of MeOH, THF, and DCE as a reaction media
ketone 2a, a,a0-dibromo ketone 3a, and ketone 7a was deter- reaction direction is mainly inuenced by the molar ratio of the
mined using pentanol-3 1a as an example. Generally, the reac- secondary alcohol, hydrogen peroxide, and hydrobromic acid.
tion was carried out by the addition of 35% aqueous solution of In the optimized reaction conditions (entry 2), a number of
H2O2 in acetonitrile for 6–10 hours to the solution of pentanol-3 monobromo ketones 2a–h and 5a–e were prepared (Table 2).
1a and 48% HBr(aq) in acetonitrile or water (Table 1).
Optimized conditions (entry 7, Table 1) were also used for the
According to the obtained data, the highest yield of mono synthesis of dibromo ketones 3a–g and 6a,b,d,e (Table 3).
bromo ketone 2a was achieved with a 10-fold molar excess of
Alcohols of unbranched structure 1a–f are easily converted
into a-bromo ketones (Table 2) and into a,a0-dibromo ketones
(Table 3) with good yields. Diisopropyl carbinol 1h is converted
only to the corresponding a-bromo ketone 2h (Table 2), the
formation of a,a0-dibromo ketone from diisopropyl carbinol 1h
is probably prevented by the steric hindrance. In the case of
isopropyl amyl carbinol 1g, two isomeric mono bromides, 2-
Table 2 Oxidation–bromination of secondary alcohols 1a–h and 4a–
e by the H2O2–HBr(aq) system to monobromo ketones 2a–h and
5a–ea
Table 3 Oxidation–bromination of secondary alcohols 1a–h and 4a–
e by the H2O2–HBr(aq) system to dibromo ketones 3a–g and 6a,b,d,ea
a
a
General procedure: to a solution of alcohol 1a–h, 4a–e (1 mmol, 88.2–
General procedure: to a solution of alcohol 1a–h, 4a–c (1 mmol, 88.2–
256.5 mg) and HBr (48% aq., 1.2 mmol, 0.136 ml) in CH3CN (1 ml) at 65– 256.5 mg) and HBr (48% aq., 6 mmol, 0.679 ml) in CH3CN (1 ml) at 65–
70 ꢁC and vigorous stirring, a solution of H2O2 (35% aq.,10 mmol, 0.860 70 ꢁC and vigorous stirring, a solution of H2O2 (35% aq., 15 mmol, 1.290
ml) in CH3CN (1 ml) was added portionwise (0.2–0.3 ml) for 6 hours. ml) in CH3CN (1 ml) was added portionwise (0.2–0.3 ml) for 10 hours.
b
c
b
The ratio of isomers 2f : 2f0 ꢂ 1 : 1 according to NMR data. The
The ratio of diastereoisomers meso : rac ¼ 1 : 3 according to NMR
ratio of isomers 2g : 2g0 ꢂ 2 : 1 according to NMR data.
data.
28634 | RSC Adv., 2018, 8, 28632–28636
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bromo-2-methyloctan-3-one 2g and 4-bromo-2-methyloctan-3- was cooled, diethyl ether (15 mL) and Na2SO3 (1 g) were added.
one 2g0 are formed in a ratio of 1 : 1 (Table 2). Oxidation– The organic layer was decanted and washed with water (5 ml),
bromination of propyl amyl carbinol 1f also results in two then dried over Na2SO4. The solvent was evaporated in
monobromo ketones, 3-bromononan-4-one 2f and 5- a vacuum of a water jet pump (20 mmHg). The products 2a–h
bromononan-4-one 2f0 (ꢂ1 : 1) (Table 2). Methyl tert-butyl and 5a–e were isolated by column chromatography on silica gel
carbinol 4a and methyl phenyl carbinol 4b are converted to a,a- in a solvent system PE : EA (100 : 1).
dibromo ketone 6a and a,a-dibromo ketone 6b (Table 3) under
optimized conditions for dibromo ketone synthesis (entry 7,
Experimental for the Table 3
Table 1). Amyl phenyl carbinol 4c undergoes only mono-
To a solution of alcohol 1a–h, 4a–e (1 mmol, 88.2–256.5 mg) and
bromination with the formation of 5c (Table 2). In the reaction
HBr (48% aqueous, 6 mmol, 0.679 ml) in CH3CN (1 ml) at 65–
medium symmetric a,a0-dibromo ketones are formed as
ꢁ
70 C and vigorous stirring, a solution of H2O2 (35% aqueous,
a mixture of meso- and rac-isomers with a rac-form preference
15 mmol, 1.290 ml) in CH3CN (1 ml) was added portionwise
(0.2–0.3 ml) for 6 hours. Aer the addition of the rst portion,
1
(ratio 1 : 3), as evidenced by H and 13C NMR spectra.
brown vapors and a bright orange color were observed. The next
Conclusions
portion of hydrogen peroxide was added aer the decolorization
of the reaction mixture (a pale-yellow color), then the reaction
Thus, we have developed a convenient one-pot method for the
mass was cooled, diethyl ether (15 mL) and Na2SO3 (1 g) were
synthesis of monobromo- and dibromo ketones by oxidation–
added. The organic layer was decanted and washed with water
(5 ml) and then dried over Na2SO4. The solvent was evaporated
bromination of secondary alcohols with the H2O2/HBr system in
acetonitrile. Formation of peroxides and products of Baeyer–
in a vacuum of a water jet pump (20 mmHg). Products 3a–g and
Villiger reaction was not detected. Amount and molar ratio of
6a,b,d,e were isolated by column chromatography on silica gel
in a solvent system PE : EA (100 : 1).
hydrogen peroxide and hydrobromic acid are the key factors for
the achievement of a high degree of selectivity. Optimized
conditions permits to synthesize a,a0-dibromo- or a,a-dibromo
Conflicts of interest
ketones with yields up to 91%. Conversion of unbranched
secondary alcohols into a,a0-dibromo ketones is the most
There are no conicts to declare.
effective.
Acknowledgements
Experimental
This work was supported by the Russian Foundation for Basic
Research (Grant no 18-03-00122 A).
Experimental for the Table 1
To a solution of alcohol 1a (1 mmol, 88.2 mg) and HBr (48%
aqueous) (1.2–6 mmol, 0.136–0.679 ml) in 1 ml of solvent
(CH3CN, CH3CN (50% aq.), H2O, DCE) at 65–70 C (for MeOH
ꢁ
Notes and references
(entry 9) and THF (entry 10), 60 ꢁC) and vigorous stirring,
a solution of H2O2 (35% aqueous, 10–15 mmol, 0.860–1.290 ml)
was added portionwise (0.2–0.3 ml) during 6–10 h. Aer the
addition of the rst portion, brown vapours and a bright orange
colour were observed. The next portions of H2O2 were added
aer the decolorization of the reaction mixture (a pale-yellow
colour), then the reaction mass was cooled, diethyl ether (15
mL) and Na2SO3 (1 g) were added. The organic layer was dec-
anted and washed with water (5 ml), then dried over Na2SO4.
The solvent was evaporated in a vacuum of a water jet pump (20
mmHg). Yields of 2a, 3a, 7a were determined by GC analysis
with heptan-4-one and undecan-6-one as the internal standard.
1 A. Amati, G. Dosualdo, L. Zhao, A. Bravo, F. Fontana,
F. Minisci and H.-R. Bjørsvik, Org. Process Res. Dev., 1998,
2, 261–269.
2 V. B. Sharma, S. L. Jain and B. Sain, Synlett, 2005, 173–175.
3 S. L. Jain, V. B. Sharma and B. Sain, Tetrahedron, 2006, 62,
6841–6847.
4 A. Podgorsek, S. Stavber, M. Zupan and J. Iskra, Green Chem.,
2007, 9, 1212–1218.
5 R. D. Patil, G. Joshi and S. Adimurthy, Ind. Eng. Chem. Res.,
2010, 49, 8100–8105.
6 M. Rasouli, M. A. Zolgol, M. H. Moslemin and
G. Chehardoli, Green Chem. Lett. Rev., 2017, 10, 117–120.
7 X. Qi, J. Wang, L. Zheng and L. Qi, Synlett, 2011, 555–558.
8 G. Joshi, R. D. Patil and S. Adimurthy, RSC Adv., 2012, 2,
2235–2239.
Experimental for the Table 2
To a solution of alcohol 1a–h, 4a–e (1 mmol, 88.2–256.5 mg) and
HBꢁr (48% aqueous, 1.2 mmol, 0.136 ml) in CH3CN (1 ml) at 65–
70 C and vigorous stirring, a solution of H2O2 (35% aqueous,
9 M.-k. Han, S. Kim, S. T. Kim and J. C. Lee, Synlett, 2015, 26,
2434–2436.
´
10 mmol, 0.860 ml) in CH3CN (1 ml) was added portionwise 10 S. E. Martın and A. a. Garrone, Tetrahedron Lett., 2003, 44,
(0.2–0.3 ml) for 6 hours. Aer the addition of the rst portion, 549–552.
brown vapors and a bright orange color were observed. The next 11 H. J. Park and J. C. Lee, Synlett, 2009, 79–80.
portions of H2O2 were added aer the decolorization of the 12 H. R. Mardani and H. Golchoubian, Tetrahedron Lett., 2006,
reaction mixture (a pale-yellow color), then the reaction mass
47, 2349–2352.
This journal is © The Royal Society of Chemistry 2018
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RSC Advances
Paper
13 S. Das and T. Punniyamurthy, Tetrahedron Lett., 2003, 44, 39 A. O. Terent'ev, V. A. Vil, I. A. Yaremenko, O. V. Bityukov,
6033–6035.
D. O. Levitsky, V. V. Chernyshev, G. I. Nikishin and
F. Fleury, New J. Chem., 2014, 38, 1493–1502.
40 J. J. Li, Name Reactions, Springer-Verlag, Berlin Heidelberg,
2003.
41 R. Breslow, J. Posner and A. Krebs, J. Am. Chem. Soc., 1963,
85, 234.
14 W. Kasprzyk, M. Galica, S. Bednarz and D. Bogdał, Synlett,
2014, 25, 2757–2760.
15 K. Sato, M. Aoki, J. Takagi, K. Zimmermann and R. Noyori,
Bull. Chem. Soc. Jpn., 1999, 72, 2287–2306.
16 D. Bogda and M. Lukasiewicz, Synlett, 2000, 143–145.
17 R. Noyori, M. Aoki and K. Sato, Chem. Commun., 2003, 1977– 42 J. Ciabattoni and E. C. Nathan, J. Am. Chem. Soc., 1969, 91,
1986. 4766–4771.
18 B. S. Chhikara, R. Chandra and V. Tandon, Synlett, 2005, 43 S. Lemaire-Audoire and P. Vogel, Tetrahedron: Asymmetry,
872–874. 1999, 10, 1283–1293.
19 B. S. Chhikara, S. Tehlan and A. Kumar, Synlett, 2005, 63–66. 44 A. O. Terent'ev, I. B. Krylov, V. A. Vil', Z. Y. Pastukhova,
20 C. Venturello and M. Gambaro, J. Org. Chem., 1991, 56, 5924–
S. A. Fastov and G. I. Nikishin, Cent. Eur. J. Chem., 2012,
10, 360–367.
5931.
21 J. Wang, L. Yan, G. Li, X. Wang, Y. Ding and J. Suo, 45 G. I. Nikishin, L. L. Sokova and N. I. Kapustina, Russ. Chem.
Tetrahedron Lett., 2005, 46, 7023–7027. Bull., 2010, 59, 391–395.
22 S. Zhang, G. Zhao, S. Gao, Z. Xi and J. Xu, J. Mol. Catal. A: 46 G. R. Krow, in Organic Reactions, ed. L. A. Paquette, John
Chem., 2008, 289, 22–27. Wiley and Sons, 1993, vol. 43, pp. 251–798.
23 M. Carraro, B. S. Bassil, A. Soraru, S. Berardi, A. Suchopar, 47 R. Michael and M. Bernard, Eur. J. Org. Chem., 1999, 737–
U. Kortz and M. Bonchio, Chem. Commun., 2013, 49, 7914–
750.
7916.
48 I. A. Yaremenko, V. A. Vil', D. V. Demchuk and
A. O. Terent'ev, Beilstein J. Org. Chem., 2016, 12, 1647–1748.
49 H. Gandhi, K. O'Reilly, M. K. Gupta, C. Horgan, E. M. O'Leary
and T. P. O'Sullivan, RSC Adv., 2017, 7, 19506–19556.
50 A. O. Terent'ev, M. M. Platonov, Y. N. Ogibin and
G. I. Nikishin, Synth. Commun., 2007, 37, 1281–1287.
´
24 L. Balbinot, U. Schuchardt, C. Vera and J. Sepulveda, Catal.
Commun., 2008, 9, 1878–1881.
25 S. Samanta, V. Pappula, M. Dinda and S. Adimurthy, Org.
Biomol. Chem., 2014, 12, 9453–9456.
26 V. Arutyunyan, T. Kochikyan, N. Egiazaryan and A. Avetisyan,
Russ. J. Org. Chem., 1995, 31, 100.
ˇ
51 K. Zmitek, M. Zupan, S. Stavber and J. Iskra, Org. Lett., 2006,
27 N. B. Barhate, A. S. Gajare, R. D. Wakharkar and
A. V. Bedekar, Tetrahedron, 1999, 55, 11127–11142.
28 V. H. Tillu, P. D. Shinde, A. V. Bedekar and R. D. Wakharkar,
Synth. Commun., 2003, 33, 1399–1403.
29 C. U. Dinesh, R. Kumar, B. Pandey and P. Kumar, J. Chem.
Soc., Chem. Commun., 1995, 611–612.
8, 2491–2494.
52 C. Schwartz and P. H. Dussault, in PATAI'S Chemistry of
Functional Groups, John Wiley & Sons, Ltd., 2014, pp. 1–38.
53 D. Opsenica, G. Pocsfalvi, Z. Juranic, B. Tinant,
´
ˇ
J.-P. Declercq, D. E. Kyle, W. K. Milhous and B. A. Solaja,
J. Med. Chem., 2000, 43, 3274–3282.
30 B. M. Choudary, Y. Sudha and P. N. Reddy, Synlett, 1994, 450. 54 Y. Li, H.-D. Hao, Q. Zhang and Y. Wu, Org. Lett., 2009, 11,
31 S. Yang, J. Liu, Z. Jin, W. Tian, H. Sun and M. Wang,
Heterocycl. Commun., 2018.
32 G. I. Nikishin, N. I. Kapustina, L. L. Sokova, O. V. Bityukov
and A. O. Terent'ev, Tetrahedron Lett., 2017, 58, 352–354.
33 INTEROX CHEMICALS LTD (GB), EP19890302334, 1989.
1615–1618.
55 A. Bunge, H.-J. Hamann and J. Liebscher, Tetrahedron Lett.,
2009, 50, 524–526.
56 P. Ghorai, P. H. Dussault and C. Hu, Org. Lett., 2008, 10,
2401–2404.
34 G. I. Nikishin, L. L. Sokova, A. O. Terent'ev and 57 B. Das, M. Krishnaiah, B. Veeranjaneyulu and B. Ravikanth,
N. I. Kapustina, Russ. Chem. Bull., 2015, 64, 2845–2850. Tetrahedron Lett., 2007, 48, 6286–6289.
35 A. O. Terent'ev, S. V. Khodykin, I. B. Krylov, Y. N. Ogibin and 58 A. O. Terent'ev, M. M. Platonov and A. V. Kutkin, Open Chem.,
G. I. Nikishin, Synthesis, 2006, 1087–1092. 2006, 4, 207.
36 A. M. Montana, J. A. Barcia, P. M. Grima and G. Kociok- 59 A. O. Terent'ev, M. M. Platonov, I. B. Krylov, V. V. Chernyshev
´
˜
¨
Kohn, Tetrahedron, 2016, 72, 6794–6806.
37 A. S. Ionkin, W. J. Marshall and B. M. Fish, Org. Lett., 2008, 60 D. Azarifar, K. Khosravi and F. Soleimanei, Molecules, 2010,
10, 2303–2305. 15, 1433.
38 I. Saikia, A. J. Borah and P. Phukan, Chem. Rev., 2016, 116, 61 K. Starkl Renar, S. Pecar and J. Iskra, Org. Biomol. Chem.,
and G. I. Nikishin, Org. Biomol. Chem., 2008, 6, 4435–4441.
6837–7042.
2015, 13, 9369–9372.
62 D. Azarifar and K. Khosravi, J. Iran. Chem. Soc., 2011, 8, 1006–
1013.
28636 | RSC Adv., 2018, 8, 28632–28636
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