Selective oxidation of primary alkanols into the "symmetrical" esters with the H2O2-MBr-HCl system

Article abstract of DOI:10.1007/s11172-011-0050-x

Oxidation of linear or branched primary alkanols with H₂O ₂-MBr (M = Li, Na, K)-HCl system in water affords the corresponding "symmetrical" esters in almost quantitative yield.

Full text of DOI:10.1007/s11172-011-0050-x

3
10
Russian Chemical Bulletin, International Edition, Vol. 60, No. 2, pp. 310—312, February, 2011
Selective oxidation of primary alkanols into
the "symmetrical" esters with the H O —MBr—HCl system
2
2
G. I. Nikishin, L. L. Sokova, and N. I. Kapustina
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
4
7 Leninsky prosp., 119991 Moscow, Russian Federation.
Eꢀmail: kap@ioc.ac.ru
Oxidation of linear or branched primary alkanols with H O —MBr (M = Li, Na, K)—HCl
2
2
system in water affords the corresponding "symmetrical" esters in almost quantitative yield.
Key words: primary alkanols, esters, hydrogen peroxide, lithium bromide, sodium bromide,
potassium bromide, oxidation.
Oxidation of alcohols to carbonyl compounds or carbꢀ
Scheme 1
oxylic acids is one of fundamental reactions in organic
chemistry.
Currently, development of novel simple and conveꢀ
nient methods for selective oxidation is topical. Besides,
the use of available, cheap, and environmentally friendly
oxidants, e.g., hydrogen peroxide, are preferable. However,
depending on the reaction conditions, hydrogen peroxide
can oxidize primary alkanols to carboxylic acids or esters.
In the presence of a system of Na WO —phase transfer
M = Li, Na, K.
R = Bu (a), nꢀC H
Et(Me)CHCH2 (e), Bu (Et)CH (f).
n
(b), nꢀC H
(c), Me CHCH CH (d),
17 2 2 2
6
13
n
8
The reaction proceeds only in the presence of all reꢀ
agents; in the absence of any of them, no reaction occurred.
The optimal reaction conditions were determined takꢀ
ing heptanꢀ1ꢀol (1b) as an example (Table 1). Heptyl hepꢀ
tanoate (2b) was prepared in quantitative yield at reꢀ
agent molar ratio 1b : H O : LiBr : HCl = 1 : 2 : 2 : 5. Deꢀ
2
4
1
,2
catalyst (PTC is methyltrioctylammonium sulfate,
II
4
(
NBu ) SO (see Ref. 3)), Co complexes, and polyoxyꢀ
4 2 4
5
metalate complexes, the reactions proceeded nonꢀselecꢀ
tively1 or required significant excess (15—20 equiv.) of
oxidant. When Br or HBr were used as redox catalysts,
,2
4
2
2
2
the reaction yielded "symmetrical" esters, the products of
esterification of the resulting acid with the excess of alcoꢀ
hol oxidized. According to the proposed mechanism, the
crease in content of H O , LiBr, or HCl resulted in deꢀ
2 2
crease in the yield of ester 2b (see Table 1, entries 1—7,
12—13). Concentration of these components in water
significantly affected the yield of the product. Thus,
when the reaction was carried out at molar ratio of
1b : H O : LiBr : HCl = 1 : 3 : 1 : 5 in 10 mL of water per
6
reaction involved the formation of acyl bromide and its
simultaneous alcoholysis. In the case of glycols bearing both
primary and secondary hydroxyl groups, a H O —HBr
2
2
2
2
system with controlled content of H O oxidized only secꢀ
1 mmol of 1b, the yield of ester 2b was 98%; at the same
reactant ratio in 20 and 30 mL of water the yields of 2b
were 20 and 10% respectively; while, in 40 mL of water,
the yield was 1% only (see Table 1, entries 8—11). Similar
tendency was observed in experiments 13—16. No effect
of the cation nature in MBr on oxidation was found (see
Table 1, entries 17 and 18).
2
2
7
ondary hydroxyl group. In the presence of FeBr (see Ref. 8)
3
or [bmim] [W O ] (bmim is 1ꢀbutylꢀ3ꢀmethylimidꢀ
4
10 23
9
azolium), secondary alkanols gave ketones, while primaꢀ
ry alkanols were resistant to oxidation. Recently, for the
9
oxidation of alkanols to esters, we suggested to use hydroꢀ
gen peroxide in the combination with two redox catalysts,
III
10
namely, Ce salts and LiBr.
The obtained results allow suggestion of the reaction
mechanism, which involved metathesis, oxidation of HBr
formed with H O to molecular bromine, and subsequent
In the present work, novel method for the synthesis of
symmetrical" esters by the oxidation of alkanols with simꢀ
"
2
2
ple oxidation system, H O —MBr—HCl, was developed.
reaction of Br with alkanol (Scheme 2). Formation of
2
2
2
It was found that hydrogen peroxide in water at 65—70 °C
in the presence of MBr (M = Li, Na, K) and hydrochloric
acid effectively oxidized linear and branched primary alꢀ
kanols 1a—f to esters 2a—f (Scheme 1).
molecular bromine was confirmed by the characteristic
color of the reaction mixture.
Most likely that the reaction of alkanols with Br proꢀ
2
ceeded via formation of hemiꢀacetal and its subsequent
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 303—305, February, 2011.
066ꢀ5285/11/6002ꢀ310 © 2011 Springer Science+Business Media, Inc.
1

Esters from primary alkanols
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 2, February, 2011
311
Table 1. Oxidation of heptanꢀ1ꢀol (1b) with the H O —MBr—HCl
system
Scheme 2
2
2
a
Entry
Molar ratio
b : H O : MBr : HCl
MBr Conversion Yield (%) of
of 1b (%) compound 2b
1
2
2
1
2
3
4
5
6
7
8
1 : 2 : 2 : 5
1 : 1 : 2 : 5
1 : 2 : 1 : 5
1 : 3 : 2 : 2
1 : 3 : 2 : 3
1 : 3 : 2 : 4
1 : 3 : 2 : 5
1 : 3 : 1 : 5
1 : 3 : 1 : 5
1 : 3 : 1 : 5
1 : 3 : 1 : 5
1 : 5 : 1 : 5
1 : 5 : 2 : 5
1 : 5 : 2 : 5
1 : 5 : 2 : 5
1 : 5 : 2 : 5
1 : 3 : 2 : 5
1 : 3 : 2 : 5
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
LiBr
NaBr
KBr
100
88
70
66
95
98
100
98
20
4
>99
87
69
65
94
96
>99
98
20
4
tanꢀ1ꢀol (1e), and 2ꢀethylhexanꢀ1ꢀol (1f) oxidized in the
optimal conditions to the corresponding esters (Table 2).
In summary, we developed simple, facile, and effective
procedure for the synthesis of esters by the oxidation of
linear and branched primary alkanols with the redox sysꢀ
c
9
d
10
11
12
13
14
15
16
17
18
e
1
1
86
100
80
10
4
85
>99
80
10
4
c
d
e
tem H O —MBr (M = Li, Na, K)—HCl in water. No
2 2
expensive reagents are required, the results of the experiꢀ
ments are well reproducible. The method is useful for the
practical applications.
100
100
>99
>99
a
Experimental
1
b (1 mmol); solvent, H O (10 mL); reaction temperature,
2
6
5—70 °C; reaction time, 3 h.
Based on the starting 1b.
b
GC analysis was performed on a Chromꢀ5 chromatograph
with the flameꢀionization detector and 3×3000 mm analytical
glass columns with 5% SEꢀ30 and 5% FFAP on Chromaton
NꢀAWꢀHMDS (0.16—0.20 mm). The product yields were deꢀ
termined by an internal standard method with the empirical corꢀ
relation coefficients. The IR spectra (Nujol) were recorded on
a Perkin—Elmer 577 spectrophotometer. The H and C NMR
spectra were recorded on a Bruker ACꢀ200 instrument in CDCl3.
The GCꢀMS analysis was performed on a Finnigan MAT
ITDꢀ700 spectrometer (EI, 70 eV, the source of ion—ionic trap
system temperature was 220 °C) connected with Carlo Erba 4200
chromatograph with a 0.2×2500 mm Ultraꢀ1 column (Hewꢀ
lett—Packard), the stationary phase (polymethylsiloxane) thickꢀ
ness 0.33 μm, helium was used as a carrier gas. The reaction
products were isolated by column chromatography (silica gel L,
c
d
e
Solvent, H O (20 mL).
2
Solvent, H O (30 mL).
2
Solvent, H O (40 mL).
2
1
13
oxidation to ester, i.e., similar to oxidation of alkanols
with a cerium ammonium nitrate—lithium bromide sysꢀ
tem.11 The aboveꢀmentioned mechanism involving forꢀ
mation of acyl bromide as the intermediate is impossible
due to its susceptibility to rapid hydrolysis to carboxylic
acid in aqueous media. At low concentration of the alꢀ
kanol in a water solution, most of bromide is consumed in
the competitive reaction with water to give hydrobromic
and unstable hypobromous acids.
6
4
0—100 μm, elution with heptane—ethyl acetate). Pentanꢀ1ꢀol
Similarly to heptanꢀ1ꢀol (1b), pentanꢀ1ꢀol (1a), noꢀ
nanꢀ1ꢀol (1c), 4ꢀmethylpentanꢀ1ꢀol (1d), 3ꢀmethylpenꢀ
(1a), heptanꢀ1ꢀol (1b), nonanꢀ1ꢀol (1с), 4ꢀmethylpentanꢀ1ꢀol
(1d), 3ꢀmethylpentanꢀ1ꢀol (1e), and 2ꢀethylhexanꢀ1ꢀol (1f)
a
Table 2. Oxidation of alcohols 1a—f with the H O —LiBr—HCl system
2
2
Alkanol
a—f
Conversion
of 1a—f (%)
Product
2a—f
Yieldb
(%)
1
С H OH (1a)
99
100
100
98
C H COOC H (2a)
98
>99
>99
98
5
11
4
9
5
11
С H OH (1b)
C H COOC H (2b)
7
15
6 13 7 15
С H OH (1c)
C H COOC H (2c)
8 17 9 19
9
19
Me CH(CH ) OH (1d)
Me CHCH CH COO(CH ) CHMe (2d)
2
2 3
2 2 2 2 3 2
EtCH(Me)CH CH OH (1e)
98
99
EtCH(Me)CH COOCH CH CH(Me)Et (2e)
97
98
2
2
2
2
2
n
n
n
Bu CH(Et)CH OH (1f)
Bu CH(Et)COOCH CH(Et)Bu (2f)
2
2
a
1
a—f (1 mmol); molar ratio, 1 : H O : LiBr : HCl = 1 : 3 : 2 : 5; solvent, H O (10 mL); reaction temperaꢀ
2 2 2
ture, 65—70 °C; reaction time, 3—3.5 h.
b
Based on the starting 1a—f.

312
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 2, February, 2011
Nikishin et al.
(
Acros) were distilled prior to use. Hydrogen peroxide (35% aq.
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2
2
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2
2
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6
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1
2
data and by comparison with authentic samples.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 09ꢀ03ꢀ00292a)
and the Council for Grants at the President of the Russian
Federation (the Program for the State Support of Leading
Scientific Schools of the Russian Federation, Grant
NShꢀ4945.2010.3).
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Nauk, Ser. Khim., 2009, 303 [Russ. Chem. Bull., Int. Ed.,
2
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Received May 31, 2010;
in revised form September 21, 2010