Oxidation of substituted β-diketones with hydrogen peroxide: Synthesis of esters through the formation of bridged 1,2,4,5-tetraoxanes

Article abstract of DOI:10.1055/s-0029-1219225

Acid-catalyzed oxidation of alkyl- and benzyl-substituted -diketones by hydrogen peroxide at 79-120C in a mixture of an alcohol and a strong acid (sulfuric acid, tetrafluoroboric acid, or perchloric acid) gave the corresponding esters through the formation of bridged 1,2,4,5-tetraoxanes. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0029-1219225

PAPER
1145
Oxidation of Substituted b-Diketones with Hydrogen Peroxide: Synthesis of
Esters through the Formation of Bridged 1,2,4,5-Tetraoxanes
O
xidation of Subs
l
b
e
-Diketone
x
s
ander O. Terent’ev,* Dmitry A. Borisov, Ivan A. Yaremenko, Yuri N. Ogibin, Gennady I. Nikishin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation
Fax +7(499)1355328; E-mail: alterex@yandex.ru
Received 16 October 2009; revised 3 December 2009
hydrogen peroxide. A bridged tetraoxane was obtained by
Abstract: Acid-catalyzed oxidation of alkyl- and benzyl-substitut-
heating 5-hydroperoxy-3,5-dimethyl-1,2-dioxolan-3-ol in
ed b-diketones by hydrogen peroxide at 79–120 °C in a mixture of
an alcohol and a strong acid (sulfuric acid, tetrafluoroboric acid, or
acetic acid (the yield was not determined).18 Oxidation of
substituted b-diketones by alkaline and neutral hydrogen
peroxide solutions gave either one dicarboxylic acid or
two monocarboxylic acids, depending on the nature of the
substituents.19 The oxidation of substituted 2-acylcyclo-
hexanones with hydrogen peroxide in tert-butyl alcohol
was accompanied by ring contraction and afforded the
corresponding cyclopentanecarboxylic acids in 80–87%
yield.20
perchloric acid) gave the corresponding esters through the forma-
tion of bridged 1,2,4,5-tetraoxanes.
Key words: esters, hydrogen peroxide, oxidations, tetraoxanes, ke-
tones
Oxidative transformations of organic peroxides have at-
tracted attention for more than a hundred years as a con-
venient and efficient tool for the formation of new C–O
bonds in molecules. Among the best known of these reac-
tions are the preparation of lactones and hydroxy acids by
the Baeyer–Villiger oxidation,1 the preparation of phenols
by the Hock process,2 the preparation of aryl sulfates by
the Elbs oxidation,3 the formation of oxygen-containing
rings by the Criegee reaction,4 the oxidative transforma-
tions of silicon peroxides5 accompanied by Si–C bond
cleavage as described by Fleming et al.,6 Tamao et al.,7
and Yablokov.8 Other reactions, such as the Kornblum–
de la Mare rearrangement of 1,2-dioxines into diketones,9
the transformation of 1,2-dioxines into epoxides,10 the re-
arrangement of indolenyl hydroperoxides into lactams,11
the synthesis of dicarboxylic acids from bishydroperox-
ides,12 the thermal decomposition of diacyl peroxides and
per esters,8,13 and some other oxidative processes,14 are
less widely used. Also worthy of mention are oxidative re-
arrangements of peroxides formed by reactions of unsat-
urated compounds with ozone15 or singlet oxygen.16
We have recently developed a procedure for the synthesis
of bridged 1,2,4,5-tetraoxanes 2 in good yields and high
selectivity by the reaction of b-dicarbonyl compounds 1
with hydrogen peroxide in the presence of a large amount
of a strong acid (sulfuric acid, tetrafluoroboric acid, or
perchloric acid).21 Diketones 1 are readily available com-
pounds that are generally prepared by the reaction of alkyl
or benzyl halides with pentane-2,4-dione in the presence
of a base.
We have now shown that 1,2,4,5-tetraoxanes 2 can be se-
lectively transformed into esters 3 by heating in an acidic
medium in the presence of hydrogen peroxide
(Scheme 1).
O
R1
O
R1
H2O2, heat
acid, R2OH
R1
O
H2O2
O
acid, R2OH
OR2
O
O
O
3a–h R2 = Bu
4a R2 = Pr
5a R2 = Et
1a–h
2a–h
During conventional research on oxidation reactions and
rearrangements involving peroxides, we discovered a new
transformation of bridged tetraoxanes prepared from b-
diketones and hydrogen peroxide.
Scheme 1 Synthesis of esters 3 from b-diketones 1 via bridged
1,2,4,5-tetraoxanes 2; for R group definitions, see product structures
in Table 3
The reactions of b-diketones with hydrogen peroxide have
been studied for many years. For example, a tetraoxane
was obtained from pentane-2,4-dione in a total yield of
18.5% in two steps via 5-hydroperoxy-3,5-dimethyl-1,2-
dioxolan-3-ol, which undergoes intramolecular cycliza-
tion in the presence of phosphorus pentoxide.17 A tetraox-
ane was also produced in trace amounts during the
sulfuric acid-catalyzed synthesis of 3,5-dihydroperoxy-
3,5-dimethyl-1,2-dioxolane from pentane-2,4-dione and
Esters 3a–c were obtained in yields of 83, 72, and 69%,
respectively, by refluxing tetraoxanes 2a–c, respectively,
for one hour in a mixture of butan-1-ol and sulfuric acid
containing a threefold molar excess of hydrogen peroxide
with respect to the tetraoxane 2.
The reaction is unusual in that the oxidation results in the
loss of two acetyl fragments and one hydrogen atom; the
CH fragment of the tetraoxane is transformed into the es-
ter group.
SYNTHESIS 2010, No. 7, pp 1145–1149
x
x
.
x
x
.2
0
1
0
Advanced online publication: 20.01.2010
DOI: 10.1055/s-0029-1219225; Art ID: P14909SS
© Georg Thieme Verlag Stuttgart · New York

1146
A. O. Terent’ev et al.
PAPER
Esters 3a, 4a, and 5a were also obtained by a one-pot pro-
cess without the isolation of the intermediate 1,2,4,5-tet-
raoxane 2a, as exemplified by the oxidation of diketone
1a. The reactions were carried out in an alcohol (ethanol,
propan-1-ol, or butan-1-ol) at 79 to 120 °C (EtOH, 79–
81 °C; PrOH, 98–100 °C; BuOH, 118–120 °C) in the
presence of 3–7 mole of hydrogen peroxide per mole of
diketone, with sulfuric acid as the catalyst and cosolvent
(0.9–7.2 mole per mole of diketone) (Table 1).
Table 2 Oxidation of Diketone 1a by Tetrafluoroboric Acid or Per-
chloric Acida
Entry
Acid
Amount (g)b
Yield (%)
1
2
3
4
5
6
HBF4
HBF4
HBF4
HBF4
HBF4
HClO4
0.35
0.5
0.75
1
77
85
62
56
50
77
Table 1 Optimization of the Conditions for the Synthesis of Esters
3a, 4a, and 5a from Diketone 1aa
1.5
0.6
O
a Reaction conditions: A 37% aq soln of H2O2 (1.21 g, 5 mol per mole
of diketone) and a 50% aq soln of HBF4 (0.7–3 g) or a 60% aq soln of
HClO4 (1 g) were added to a soln of the diketone (0.5 g) in BuOH (10
mL) at r.t., and the mixture was then refluxed for 1 h.
H2O2, ROH
H2SO4
O
OR
O
1a
3a R = Bu
4a R = Pr
5a R = Et
b Weight based on 100% (concentrated) acid.
Entry
1
H2O2 (equiv) H2SO4 (g)
R1OH
Yield (%)
54
molar excess of hydrogen peroxide were extended to the
oxidation of b-diketones 1a–h to give the corresponding
butyl arylacetates 3a–e and butyl alkanoates 3f–h
(Table 3).
3
5
7
5
5
5
5
3
5
7
5
5
5
1
EtOH
EtOH
EtOH
EtOH
EtOH
PrOH
PrOH
BuOH
BuOH
BuOH
BuOH
BuOH
BuOH
2
1
60
3
1
52
The yields of the esters obtained by the oxidation of the
various diketones varied within a rather narrow range
(67–88%), which suggests that analogous results should
be obtained with structurally similar b-dicarbonyl com-
pounds.
4
0.5
2
53
5
44
6
0.5
1
70
Table 3 Structures and Yields of Esters 3a–h
7
72
Product
Yield (%)
86
8
1
76
O
9
1
86
3a
OBu
10
11
12
13
1
80
OMe
0.25
0.5
2
65
O
3b
3c
73
67
83
OBu
48
O
a Reaction conditions: A 37% aq soln of H2O2 (3–7 mol/mol diketone)
and a soln of H2SO4 (0.25–2 g, 2.55–20.4 mmol) in R1OH (4 mL)
were added to a soln of diketone 1a (0.5 g, 2.84 mmol) in R1OH (6
mL) at r.t., and then the mixture was refluxed for 1 h.
OBu
O2N
O
3d
3e
83
81
OBu
The highest yield of ester was achieved by performing the
reaction in butan-1-ol (3a), probably because of the higher
reaction temperature attainable. The use of 5–7 moles of
H2O2 per mole of 1a, together with 0.5–1 g (1.8–3.6 moles
per mole of 1a) of sulfuric acid, was optimal for all the al-
cohols that we studied. Instead of sulfuric acid, acids such
as tetrafluoroboric acid or perchloric acid can also serve
as catalysts for this reaction (Table 2).
O
OBu
O
OBu
3f
88
OBu
Aqueous tetrafluoroboric or perchloric acid solutions
used in the same amounts as sulfuric acid gave similar
yields of ester 3a (Table 1).
3g
3h
75
71
O
O
OBu
The optimized conditions for the oxidation of 1a to give
3a in butan-1-ol containing sulfuric acid and a fivefold
BuO
O
Synthesis 2010, No. 7, 1145–1149 © Thieme Stuttgart · New York

PAPER
Oxidation of Substituted b-Diketones
1147
O
O
O
O
O
O
acid
OH
O
O
HO
O
O
R1
R1
R1
2
O
H
O
O
O
O
O
O
R1
O
H2O2, acid, R2OH
O
or
OR2
– H+
O
OH
R1
R1
O
O
3
A
R1
Scheme 2 A possible mechanism for the oxidative transformation of tetraoxanes 2 into esters 3
CAUTION: Although we have encountered no difficulties in work-
ing with peroxides, precautions, such as the use of blast shields and
fume hoods, and the avoidance of transition metal salts, heating, or
shaking, should be taken.
We suggest that the transformation of tetraoxanes 2 pro-
ceeds through a series of acid-catalyzed rearrangements
(related to the Baeyer–Villiger and Hock processes) to
form intermediates A (diacetoxy derivatives), which are
transformed into esters 3 through the oxidation of the CH-
containing fragment22 and esterification (Scheme 2).
Esters 3a–c by Oxidation of Tetraoxanes 2a–c; General Proce-
dure
37% aq H2O2 (0.22–0.25 g, 2.37–2.7 mmol; 3 equiv) and a soln of
H2SO4 (0.5 g, 5.1 mmol) in BuOH (2 mL) were added to a soln of
tetraoxane 2a–c (0.2 g, 0.79–0.9 mmol) in BuOH (3 mL) at r.t., and
mixture was refluxed for 1 h. CHCl3 (15 mL) was then added, and
H2O was removed by azeotropic distillation (~2 h). The mixture
was washed sequentially with H2O (5 mL), 5% aq NaHCO3 (5 mL),
and H2O (5 mL), then dried (Na2SO4) and concentrated in vacuo
(20–40 mm Hg). The product was purified by chromatography [sil-
ica gel, PE–EtOAc (gradient 0–20% EtOAc)]; yield: 3a, 83%; 3b,
72; 3c, 69%.
Similar results have been obtained in the oxidation of cy-
clic b-diketones with a methyl(trioxo)rhenium(VII)–
hydrogen peroxide system;23 this reaction involves hy-
droxylation as the first step followed by a Baeyer–Villiger
rearrangement and a second oxidation step to form dicar-
boxylic and monocarboxylic acids.
In summary, we have developed a new acid-catalyzed ox-
idative transformation of alkyl- and benzyl-substituted b-
diketones into esters by the action of hydrogen peroxide
through the formation of bridged 1,2,4,5-tetraoxane inter-
mediates. Oxidation of the diketone at 79 to 120 °C in a
mixture of an alcohol and a strong acid (sulfuric, tetraflu-
oroboric, or perchloric acid) leads to the loss of two acetyl
fragments and one hydrogen atom, and the transformation
of the CH fragment into a carboxy group. The reaction
provides a new route to carboxylic acid esters from alkyl
or aryl halides through condensation with pentane-2,4-di-
one, followed by oxidation of the resulting substituted b-
diketones with hydrogen peroxide in alcoholic solution.
The approach can be used as an alternative to the synthesis
of carboxylic acids by the Grignard reaction of alkyl or
aryl halides with carbon dioxide.
Butyl Phenylacetate (3a; Table 1, Entry 9)
37% aq H2O2 solution (1.21 g, 13.15 mmol) and a soln of H2SO4 (1
g, 10.2 mmol) in BuOH (4 mL) were added to a soln of diketone 1a
(0.5 g, 2.63 mmol) in BuOH (6 mL) at r.t., and the mixture was re-
fluxed for 1 h. CHCl3 (30 mL) was added, and H2O was removed by
azeotropic distillation (~2 h). The mixture was washed sequentially
with H2O (10 mL), 5% aq NaHCO3 (10 mL), and H2O (10 mL), then
dried (Na2SO4) and concentrated in vacuo (20–40 mm Hg). The
product was purified by chromatography [silica gel, PE–EtOAc
(gradient 0–10% EtOAc)]; yield: 0.44 g (2.26 mmol, 86%).
Butyl Phenylacetate (3a; Table 2, Entry 2)
37% aq H2O2 (1.21 g, 13.15 mmol) and 50% aq HBF4 (1 g, 5.7
mmol) were added to a soln of diketone 1a (0.5 g, 2.63 mmol) in
BuOH (10 mL) at r.t., and the mixture was refluxed for 1 h. CHCl3
(30 mL) was added, and H2O was removed by azeotropic distilla-
tion (~2 h). The product was finally isolated as described above;
yield: 0.43 g (2.24 mmol, 85%).
NMR spectra were recorded in CDCl3 soln on a Bruker Avance 300
1
spectrometer at 300.13 MHz for H and 75.48 MHz for 13C. TLC
analyses were carried out on standard silica-gel chromatography
plates. Chromatographic separations were performed on silica gel
(63–200 mesh). Acetylacetone, petroleum ether (PE), EtOAc,
EtOH, n-PrOH, n-BuOH (all of reagent grade, Acros) were distilled
before use. H2SO4, HClO4, (60% aq soln), HBF4 (50% aq soln), and
a 37% aq soln (all of high-purity grade, domestic production) were
used without additional purification. The b-diketones 1a,24 1b,21
1c,25 1d,26 1e,21 1f,271g,28and 1h29 were prepared according to
known procedures. Tetraoxanes 2a–c were prepared as described
previously.21
Esters 3a–h; General Procedure
37% aq H2O2 (0.98–1.47 g, 10.70–16.05 mmol, 5 mol per mol of
diketone 1a–h) and a soln of H2SO4 (1 g, 10.2 mmol) in BuOH (4
mL) were added to a solution of diketone 1a–h (0.5 g, 2.14–3.21
mmol) in BuOH (6 mL) at r.t., and the mixture was refluxed for 1 h.
CHCl3 (30 mL) was added, and H2O was removed by azeotropic
distillation (~2 h). The product was finally isolated as described
above.
Butyl Phenylacetate (3a)30
Colorless oil; yield: 86%.
Synthesis 2010, No. 7, 1145–1149 © Thieme Stuttgart · New York

1148
A. O. Terent’ev et al.
PAPER
1H NMR (300.13 MHz, CDCl3): d = 0.99 (t, J = 7.33 Hz, 3 H,
CH3CH2), 1.33–1.52 (m, 2 H, CH3CH2), 1.55–1.75 (m, 2 H,
CH3CH2CH2), 3.67 (s, 2 H, CH2Carom), 4.16 (t, J = 6.9 Hz, 2 H,
CH2O), 7.17–7.45 (m, 5 H, CaromH).
126.15, 126.58, 127.66, 128.32, 129.89, 138.03 (Carom), 171.70
(CO).
Butyl Adamantane-1-carboxylate (3f)35
Colorless oil; yield: 88%.
13C NMR (75.48 MHz, CDCl3): d = 13.56, 18.98, 30.54
(CH3CH2CH2), 41.38 (CH2CO), 64.62 (CH2O), 126.90, 128.42,
129.13, 134.14 (Carom), 171.53 (CO).
1H NMR (300.13 MHz, CDCl3): d = 0.90 (t, J = 7.34 Hz, 3 H,
CH3CH2), 1.13–2.05 (m, 19 H, CHadamantyl
CH3CH2CH2), 4.02 (t, J = 6.2 Hz, 2 H, CH2O).
13C NMR (75.48 MHz, CDCl3): d = 13.67, 19.12, 30.69
(CH3CH2CH2), 27.96 (CH), 36.51, 38.84 (CH2,adamantyl), 40.65 (C),
63.80 (CH2O), 177.68 (CO).
,
CH2,adamantyl,
Propyl Phenylacetate (4a)31
Colorless oil; yield: 72%.
1H NMR (300.13 MHz, CDCl3): d = 0.98 (t, J = 7.34 Hz, 3 H,
CH3CH2), 1.63–1.78 (m, 2 H, CH3CH2), 3.68 (s, 2 H, CH2Carom),
4.12 (t, J = 6.6 Hz, 2 H, CH2O), 7.17–7.44 (m, 5 H, CaromH).
Butyl Pentanoate (3g)36
Colorless oil; yield: 75%.
Ethyl Phenylacetate (5a)32
Colorless oil; yield: 60%.
1H NMR (300.13 MHz, CDCl3): d = 1.31 (t, J = 7.0 Hz, 3 H, CH3),
3.67 (s, 2 H, CH2Carom), 4.21 (q, J = 7.0 Hz, 2 H, CH2O), 7.19–7.43
(m, 5 H, CaromH).
1H NMR (300.13 MHz, CDCl3): d = 0.78–0.96 (m, 6 H, CH3), 1.19–
1.42 (m, 4 H, CH2), 1.51–1.65 (m, 4 H, CH2), 2.26 (t, J = 7.34 Hz,
2 H, CH2CO), 4.04 (t, J = 6.6 Hz, 2 H, CH2O).
13C NMR (75.48 MHz, CDCl3): d = 13.64, 13.87, 19.10, 22.72,
30.67, 34.06, 39.87, 64.03 (CH3CH2CH2CH2, CH2O), 173.91 (CO).
Butyl (2-Methoxyphenyl)acetate (3b)
Slightly yellow oil; yield: 73%.
Dibutyl Succinate (3h)37
Colorless oil; yield: 71%.
1H NMR (300.13 MHz, CDCl3): d = 0.92 (t, J = 7.34 Hz, 3 H,
CH3CH2), 1.25–1.43 (m, 2 H, CH3CH2), 1.54–1.67 (m, 2 H,
CH3CH2CH2), 3.63 (s, 2 H, CH2Carom), 3.81 (s, 3 H, CH3O), 4.11 (t,
J = 6.6 Hz, 2 H, CH2O), 6.83–6.95 (m, 2 H, CaromH), 7.11–7.29 (m,
2 H, CaromH).
13C NMR (75.48 MHz, CDCl3): d = 13.59, 18.98, 30.62
(CH3CH2CH2), 35.95 (CH2CO), 55.29 (CH3O), 64.36 (CH2O),
110.35, 120.40, 128.37, 130.75 (CaromH), 123.21 (CaromCH2),
157.46 (CaromO), 171.85 (CO).
1H NMR (300.13 MHz, CDCl3): d = 0.89 (t, J = 7.34 Hz, 6 H,
CH3CH2), 1.27–1.41 (m, 4 H, CH3CH2), 1.51–1.63 (m, 4 H,
CH3CH2CH2), 2.58 (s, 4 H, COCH2CH2CO), 4.05 (t, J = 6.6 Hz, 4
H, CH2O).
13C NMR (75.48 MHz, CDCl3): d = 13.58 (CH3), 19.01 (CH3CH2),
29.12, 30.54 (COCH2CH2CO, CH3CH2CH2), 64.47 (CH2O), 172.24
(CO).
Acknowledgment
Anal. Calcd for C13H18O3: C, 70.24; H, 8.16. Found: C, 70.41; H,
8.35.
This work was supported by the Program for Support of Leading
Scientific Schools of the Russian Federation (Grant NSh
2942.2008.3).
Butyl (4-Nitrophenyl)acetate (3c)33
Slightly yellow oil; yield: 67%.
1H NMR (300.13 MHz, CDCl3): d = 0.87 (t, J = 7.34 Hz, 3 H,
CH3CH2), 1.24–1.39 (m, 2 H, CH3CH2), 1.50–1.63 (m, 2 H,
CH3CH2CH2), 3.70 (s, 2 H, CH2Carom), 4.80 (t, J = 7.0 Hz, 2 H,
CH2O), 7.43 (d, J = 8.1 Hz, 2 H, CaromHCaromCH2), 8.14 (d, J = 8.1
Hz, 2 H, CaromHCaromNO).
13C NMR (75.48 MHz, CDCl3): d = 13.50, 18.95, 30.44
(CH3CH2CH2), 40.94 (CH2CO), 65.12 (CH2O), 123.56, 130.18
(CaromH), 141.46 (CaromCH2), 147.07 (CaromN), 170.09 (CO).
References
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Butyl (4-Methylphenyl)acetate (3d)34
Slightly yellow oil; yield: 83%.
1H NMR (300.13 MHz, CDCl3): d = 0.92 (t, J = 7.34 Hz, 3 H,
CH3CH2), 1.29–1.43 (m, 2 H, CH3CH2), 1.54–1.66 (m, 2 H,
CH3CH2CH2), 2.33 (s, 3 H, CH3Carom), 3.58 (s, 2 H, CH2Carom), 4.09
(t, J = 6.6 Hz, 2 H, CH2O), 7.07–7.21 (m, 4 H, CaromH).
13C NMR (75.48 MHz, CDCl3): d = 13.58, 19.03, 30.60
(CH3CH2CH2), 20.96 (CH3Carom), 40.99 (CH2CO), 64.61 (CH2O),
128.09, 129.02, 129.14, 136.51 (Carom), 171.79 (CO).
Butyl (3-Methylphenyl)acetate (3e)32
Slightly yellow oil; yield: 81%.
1H NMR (300.13 MHz, CDCl3): d = 0.90 (t, J = 7.34 Hz, 3 H,
CH3CH2), 1.28–1.40 (m, 2 H, CH3CH2), 1.52–1.65 (m, 2 H,
CH3CH2CH2), 2.32 (s, 3 H, CH3Carom), 3.56 (s, 2 H, CH2Carom), 4.08
(t, J = 7.0 Hz, 2 H, CH2O), 7.03–7.23 (m, 4 H, CaromH).
13C NMR (75.48 MHz, CDCl3): d = 13.56, 19.0, 30.54
(CH3CH2CH2), 21.22 (CH3Carom), 41.30 (CH2CO), 64.61 (CH2O),
(7) Tamao, K.; Ishida, N.; Kumada, M. J. Org. Chem. 1983, 48,
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Synthesis 2010, No. 7, 1145–1149 © Thieme Stuttgart · New York

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