Oxidation of β-dicarbonyl compounds with tert-butyl hydroperoxide in the presence of vanadyl acetylacetonate

Article abstract of DOI:10.1134/S1070363211030182

Oxidation of β-dicarbonyl compounds with tert-butyl hydroperoxide in the presence of vanadyl acetylacetonate (benzene, 20°C) involves the activated methylene group with intermediate formation of trioxo derivatives and is accompanied by decomposition of carbon skeleton. The oxidation products are carbon dioxide, carboxylic acids, and tert-butyl and peroxy esters derived from the latter.

Full text of DOI:10.1134/S1070363211030182

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 3, pp. 550–558. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © L.P. Stepovik, M.V. Gulenova, I.A. Kalacheva, A.Yu. Potkina, 2011, published in Zhurnal Obshchei Khimii, 2011, Vol. 81, No. 3,
pp. 454–462.
Oxidation of β-Dicarbonyl Compounds with tert-Butyl
Hydroperoxide in the Presence of Vanadyl Acetylacetonate
L. P. Stepovik, M. V. Gulenova, I. A. Kalacheva, and A. Yu. Potkina
Lobachevskii Nizhnii Novgorod State University, pr. Gagarina 23, Nizhnii Novgorod, 603950 Russia
e-mail: gulmv@rambler.ru
Received March 25, 2010
Abstract—Oxidation of β-dicarbonyl compounds with tert-butyl hydroperoxide in the presence of vanadyl
acetylacetonate (benzene, 20°C) involves the activated methylene group with intermediate formation of trioxo
derivatives and is accompanied by decomposition of carbon skeleton. The oxidation products are carbon
dioxide, carboxylic acids, and tert-butyl and peroxy esters derived from the latter.
DOI: 10.1134/S1070363211030182
Reactions of β-diketones with peroxy compounds
are governed by both oxidant nature and conditions.
For instance, oxidation of alkyl-substituted β-diketones
(benzene, 20°C) at any reactant ratio leads to elimina-
tion of the ligand and its oxidation mainly to acetic
acid and carbon dioxide through intermediate forma-
tion of pentane-2,3,4-trione and diacetyl carbonate [6].
(
pentane-2,4-dione derivatives) with hydrogen
peroxide in alcoholic medium (20–25°C) in the
presence of strong acids leads to the formation of
If the ratio (acac) VO–t-BuOOH exceeded 1:10, the
evolution of oxygen (partly in the singlet state) was
observed.
2
1
,2,4,5-tetraoxanes in 47 to 77% yield [1]. The major
products of analogous processes occurring at elevated
temperature (80–120°C) are esters formed via subsequent
reaction of 1,2,4,5-tetraoxanes with hydrogen peroxide
and alcohol. Here, 1,2,4,5-tetraoxane molecule loses
In the present work we examined reactions of β-
dicarbonyl compounds with tert-butyl hydroperoxide
in the presence of vanadyl acetylacetonate (I). As
substrates we selected compounds containing both
aliphatic and aromatic substituents at the carbonyl
group: pentane-2,4-dione (III), 1-phenylbutane-1,3-
dione (IV), 1,3-diphenylpropane-1,3-dione (V), 1,5-
diphenylpentane-1,3,5-trione (VI), cyclohexane-1,3-
dione (VII), and ethyl benzoylacetate (VIII). The
substrate–t-BuOOH molar ratio was varied from 1:4 to
two CH C fragments [2].
3
Reactions of hydrogen peroxide with enolizable
β-dicarbonyl compounds, such as pentane-2,4-dione,
3
-methylpentane-2,4-dione, and ethyl acetoacetate, in
the presence of molybdenum(VI) and tungsten(VI)
peroxo complexes are accompanied by heat evolution,
and they result in the cleavage of the C–C bond
between the central carbon atom and the acetyl group.
In all cases, the final product is acetic acid, and
oxidation of pentane-2,4-dione and ethyl acetoacetate
is accom-panied by liberation of carbon dioxide [3–5].
It was found that oxidation of acetylacetone with
hydrogen peroxide in the presence of sodium
molybdate involves intermediate formation of a com-
plex of metal compound with pentane-2,3,4-trione
dihydrate in the coordination sphere of molybdenum(VI)
without participation of paramagnetic species [4, 5].
1
:10, depending on the substrate nature, so as to
ensure its complete conversion. The ratio vanadyl
acetylacetonate (I)–t-butyl hydroperoxide (II) ranged
from 1:50 to 1:100, i.e., the amount of compound I
may be regarded as catalytic. All reactions were
carried out in benzene at room temperature. The
reaction was assumed to be complete when carbon
dioxide no longer evolved. The reactions of pentane-
2
,4-dione and cyclohexane-1,3-dione with t-BuOOH
were exothermic and were complete in 3–4 h. Phenyl
ketones IV and VI reacted at 20°C in 20–24 h, and at
5
0°C, in 5–6 h. In all cases, the major products were
We previously showed that the reaction of vanadyl
acetylacetonate (I) with tert-butyl hydroperoxide (II)
carbon dioxide, carboxylic acids, and tert-butyl and
peroxy esters (Table 1).
5
50

OXIDATION OF β-DICARBONYL COMPOUNDS WITH tert-BUTYL HYDROPEROXIDE
551
The data in Table 1 show that diketones III–V react
with tert-butyl hydroperoxide at the methylene
group with decomposition of the carbon skeleton.
Although all the examined β-dicarbonyl compounds
exist as equilibrium mixtures of ketone and enol
tautomers, the structure of the isolated products
indicates that they react just as β-diketones. On the
other hand, positive test for epoxide ring suggests that
t-BuOOH reacts with the enol form of the substrates.
However, the amount of epoxy derivatives is very
small. By analogy with the reaction of vanadyl
acetylacetonate with hydroperoxide II [6], we
presumed the formation of triketones in the first step
(Scheme 1).
Scheme 1.
(
acac) VO
2
R
C
O
CH2
C
O
R' + 2 t-BuOOH
R
C
O
C
O
C
O
R' + H O + 2 t-BuOH
2
o
2
0 C, C H
6 6
R = R′ = Me; R = Me, R′ = Ph; R = R′ = Ph.
The subsequent nucleophilic reaction of triketones
Scheme 3.
with t-BuOOH (as reported previously for α-diketones
RC(O)O
t-BuOOH
_t-BuOH
[7–9]) should lead to unsymmetrical carboxylic acid
A
C
O
anhydrides A (Scheme 2; R = R′ was assumed for the
sake of simplicity).
RC(O)O
(
RCO) O + CO2
2
Scheme 2.
Anhydrides are also capable of reacting with alcohol
or hydroperoxide to give esters or peroxy esters, which
were detected among oxidation products of all the
examined β-dicarbonyl compounds; in addition, free
acids may be formed. The latter were identified as
R
C
O
C
O
C
O
R + t-BuOOH
OH
C
O
R
C
C
O
R
Table 1. Products of oxidation of β-diketones RC(O)CH
2
·
OOBu-t
C(O)R′ with tert-butyl hydroperoxide in the presence of
a
(
acac)
2
VO, (PhH, 20°C, mol per mole of diketone)
R
C
O
O
C
O
C
O
R
_t-BuOH
R = R′ = Me; R = Ph, R′ = Me; R = R′ = Ph;
Product
b
b
b
15 : 60 : 1
10 : 50 : 1
10 : 50 : 1
A
СО
2
0.86
3.40
0.03
0.09
–
0.70
4.36
0.04
0.12
0.04
0.14
0.74
0.69
0. 89
4.68
–
Intermediate formation of α-hydroxy-α-tert-butyl-
dioxy ketone which is then converted into adipic an-
hydride was detected previously in the reaction of
cyclohexane-1,2-dione with t-BuOOH [8].
t-BuOH
MeC(O)OBu-t
MeC(O)OOBu-t
PhC(O)OBu-t
PhC(O)OOBu-t
MeC(O)OH
PhC(O)OH
–
Hydrolysis of unsymmetrical anhydride A should
produce a mixture of carboxylic acid and α-keto acid.
However, all our attempts to detect benzoylformic acid
or its ester in the oxidation of diketone V were
unsuccessful. Furthermore, Schemes 1 and 2 do not
rationalize formation of carbon dioxide. We believe
that the second C–C bond in anhydride A is oxidized
to give diacyl carbonate and that the latter undergoes
decomposition with liberation of carbon dioxide
according to Scheme 3.
0.04
0.06
–
–
c
1.39
–
1.74
a
Averaged data.
Ratio RC(O)CH
b
c
2
C(O)R′–t-BuOOH–(acac)
2
VO.
Pyruvic acid was also detected qualitatively (as 2,4-dinitro-
phenylhydrazone); after treatment with diazomethane, methyl
pyruvate was detected.
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STEPOVIK et al.
Table 2. Products of oxidation of 1,5-diphenylpentane-1,3,5-
trione with tert-butyl hydroperoxide in the presence of
and benzoic acid, acetophenone was isolated as one of
the main products (Table 2); it can be formed as a
result of decarboxylation of benzoylacetic acid. The
above compounds (Table 2) may be formed via
oxidation of one methylene group in triketone VI
according to Schemes 1–3 and subsequent trans-
formations of diacyl carbonate B (Scheme 5).
(
acac)
2
VO (molar ratio 10:100:1, PhH, 20°C, mol per mole
of the triketone)
a
Product
Yield
СО
2
1.80
t-BuOH
8.78
0.53
0.16
0.14
0.08
1.14
tert-Butyl benzoylacetate was identified among the
products, whereas neither free benzoylacetic acid nor
its methyl ester was detected. This means that
benzoylacetic acid is completely converted into aceto-
phenone. However, in keeping with the data given in
Table 2, the major oxidation product of 1,5-
diphenylpentane-1,3,5-trione (VI) is benzoic acid.
Moreover, the yield of carbon dioxide approaches
PhCOCH
3
PhC(O)OBu-t
PhC(O)OOBu-t
2
PhC(O)CH COOBu-t
PhC(O)OH
Averaged data.
2
mol per mole of the substrate. Therefore, apart from
a
processes described by Scheme 5, triketone VI is
oxidized at the second methylene group, which leads
to almost complete decomposition of the substrate.
Benzoic anhydride thus formed gives rise to benzoic
and peroxybenzoic acid esters.
methyl esters by IR spectroscopy. As follows from the
data in Table 1, the yields of esters and peroxy esters
are considerably lower than the yields of carboxylic
acids, which suggests alternative way of their
formation. Presumably, this alternative way is
hydrolysis of anhydrides and diacyl carbonates
As noted above, cyclohexane-1,3-dione is oxidized
with hydroperoxide II most readily in the presence of
complex I. It is known that cyclohexane-1,3-dione
exists preferentially in the enol form. At a substrate–t-
(
Scheme 4).
BuOOH–(acac) VO ratio of 10:40:1 (C H , 20°C) we
Scheme 4.
2
6
6
isolated 0.87 equiv of CO and 3.41 equiv of t-BuOH.
2
RC(O)O
RC(O)O
The titration of the reaction solution with 0.1 N NaOH
revealed 1.62 equiv of carboxy groups, i.e., carboxylic
acids are the major products. By analogy with acyclic
β-diketones (Schemes 1–4) we presumed formation of
pentanedioic acid as the major product, as well as its
tert-butyl ester and monoperoxy ester.
C
O + H O
2 RCOOH + CO2
2
This fact confirms the formation of water in the
oxidation of diketones to triketones (Scheme 1). In the
oxidation of triketone VI, apart from carbon dioxide
Scheme 5.
4
t-BuOOH, (acac) VO
2
PhCCH CCH CPh
PhC O
O
C
O
O
C
O
CH2 CPh
O
2
2
_4
t-BuOH,
_
O
O
O
H O
2
B
H O
_CO
2
2
PhCCH COOH + PhCOOH +CO
PhC O
O
C
CH2 CPh
2
2
O
O
O
t-BuOH
2
CO + PhCOCH3
PhCOOH + PhC(O)CH COOBu-t
2
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OXIDATION OF β-DICARBONYL COMPOUNDS WITH tert-BUTYL HYDROPEROXIDE
553
After treatment of the reaction solution with
diazomethane, we identified dimethyl pentanedioate
and methyl tert-butyl pentanedioate (0.26 and
cyclohexane-1,3-dione is not larger than 30%.
However, the high yield of CO suggests cleavage of
2
the cyclohexane ring. Apart from the above products,
acetaldehyde, ethyl acetate, methyl 2-methylbutanoate,
and methyl 5-oxotetrahydrofuran-2-carboxylate were
identified on a qualitative level, and other unidentified
compounds were detected. These findings indicate that
the oxidation of diketone VII involves methylene
groups in the ring (Scheme 6).
0
.05 equiv, respectively). We have synthesized an
authentic sample of tert-butyl monoperoxypentanedioate,
but this compound was not detected among the
oxidation products. The overall yield of pentanedioic
acid and its ester did not exceed 30%, indicating that
the contribution of the reaction of the ketone form of
Scheme 6.
O
COOH
(CH )
C
O
C
C
[
(acac) VO, t-BuOOH]
H O
2
2
CO +
O
2
2 3
C
O
O
COOH
t-BuOH
t-BuOOH
_
_
_
_
HOOC (CH ) COOBu-t
HOOC (CH ) C(O)OOBu-t
2 3
2
3
Analogous processes involving oxidation of methylene
group are typical of functionally substituted derivatives
having an oxo group in the β-position. We examined
the reaction of ethyl benzoylacetate (VIII) with
hydroperoxide II in the presence of vanadium complex
I (reactant molar ratio 10:40:1). In all cases the
products were benzoic acid, carbon dioxide, and ethyl
hydrogen oxalate. The amounts of the oxidation
products almost did not change upon variation of the
amount of the oxidant. The following products were
identified at a reactant ratio of 10:40:1, mol per mole
of VIII: t-BuOH, 3.70; ethanol, 0.07; CO , 0.26;
2
benzoic acid, 0.30; ethyl oxalate, 0.13; tert-butyl benzoate,
0.02; tert-butyl peroxybenzoate, 0.02. The formation of
these compounds may be rationalized assuming oxida-
tion of the methylene group in ethyl benzoylacetate to
give 3-phenyl-2,3-dioxopropionic acid ester and mixed
benzoic 2-ethoxy-2-oxoacetic anhydride (Scheme 7).
Scheme 7.
2
t-BuOOH
acac) VO
_
_
PhCCH COOEt
2 t-BuOH + H
2
O + PhC C COOEt
O O
2
(
2
O
t-BuOOH
_t-BuOH
_
_ _
PhC O C COOEt
O
O
We failed to isolate 3-phenyl-2,3-dioxopropionic
acid ester, but its formation followed from the IR data.
The IR spectrum of the nonvolatile residue, recorded
first of these belongs to ester VIII, and the other bands
together with the band at 1712 cm (C=O, ketone) may
be assigned to ethyl 3-phenyl-2,3-dioxopropionate.
–1
–
1
in the region 750–1750 cm , contained all absorption
bands intrinsic to the initial ester, but bands belonging
to stretching vibrations of the C(O)–O–C bonds (1146–
The formation of mixed anhydride was confirmed
by the identification of tert-butyl benzoate and tert-
butyl peroxybenzoate. Hydrolysis of that anhydride
yields benzoic acid and ethyl hydrogen oxalate. The
latter undergoes partial oxidation to carbon dioxide
and ethanol (Scheme 8).
–
1
1
265 cm ) were broadened, and their resolution was
impaired. In the region corresponding to carbonyl
stretching vibrations we observed two doublets at
–1
1
687/1682 (PhCO) and 1737/1733 cm [C(O)OR]. The
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 3 2011

5
54
STEPOVIK et al.
1:5 (benzene, 20°C, 20 h). We examined oxidation of
Scheme 8.
t-BuOOH
1,3-diphenylpropane-1,3-dione (V) with tert-butyl
hydroperoxide in the presence of vanadyl acetyl-
acetonate (I), as well as the reaction of V with the
_
HO(O)C C(O)OEt
HO(O)COC(O)OEt
_t-BuOH
system V(OBu-t) –t-BuOOH (molar ratio 1:1:6,
benzene, 20°C). Among the oxidation products we
2
CO + EtOH
4
2
Unlike β-diketones whose complete conversion
identified (mol per mole of V): t-BuOH, 7.50; CO ,
2
may be attained by choosing an appropriate t-BuOOH–
substrate ratio, up to 40% of initial ethyl benzoyl-
acetate remains unchanged even in the presence of
0.90; benzoic acid, 1.60; tert-butyl benzoate, 0.03; tert-
butyl peroxybenzoate, 0.07. The products isolated in
the reactions with vanadyl acetylacetonate and
vanadium tetra-tert-butoxide were identical, which
suggests common mechanism of their formation.
6
equiv of the oxidant. The latter is consumed almost
completely, but up to 30% of its amount is reduced to
t-BuOH and O2.
The reaction of (t-BuO) V [10] and (acac) VO [6]
4
2
With a view to elucidate the nature of oxidant for
the methylene group in β-dicarbonyl compounds we
used diketone V as model compound. Compound V
did not react with hydroperoxide II at a molar ratio of
with tert-butyl hydroperoxide (II) includes the
formation of vanadium-containing peroxides and
trioxides. The latter decompose both with liberation of
singlet oxygen and homolytically (Scheme 9).
Scheme 9.
а
1
_
O + [V] OBu-t
2
t-BuOOH
_t-BuOH
b
_
_
_
[
V] OOBu-t
[V] OOOBu-t
[V] O + OOBu-t
c
_
[
V] OO + OBu-t
In the presence of oxygen-centered radical species
singlet oxygen is converted into triplet [11]. Oxidation
to be one of the best oxidants for secondary alcohols
[12].
of C–H bonds in the system (t-BuO) V–t-BuOOH with
4
Homolytic character of the oxidation of methylene
group is confirmed by the ESR data. The oxidation of
dibenzoylmethane (PhCO) CH with vanadyl acetyl-
oxygen (Scheme 9, path a) is initiated by oxygen-
centered radicals and follows homolytic pattern [10].
Taking into account published data and our results, we
presumed that in the reactions under study methylene
group is oxidized to carbonyl by the action of oxygen
2
2
acetonate (I)–t-BuOOH and (t-BuO) V–t-BuOOH was
4
studied by ESR spectroscopy in the presence of N-
benzylidene-tert-butylamine N-oxide (C-phenyl-N-
tert-butylnitrone, (PBN) as spin trap. In both cases, the
generated by reaction of (acac) VO with t-BuOOH [6].
2
The formation of trioxo derivatives may be illustrated
by Scheme 10.
ESR spectra were identical: they were a triplet of
15
doublets with hyperfine coupling constants a ( N) =
i
Dibenzoylmethanol should be transformed into
1.32 mT, a (H) = 0.152 mT, g = 2.0060 (see figure). In
i
i
ketone, for the system (acac) VO–t-BuOOH is known
the case of (t-BuO) V the signal appeared immediately
2
4
Scheme 10.
XO
_XOH
O2
(
PhCO) CH
(PhCO) CH
(PhCO) CHOO
2
2
2
2
0
.5 (PhCO) C=O + 0.5 (PhCO) CHOH + O
2 2 2
(
PhCO) CHOO
2
CH2
(
PhCO) CHOOH
(PhCO) CO + H O
2 2
2
·
·
·
·
X = [V]–OO ; t-BuOO ; [V]–O ; t-BuO .
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 3 2011

OXIDATION OF β-DICARBONYL COMPOUNDS WITH tert-BUTYL HYDROPEROXIDE
555
after mixing of the reactants, whereas in the reaction
with (acac) VO, the signal appeared in 25 min. After
1
2
1
2
1
1
2
1 1
2
1
h, its intensity increased, indicating its generation
with time. Insofar as the observed hyperfine coupling
constants differed from those typical of PBN adducts
·
with tert-butylperoxy radicals [13, 14] and V(O)OO
[10], we believe that the spectrum belongs to the
adduct of PBN with peroxy radical derived from the
substrate. After some time, a minor triplet signal
(
2
1:1:1) appeared, whose isotropic parameters [g =
i
1
5
.0069, a ( N) = 0.790 mT] corresponded to benzoyl-
i
·
Н
tert-butylnitroxyl radical PhC(O)N(O )Bu-t. The latter
was formed as a result of oxidation of PBN with
singlet oxygen or peroxy radicals [15].
0
.5 mT
2 2 2
ESR spectrum of (PhCO) CH –t-BuOOH–(acac) VO (1:5:0.1)
in benzene in the presence of PBN, recorded at 20°C in
20 min after mixing the reactants (degassed sample):
OOCH(COPh)2
·
·
2
(1) (PhCO) CHOOCH(Ph)N(Bu-t)O , (2) PhC(O)N(Bu-t)O .
_
_ _
Ph C N Bu-t
the amount of hydroperoxide necessary for complete
conversion of β-diketone always exceeds its stoi-
chiometric amount. Incomplete conversion of ethyl
benzoylacetate may be rationalized in terms of com-
petition between generation of oxygen and oxidation
of the methylene group in the substrate.
H O
Apart from Scheme 10 proposed for the oxidation
of methylene group, nucleophilic addition of tert-butyl
hydroperoxide or vanadium-containing peroxy com-
pound at the carbonyl group of the substrate and
subsequent transformation into triketone [6] cannot be
ruled out. With a view to verify whether the latter path
is possible diketone V was brought into reaction with
N-(2-oxidophenyl)salicylideneaminato(tert-butylperoxo)-
vanadyl (IX) (1:2, methylene chloride, 20°C). It is
known that peroxy compounds of this type act as
hydroxylating agents toward aliphatic and aromatic
compounds [16]. In the reaction of peroxide IX with
It should be noted that systems based on t-BuOOH
and chromium(III) and cobalt(II) acetylacetonates,
which also generate oxygen, do not oxidize 1,3-di-
phenylpropane-1,3-dione. Coordinately unsaturated
(acac) Co is likely to form a complex with diketone V,
2
resulting in sharp deceleration of the reaction between
components of the oxidizing system.
diketone V (2 days) we isolated 0.72 equiv of CO and
2
We can conclude that tert-butyl hydroperoxide in
the presence of vanadyl acetylacetonate (I) is an effect-
tive oxidant toward β-dicarbonyl compounds. The oxida-
tion process involves the decomposition of the sub-
strate carbon skeleton, the formation of carboxylic
acids, and the liberation of carbon dioxide. Complex I
catalyzes these reactions. Oxidation of methylene group
to carbonyl with the formation of trioxo com-pounds
follows mainly homolytic pattern according to
Schemes 9 and 10. The subsequent nucleophilic reac-
tion of trioxo compounds with tert-butyl hydro-
peroxide or vanadium-containing peroxides leads to
oxidative cleavage of carbon–carbon bonds, yielding
final products through the corresponding carboxylic
acid anhydrides.
0
.56 equiv of benzoic acid, whereas neither benzoic
nor peroxybenzoic acid ester was detected. The
process was fairly complicated; the oxidation was
likely to be accompanied by decomposition of the
peroxide and formation of tarry products that were
insoluble in diethyl ether and arenes; therefore, we
failed to perform complete qualitative analysis of the
products. No signals were observed in the ESR spectra
both in the absence and in the presence of spin traps
[tert-butylnitrone, C-phenyl-N-tert-butylnitrone]. Thus
the results of the reaction of dibenzoylmethane with
peroxide IX indicated that vanadium-containing
peroxy compounds can participate in the oxidation of
C–H bond, but this reaction direction is minor.
Free oxygen (~20%, calculated on the initial
amount of the hydroperoxide) was detected in addition
to the oxidation products of diketone V given in
Table 1. Liberation of oxygen was also observed in the
reaction with vanadium tetra-tert-butoxide. Therefore,
EXPERIMENTAL
The IR spectra were recorded in KBr or from thin
films on an IR-Prestige-21 spectrometer. The ESR
spectra were obtained on a Bruker ER-200D-SRC
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 3 2011

5
56
STEPOVIK et al.
spectrometer equipped with an ER 4105DR double
resonator (operating frequency ~9.5 GHz) and ER
the mixture until barium carbonate no longer se-
parated. The precipitate of BaCO was filtered through
3
4
111VT temperature control unit. Diphenylpicrylhyd-
a glass frit and dried at 100°C until constant weight.
razyl (DPPH) was used as reference for the
determination of g factor. Analysis was performed in
the probe of the ESR spectrometer. The reaction
solutions were preliminarily degassed to improve
resolution and remove oxygen generated by reaction of
compounds I and II. The concentration of vanadyl
acetylacetonate (I) did not exceed 0.005 M.
Vanadyl acetylacetonate (I) was synthesized from
V O via successive treatment with freshly distilled
2
5
acetylacetone and with a solution of sodium carbonate
19]; mp 252°C [20]. Pentane-2,3,4-trione was pre-
pared by oxidation of pentane-2,4-dione with p-
nitroso-N,N-dimethylaniline; bp 55–57°C (12 mm)
[
[
21]. Vanadium tetra-tert-butoxide was synthesized by
Chromatographic analysis of liquid products was
performed on a Tsvet-160 chromatograph equipped
with a flame ionization detector; carrier gas argon;
sorbent Chromaton N-AW-DMCS. Volatile com-
ponents (tert-butyl alcohol, ethanol, pentane-2,4-dione,
methyl acetate) were analyzed using a 2400×3-mm
column packed with 10% of poly(ethylene glycol)
adipate on TZKM fire-brick, oven temperature 50–80°C).
tert-Butyl acetate and tert-butyl peroxyacetate were
analyzed using a 3000×3-mm column; stationary
phase 5% SP-2401, oven temperature 50°C. Car-
boxylic acid ester (methyl benzoate, tert-butyl benzo-
ate, isopropyl benzoate, ethyl methyl oxalate), aceto-
phenone, etc. were identified on a 1200×3-mm column;
stationary phase 15% of Apiezon, oven temperature
exchange reaction of vanadium trichloride and lithium
tert-butoxide at a ratio of 1:2 in hexane, followed by
heating for 2 h under reflux. Removal of the solvent
and subsequent vacuum distillation gave V(OBu-t) as
4
a dark blue liquid, which was very sensitive to
atmospheric oxygen and moisture; bp 89–90°C (1 mm)
[22]. N-(2-Oxidophenyl)salicylideneaminato(tert-butyl-
peroxo)vanadyl was obtained by successive treatment
of (i-PrO) VO with N-salicylidene-2-aminophenol and
3
tert-butyl hydroperoxide [23]; the complex was
isolated as dark brown crystals which were stable at 2–
10°C; its activity was 99%. Found: O 4.29%.
act
C H NO V. Calculated: O 4.36%. The IR spectrum
1
7
18
5
act
of the complex was identical to that reported pre-
viously. The concentration of tert-butyl hydroperoxide
was no less than 99.6–99.8%. The following com-
mercial reagents were used: 1-phenylbutane-1,3-dione
(98%, Acros Organics), 1,5-diphenylpentane-1,3,5-
trione (≥98%, Fluka), 1-phenylbutane-1,3-dione
(>98%, Fluka), ethyl benzoylacetate (95%, Fluka),
cyclohexane-1,3-dione (97%, Alfa Aesar).
1
35–150°C. Ethyl benzoyl acetate was determined
using a 1200×3-mm column packed with 5% of OV-
7 on Inerton Super; oven temperature 165–170°C.
1
The components were quantitated by the external
standard technique using authentic samples in each case.
The amount of aliphatic acids in nonvolatile
residues was determined according to the procedure
described in [17]. Carboxylic acids were identified as
methyl esters after treatment with diazomethane.
Quantitative analysis of hydroperoxides was
performed by iodometric titration. Carbonyl com-
pounds were identified as 2,4-dinitrophenylhydrazones
by the melting point and by TLC using authentic
samples [Silpearl, Silufol UV-254; benzene or
benzene–diethyl ether (18:1)]. The amount of liberated
oxygen was determined by the weight of benzoic acid
formed by reaction of oxygen with benzaldehyde [18].
In order to determined the amount of carbon dioxide,
the oxidation of β-diketones was carried out in a two-
necked flask equipped with a reflux condenser. The
latter was connected sequentially to two gas-washing
bottles charged with a saturated solution of Ba(OH)2.
The system was preliminarily evacuated and filled
with argon. The flask was charged with a mixture of
reactants, and argon was passed periodically through
Oxidation of pentane-2,4-dione with (acac) VO–
2
t-BuOOH (15:1:60) in benzene. A flask was charged
with 0.04 g of vanadyl acetylacetonate (I), 0.24 g of
acetylacetone, and 0.86 g of t-BuOOH in 20 ml of
benzene. After 15 min, the mixture spontaneously
warmed up, and evolution of CO started. After 14 h,
2
the amount of BaCO was 0.42 g (0.09 g of CO ). The
3
2
solvent was distilled into a trap cooled with liquid
nitrogen. Chromatographic analysis of the distillate
showed the presence of 0.57 g of t-BuOH, 0.002 g of
tert-butyl peroxyacetate, and 0.01 g of tert-butyl
acetate and, after treatment with diazomethane, 0.23 g
of methyl acetate. The amount of acetic acid (0.19 g)
was also confirmed by titration of the distillate with a
0.1 N solution of NaOH. According to the TLC data,
the volatile products before and after treatment with
diazomethane contained pyruvic acid and its methyl
ester (identified as the corresponding 2,4-dinitro-
phenylhydrazones).
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OXIDATION OF β-DICARBONYL COMPOUNDS WITH tert-BUTYL HYDROPEROXIDE
557
0.33 g, was added to 0.033 g of (acac) VO in 15 ml of
2
Reaction of 1,3-diphenylpropane-1,3-dione with
(
acac) VO–t-BuOOH (10:1:50). A flask was charged
benzene. The originally greenish–blue solution turned
dark green in a few minutes, indicating formation of a
vanadyl complex with triketone VI. tert-Butyl
hydroperoxide, 1.13 g, was then added, and the solu-
tion immediately turned wine red due to formation of
either vanadium complexes with hydroperoxide or
vanadium peroxo compounds. The reaction mixture
was kept for 20 h. During that time, the main amount
of carbon dioxide liberated. When the liberation of CO2
was complete, the solution became transparent and
2
with 0.034 g of (acac) VO, 0.28 g of diketone V, and
0
(
solution turned red–brown, and no solid separated. The
amount of BaCO was 0.22 g (0.049 g of CO ). The
solvent was recondensed into a trap; the condensate
contained 0.43 g of tert-butyl alcohol and 0.01 g of
tert-butyl benzoate (according to the GLC data).
2
.56 g of tert-butyl hydroperoxide in 12 ml of benzene
20°C). After 20 h, the originally violet–red transparent
3
2
In a parallel run, the concentrations of tert-butyl
peroxybenzoate and benzoic acid in the reaction
solution were determined before removal of volatile
products. The amount of tert-butyl peroxybenzoate
orange–red. We isolated 0.38 g of BaCO (0.084 g of
3
CO ). According to the GLC data, the reaction solution
2
contained 0.78 g of t-BuOH, 0.075 g of acetophenone,
0
.034 g of tert-butyl benzoate, and 0.022 g of tert-
was determined by reaction with (i-PrO) Al [24]. For
3
butyl benzoylacetate. tert-Butyl benzoylacetate was
identified by IR spectroscopy, and its amount was
determined by chromatography (by ethyl benzoyl-
acetate). Treatment of a part of the reaction solution
with 2,4-dinitrophenylhydrazine gave acetophenone
this purpose, a sample of the reaction mixture was
treated with excess aluminum triisopropoxide, and the
resulting mixture was heated for 10 h at 70°C in a
sealed ampule. By chromatography we determined
0
0
.01 g of isopropyl benzoate, which corresponds to
.012 g of tert-butyl peroxybenzoate. Acetone was
2
,4-dinitrophenylhydrazone, mp 246–247°C (the same
for mixed sample). Treatment of a sample withdrawn
from the solution with aluminum triisopropoxide gave
0.03 g of isopropyl benzoate, which corresponds to
0.038 g of tert-butyl peroxybenzoate. The amount of
benzoic acid (0.17 g) was determined from the weight
of methyl benzoate (0.194 g) obtained by treatment of
the reaction solution with diazomethane. Benzoyl-
formic acid (a possible dibenzoylacetone oxidation
products) was not detected as methyl ester.
identified by TLC as 2,4-dinitrophenylhydrazone.
Benzoic acid was determined as follows. A part of
the reaction solution was treated with 10% sulfuric
acid, the organic phase was separated, and the aqueous
acid layer was thoroughly extracted with diethyl ether.
The extracts were combined with the organic phase,
dried over Na SO , and treated with diazomethane.
2
4
The amount of methyl benzoate was 0.28 g.
The reaction was also accompanied by liberation of
oxygen which was determined according to the
procedure described in [18]. The reaction was carried
out in an H-shaped ampule, one arm of which was
charged with 0.2 ml of benzaldehyde, and the other,
In a special experiment, when evolution of carbon
dioxide terminated, benzene and volatile products were
condensed in a trap cooled with liquid nitrogen. The
residue was a thick greenish–brown material including
white crystals. It was hydrolyzed with a 10% solution
of sulfuric acid and extracted with freshly distilled
diethyl ether. The amount of tert-butyl peroxybenzoate
in the extract was determined by iodometric titration in
with 0.013 g of (acac) VO, 0.22 g of tert-butyl-
2
hydroperoxide, and 0.11 g of 1,3-diphenylpropane-1,3-
dione in 5 ml of benzene. The contents of both arms
were frozen, and the ampule was degassed and sealed.
Evolution of oxygen was observed upon defrosting,
and the reaction solution turned cherry red. After
2
+
the presence of Fe .
Oxidation of ethyl benzoylacetate with (acac) VO–
2
2
days, the ampule with benzoic acid was sealed off,
t-BuOOH (10:1:60). The reaction mixture consisted
and excess benzaldehyde was removed. The amount of
benzoic acid was determined by weighing, as well as
by titration with a 0.1 N solution of sodium hydroxide
in the presence of phenolphthalein. The amount of
benzoic acid was 0.08 g, which corresponded to
of 0.033 g of (acac) VO, 0.25 g of ester VIII, and
2
0
.71 g of t-BuOOH in 10 ml of benzene. After 20 min,
the originally crimson solution turned red, and after
h, orange. We isolated 0.066 g of BaCO . The
1
3
reaction solution contained 0.47 g of t-BuOH, 0.004 g
of ethanol, 0.005 g of tert-butyl benzoate, 0.007 g of
tert-butyl peroxybenzoate, and 0.105 g of unreacted
ester VIII.
0
.010 g of oxygen.
Reaction of 1,5-diphenylpentane-1,3,5-trione with
(
acac) VO–t-BuOOH (10:1:100). Triketone VI,
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 3 2011

5
58
STEPOVIK et al.
Freidin, B.G., Zh. Prikl. Khim., 1984, vol. 57, no. 7,
After treatment with diazomethane, 0.042 g of
p. 1830.
methyl benzoate (0.038 g of PhCOOH) and 0.02 g of
ethyl methyl oxalate (0.018 g of ethyl hydrogen
oxalate) were determined. When the benzene solution
was kept for about 2 days at room temperature, it
turned light yellow. A blue solid separated at the
bottom of the flask; in keeping with published data, it
was vanadium(IV) oxide.
8. Perkel’, A.L. and Freidin, B.G., Zh. Prikl. Khim., 1979,
vol. 52, no. 8, p. 1829.
9
. Stepovik, L.P., Dodonov, V.A., and Smyslova, T.N., Zh.
Obshch. Khim., 1992, vol. 62, no. 1, p. 123.
1
0. Stepovik, L.P., Gulenova, M.V., Tishkina, A.N., and
Cherkasov, V.K., Russ. J. Gen. Chem., 2007, vol. 77,
no. 7, p. 1254.
The reactions of 1-phenylbutane-1,3-dione and
11. Moiseev, I.I., Gekhman, A.E., Minin, V.V., and Larin, G.M.,
cyclohexane-1,3-dione with tert-butyl hydroperoxide
in the presence of (acac) VO, as well as the oxidation
with (t-BuO) V–t-BuOOH, were carried out in a
Kinet. Katal., 2000, vol. 41, no. 2, p. 191.
12. Kaneda, K., Kawanishi, Y., Jitsukawa, K., and Teranishi, S.,
2
4
Tetrahedron Lett., 1983, vol. 24, no. 45, p. 5009.
similar way, and the products were analyzed as
described above. In the oxidation of benzoylacetone,
acetic and benzoic acids in the condensed volatile
fraction and in the hydrolyzate of nonvolatile residue,
respectively, were analyzed as methyl esters after
treatment with diazomethane. The amounts of tert-
butyl peroxyacetate and tert-butyl peroxybenzoate
were determined from the amounts of the
corresponding isopropyl esters and acetone after
treatment of the reaction solution with aluminum
triisopropoxide.
1
3. Stepovik, L.P., Martynova, I.M., Dodonov, V.A., and
Cherkasov, V.K., Izv. Ross. Akad. Nauk, Ser. Khim.,
2002, no. 4, p. 590.
14. Merritt, M.V. and Johnson, R.A., J. Am. Chem. Soc.,
1977, vol. 99, no. 11, p. 3713.
15. Zubarev, V.E., Metod spinovykh lovushek. Primenenie v
khimii, biologii, meditsine (Spin Trap Technique.
Applications in Chemistry, Biology, and Medicine),
Moscow: Mosk. Gos. Univ., 1984.
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6. Conte, V., Di Furia, F., and Licini, G., Appl. Catal. A:
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7. Bauer, K.H., Die organische Analyse, Leipzig: Geest
1
and Portig, 1950, 2nd ed. Translated under the title
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