Colloid and nanosized catalysts in organic synthesis: V. Reactions of alkyl halides and alcohols with ?2-diketones in the presence of metal nanoparticles

Article abstract of DOI:10.1134/S1070363214080076

Reaction of copper, nickel, and iron nanoparticles with ?2-diketones directly yields corresponding metal ?2-diketonates. Reaction of alkyl halides, ?2-diketones, and nanodispersed metals leads to a mixture of monoketone and the alkylated ?2-diketone. When alcohol is used as the alkylating agent instead of alkyl halide, corresponding ester is formed.

Full text of DOI:10.1134/S1070363214080076

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 8, pp. 1491–1495. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © Yu.V. Popov, V.M. Mokhov, 2014, published in Zhurnal Obshchei Khimii, 2014, Vol. 84, No. 8, pp. 1263–1267.
Colloid and Nanosized Catalysts in Organic Synthesis:
1
V. Reactions of Alkyl Halides and Alcohols with β-Diketones
in the Presence of Metal Nanoparticles
Yu. V. Popov and V. M. Mokhov
Volgograd State Technical University, pr. Lenina 28, Volgograd, 400131 Russia
e-mail: tons@vstu.ru
Received January 16, 2014
Abstract—Reaction of copper, nickel, and iron nanoparticles with β-diketones directly yields corresponding
metal β-diketonates. Reaction of alkyl halides, β-diketones, and nanodispersed metals leads to a mixture of
monoketone and the alkylated β-diketone. When alcohol is used as the alkylating agent instead of alkyl halide,
corresponding ester is formed.
Keywords: catalysis, nanoparticle, alkylation, β-diketone, alcohol, alkyl halide, ester
DOI: 10.1134/S1070363214080076
β-Diketones are widely used as core reagents for
preparation of drugs, dyes, and certain heterocyclic
compounds. The reported methods of β-diketones
alkylation include reaction of metal diketonates with
alkyl halides [2] and direct alkylation of β-diketones
with strained propellane hydrocarbons [3, 4]. The both
approaches suffer from serious drawbacks: the first
method implies additional stage of the β-diketonate
preparation, whereas limited choice of alkylating agents
is available for the second method. In view of the
above, development of β-diketones modification
methods is of primary importance.
To the best of our knowledge, direct interaction of
metal nanoparticles with 2,4-pentanedione was not
previously reported. However, our experiment revealed
that reaction of nanodispersed copper with 2,4-pen-
tanedione resulted in formation of almost stoi-
chiometric amount of copper pentadionate. We found
that the described reaction occurred in the cases of
other transition metal nanoparticles, in particular,
nickel, cobalt, and iron. In the presence of nickel, the
reaction proceeded readily without heating.
From the point of view of selectivity and simplicity,
the reported method is advantageous over the tradi-
tional methods of metals acetylacetonates synthesis in
the presence of bases and solvents upon prolonged
heating [5, 6]. In the case of the reported reaction with
metal nanoparticles, the reaction was complete in 5
(Ni) to 30 (Cu) min. The yields were close to
quantitative, and no additional reagents were needed.
Previously we demonstrated that reaction of 1-bromo-
adamantane with 2,4-pentanedione in the presence of
equimolar amount of copper nanoparticles yielded 3-
(
adamant-1-yl)pentate-2,4-dione. We suggested that
the reaction proceeded through formation of copper
,4-pentadionate intermediate. In order to support this
2
suggestion, in this work we attempted the reaction of
nanodispersed copper with 2,4-pentanedione. Violent
reaction with gas evolution occurred upon heating of
the components (the β-diketone being in excess) above
Pure copper(II) 2,4-pentadionate was isolated and
introduced into the reaction with 1-bromoadamantane
(
Scheme 1).
1
00ºC.
The reaction was complete within 12 h, and 3-
adamant-1-ylpentan-2,4-dione was formed with 64%
yield. Chromatography–mass spectrometry of the
product confirmed formation of 1-adamantylacetone as
side product. Properties of the isolated products
coincided with the reference data [7, 8]. Structure of 3-
o
O
O
110 C
O
O
O
O
+ Cuo
2
Cu
+ H2
1
For communication IV, see [1].
1
491

1
492
POPOV, MOKHOV
Scheme 1.
o
O
O
O
O
140 C
+
Cu
+
Br
O
O
O
Scheme 2.
O
O
o
1
40 C
O
O
+ Cuo
R
R Hlg +
R
+
O
Iа−Ic
IIа−IIc
R = 1-adamantyl , Hlg = Br (а); R = benzyl, Hlg = Cl (b); R = 1-octyl, Hlg = I (c).
Scheme 3.
O
O
O
o
o
o
o
Cu (Ni , Co ), 110 C
ROH +
R + CH C(O)CH
3 3
O
IVа−IVd
Vа−Vd
R = 1-hexyl (а), 1-octyl (b), cyclohexyl (c), benzyl (d).
adamant-1-ylpentan-2,4-dione was further confirmed
formation mechanism are outside the scope of this
paper and will be reported separately.
1
by H NMR spectroscopy.
Further, we carried out the reactions of 2,4-pentane-
dione with 1-bromoadamantane or benzyl chloride in
the presence of nickel nanoparticles. 3-(Adamant-1-yl)-
pentan-2,4-dione (IIa) and 2-benzylpentan-2,4-dione
To our knowledge, we were the first to conduct the
one-pot reaction between alkyl halide, 2,4-pentane-
dione, and nanodispersed copper, without the prior
formation of copper 2,4-pentanedionate. The one-pot
synthesis significantly simplified alkylation of β-diketones,
but it was necessary to investigate the possibility of the
Wurtz reaction between the alkyl halide and metal
under the reaction conditions. 1-Bromoadamantane,
benzyl chloride, and 1-iodoctane were used as
alkylating agents. The reaction was carried out at the
(IIb), respectively, were obtained, and their structures
1
were confirmed by H NMR and mass spectrometry. It
was found that in the case of nickel nanoparticles the
diketone was the major product (up to 77 wt %), but
total yield of the reaction products was somewhat
lower than in the presence of copper nanoparticles.
3
1
-fold molar excess of 2,4-pentanedione for 8–12 h at
10–140ºC (Scheme 2).
Previously it was shown that metal nanoparticles
catalyzed alkylation of ketones with alcohols [9, 10].
As alcohols are generally better available than the
corresponding alkyl halides, we attempted alkylation
of 2,4-pentanedione with alcohols.
The reaction resulted in formation of 3-alkyl(aralkyl)-
,4-pentanediones Ia–Ic mixtures with the cor-
2
responding 1-alkyl(aralkyl)propan-2-ones IIa–IIc. The
product ratio varied from 1 : 9 to 1 : 1, the total yield
reaching 80 mol %. No significant amounts of the
Wurtz reaction products were isolated.
Reaction of alcohols with 2,4-pentanedione in the
presence of transition metal nanoparticles was carried
out at 110ºC; the volatile product distilled off in the
course of the reaction was identified as acetone. The
only reaction products were acetates Va–Vg, instead of
the expected dicarbonyl compounds (Scheme 3).
1
-Adamantylpropan-2-one (IIa), 4-phenylbutan-2-
one (IIb), and undecan-2-one (IIc) were apparently
formed due to decomposition of the target diketones
under the reaction conditions. Optimization of the
reaction conditions and elucidation of the side products
The above-described reaction is not convenient to
prepare the corresponding esters, but it is peculiar from
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COLLOID AND NANOSIZED CATALYSTS IN ORGANIC SYNTHESIS: V.
1493
the fundamental point of view. According to the
referenced procedures, such reactions of β-diketones
proceed at 150-250ºC or for up to 100 h at 60ºC in the
presence of large excess of alkali or hydrogen chloride
mantan-1-yl)pentan-2,4-dione Ia, bp 222–224ºC
1
(20 mmHg), mp 89–91ºC (mp 90ºC [7]). H NMR
spectrum, δ, ppm: 1.55–1.64 m (12H, 6CH ), 1.92 s
2
(3H, 3CH), 2.07 s (6H, 2CH CO), 3.3 s [1H, CH(CO) ].
2
2
(
the catalyst to diketone molar ratio of ≥ 1 : 1) [11, 12].
Mass spectrum (electron ionization, 70 eV), m/e (I ,
rel
+
+
In this work we utilized Ni, Co, and Cu nanoparticles
without any other catalyst, and the reaction time was of
%): 234 [M] (6), 192 [M – CH – CO] (9), 149
3
+
+
[AdCH ] (6), 135 [Ad] (100).
2
8
h at 110ºC. The esters Va–Vd were formed with
b. A mixture of 10 g (0.038 mol) of copper(II)
acetylacetonate, 15 g (0.07 mol) of 1-bromoada-
mantane, and 10 g (0.1 mol) of 2,4-pentanedione was
heated at 130–140ºC for 10 h. The reaction product
was isolated as described in procedure a to give 8.2 g
(0.035 mol, 45%) of 3-(adamantan-1-yl)pentan-2,4-
dione Ia. The product parameters were identical to
those of the compound obtained via procedure a.
yield up to 98%. Nickel and cobalt nanoparticles were
more active catalysts of the reaction than copper ones.
We suggest that due to the high reactivity, the metal
nanoparticles could directly react with alcohols to give
0
the alcoholates: 2ROH + M = (RO) M + H . Further
2
2
reaction stages were similar to the mechanism of
alcoholysis in the presence of alkali [11]. Evidently,
such transformations resulted in formation of acetone
and the corresponding esters.
6
.3 g (0.033 mol, 47%) of adamantan-1-yl-propan-
2
-one IIa was isolated in the course of the reaction
2
0
To conclude, in this work we have reported for the
first time that alkyl halides react with β-diketones in
the presence of nanodispersed metals to give the
alkylation products. The reaction of alcohols with β-
diketones in the presence of metal nanoparticles yields
corresponding esters.
mixture distillation. bp 150–53ºC (20 mmHg), n
D
2
0
1
.5016 {bp 102–104ºC (2 mmHg), n 1.5011 [14]}.
D
Mass spectrum (electron ionization, 70 eV), m/e
+
+
+
(
(
I , %): 192 [M] (8), 149 [AdCH ] (5), 135 [Ad]
rel
2
100).
c. A mixture of 3 g (0.051 mol) of nickel nano-
EXPERIMENTAL
particles and 20 g (0.20 mol) of 2,4-pentanedione was
heated for 1 h at 110ºC. Then 21.5 g (0.1 mol) of 1-
bromoadamantane was added, and the resulting
mixture was heated for 12 h at 130–140ºC. The
reaction product was isolated as described in procedure
a to give 15.4 g (0.066 mol, 66%) of 3-(adamantan-1-
yl)pentan-2,4-dione Ia. The product parameters were
identical to those of the compound obtained via
procedure a.
1H NMR spectra were recorded using the Varian
Mercury 300 spectrometer (300 MHz, CCl solution,
4
HMDS or TMS as the internal reference). Chromato-
graphy–mass spectral analysis was carried out with the
Varian Saturn 2100T/GC3900 device.
Copper(II) acetylacetonate. 3.4 g (0.053 mol) of
copper nanoparticles and 25 mL (0.244 mol) of 2,4-
pentanedione were heated at 110ºC for 1 h. Then the
reaction mixture was filtered, excess of 2,4-pentane-
dione was distilled off, and the solid product was dried
to give 13.7 g (0.052 mol, 99%) of copper acetyl-
acetonate. mp 284–286ºC, decomp. (286ºC, decomp.
3
-Benzylpentan-2,4-dione (Ib). a. A mixture of
.5 g (0.055 mol) of copper nanoparticles and 17 g
0.17 mol) of 2,4-pentanedione was heated for 1 h at
10ºC. Then 7 g (0.055 mol) of benzyl chloride was
added, and the resulting mixture was heated for 8 h at
30-140ºC. The reaction product was isolated as
described in preparation of Ia to give 5.75 g (0.03 mol,
5%) of 2-benzylpentan-2,4-dione Ib, bp 175–178ºC
3
(
1
[
13]).
-(Adamantan-1-yl)pentan-2,4-dione (Ia). a. A mix-
ture of 3.7 g (0.058 mol) of copper nanoparticles, 24 g
0.24 mol) of 2,4-pentanedione, and 10 g (0.046 mol)
of 1-bromoadamantane was heated for 6 h at 100–
40ºC. Then the reaction mixture was cooled down,
1
3
5
(
1
(
25 mmHg) {bp 150–154ºC (15 mmHg) [15]}. H
NMR spectrum, δ, ppm: 2.02 s (6H, 2CH CO), 2.78 d
3
1
(
2H, CH ), 3.57 s (0.2H, CH of the keto form), 7.06–
2
treated with 10 wt % aqueous sulfuric acid, stirred, and
filtered. The filtrate was extracted with diethyl ether
and washed with water. The ether and excess of 2,4-
pentanedione were distilled off from the organic
fraction, and the product was isolated by vacuum
distillation to give 7 g (0.03 mol, 65%) of 3-(ada-
7
.50 m (5H, C H ), 9.76 br.s (0.8H, OH of the enol
6
5
form).
8.1 g (0.055 mol, 43%) of 4-phenylbutan-2-one IIb
was isolated in the course of the reaction mixture
1
distillation. bp 234–236ºC (bp 235ºC [16]). H NMR
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 8 2014

1
494
POPOV, MOKHOV
0.83 t (3H, CH J 12 Hz), 1.24 m (10H, 5CH ), 1.53 m
spectrum, δ, ppm: 1.90 s (2H, CH ), 2.53 t (2H, CH , J
3
2
3,
2
1
4.4 Hz ), 2.70 t (2H, CH , J 14.2 Hz), 6.92–7.08 m
(2H, CH ), 1.89 s (3H, CH COO), 3.91 t (2H, CH O, J
2
2
3
2
(
5H, C H ).
13.5 Hz).
6
5
b. A mixture of 3 g (0.051 mol) of nickel nano-
Cyclohexyl acetate (Vc). a. Prepared similarly
from 6.4 g (0.1 mol) of copper nanoparticles, 14.6 g
(0.146 mol) of 2,4-pentanedione and 9.6 g (0.096 mol)
of cyclohexanol. Yield 9.8 g (0.068 mol, 71%), bp
particles and 10 mL (0.098 mol) of 2,4-pentanedione
was heated for 1 h at 110ºC. Then 11.5 mL (0.1 mol)
of benzyl chloride was added, and the resulting
mixture was heated for 8 h at 130–150ºC. The reaction
product was isolated as described in procedure a to
give 3-benzylpentan-2,4-dione Ib; yield 36%, bp 175–
1
175–177ºC (173ºC [19]). H NMR spectrum, δ, ppm:
1.17–1.31 m (6H, 3CH ), 1.71 m (4H, 2CH ), 1.89 s
2
2
(3H, CH COO), 4.58 c (1H, CH–O).
3
1
78ºC (10 mmHg).
-n-Octylpentan-2,4-dione (Ic). A mixture of 7 g
0.109 mol) of copper nanoparticles and 40 g (0.4 mol)
of 2,4-pentanedione was heated for 1 h at 110ºC. Then
7.6 g (0.198 mol) of 1-iodooctane was added, and the
b. Prepared similarly from 3 g (0.051 mol) of nickel
nanoparticles, 12 g (0.12 mol) of 2,4-pentanedione,
and 10.8 g (0.1 mol) of cyclohexanone. Yield 10.5 g
(0.073 mol, 73%), bp 175–177ºC.
3
(
4
Benzyl acetate (Vd). a. Prepared similarly from
resulting mixture was heated for 8 h at 120–130ºC.
The reaction product was isolated as described in
preparation of Ia to give 28.6 g (0.135 mol, 68%) of 3-
n-octylpentan-2,4-dione Ic, bp 145–146ºC (10 mmHg)
3
g (0.051 mol) of cobalt nanoparticles, 12 g (0.12 mol)
of 2,4-pentanedione, and 10.8 g (0.1 mol) of benzyl
alcohol. Yield 14.7 g (0.098 mol, 98%), bp 210–212ºC
1
(
213.5ºC [18]). H NMR spectrum, δ, ppm: 1.85 s (3H,
{
(
145–148ºC (11 mmHg) [17]}. Mass spectrum
CH COO), 4.91 s (2H, CH O), 7.09–7.17 m (5H, C H ).
3
2
6
5
electron ionization, 70 eV), m/e (I , %): 197 [M –
rel
+
+
+
CH ] (1), 183 [M – C H ] (2), 169 [M – C H ] (2),
b. Prepared similarly from 3 g (0.051 mol) of nickel
nanoparticles, 12 g (0.12 mol) of 2,4-pentanedione,
and 10.8 g (0.1 mol) of benzyl alcohol. Yield 14.5 g
(0.097 mol, 97%), bp 209–213ºC.
3
2
5
3
7
+
+
1
55 [M – C H ] (2), 127 [M – C H ] (1), 113 [M –
4
9
6
13
+
+
C H ]
(2), 71 [CH COCH CH ]
(100), 57
7
15
3
2
2
+
+
[
CH COCH ] (70), 43 [CH CO] (26).
3
2
3
4
.8 g (0.029 mol, 15%) of n-undecan-2-one IIc was
ACKNOWLEDGMENTS
isolated in the course of the reaction mixture
The work was financially supported by Ministry of
Science and Education of Russian Federation in the
scope of the basic part of Governmental contract no.
1
distillation. bp 221–223ºC (bp 226ºC [18]). H NMR
spectrum, δ, ppm: 0.83 t (3H, CH J 11.4 Hz), 1.11-
3
,
1
.51 m (14H, 7CH ), 1.96 s (3H, COCH ), 2.28 t (2H,
2
3
2
014/16 (project no. 2679).
CH CO, J 14 Hz).
2
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pentanedione was heated for 1 h at 110ºC. Then
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0.1134/S107036321408012X
1
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2
3
. Moreno-Manas, M., Marquet, J., and Vallribera, A.,
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1
1
72ºC (169.2ºC [18]). H NMR spectrum, δ, ppm: 0.84
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3
,
2
1
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3
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2
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1
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