Study on the synthesis of 1,2-diketones

Article abstract of DOI:10.1080/15533171003766600

A novel method is discussed for preparation of 1,2-diketones: Esters 1 was used as starting material, the intermediate enol 2 was obtained from sodium and trimethylsilyl chloride via acyloin condensation reaction, while bromine water was used in the further experiment as the oxidation reagent to oxidize compound 2 in the mixed solvent THF/H₂O. Four kinds of 1,2-diketones have been synthesized in the new way, one is straight chain compound 3a, 3b and the other is ring compound 3c, 3d. The target compounds were confirmed by IR and ¹HNMR. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533171003766600

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Study on the Synthesis of 1,2-diketones
Peng Liu a , Yu-Mei Zhang a & Hong-Li Zhang a
a College of Sciences, Hebei University of Science & Technology, Shijiazhuang, China
Published online: 10 May 2010.
To cite this article: Peng Liu , Yu-Mei Zhang & Hong-Li Zhang (2010) Study on the Synthesis of 1,2-diketones, Synthesis
and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:4, 266-267
To link to this article: http://dx.doi.org/10.1080/15533171003766600
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:266–267, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533171003766600
Study on the Synthesis of 1,2-diketones
Peng Liu, Yu-Mei Zhang, and Hong-Li Zhang
College of Sciences, Hebei University of Science & Technology, Shijiazhuang, China
Synthesis of Hexane-3,4-dione 3a
A novel method is discussed for preparation of 1,2-diketones:
Esters 1 was used as starting material, the intermediate enol 2
was obtained from sodium and trimethylsilyl chloride via acyloin
condensation reaction, while bromine water was used in the further
experiment as the oxidation reagent to oxidize compound 2 in the
mixed solvent THF/H2O. Four kinds of 1,2-diketones have been
50 mL toluene and 2.2 g (92.7 mmol) Na contained in a
250 mL three-neck flask, to the mixture 10.0 g (92.0 mmol).
TMSCl was added under vigorous stirring, then ethyl propi-
onate 1a 3.0 g(30.0 mmol) was slowly added dropwise. When
the addition was complete, the reaction mixture was stirred for
synthesized in the new way, one is straight chain compound 3a, 3b about 8 hours at refluxing temperature. After cooling, the mix-
and the other is ring compound 3c, 3d. The target compounds were
ture is filtered and concentrated in vacuo, gave intermediate enol
2a. IR (KBr) υ cm−1: 3029(HC CH), 1677(C C),1252(C-Si).
2a and 10 mL THF contained in a 100 mL two-neck flask, 13
mL H2O were added into the solution, then 40% bromine water
was added until the bromine water does not fade. The excessive
bromine was neutralized by an appropriate amount of propenol.
The crude product mixture is extracted with methylene chloride
and dried with magnesium sulfate and concentrated in vaccuo.
Pure 1,2-diketones was obtained by distillation under reduced
pressure (52–54◦,1810 Pa) and characterized by IR and 1H NMR
spectral data. The desired 1,2-diketone 3a(2.60 g, 62.5%.), col-
orless liquid.
confirmed by IR and 1HNMR.
Keywords 1,2-diketone, synthesis, acyloin condensation, oxidation
INTRODUCTION
1,2-diketones, as an interesting building block, has important
application in synthesis chemistry[1,2] and they are one class of
important intermediates that are used widely in organic synthe-
sis. It was used in the synthesis of ring-enlargement reactions
and special structure compounds.[3,4] Moreover, 1,2-diketones
are widely employed in the preparation of heterocycles.[5]
As such, we studied the 1,2-diketones compounds synthetic
methodologies. The synthetic methods for constructing 1,2-
diketones have been reported.[6,7] In this article, we found a
new 1,2-diketones synthetic method and synthesized two kinds
of 1, 2-diketones in this way (Scheme 1).
The IR spectrum indicated the presence of 2950 cm−1
1
(–CH3), 2850(–CH2, –CH3), 1710 (-C O); HNMR spectrum
(CDCl3)δppm: 2.72(q, 4H, COCH2-), 1.04(t, 6H, -CH3).
Synthesis of Dodecane-6,7-dione 3b
50 mL toluene and 2.2 g (92.7 mmol) Na contained in a
250 mL three-neck flask, to the mixture 10.0 g (92.0 mmol)
TMSCl was added under vigorous stirring, then ethyl caproate
1a 4.0 g(21.0 mmol) slowly added dropwise. When the addi-
tion was complete, the reaction mixture was stirred for about
8 hours at refluxing temperature. After cooling, the mixture is
filtered and concentrated in vaccuo, given intermediate enol 2a.
IR (KBr) υ cm−1: 3029(HC CH), 1677(C C),1252(C-Si). 2a
and 10 mL THF contained in a 100 mL two-neck flask, 13 mL
H2O were added into the solution, then 40% bromine water
was added until the bromine water did not fade. The excessive
bromine was neutralized by an appropriate amount of propenol.
The crude product mixture is extracted with methylene chloride
and dried with magnesium sulfate and concentrated in vaccuo.
Pure 1,2-diketone was obtained by column chromatography (sil-
ica, petroleum ether/EtOAc=15:1) and characterized by IR and
1H NMR spectral data. The desired 1,2-diketone 3a (2.60 g,
62.5%.), Yellow solid, M.p. 33–34◦C.
EXPERIMENTAL
General Procedure
All reactions were carried out under argon and monitored by
thin-layer chromatograph (TLC). Melting point (uncorrected)
was measured with a XT4 melting point apparatus. H NMR
spectra were recorded on a Varian EM-300 spectrometer, using
CDCl3 as solvent and TMS as the internal standard.
1
Received 18 January 2010; accepted 1 February 2010.
This work was financially supported by the fundamental research
fund of Hebei University of Science & Technology (XL200751).
Address correspondence to Yu-Mei Zhang, College of Sciences,
Hebei University of Science & Technology, Shijiazhuang 050018,
China. E-mail: zhangym.jy@gmail.com
266

STUDY ON THE SYNTHESIS OF 1,2-DIKETONES
267
TMSO
R
OTMS
R
RESULTS AND DISCUSSION
O
R
O
R
Br2
Na/Toluene
reflux
RCO2R
+ TMSCl
Esters were used as starting material, 1,2-diketones 3a–3d
were synthesized using the new method. The products 3 were
characterized by IR and 1H-NMR. The spectroscopic data of the
products are found to be identical with expected structures.
The new method we provides here is an easier procedure to
synthesize the 1,2-diketones. The preparation of intermediate
enol 2 is a key step. In the synthesis of intermediate enol 2, the
sodium should be broken down bit by bit as soon as possible to
improve the reaction yield, while the reaction was carried out
under nitrogen. The ester 1 must be slowly added so as to avoid
the by-products.
THF/H2O
1
2
3
O
3a
1a
COOEt
O
O
3b
1b
COOEt
O
O
1c
1d
EtOOC(CH2)7COOEt
EtOOC(CH2)8COOEt
3c
O
O
3d
With ethyl acetate as reactant, the reaction did not occur. An
analysis of the causes may be due to low boiling point of ethyl
acetate, the high reaction temperature is not accessible enough.
O
SCH. 1. Synthesis of 1,2-diketones 3.
CONCLUSION
The IR spectrum indicated the presence of 2940 cm−1
(–CH3), 2850(–CH2, –CH3), 1712 (-C=O); 1HNMR spec-
trum (CDCl3)δppm: 2.71(t, 4H, COCH2-), 1.59(m, 4H, -CH2-),
1.28(m, 8H, -CH2CH2-), 0.89(t, 6H, CH3-).
In conclusion, we found a new method of synthesizing 1,2-
diketone and synthesized four kinds of 1,2-diketones in this way.
The target compounds were confirmed by IR and 1HNMR.
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Synthesis of Cyclononane-1,2-dione 3c
1,2-diketones 3c were prepared in a similar manner to that
for the preparation of 3a, starting with azelaic acid diethyl
ester 1c. The desired 1,2-diketone 3c was obtained by col-
umn chromatography (silica, petroleum ether/EtOAc=150:1).
Compound 3c is yellow liquid (1.68g, 51.9%). The IR spectrum
indicated the presence of 2895(–CH2), 1741 (-C=O); 1HNMR
spectrum (CDCl3) δppm: 2.68(t, 4H, COCH2-), 1.76(m, 4H,
-CH2-), 1.48(m, 4H, -CH2CH2-), 1.28(m, 2H, -CH2-).
Synthesis of Cyclodecane-1,2-dione 3d
1,2-diketones 3d were prepared in similar manner to that for
the preparation of 3b, starting with dimethyl sebacate 1d. The
desired 1,2-diketone 3d was obtained by column chromatogra-
phy (silica, petroleum ether/EtOAc=200:1). Compound 3d is
yellow solid (1.68g, 49.8%), M.p. 32–33◦C. The IR spectrum
indicated the presence of 2896(–CH2), 1693 (-C O); 1HNMR
spectrum (CDCl3)δppm: 2.65(t, 4H, COCH2-), 1.89(m, 4H, -
CH2-), 1.46(m, 4H, -CH2CH2-), 1.26(m, 4H, -CH2CH2-).
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