Effect of imidazolium salts on the catalytic reaction of 1,3-dioxolanes with methyl diazoacetate

Article abstract of DOI:10.1134/S1070363211010166

Effect of imidazolium salts, [bmim]⁺Cl^-, [bmim] ⁺BF₄ ^-, and [bmim]⁺PF₆ ^-, on the reaction of 1,3-dioxolanes with methyl diazoacetate in the presence of copper-containing catalysts was studied. The product composition was found to depend on the reaction conditions and the nature and ratio of components of the catalytic system.

Full text of DOI:10.1134/S1070363211010166

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 1, pp. 106–108. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © L.N. Ivanova, R.M. Sultanova, S.S. Zlotskii, 2011, published in Zhurnal Obshchei Khimii, 2011, Vol. 81, No. 1, pp. 110–112.
Effect of Imidazolium Salts on the Catalytic Reaction
of 1,3-Dioxolanes with Methyl Diazoacetate
a
a
b
L. N. Ivanova , R. M. Sultanova , and S. S. Zlotskii
a
Institute of Organic Chemistry, Ufa Research Center, Russian Academy of Sciences,
pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
b
Ufa State Petroleum Technological University, ul. Kosmonavtov 1, Ufa, 450062 Bashkortostan, Russia
e-mail: nocturne@mail.ru
Received April 5, 2010
+
–
+
–
+
–
4 6
Abstract—Effect of imidazolium salts, [bmim] Cl , [bmim] BF , and [bmim] PF , on the reaction of 1,3-
dioxolanes with methyl diazoacetate in the presence of copper-containing catalysts was studied. The product
composition was found to depend on the reaction conditions and the nature and ratio of components of the
catalytic system.
DOI: 10.1134/S1070363211010166
The ability of alkyl diazoacetates to form products
of insertion into σ-bonds opens wide prospects in
carbofunctionalization of compounds having no multi-
ple bonds [1]. For example, reactions of homologs and
heteroanalogs of 1,3-dioxolanes, such as 1,3-dioxanes,
(see table) with methyl diazoacetate and found that the
use of imidazolium salts as co-catalysts increases the
yield of methyl 1,4-dioxane-2-carboxylates to 30% and
reduces the yield of methoxycarbonylcarbene dimeriza-
tion products to 5–14%. The reactions were carried out
in the temperature range from 25 to 75°C by adding a
solution of methyl diazoacetate in methylene chloride
or 1,2-dichloroethane to the corresponding 1,3-di-
oxolane containing catalyst, the molar ratio 1,3-di-
1
,3-oxazolidines, and 1,3-oxathiolanes, with methyl
diazoacetate in the presence of Rh (OAc) lead to the
2
4
formation of formal insertion products of methoxycar-
bonylcarbene into carbon–heteroatom bond [2, 3]. The
use in these reactions of copper compounds, e.g.,
Cu(OTf) and CuSO , provides less satisfactory results
+
–
oxolane–methyl diazoacetate–catalyst–[bmim] X being
1:1:0.01:0.01. As imidazolium salts we used
2
4
+
–
+
–
+
–
[4]. On the other hand, it was noted [5] that ionic
[bmim] Cl , [bmim] BF , and [bmim] PF , and various
4 6
liquids based on imidazolium salts promote reactions
catalyzed by Lewis acids, metal complexes, and
organocatalysts.
copper, rhodium, and ruthenium compounds were tried
as catalyst [Cu(OAc)2, CuOTf·C H , Cu(OTf)2,
6
6
Rh (CF CO ) , Rh (OAc) , Ru (OAc) Cl]. It was
2
3
2 4
2
4
2
4
+
–
6
found that in the presence of [bmim] PF the most
In the present work we examined catalytic reactions
effective were Cu(OTf) and Cu(acac) . No reaction
2
2
of 2-isopropyl- and 2-phenyl-1,3-dioxolanes Ia and Ib
occurred between methyl diazoacetate and 1,3-
H
H
H
+
−
[
Cu]/[bmim] X
R
R
R
O
O
O
+ N CHCO Me
+
+
2
2
O
CO Me
O
H
O
2
MeOCO
CO Me
2
H
CO Me
2
Ia, Ib
trans-IIа, IIb
cis-IIа, IIb
III
N
+ N
bmim =
R= i-Pr (a), Ph (b); X = Cl, BF
06
−
X
4 6
, PF .
1

EFFECT OF IMIDAZOLIUM SALTS ON THE CATALYTIC REACTION
107
a
Reaction of 1,3-dioxolanes Ia and Ib with methyl diazoacetate
Yield, % (trans–cis ratio)
Initial 1,3-di-
oxolane no.
Catalyst
Temperature, °C
40
II
III
aldehyde
+
–
6
Ia
Cu(OTf)
2
/[bmim] PF
–
–
36 (3:1)
99 (1:1)
95 (3:1)
58 (3:1)
–
–
–
–
+
–
Cu(acac)
Cu(acac)
Cu(acac)
2
2
2
/[bmim] Cl
/[bmim] BF
/[bmim] PF
+
–
4
5 (1:1)
42 (6:1)
+
–
6
+
–
Cu(acac)
Cu(acac)
Cu(acac)
2
2
2
/[bmim] Cl
/[bmim] BF
/[bmim] PF
75
25
40
–
99 (1:1)
87 (2:1)
94 (1:1)
–
–
–
+
–
4
13 (3:1)
6 (2:1)
+
–
6
+
–
Ib
Cu(OTf)
Cu(OTf)
Cu(OTf)
2
/[bmim] Cl
/[bmim] BF
/[bmim] PF
9 (2:1)
25 (2:1)
7 (2:1)
41 (1:1)
14 (1:1)
12 (2:1)
8
15
14
+
–
4
2
2
+
–
6
+
–
Cu(OTf)
Cu(OTf)
Cu(OTf)
Cu(OTf)
2
2
2
2
/[bmim] Cl
/[bmim] BF
/[bmim] PF
/[bmim] PF
14 (2:1)
25 (6:1)
30 (6:1)
54 (3:1)
14 (1:1)
5 (4:1)
12 (3:1)
24 (2:1)
24
8
6
+
–
4
+
–
6
+
– b
6
10
+
–
Cu(OTf)
Cu(OTf)
2
2
/[bmim] Cl
/[bmim] BF
75
19 (6:1)
24 (4:1)
3 (2:1)
9 (2:1)
18
42
+
–
4
a
+
–
b
Molar ratio dioxolane I–N
[
2
CHCO
2
Me–[Cu]–[bmim] X 100:100:1:1; reaction time 24 h. Molar ratio dioxolane I–N
2
CHCO
2
Me–
+
–
Cu]–[bmim] X 100:200:1:1. Excess methyl diazoacetate decomposed to give dimethyl fumarate, dimethyl maleate, and higher
oligomers.
dioxolanes Ia and Ib if any of the above components
was absent. It should also be noted that we detected no
products of insertion of methoxycarbonylcarbene into
C–H or O –C bonds in 1,3-dioxolanes. Neither 2-di-
chloromethyl-2-isopropropyl- nor 2-dichloromethyl-2-
phenyl-1,3-dioxolane reacted with methyl diazoacetate
under analogous conditions.
40 and 75°C. Among the examined ionic liquids,
+
–
[bmim] PF turned out to ensure the best results: the
6
yield of stereoisomeric esters IIa was 42%, and the
trans–cis ratio was 6:1. Presumably, at 75°C the
catalyst primarily promotes dimerization of alkoxy-
carbonylcarbene (the yield of esters III considerably
increases), while the insertion process with formation
of stereoisomeric esters IIa is characterized by a poor
yield (6–13%).
3
4
The reaction of 2-phenyl-1,3-dioxolane (Ib) with
methyl diazoacetate in the presence of Cu(OTf) and
2
+
–
6
[
bmim] PF at 40°C gave a mixture of cis- and trans-
The yields and isomeric compositions of the
products formed by reactions of 1,3-dioxolanes Ia and
Ib with methyl diazoacetate were determined by NMR
spectroscopy. The stereoisomer ratio of 1,4-dioxanes
IIa and IIb was calculated from the intensities of
isomeric methyl 3-phenyl-1,4-dioxane-2-carboxylates
at a ratio of 1:6 in an overall yield of 30%. The best
results were obtained at 40°C. At 25°C the yield of
stereoisomeric esters IIb did not exceed 25% (trans–
cis ratio 2:1), whereas at 75°C the main process was
decomposition of initial acetal Ib to benzaldehyde,
which is consistent with the data of [6]. Such ionic
2
3
signals from protons at the C and C atoms. Doublet
1
signals at δ 4.59 and 4.62 ppm in the H NMR
2
3
spectrum of IIb were assigned to protons on C and C
+
–
4
+
–
6
liquids as [bmim] BF and [bmim] PF ensured
linked to the methoxycarbonyl and phenyl groups,
maximal stereoselectivity in the carbene insertion
process (trans–cis ratio 6:1). According to published
data [7], the reaction of acetal Ib with methyl
diazoacetate in the presence of Rh (OAc) afforded
only trans isomer IIb. In our experiments, both cis and
trans isomers were obtained, and their yield and ratio
depended on the ionic liquid used.
respectively, in the trans isomer. The vicinal coupling
constant JHH equal to 8.8 Hz indicated axial
orientation of both 2-H and 3-H and hence equatorial
orientation of the methoxycarbonyl and phenyl groups.
The doublets at δ 4.56 and 4.57 ppm were assigned to
3
2
4
2-H and 3-H, respectively, in the cis isomer; the
3
corresponding coupling constant J was 4.2 Hz.
HH
1
3
Insertion of alkoxycarbonylcarbenes into acetal Ia
In the C NMR spectrum of compound IIb, signals
2
3
was successful only in the presence of Cu(acac) at
from C and C of the trans isomer were located in a
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 1 2011

1
08
IVANOVA et al.
weaker field relative to the corresponding signals of
the cis isomer: their chemical shifts are δC 80.9,
evolved. After 3 h, the solvent was removed under
reduced pressure, petroleum ether (bp 40–70°C) was
added to the residue, and the catalytic system was
separated as a dark brown oil. The solution in petro-
leum ether was evaporated under reduced pressure.
The yields of the products were determined from the
8
0.0 ppm (trans) and 75.7, 74.7 ppm (cis).
The formation of the trans isomer of IIb is
preferred. Analogous relation is observed for 1,4-
2
3
dioxane IIa. Protons on C and C in trans-IIa (linked
to the methoxycarbonyl and isopropyl groups, respec-
tively) resonated as multiplets at δ 3.75 and 3.2 ppm,
and multiplet signals at δ 3.7 and 3.23 ppm were
1
H NMR spectra using CH Cl as internal reference.
2
2
The spectral parameters of compounds IIa and IIb
were consistent with those reported [4].
1
3
assigned to 2-H and 3-H in the cis isomer. In the
NMR spectrum of stereoisomer mixture trans-IIa/cis-
C
ACKNOWLEDGMENTS
2
3
IIa, signals from C and C of the trans isomer
δC 73.4, 79.6 ppm) appeared in a weaker field relative
The authors thank Prof. V.A. Dokichev for helpful
discussion, support, and interest in this study.
(
to those of the cis isomer (δ 76.1, 79.2 ppm).
C
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1
2
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1
13
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3
analyzed by gas–liquid chromatography on
a
3
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methyl diazoacetate (general procedure). Dioxolane Ia
or Ib, 1.3 mmol, was added to a solution of
6
.Khanova, M.D., Sultanova, R.M., Zlotskii, S.S., and
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0
0
.013 mmol of the corresponding copper catalyst and
.013 mmol of ionic liquid in 5 ml of methylene
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2
2
a solution of 1.3 mmol of methyl diazoacetate in 5 ml
of methylene chloride was slowly added dropwise
under stirring until gaseous products no longer
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 1 2011