Lewis acid-catalyzed reactions of donor-acceptor cyclopropanes with furan derivatives

Article abstract of DOI:10.1016/j.tet.2009.04.061

Lewis acid-catalyzed reactions of dialkyl 2-arylcyclopropane-1,1-dicarboxylates with 2,5-dimethylfuran were found to give products of [3+2]-cycloaddition to C(2)-C(3) bond, which contain reactive vinyl ether moiety. These adducts can be further transforme

Full text of DOI:10.1016/j.tet.2009.04.061

Tetrahedron 65 (2009) 5385–5392
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Lewis acid-catalyzed reactions of donor–acceptor cyclopropanes
with furan derivatives
*
Alexey O. Chagarovskiy, Ekaterina M. Budynina , Olga A. Ivanova, Yuri K. Grishin,
Igor V. Trushkov, Pavel V. Verteletskii
M.V. Lomonosov Moscow State University, Department of Chemistry, Leninskie Gory, 1-3, Moscow 119991, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Lewis acid-catalyzed reactions of dialkyl 2-arylcyclopropane-1,1-dicarboxylates with 2,5-dimethylfuran
were found to give products of [3þ2]-cycloaddition to C(2)–C(3) bond, which contain reactive vinyl
ether moiety. These adducts can be further transformed into various products depending on the Lewis
acid, the nucleophilicity of aryl group in starting cyclopropane and the ratio of reagents. The vinyl
ether moiety can attack the appropriate nucleophilic center in intramolecular or intermolecular mode
or can undergo cycloaddition to the second equivalent of donor–acceptor cyclopropane. Alternatively,
2,5-diphenylfuran formed Friedel–Crafts products only when reacted with donor–acceptor
cyclopropanes.
Received 5 February 2009
Received in revised form 2 April 2009
Accepted 17 April 2009
Available online 24 April 2009
Keywords:
Cycloaddition
Aromatic substitution
Cyclopropanes
Furans
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
withdrawing substituent(s). Thus, the donor–acceptor cyclopro-
panes can be considered as synthon of 1,3-dipole of A-type
During the last two decades, donor–acceptor cyclopropanes
have attracted significant attention from organic chemists due to
the broad scope of their reactivity.1 Indeed, the presence of
electron-releasing groups increases the cyclopropane reactivity
toward electrophiles.2 On the other hand, electron-withdrawing
groups activate cyclopropanes to attack by nucleophiles (homo-
Michael addition).3 Moreover, donor–acceptor cyclopropanes have
been demonstrated to form [3þ2]-cycloadducts with various
compounds bearing C]C,4 C]O,5 C]N,6 N]N,7 C^C,8 or C^N9
bonds via either a concerted or a stepwise mechanism (path a on
Scheme 1). [3þ3]-Cycloadditions of nitrones,10 azomethine im-
ines,11 and isoquinoline-N-oxides12 to the donor–acceptor cyclo-
propanes have also been described (path b on Scheme 1). A broad
scope of polyfunctionalized five- and six-membered carbocycles
and heterocycles can be synthesized via these reactions. They
have also been applied toward the total synthesis of some bio-
active natural compounds13 as well as for the construction of
complex polycyclic cores of some others.4b,14 In all these pro-
cesses, cyclopropanes react with a nucleophilic counterpart via
the carbon atom bearing the cation-stabilizing group and with the
electrophile via the carbon connected to the electron-
(Scheme 1).
Recently we have demonstrated, for the first time, the
possibility of Lewis acid-mediated [4þ3]-cycloaddition of the
donor–acceptor cyclopropanes (1) to 1,3-diphenylisobenzo-
furan (path c on Scheme 1).15 In this transformation, 1 reacted
as three-carbon dienophile, isobenzofuran being a typical 1,3-
diene. The related [4þ3]-cycloaddition was realized earlier for
allyl cations.16,17 Furans were shown to react as 4
p-units with
some other dienes leading to [4þ4] cycloadducts.18 However,
the most studied process wherein furans show diene behavior
is the Diels–Alder reaction. Both intra- and intermolecular
modes of this process which lead to 7-oxanorbornene de-
rivatives (or products of their further transformations) have
been widely applied.19 At the same time, furans participate in
cycloaddition processes as a 2p-component too. This mode of
interaction is impossible for 1,3-diphenylisobenzofuran but can
be realized for furan itself and its various 2- or 2,5-substituted
derivatives. Indeed, examples of [1þ2]-,20 [2þ2]-,21 [3þ2]-,22
and [4þ2]-cycloadditions23 to the C(2)–C(3) furan bond as well
as formation of some bis-adducts were described. Therefore,
we decided to carefully investigate reactions between different
furan derivatives and cyclopropanes 1 aiming to determine the
preferable mode of their interactions depending on the nature
of substituents in furans and cyclopropanes as well as on the
Lewis acid applied.
* Corresponding author. Tel.: þ7 905 5741870.
E-mail address: ekatbud@org.chem.msu.ru (E.M. Budynina).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.04.061

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A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
CO2R
CO2R
A
B
A
B
[3+2]
[3+3]
a
R2
N
RO2C
X
CO2R
R1
R1
CO2R
CO2R
OR
MLn
O
b
X
N
MLn
R2
Ph
O
RO
O
1
A
Ph
O
CO2R
CO2R
Ph
c
Ph
[4+3]
Scheme 1. Various cycloaddition reactions of donor–acceptor cyclopropanes.
2. Results and discussion
0.5%
4.3%
2.1. [3D2]-Cycloaddition reactions of donor–acceptor
cyclopropanes with furans
EtO2C
EtO2C
H
H
1.4%
3.5%
Me
We first examined the effect of substituents in the furan ring on
its reactivity toward diethyl 2-(2-thienyl)cyclopropane-1,1-dicar-
boxylate (1a). This compound was selected as a model donor–ac-
ceptor cyclopropane as it was shown earlier to be effective in both
[3þ2]- and [4þ3]-cycloaddition reactions in the presence of
Yb(OTf)3. However, we failed to isolate any cycloaddition products
from the reaction of 1a with unsubstituted furan (2a) under the
same reaction conditions; only furan polymerization products were
formed in this case. 2,5-Diarylfurans are known to be much more
stable to acids than furan itself. So, we tried to introduce 2,5-
diphenylfuran (2b) into reaction with 1a. Indeed, we found no
polymerization of this substrate, however, 2b showed no reactivity
toward cyclopropane 1a either.
Nevertheless, we succeeded in performing the reaction of
cyclopropane 1a with 2,5-dimethylfuran (2c) in methylene chloride
in the presence of Yb(OTf)3. This process was found to be regio- and
stereoselective leading to a single 1:1 adduct 3a in 76% NMR yield.
Analysis of NMR data allowed us to identify 3a as the product of
[3þ2]-cycloaddition of cyclopropane 1a to C(2)–C(3) bond of furan
2c (Scheme 2). Thus, the 1H NMR spectrum of 3a contains
O
H
Me
S
1.5%
Figure 1. Some NOE data for compound 3a.
characteristic signals at dH 2.99, 3.30, and 3.53 ppm, which corre-
spond to the AMX system of the CH2–CH fragment (2J 13.1 Hz, 3J
14.4 and 5.3 Hz). A significant upfield shift of the methyl group
signal in comparison with that for the starting compound 2c (dH
1.48 vs 2.23 ppm) is obviously caused by the loss of furan aroma-
ticity. The relative configuration of 3a was determined by NOE
experiments (Fig. 1). It was found that the methine protons at the
C(3a) and C(6) atoms as well as the methyl group at the C(6a) atom
of cyclopenta[b]furan 3a have a cis,cis-orientation. The further
chemical transformations of 3a confirm also its structure. The
presence of the vinyl ether moiety in 3a is in accordance with its
lability during purification on silica too.
In comparison to the results observed with 1a, dimethyl ester 1b
reacted with 2c yielding syn-cycloaddition product 3b as a mixture
of two diastereomers in a 9:1 ratio (Fig. 2). We estimated the rel-
ative stability of major and minor diastereomers of 3b using
quantum chemical calculations at HF/6-31G basis set (Fig. 2).24 We
CO2R
+
Me
Me
Ar
O
CO2R
1a-c
2c
Yb(OTf)3
MeO2C
MeO2C
RO2C
H
H
H
MeO2C
MeO2C
RO2C
Me
Me
Me
O
O
O
Me
Me
S
S
Me
Ar
3a-c
3b
1a, 3a: R=Et, Ar=Th, 76%, d.r. > 95 : 5
1b, 3b: R=Me, Ar=Th, 53%, d.r. 90 : 10
1c, 3c: R=Et, Ar=Ph, 60%, d.r. > 95 : 5
isomers ratio
Erel (0)
9:1
- 2.2 kcal/mol
Scheme 2.
Figure 2. Two possible diastereomers of 3b.

A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
5387
found that the minor diastereomer of 3b is 2.2 kcal/mol more stable
CO2Me
CO2Me
1b
S
+
than major one. However, on the basis of all experimental data we
believe that stereoselectivity of this reaction is a result of kinetic
but not thermodynamic control, i.e., the major isomer of 3b has the
same relative stereochemistry as 3a.
Me
Me
O
2c
SnCl4
CH2Cl2
Unfortunately, the corresponding reactions with 2-methylfuran
(2d) gave complex reaction mixtures containing both simple
cycloadducts to C(2)–C(3) and C(4)–C(5) furan 2d bonds and some
oligomerization products.
The less reactive dimethyl 2-phenylcyclopropane-1,1-
dicarboxylate (1c) failed to interact with 2c under the same re-
action conditions. Earlier we found that SnCl4 is more efficient than
Yb(OTf)3 for initiation of the reaction of donor–acceptor cyclopro-
panes with anthracenes.25 Similarly, 1c reacted with 2c in the
presence of SnCl4. A single set of product signals was found in 1H
and 13C NMR spectra of the formed reaction mixture. These signals
are very similar to those for 3a. Therefore, the structure of product
was assigned as 3c (Scheme 2).
-50 °C rt
H
Me
MeO2C
MeO2C
O
Me
S
5a, 71%
Scheme 4.
spectrum of 5a reveals two AMX systems at dH 1.61, 2.24, and
3.37 ppm (2J 13.1 Hz, 3J 12.1 and 2.9 Hz) and dH 2.29, 2.93, and 3.39
(2J 14.4 Hz, 3J 7.0 Hz, and 3Jꢀ0.3 Hz). These signals correspond to the
protons of two isolated CH2–CH fragments. Other characteristic
signals at dH 6.71 and 7.13 ppm form an AX system corresponding to
the 2,3-disubstituted thiophene moiety. The value of 3J coupling
constant for these signals (5.1 Hz) is typical for protons at C(2) and
C(3) carbon atoms of thiophene ring. The relative stereochemistry
of tetracycle 5a was deduced from NOE experiments.
The formation of 5a is two-step process. The [3þ2]-cycloadduct
3b was formed in the first step of this reaction. On the contrary to
the softer Lewis acid Yb(OTf)3, SnCl4 catalyzed the further intra-
molecular cyclization of 3b through an electrophilic attack of the
vinyl ether moiety of 3b onto the C(3) atom of thiophene affording
5a. Both inter- and intramolecular analogues of this reaction are
known.26 To prove this mechanism, we treated [3þ2]-cycloadduct
3b with SnCl4 and found that it was isomerized under these con-
ditions into compound 5a (Scheme 5).
Cyclopropane 1d failed to form the analogous tetracyclic adduct
even under more harsh reaction conditions. It means that not only
the catalyst but also the nucleophilicity of the aromatic substituent
in the starting cyclopropane influences the possibility of further
transformations of the initial cycloadduct. The thiophene ring is
more nucleophilic than the phenyl moiety and undergoes electro-
philic attack. To prove this supposition, we performed the SnCl4-
catalyzed reaction of 2c with cyclopropane 1e, which has highly
nucleophilic trimethoxyphenyl substituent. Indeed, we obtained
the product 5b in high yield as a single stereoisomer (Scheme 6).
The NMR data for the saturated tricyclic moiety of compound 5b
are rather similar to those for compound 5a. Thus, the 1H spectrum
of 5b has two AMX type groups of signals corresponding to two
isolated CH2–CH fragments: at dH 1.66, 2.27, and 3.29 ppm (2J
2.2. Friedel–Crafts reaction of 2,5-diphenylfuran (2b) with
donor–acceptor cyclopropanes
The previous results showed that SnCl4 has higher catalytic
activity in reactions of donor–acceptor cyclopropanes in compari-
son with Yb(OTf)3. As 2,5-diphenylfuran did not react with 1 under
Yb(OTf)3 catalysis, we tried to perform reaction of the donor–ac-
ceptor cyclopropanes with 2b in the presence of SnCl4. We found
that 2b interacted with 1d under these reaction conditions but no
cycloaddition products were identified in the reaction mixture. The
Friedel–Crafts alkylation product 4 was a single isolated compound
in this case (Scheme 3). In the 1H NMR spectrum, the characteristic
signals at dH 2.60, 2.76, 3.43, and 4.32 ppm correspond to CH–CH2–
CH fragment of substituent’s open chain.
These results are similar to those for reactions of 1 with an-
thracenes when both cycloaddition and Friedel–Crafts products
were formed depending on the substituents in the aromatic
counterpart.25
2.3. Tandem [3D2]-cycloaddition/intramolecular
electrophilic aromatic substitution of donor–acceptor
cyclopropanes with furans
Encouraged by the results obtained with SnCl4 as a catalyst, we
decided to re-investigate reactions of donor–acceptor cyclopro-
panes with furan 2c using this Lewis acid with the primary goal to
optimize the reaction conditions. However, we found that instead
of simple adduct 3b its isomer 5a was formed in 71% yield from 1b
and 2c in the presence of SnCl4 (Scheme 4). On the contrary to 3b,
5a was obtained as a single diastereomer. Thus, the 1H NMR
CO2Me
CO2Me
S
+
+
Ph
Ph
Me
Me
O
Ph
CO2Me
O
2c
CO2Me
1b
1d
2b
SnCl4
Yb(OTf)3
CH2Cl2
CH2Cl2, rt
-50 °C rt
H
CO2Me
CO2Me
MeO2C
Me
H
MeO2C
MeO2C
Ph
δ−
MeO2C
SnCl4
δ+
O
Me
Me
O
CH2Cl2
-50 °C
S
Me
3b
Ph
Ph
rt
S
O
4, 65%
5a
Scheme 3.
Scheme 5.

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A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
CO2Me
CO2Me
CO2Me
MeO
MeO
+
Me
Ph
+
Me
2c
Me
O
Me
O
CO2Me
1d
2c
1e
SnCl4
OMe
SnCl4
CH2Cl2
CH2Cl2
-50 °C
Δ
-50 °C rt
Me
MeO2C
MeO2C
H
Me
H
MeO2C
MeO2C
O
O
Me
Me
Me
O
Me
Ph
OMe
OMe
6, 69%, d.r. 4:1
MeO
Scheme 7.
5b, 76%
Scheme 6.
the 13C NMR spectrum, the CH3 groups of the furan moiety are
more shielded (dC 13.2 and 13.4 ppm) versus those of saturated
cycle (dC 25.7 and 30.1 ppm). Further, the singlet at dH 5.73 ppm
for the isolated proton of the CH group with dC 106.1 ppm is
a quite characteristic pattern corresponding to the trisubstituted
furan ring. The structure of product 6 is in agreement with the
formation of [3þ2] cycloadduct 3c during reaction between 1c and
2c in a ratio of 1:1. Moreover, the isolation of 6 as a mixture of two
isomers is in full accordance with the formation of single isomer of
3c in the cycloaddition process.
13.4 Hz, 3J 12.1 and 3.0 Hz) and at dH 2.39, 2.78, and 3.21 ppm (2J
14.4 Hz, 3J 7.5 and 0.7 Hz). In accordance with the molecular
structure of 5b, the 1H and 13C NMR spectra have only one signal of
aromatic CH group at rather high field (dH 6.45 ppm, dC 107.8 ppm)
due to strong shielding effects of substituents. The NOE measure-
ments also show that 5a and 5b have the same relative configu-
rations (Fig. 3).
2.4. Tandem [3D2]-cycloaddition/intermolecular
electrophilic aromatic substitution of donor–acceptor
cyclopropane with furans
2.5. Tandem [3D2]/[3D2]-cycloadditions of donor–acceptor
cyclopropane with furans
The formation of tetracyclic products 5 is a result of double bond
activation in the monoadduct 3 by SnCl4, which leads to intra-
molecular attack onto the nucleophilic aryl group. If the nucleo-
philicity of the aryl group in the starting cyclopropane 1 is small
enough for participation in this process, the corresponding in-
termolecular process can be realized. Cyclopropane 1d failed to give
any cyclization product of type 5. So instead, we studied its reaction
with an excess of 2,5-dimethylfuran (2c). We found that in the
presence of SnCl4, this interaction led to compound 6, which is the
product of addition of the second furan molecule to the double
bond of the intermediate monoadduct of [3þ2]-cycloaddition 3c.
Compound 6 was isolated as a mixture of two diastereomers in
a 4:1 ratio (Scheme 7).
In the reactions discussed in Sections 2.3 and 2.4 the in-
termediate monoadducts 3 were further transformed with the
participation of the double bond of the enol ether moiety formed.
However, this double bond can also react with another donor–
acceptor cyclopropane similarly to many other examples of this
cycloaddition.4 Therefore, we supposed that it is possible to
perform reaction of furans with 2 equiv of cyclopropanes with
formation of products of double cycloaddition. Indeed, we found
that moderate heating of furan 2c with an excess of cyclopropane
1d afforded bis-adduct 7a as a single isomer in high yield
(Scheme 8).
The two singlets of the methyl groups in the upfield region of 1H
NMR spectrum of 7a (dH 1.30 and 1.85 ppm) showed that these
groups connect to the C(2) and C(5) atoms of tetrahydrofuran
moiety. The spectrum of the cyclic skeleton protons reveals su-
In the 1H NMR spectrum of the major diastereomer of 6 two
AMX systems are present at dH 1.60, 2.60, and 3.37 ppm (2J
12.9 Hz, 3J 9.4 and 8.6 Hz) and dH 2.34, 2.63, and 2.90 ppm (2J
5.6 Hz, 3J 14.4 and 12.9 Hz). These signals correspond to two CH2–
CH fragments of saturated cyclopenta[b]furan moiety. Hydrogen
atoms of the methyl groups connected to tetrahydrofuran ring give
resonance signals at higher field (dH 1.21 and 1.44 ppm) in com-
parison with methyl groups at C(2) and C(5) carbon atoms of
dimethylfuran (dH 2.11 and 2.19 ppm, respectively). Oppositely, in
perposition of signals of C2H2–C3H and C6H2–C7H–C7aH–C7b
H
CO2Me
Ph
+
Me
Me
O
CO2Me
1d
2c
SnCl4
CH2Cl2
-50 °C
Δ
MeO2C
H
Me
H
MeO2C
H
MeO2C
Ph
O
H
H
MeO2C
Me
H
CO2Me
CO2Me
H
O
Ph
Me
Me
OMe
OMe
MeO
7a, 82%
Scheme 8.
Figure 3. Some NOE responses for compound 5b.

A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
5389
10.6%
CO2Me
CO2Me
H 7
S
MeO2C
MeO2C
Me
Ph
7a
+
1.3%
Me
O
7b
H
H
6
2'
H
H
19.6%
2c
1b
16.7%
2.1%
3.5%
H 6'
CO2Me
CO2Me
Yb(OTf)3
H
1.4%
O
2
CH2Cl2, rt
Ph
3
2.5%
Me
H
Me
MeO2C
4.0%
1.9%
2-Th
H
H
MeO2C
Figure 4. Some NOE data for compound 7a.
CO2Me
CO2Me
O
2-Th
Me
Me
fragments (see Experimental part and Fig. 4). Weak long-range
spin–spin coupling exists between H2b and H7b protons of two
fragments (4J 1.0 Hz). Note that the vicinal spin–spin coupling
constant for protons H7a and H7b, which belong to the tetrahy-
drofuran ring has also a rather small value (3J 1.8 Hz). Stereo-
chemical assignment was established using the results of NOE
experiments, which are represented in Figure 4.
7b, 94%, d.r. 66:34
Scheme 9.
concluded that the major isomer of 7b has the same relative con-
figuration as 7a.
The determined structure of compound 7a was unambiguously
proven by single-crystal X-ray analysis (Fig. 5). The central tetra-
hydrofuran ring of 7a is almost flat compared to the cyclopentane
rings, which have the typical envelope conformations where C(6)
and C(2) atoms (numeration on Fig. 5) are out of the ring planes and
directed to the central five-membered ring. It is interesting that
C(4a)–C(5) bond in 7a is rather long (1.58 Å). Another bond be-
tween carbon atom bearing two methoxycarbonyl groups and
tetrahydrofuran ring [C(1)–C(7b)] is also slightly elongated (bond
length is 1.56 Å).
3. Conclusions
Contrary to our previous results concerning the [4þ3]-cyclo-
addition of donor–acceptor cyclopropanes to 1,3-diphenyliso-
benzofuran,15 2,5-dimethylfuran reacts with these cyclopropanes
through [3þ2]-cycloaddition to the C(2)–C(3) bond. Due to the
presence of the reactive vinyl ether moiety, under more harsh
reaction conditions these cycloadducts can be further trans-
formed into different products depending on the ratio of re-
agents and the nature of substituents in the starting
cyclopropanes. When the cyclopropane/furan ratio was 2:1,
products of double [3þ2]-cycloaddition were isolated in good
yields independent of the nature of the aryl group. Oppositely,
when an excess of furan was used, the initial product of the re-
action between 2,5-dimethylfuran and 2-phenylcyclopropane-
1,1-diester interacted with the second furan molecule by Lewis
acid-induced Friedel–Crafts alkylation. However, if the cyclo-
propane contained more nucleophilic aryl groups, the products
of intramolecular alkylation were formed. 2,5-Diphenylfuran
failed to give any cycloaddition product in the reactions with 2-
phenylcyclopropane-1,1-diesters but yielded the product of
The formation of asymmetric product 7a in this reaction is in
accordance with the different polarization of C]C bonds in the
starting furan 2c and in vinyl ether moiety of the intermediate
monoadduct 3c. The electrophilic center of activated cyclopropane
1d attacks the
vinyl ether 3c.
a-carbon atom of furan 2c but the b-carbon atom of
The analogous compound 7b was formed in a high yield in the
reaction of furan 2c with dimethyl 2-(2-thienyl)cyclopropane-1,1-
dicarboxylate (1b) in the presence of 10 mol % of Yb(OTf)3 (Scheme 9).
However, this product was isolated as a mixture of two di-
astereomers in a ratio of 2:1. A comparison of the spectral data for
compounds 7a and 7b revealed that chemical shifts and coupling
constants, which correspond to tricyclic framework of major iso-
mer of 7b have the similar values with those for 7a. Thus, we
Friedel–Crafts alkylation on the
b-carbon atom. Reactions of
donor–acceptor cyclopropanes with 3- and 3,4-substituted fu-
rans as well as with furans containing electron-withdrawing
groups are under investigation now.
4. Experimental
4.1. General remarks
NMR spectra were recorded on a ‘Bruker Avance-400’ (400 MHz
for 1H and 100 MHz for 13C NMR) spectrometer at room temper-
ature; the chemical shifts
d were measured in parts per million
with respect to the solvent (CDCl3, 1H: dH¼7.26 ppm, 13C:
dC¼77.13 ppm). Splitting patterns are designated as s, singlet; d,
doublet; t, triplet; q, quartet; m, multiplet; dd, double doublet.
Coupling constants (J) are in hertz. The structures of all compounds
were elucidated with the aid of 1D NMR (1H, 13C, DEPT-90 and 135)
and 2D NMR (1H, 1H COSY and 13C, 1H XHCORR) spectroscopy. MS
were recorded on the MALDI-TOF mass-spectrometer ‘Bruker
Ultraflex’ in positive mode, dithranol was used as a matrix. Melting
points (mp): Electrothermal 9100 capillary melting point appara-
tus, the values are uncorrected. Column chromatography was
performed on silica gel 60 (230–400 mesh, Merck). TiCl4, SnCl4,
Yb(OTf)3, and all studied furans are available commercially. 2-Aryl-
Figure 5. Single-crystal X-ray structure of 7a.
1,1-cyclopropane diesters
1
were prepared by published

5390
A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
procedures.27 All the reactions were carried out using freshly dis-
tilled and dry solvents.
(CH3O), 58.6 (CH), 63.8 (C), 93.0 (CH]), 93.9 (C), 124.6 (CH, Th),
125.9 (CH, Th), 126.2 (CH, Th), 141.2 (C, Th), 157.3 (C), 169.5 (CO2Me),
172.0 (CO2Me). MS MALDI-TOF: m/z¼336 [M]þ. HRMS MALDI-TOF:
m/z¼336.1024 [M]þ (336.1031 calcd for C17H20O5S).
4.2. General procedure for Yb(OTf)3 catalyzed reactions of
donor–acceptor cyclopropanes with furans
4.4.3. (3aSR,6SR,6aRS)-Diethyl 2,6a-dimethyl-6-phenyl-6,6a-
dihydro-3aH-cyclopenta[b]-furan-4,4(5H)-dicarboxylate (3c)
Compound 1c (200 mg, 0.76 mmol), 2c (200 mg, 2.1 mmol), and
Yb(OTf)3 (24 mg, 0.038 mmol) in 10 mL of PhCl was stirred under
reflux for 6 h. Petroleum ether–chloroform (1:1) mixture was used
as an eluent. Yield of crude 3c 160 mg (60%); slight yellow oil; Rf
The solution of cyclopropane 1, furan 2, and Yb(OTf)3 (5 mol % to
1) in CH2Cl2 or PhCl was stirred under an Ar atmosphere in the
presence of 4 Å molecular sieves under the conditions specified.
The reaction progress was monitored by TLC and 1H NMR. The
solvent was evaporated under reduced pressure. The residue was
purified by column chromatography on silica gel.
0.34 (CHCl3); 1H NMR (CDCl3, 400 MHz):
d
1.27 (m, 6H, 2ꢃCH3), 1.52
(s, 3H, CH3), 1.60 (s, 3H, CH3), 2.20–2.40 (m, 2H, CH2), 2.71–2.75 (m,
4.3. General procedure for SnCl4-catalyzed reactions of
donor–acceptor cyclopropanes with furans
1H, CH), 3.58–3.62 (m, 1H, CH), 4.19–4.38 (m, 5H, CH], 2ꢃOCH2),
7.25–7.42 (m, 5H, Ph); 13C NMR (CDCl3, 100 MHz):
d 13.8 (CH3), 14.1
(2ꢃCH3), 23.8 (CH3), 38.4 (CH2), 53.1 (CH), 58.5 (CH), 61.1 (CH2O),
61.6 (CH2O), 63.8 (C), 93.1 (CH), 94.0 (C), 126.5 (CH, Ph), 127.9
(2ꢃCH, Ph), 128.6 (2ꢃCH, Ph), 137.5 (C), 157.1 (C), 169.3 (CO2Et),
171.7 (CO2Et). HRMS MALDI-TOF: m/z¼358.1772 [M]þ (358.1780
calcd for C21H26O5).
A solution of SnCl4 in CH2Cl2 was added dropwise to a vigorously
stirred solution of cyclopropane 1 and furan 2 in CH2Cl2 at ꢁ50/
ꢁ60 ꢂC under an Ar atmosphere. The reaction mixture was allowed
to warm to room temperature, stirred under conditions specified,
and poured into 10 mL of saturated aqueous NaHCO3. After ex-
traction with CH2Cl2 (3ꢃ10 mL), combined organic layers were
4.5. Friedel–Crafts reaction of 2,5-diphenylfuran (3d) with
donor–acceptor cyclopropanes
washed with Trilon
B
solution (3ꢃ10 mL) then with water
(2ꢃ10 mL), dried with anhydrous Na2SO4, and concentrated under
reduced pressure. The residue was purified by column chroma-
tography on silica gel.
4.5.1. Dimethyl 2-(2-(2,5-diphenylfuran-3-yl)-2-
phenylethyl)malonate (4)
A solution of SnCl4 (0.12 mL, 1.0 mmol) in 1 mL of CH2Cl2 was
added dropwise to a solution of 1d (200 mg, 0.85 mmol) and 2b
(190 mg, 0.86 mmol) in 8 mL of CH2Cl2 under specified conditions
and stirred at room temperature for 23 h. Petroleum ether–chlo-
roform (4:1) mixture was used as an eluent. Yield of 4 250 mg
(65%); colorless solid; mp 107.8–108.0 ꢂC; Rf 0.41 (CHCl3); 1H NMR
4.4. [3D2]-Cycloaddition of donor–acceptor cyclopropanes to
2,5-dimethylfuran
4.4.1. Diethyl (3aSR,6RS,6aSR)-2,6a-Dimethyl-6-(thiophen-2-yl)-
6,6a-dihydro-3aH-cyclopenta[b]-furan-4,4(5H)-dicarboxylate (3a)
Compound 1a (200 mg, 0.75 mmol), 2c (200 mg, 2.1 mmol), and
Yb(OTf)3 (24 mg, 0.037 mmol) in 8 mL of CH2Cl2 was stirred at room
temperature for 24 h. Petroleum ether–chloroform (1:1) mixture
was used as an eluent. Compound 3a was isolated in 76% yield
(210 mg) as crude compound, which can not be fully purified due to
partial decomposition during column chromatography; slight yel-
(CDCl3, 400 MHz):
d
2.60 (ddd, 2J¼13.9 Hz, 3J¼6.1, 9.9 Hz, 1H, CH2),
2.76 (ddd, 2J¼13.9 Hz, 3J¼6.3, 9.1 Hz, 1H, CH2), 3.43 (dd, 3J¼6.1,
9.1 Hz, 1H, CH), 3.47 (s, 3H, CH3O), 3.72 (s, 3H, CH3O), 4.32 (dd,
3J¼6.3, 9.9 Hz,1H, CH), 6.89 (s,1H, CH), 7.28–7.48 (m,11H, Ph), 7.64–
7.67 (m, 2H, Ph), 7.78–7.82 (m, 2H, Ph); 13C NMR (CDCl3, 100 MHz):
d
36.1 (CH2), 39.4 (CH), 49.9 (CH), 52.3 (CH3O), 52.6 (CH3O), 106.6
low oil; Rf 0.26 (CHCl3); 1H NMR (CDCl3, 400 MHz):
d
1.27 (t,
(CH, Fu), 123.9 (2ꢃCH, Ph), 124.0 (C), 126.5 (2ꢃCH, Ph), 126.8 (CH,
Ph), 127.6 (2ꢃCH, Ph), 127.7 (2ꢃCH, Ph), 128.6 (2ꢃCH, Ph), 128.8
(2ꢃCH, Ph), 128.9 (2ꢃCH, Ph), 130.5 (C), 131.0 (C), 143.1 (C), 149.7
(C), 153.1 (C), 169.7 (CO2Me), 169.8 (CO2Me). Anal. Calcd for
C29H26O5: C, 76.63; H, 5.77. Found: C, 76.80; H, 5.64.
3J¼7.2 Hz, 3H, CH3), 1.29 (t, 3J¼7.2 Hz, 3H, CH3), 1.48 (s, 3H, CH3),
1.78 (s, 3H, CH3), 2.37 (dd, 2J¼13.1 Hz, 3J¼5.3 Hz, 1H, CH2), 2.75 (dd,
3
2J¼13.1 Hz, 3J¼14.4 Hz, 1H, CH2), 3.29 (dd, J¼5.3, 14.4 Hz, 1H, CH),
3.83 (br s, 1H, CH), 3.61–3.73 (m, 4H, 2ꢃCH2O), 4.33 (br s, 1H, CH]),
6.91 (br d, 3J¼3.4 Hz, 1H, Th), 6.98 (dd, 3J¼3.4, 5.0 Hz, 1H, Th), 7.23
(br d, 3J¼5.0 Hz, 1H, Th); 13C NMR (CDCl3, 100 MHz):
d
13.8 (CH3),
4.6. Tandem [3D2]-cycloaddition/intramolecular
electrophilic aromatic substitution of donor–acceptor
cyclopropanes with furans
14.1 (CH3), 14.2 (CH3), 23.6 (CH3), 38.6 (CH2), 48.9 (1JCH¼121 Hz,
CHTh), 58.4 (1JCH¼147 Hz, CH), 61.2 (CH2O), 61.7 (CH2O), 63.9 (C),
93.0 (1JCH¼173 Hz, CH]), 93.3 (C), 124.6 (CH, Th), 125.8 (CH, Th),
126.2 (CH, Th), 140.7 (C, Th), 157.2 (C), 169.3 (CO2Et), 171.7 (CO2Et).
HRMS MALDI-TOF: m/z¼364.1338 [M]þ (364.1344 calcd for
C19H24O5S).
4.6.1. Dimethyl (4RS,5aSR,6SR,8aRS)-4,5a-dimethyl-5a,6,8,8a-
tetrahydro-4,6-methanocyclopenta[b]thieno[2,3-d]pyran-7,7(4H)-
dicarboxylate (5a)
A solution of SnCl4 (0.20 mL, 1.8 mmol) in 1 mL of CH2Cl2 was
added dropwise to a solution of 1b (200 mg, 0.83 mmol) and 2c
(200 mg, 2.1 mmol) in 8 mL of CH2Cl2 under specified conditions
and stirred at room temperature for 23 h. Petroleum ether–chlo-
roform (2:1) mixture was used as an eluent. Yield of 5a 200 mg
(71%); colorless solid; mp 103.0–103.2 ꢂC; Rf 0.35 (CHCl3); 1H NMR
4.4.2. (3aSR,6RS,6aSR)-Dimethyl 2,6a-dimethyl-6-(thiophen-2-yl)-
6,6a-dihydro-3aH-cyclopenta[b]-furan-4,4(5H)-dicarboxylate (3b)
Compound 1b (200 mg, 0.83 mmol), 2c (200 mg, 2.1 mmol), and
Yb(OTf)3 (27 mg, 0.042 mmol) in 8 mL of CH2Cl2 was stirred at
room temperature for 24 h. Petroleum ether–chloroform (1:1)
mixture was used as an eluent. Yield of crude 3b 150 mg (53%) as
a 9:1 mixture of diastereomers; slight yellow oil; Rf 0.26 (CHCl3); 1H
(CDCl3, 400 MHz):
d
1.59 (s, 3H, CH3), 1.61 (dd, 2J¼13.1 Hz,
3J¼2.9 Hz, 1H, C(9)H2), 1.66 (s, 3H, CH3), 2.24 (dd, 2J¼13.1 Hz,
3J¼12.1 Hz, 1H, C(9)H2), 2.29 (dd, 2J¼14.4 Hz, 3J¼7.0 Hz, 1H, C(8)H2),
2.93 (br d, 2J¼14.4 Hz, 1H, C(8)H2), 3.37 (dd, 3J¼2.9, 12.1 Hz, 1H,
C(6)H), 3.39 (br d, 3J¼7.0 Hz, 1H, C(8a)H), 3.47 (s, 3H, OCH3), 3.72 (s,
NMR (CDCl3, 400 MHz): d for major isomer 1.45 (s, 3H, CH3), 1.75 (s,
3H, CH3), 2.99 (dd, 2J¼14.0 Hz, 3J¼5.7 Hz, 1H, CH2), 3.30 (dd,
2J¼14.0 Hz, 3J¼5.3 Hz, 1H, CH2), 3.53 (m, 1H, CH), 3.63 (m, 1H, CH),
3.72 (s, 3H, CH3O), 3.74 (s, 3H, CH3O), 4.34 (br s, 1H, CH]), 6.84 (br
d, 3J¼3.4 Hz, 1H, Th), 6.94 (dd, 3J¼3.4, 5.0 Hz, 1H, Th), 7.18 (br d,
3H, OCH3), 6.71 (d, 3J¼5.1 Hz, 1H, Th), 7.13 (d, 3J¼5.1 Hz, 1H, Th); 13
C
NMR (CDCl3, 100 MHz): d 22.7 (CH3), 23.5 (CH3), 41.2 (C(8)H2), 46.3
3J¼5.0 Hz, 1H, Th); 13C NMR (CDCl3, 100 MHz):
d
for major isomer
(C(6)H), 48.0 (C(9)H2), 52.3 (C(8a)H), 53.0 (2ꢃCH3O), 61.7 (C), 79.7
13.7 (CH3), 23.6 (CH3), 38.7 (CH2), 48.9 (CHTh), 52.8 (CH3O), 53.0
(C), 91.2 (C),121.5 (CH, Th),124.1 (CH, Th),137.6 (C, Th),144.4 (C, Th),

A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
5391
170.4 (CO2Me), 173.1 (CO2Me). Anal. Calcd for C17H20O5S: C, 60.70;
H, 5.99. Found: C, 60.61; H, 6.05.
(58 mg, 0.6 mmol) in 10 mL of CH2Cl2 under the specified condi-
tions and stirred at room temperature for 2 h and under reflux for
3 h. Petroleum ether–chloroform (2:1) mixture was used as an el-
uent. Yield of 7a 280 mg (82%); colorless solid; mp 145.0–147.0 ꢂC;
4.6.2. Dimethyl (3RS,3aSR,5SR,9bRS)-6,7,8-trimethoxy-3a,5-
dimethyl-3,3a,5,9b-tetrahydro-3,5-methanocyclopenta[c]-
isochromene-2,2(1H)-dicarboxylate (5b)
A solution of SnCl4 (0.23 mL, 2.0 mmol) in 1 mL of CH2Cl2 was
added dropwise to solution of 1e (320 mg, 1.0 mmol) and 2c
(100 mg, 1.0 mmol) in 10 mL of CH2Cl2 under the specified condi-
tions and stirred at room temperature for 18 h. Petroleum ether–
chloroform (2:1) mixture was used as an eluent. Yield of 5b 320 mg
(76%); colorless solid; mp 98.0–99.0 ꢂC; Rf 0.10 (CHCl3); 1H NMR
Rf 0.25 (CHCl3); 1H NMR (CDCl3, 400 MHz):
d 1.30 (s, 3H, CH3), 1.85
(s, 3H, CH3), 2.14 (dd, 2J¼13.6 Hz, 3J¼5.7 Hz, 1H, HCH(6)), 2.27 (ddd,
2J¼13.2 Hz, 3J¼5.7 Hz, 4J¼1.0 Hz, 1H, HCH(2)), 2.52 (dd, 3J¼14.7,
5.7 Hz, 1H, CH(3)), 2.61 (dd, 3J¼9.4, 1.8 Hz, 1H, CH(7a)), 2.94 (dd,
2J¼13.2 Hz, 3J¼14.7 Hz, 1H, HCH(20)), 3.14 (dd, 2J¼13.6 Hz,
3J¼15.1 Hz, 1H, HCH(60)), 3.18 (d, 3J¼1.8 Hz, 1H, CH(7b)), 3.43 (s, 3H,
CH3O), 3.61 (s, 3H, CH3O), 3.69 (s, 3H, CH3O), 3.75 (s, 3H, CH3O),
3.95 (ddd, 3J¼5.7, 9.4,15.1 Hz,1H, CH(7)), 7.19–7.41 (m,10H, CH, Ph);
(CDCl3, 400 MHz):
d
1.53 (s, 3H, CH3), 1.66 (dd, 2J¼13.4 Hz,
13C NMR (CDCl3, 100 MHz):
d
23.6 (JCH¼127 Hz, CH3), 25.3
3J¼3.0 Hz, 1H, C(10)H2), 1.82 (s, 3H, CH3), 2.27 (dd, 2J¼13.4 Hz,
3J¼12.1 Hz, 1H, C(10)H2), 2.39 (dd, 2J¼14.4 Hz, 3J¼7.5 Hz, 1H,
C(1)H2); 2.78 (dd, 2J¼14.4 Hz, 3J¼0.7 Hz, 1H, C(1)H2), 3.21 (dd,
3J¼0.7, 7.5 Hz, 1H, C(9b)H), 3.29 (dd, 3J¼3.0, 12.1 Hz, 1H, C(3)H), 3.71
(s, 3H, CH3O), 3.72 (s, 3H, CH3O), 3.74 (s, 6H, 2ꢃCH3O), 3.80 (s, 3H,
(1JCH¼126 Hz, CH3), 36.4 (1JCH¼136 Hz, C(6)H2), 37.8 JCH¼136 Hz,
C(2)H2), 44.6 (1JCH¼128 Hz, C(7)H), 51.7 (1JCH¼147 Hz, CH3O), 52.4
(1JCH¼148 Hz, CH3O), 52.5 (1JCH¼148 Hz, CH3O), 52.9 (1JCH¼148 Hz,
CH3O), 53.5 (1JCH¼124 Hz, C(3)H), 56.7 (1JCH¼141 Hz, C(7b)H), 59.4
(1JCH¼135 Hz, C(7a)H), 63.7 (C), 68.4 (C), 93.9 (C), 97.4 (C), 123.5
(CH, Ph), 126.8 (CH, Ph), 127.3 (2ꢃCH, Ph), 128.3 (2ꢃCH, Ph), 128.4
(2ꢃCH, Ph), 129.7 (2ꢃCH, Ph), 137.7 (C), 139.3 (C), 169.3 (CO2Me),
170.2 (CO2Me), 171.7 (CO2Me), 171.8 (CO2Me). Anal. Calcd for
C32H36O9: C, 68.07; H, 6.43. Found: C, 68.18; H, 6.27.
1
CH3O), 6.45 (s, 1H, CH, Ar); 13C NMR (CDCl3, 100 MHz):
d 23.8
(1JCH¼127 Hz, CH3), 25.2 (1JCH¼127 Hz, CH3), 41.3 (1JCH¼136 Hz,
C(1)H2), 47.3 (1JCH¼132 Hz, C(10)H2), 48.7 (1JCH¼134 Hz, C(9b)H),
52.0 (1JCH¼148 Hz, CH3O), 52.8 (1JCH¼148 Hz, CH3O), 53.3
(1JCH¼141 Hz, C(3)H), 55.8 (1JCH¼144 Hz, CH3O), 60.5 (1JCH¼144 Hz,
CH3O), 60.6 (1JCH¼144 Hz, CH3O), 61.3 (C), 80.3 (C), 89.9 (C), 107.8
(1JCH¼153 Hz, CH, Ar), 129.5 (C, Ar), 133.7 (C, Ar), 140.6 (C, Ar), 149.1
(C, Ar), 152.6 (C, Ar), 170.3 (CO2Me), 172.8 (CO2Me). Anal. Calcd for
C22H28O8: C, 62.85; H, 6.71. Found: C, 62.65; H, 6.73.
4.8.2. Tetramethyl 3a,4a-dimethyl-3,7-di-2-thienyloctahydro-
dicyclopenta[b,d]furan-1,1,5,5-tetracarboxylate (7b)
Compound 1b (200 mg, 0.83 mmol), 2c (40 mg, 0.4 mmol), and
Yb(OTf)3 (26 mg, 0.042 mmol) in 10 mL of CH2Cl2 was stirred at
room temperature for 72 h. Petroleum ether–chloroform (4:1)
mixture was used as an eluent. Yield of 7b 220 mg (94%); mixture of
two isomers (dr 2:1); colorless solid; mp 158.0–160.0 ꢂC; Rf 0.33
4.7. Tandem [3D2]-cycloaddition/intermolecular
electrophilic aromatic substitution of donor–acceptor
cyclopropanes with furans
(CHCl3); 1H NMR (CDCl3, 400 MHz):
d for major isomer 1.36 (s, 3H,
CH3), 1.80 (s, 3H, CH3), 2.28 (dd, 2J¼13.6 Hz, 3J¼5.9 Hz, 1H, CH2),
2.36 (ddd, 2J¼13.2 Hz, 3J¼5.8 Hz, 4J¼1.0 Hz, 1H, CH2), 2.52 (dd,
3J¼1.3, 9.4 Hz, 1H, CH), 2.80 (dd, 2J¼13.2 Hz, 3J¼14.4 Hz, 1H, CH2),
2.93 (dd, 3J¼5.8, 14.4 Hz, 1H, CH), 3.07 (dd, 2J¼13.6 Hz, 3J¼14.7 Hz,
1H, CH2), 3.34 (m, 1H, CH), 3.61 (s, 3H, CH3O), 3.66 (s, 3H, CH3O),
3.71 (s, 3H, CH3O), 3.76 (s, 3H, CH3O), 4.20 (ddd, 3J¼5.9, 9.4, 14.7 Hz
1H, CH), 6.84 (br d, 3J¼3.5 Hz, 1H, Th), 6.88–6.92 (m, 2H, Th), 7.02
(dd, 3J¼3.5, 5.1 Hz, 1H, Th), 7.17 (dd, 3J¼5.1 Hz, 4J¼0.8 Hz, 1H, Th),
4.7.1. Dimethyl 2-(2,5-dimethyl-3-furyl)-2,6a-dimetyl-6-
phenylhexahydro-4H-cyclopenta[b]furan-4,4-dicarboxylate (6)
A solution of SnCl4 (0.12 mL, 1.0 mmol) in 1 mL of CH2Cl2 was
added dropwise to solution of 1d (200 mg, 0.85 mmol) and 2c
(240 mg, 2.5 mmol) in 10 mL of CH2Cl2 under the specified condi-
tions and stirred under reflux for 23 h. Petroleum ether–chloroform
(4:1) mixture was used as an eluent. Yield 6 250 mg (69%) as
a mixture of isomers (dr 4:1); colorless oil; Rf 0.50 (CHCl3); 1H NMR
4
7.23 (dd, 3J¼5.1 Hz, J¼0.8 Hz, 1H, Th); 13C NMR (CDCl3, 100 MHz):
(CDCl3, 400 MHz):
d
for major isomer 1.21 (s, 3H, CH3), 1.44 (s, 3H,
d for major isomer 23.7 (CH3), 25.2 (CH3), 38.5 (CH2), 40.5 (CH2),
CH3), 1.60 (dd, 2J¼12.9 Hz, 3J¼8.6 Hz, 1H, CH2), 2.11 (s, 3H, CH3), 2.19
(s, 3H, CH3), 2.34 (dd, 2J¼12.9 Hz, 3J¼5.6 Hz, 1H, CH2), 2.60 (dd,
2J¼12.9 Hz, 3J¼9.4 Hz, 1H, CH2), 2.63 (dd, 3J¼5.6, 14.4 Hz, 1H, CH),
2.90 (dd, 2J¼12.9 Hz, 3J¼14.4 Hz, 1H, CH2), 3.37 (dd, 3J¼8.6, 9.4 Hz,
1H, CH), 3.76 (s, 3H, CH3O), 3.80 (s, 3H, CH3O), 5.73 (s, 1H, CH, Fu),
40.7 (CH), 49.2 (CH), 52.0 (CH3O), 52.5 (CH3O), 52.6 (CH3O), 52.9
(CH3O), 56.7 (CH), 59.8 (CH), 63.7 (C), 68.3 (C), 93.5 (C), 97.6 (C),
124.3 (CH, Th), 124.8 (CH, Th), 125.2 (CH, Th), 125.4 (CH, Th), 126.1
(CH, Th), 126.9 (CH, Th), 140.7 (C, Th), 142.8 (C, Th), 169.1 (CO2Me),
169.9 (CO2Me), 171.6 (CO2Me), 171.8 (CO2Me);
d for minor isomer
7.22–7.32 (m, 5H, Ph); 13C NMR (CDCl3, 100 MHz):
d
for major iso-
25.4 (CH3), 26.6 (CH3), 40.5 (CH2), 42.4 (CH2), 47.3 (CH), 49.8 (CH),
52.2 (OCH3), 52.3 (OCH3), 52.6 (OCH3), 53.2 (OCH3), 62.0 (CH), 65.2
(CH), 62.9 (C), 69.3 (C), 95.1 (C), 97.1 (C), 123.2 (CH, Th), 123.3 (CH,
Th), 124.9 (CH, Th), 125.7 (CH, Th), 126.1 (CH, Th), 126.9 (CH, Th),
140.6 (C, Th), 147.8 (C, Th), 169.6 (CO2Me), 169.7 (CO2Me), 171.8
(CO2Me), 172.2 (CO2Me). Anal. Calcd for C28H32O9S2: C, 58.32; H,
5.59. Found: C, 58.33; H, 5.63.
mer 13.2 (CH3), 13.4 (CH3), 25.7 (CH3), 30.1 (CH3), 36.8 (CH2), 42.7
(CH2), 52.6 (CH3O), 53.0 (CH), 53.4 (CH), 54.4 (CH3O), 62.4 (C), 80.4
(C), 91.2 (C), 106.1 (CH), 126.5 (CH), 127.5 (2ꢃCH), 129.7 (2ꢃCH),
138.1 (C), 145.5 (C), 148.2 (2ꢃC), 170.5 (CO2Me), 172.2 (CO2Me);
d for
minor isomer 13.1 (CH3), 13.4 (CH3), 28.8 (CH3), 29.8 (CH3), 35.8
(CH2), 43.3 (CH2), 52.6 (CH3O), 53.5 (CH), 53.7 (CH), 54.4 (CH3O),
62.3 (C), 81.2 (C), 90.5 (C), 106.1 (CH), 126.3 (2ꢃCH), 127.6 (CH),
129.6 (2ꢃCH), 137.8 (C), 143.8 (C), 148.2 (2ꢃC), 170.2 (CO2Me), 172.0
(CO2Me). Anal. Calcd for C25H30O6: C, 70.40; H, 7.09. Found: C,
70.05; H, 6.68.
4.9. X-ray structure determination of compound 7a
C32H36O9, M¼564.61, T¼120(2) K, ¼0.71073 Å, triclinic, space
l
4.8. Tandem [3D2]/[3D2]-cycloadditions of donor–acceptor
cyclopropanes with furans
group P-1, a¼8.7876(6) Å, b¼10.9970(8) Å, c¼15.6556(11),
a
¼85.000(5)ꢂ,
b
¼87.032(5)ꢂ,
g
¼73.430(5)ꢂ, V¼1443.99(18) Å3,
Z¼2, dcalcd¼1.299 Mg/m3,
m
¼0.095 mmꢁ1
F(000)¼600, crystal
,
4.8.1. Tetramethyl (3RS,3aSR,4aRS,7RS,7aRS,7bRS)-3a,4a-dimethyl-
3,7-diphenyloctahydrodicyclopenta[b,d]furan-1,1,5,5-
tetracarboxylate (7a)
A solution of SnCl4 (0.28 mL, 2.4 mmol) in 1 mL of CH2Cl2 was
added dropwise to a solution of 1d (320 mg, 1.4 mmol) and 2c
size¼0.35ꢃ0.15ꢃ0.10 mm3, reflections collected¼15,989, in-
dependent reflections¼7616 [R(int)¼0.0250], refinement method-
¼full-matrix least-squares on F2, goodness-of-fit on F2¼1.001, final
R indices [I>2
s
(I)] R1¼0.0563, wR2¼0.1433, largest diff. peak and
hole¼0.369 and ꢁ0.235 e Åꢁ3
.

5392
A.O. Chagarovskiy et al. / Tetrahedron 65 (2009) 5385–5392
11. Parreault, C.; Goudreau, S. R.; Zimmer, L. E.; Charette, A. B. Org. Lett. 2008, 10,
Crystallographic data for compound 7a have been deposited
689–692.
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC 717759. Copies of the data can be obtained,
free of charge, on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (fax: þ44 (0) 1223 336033 or e-mail:
deposit@ccdc.cam.ac.uk).
12. Ding, Q.; Wang, Z.; Wu, J. Tetrahedron Lett. 2009, 50, 198–200.
13. (a) Carson, C. A.; Kerr, M. A. Angew. Chem., Int. Ed. 2006, 45, 6560–6563; (b)
Young, I. S.; Kerr, M. A. J. Am. Chem. Soc. 2007, 129, 1465–1469; (c) Morales, C. L.;
Pagenkopf, B. L. Org. Lett. 2008, 10, 157–159.
14. (a) Young, I. S.; Kerr, M. A. Org. Lett. 2004, 6, 139–141; (b) Young, I. S.; Williams,
J. L.; Kerr, M. A. Org. Lett. 2005, 7, 953–955.
15. Ivanova, O. A.; Budynina, E. M.; Grishin, Yu. K.; Trushkov, I. V.; Verteletskii, P. V.
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Acknowledgements
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We thank the Russian Foundation of Basic Research (Project 09-
03-00244-a) for financial support of this work.
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