Lewis acid catalyzed reactions of donor-acceptor cyclopropanes with anthracenes

Article abstract of DOI:10.1002/ejoc.200800620

The reactions of 2-aryl-1,1-cyclopropane diesters with anthracene derivatives were studied for the first time. Three kinds of reaction products are formed depending on the nature of the aryl group and the substituents in the anthracene. The first one is the product of [4+3] cycloaddition of cyclopropane to a diene moiety of anthracene. The second one also has a seven-membered ring and is formed by the Lewis acid catalyzed electrophilic attack of cyclopropane onto the C9 atom of anthracene followed by intramolecular attack of the formed arenonium ion on aryl group of the starting cyclopropane. Lastly, the common Friedel-Crafts products are formed. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800620

FULL PAPER
DOI: 10.1002/ejoc.200800620
Lewis Acid Catalyzed Reactions of Donor–Acceptor Cyclopropanes with
Anthracenes
Olga A. Ivanova,*[a] Ekaterina M. Budynina,[a] Yuri K. Grishin,[a] Igor V. Trushkov,[a] and
Pavel V. Verteletskii[a]
Keywords: Cycloaddition / Aromatic substitution / Cyclopropanes / Dienes / Lewis acids
The reactions of 2-aryl-1,1-cyclopropane diesters with an-
thracene derivatives were studied for the first time. Three
kinds of reaction products are formed depending on the na-
ture of the aryl group and the substituents in the anthracene.
The first one is the product of [4+3] cycloaddition of cyclopro-
pane to a diene moiety of anthracene. The second one also
has a seven-membered ring and is formed by the Lewis acid
catalyzed electrophilic attack of cyclopropane onto the C9
atom of anthracene followed by intramolecular attack of the
formed arenonium ion on aryl group of the starting cyclopro-
pane. Lastly, the common Friedel–Crafts products are
formed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
Cyclopropanes have found a wide range of applications
in modern organic synthesis.[1] Introduction of various
functional groups into the cyclopropane ring extends its re-
activity significantly. Thus, cyclopropanes with electron-
withdrawing groups are prone to reactions with nucleo-
philes acting as a homo Michael acceptor similar to elec-
tron-deficient alkenes.[2] Cyclopropanes bearing electron-
donating groups show increased sensitivity to electrophilic
agents.[1,3] Donor–acceptor cyclopropanes have the broad-
est scope of reactivity.[4] They react with both nucleophiles
and electrophiles. However, the most interesting synthetic
application of donor–acceptor cyclopropanes is related to
their ability to react, under Lewis acid mediated conditions,
with double or triple bonds, such as C=C,[5] CϵC,[6]
C=O,[7] C=N,[8] CϵN,[9] and N=N[10] through [3+2] cyclo-
addition reactions to afford five-membered carbo- and het-
erocycles. In these reactions donor–acceptor cyclopropanes
can be considered as 1,3-dipole equivalents of type A
(Scheme 1). Moreover, donor–acceptor cyclopropanes are
able to react with nitrones in the presence of Lewis acids to
produce tetrahydro-1,2-oxazine derivatives by [3+3] cyclo-
addition reactions.[11]
Scheme 1.
(Scheme 2).[12] Herein we report our results on the reactions
of donor–acceptor cyclopropanes with anthracenes as
dienes.
Scheme 2.
Results and Discussion
Reactions of 2-Aryl-1,1-cyclopropane Diesters with
Anthracene
Recently, we reported the first example of a [4+3] cyclo-
addition of donor–acceptor cyclopropanes. In these
Yb(OTf)3-catalyzed reactions, 2-aryl-1,1-cyclopropane dies-
ters added to 1,3-diphenylisobenzofuran as three-carbon
The first process to be studied was the reaction between
2-phenyl-1,1-bis(ethoxycarbonyl)cyclopropane (1a) and an-
thracene (2a) (Scheme 3). Earlier we found that the best
yields in the [4+3] cycloaddition of 2-aryl-1,1-cyclopropane
diesters to 1,3-diphenylisobenzofuran were obtained when
reactions were performed in CH2Cl2 in the presence of
Yb(OTf)3 as a catalyst.[12] Unfortunately, under the same
reaction conditions the desired cycloaddition product 3a
was formed from cyclopropane 1a and anthracene (2a) in a
dienophiles
to
form
seven-membered
skeletons
[a] Department of Chemistry, M.V. Lomonosov Moscow State
University,
Leninskie gory 1/3, Moscow 119991, Russia
Fax: +7-495-932-8846
E-mail: iv@org.chem.msu.ru
Eur. J. Org. Chem. 2008, 5329–5335
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5329

O. A. Ivanova et al.
FULL PAPER
very small amount. At room temperature, conversion was spectroscopic data, 4c has a tribenzobicyclo[3.2.2]nonane
low, and the increase in the reaction temperature led to con- framework with two CH bridgehead groups, an aliphatic
siderable polymerization of cyclopropane 1a. Therefore, we CH2CH(CO2Me)2 side chain, and an alicyclic CH group.
examined alternative Lewis acids and found that the best
Similar adduct 4d was also the major product (71%
results were obtained when cyclopropane 1a was added to yield) in the reaction of 2-(2-thienyl)cyclopropane (1d;
anthracene (2a) at –40 °C in the presence of TiCl4 (1:1.1:1.2 Scheme 5). However, in this case [4+3] cycloadduct 3d was
ratio) followed by warming of the reaction mixture to room also formed in low yield (14%).
temperature whilst stirring for 4 h. Under these reaction
The possible mechanism for the formation of 4 is pre-
conditions, [4+3] cycloadduct 3a was obtained as a single sented in Scheme 6 for the reaction of 1d. Lewis acid in-
1
product in 85% yield. Its structure was proved by H and duces cyclopropane ring opening into 1,3-zwitterionic inter-
13C NMR spectroscopy, which confirmed the formation of mediate A, which is stabilized by an electron-enriched aryl
3
the bicyclic skeleton. The expected J value for the proton group. Electrophilic attack of intermediate A at C9 of an-
of a bridgehead CH group connected to a CHAr group thracene leads to intermediate B. The new cationic center
must be small, as the H–C–C–H dihedral angle is close to in B can interact with two nucleophilic centers (paths a and
90 °. Indeed, the protons of both bridgehead CH groups b). Attack at the enolate-like C2 atom of the malonyl moi-
give characteristic broadened singlets (δ = 4.06 and ety leads to the [4+3] cycloaddition product 3d (path a).
5.02 ppm, cf. Experimental Section). Other alicyclic protons This path predominates when the aryl group has moderate
gave an AMX-type spectrum.
nucleophilicity. Thiophene is more reactive towards electro-
philes than benzene. As a result, the thienyl moiety attacks
the cationic center in B to give 4d (path b), which competes
efficiently with the [4+3] way of cyclization (path a). The
nucleophilicity of 1,2,3-trimethoxybenzene is even higher.
Therefore, in the case of cyclopropane 1c, interaction of the
electrophilic center with the electron-enriched aryl group
(path b) is the only transformation for intermediate B.
Scheme 3.
To investigate the scope of this reaction, cyclopropanes
1b–d were studied under the same conditions. Cyclopropane
1b reacted in a similar manner to produce [4+3] cycload-
dition product 3b (Scheme 3). A single product was also
obtained when cyclopropane 1c with three donor substitu-
ents in the phenyl ring was treated with anthracene (2a) and
1
TiCl4. However, careful analysis of the H and 13C NMR
spectroscopic data showed that a different product, 4c, was
formed in this reaction (Scheme 4). According to the NMR
Scheme 4.
Scheme 6.
Scheme 5.
5330
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 5329–5335

Lewis Acid Catalyzed Reactions of Cyclopropanes with Anthracenes
Thus, the competitive formation of two kinds of products Reactions of 2-Phenyl-1,1-cyclopropane Diesters with 2,3-
in the reactions of anthracene with cyclopropane 1d can be Benzanthracene
explained by the realization of the stepwise mechanism. The
We found that 2,3-benzanthracene (2b) reacted with do-
nor–acceptor cyclopropanes similarly to anthracene. For
example, [4+3] cycloaddition product 6 (Scheme 8) was ob-
tained from tetracene (2b) and donor–acceptor cyclopro-
pane 1e under catalysis by TiCl4 or SnCl4.
direction of cyclization depends on the nucleophilic reactiv-
ity of the aryl group in the starting cyclopropane. When
the nucleophilicity of the aromatic substituent is low, [4+3]
cycloadducts are formed, but when the aryl group is suffi-
ciently nucleophilic, the electrophilic cyclization onto the
aromatic moiety becomes the main reaction path. The for-
mation of only 4c from cyclopropane 1c is in full accord-
ance with the above mechanism. It is logical to suppose that
[4+3] cycloadducts 3a,b are formed in reactions of anthra-
cene with cyclopropanes 1a,b by the same mechanism, but
some additional experiments are needed for confirmation
of this conclusion. As one of these experiments, we hy-
drolyzed the reaction mixtures of cyclopropanes 1a–d with
anthracene (2a) before full conversion of the reagents. We
found that open-chain byproducts 5 were obtained after
quenching. When cyclopropane 1a was treated with TiCl4
in the absence of anthracene, chloride 5a was the only prod-
uct of the reaction (Scheme 7). The formation of 5a is cir-
cumstantial evidence for the generation of open-chain inter-
mediate A.
Reactions of 2-Aryl-1,1-cyclopropane Diesters with 9-Methyl-
anthracene and 9,10-Dimethylanthracene
In agreement with our hypothesis, the reactions of cyclo-
propanes 1a,b with 9-methylanthracene (2c) and 9,10-di-
methylanthracene (2d) failed to produce cycloaddition
products 3 and 4. In these reactions only electrophilic sub-
stitutions of the anthracene derivatives were observed.
Thus, in the reaction of cyclopropane 1a with 2c
(Scheme 9), open-chain intermediate A attacked the unsub-
stituted C10 atom by the cationic center to afford product
7 in good yield. When both the C9 and C10 positions were
substituted, as it was in 2d, electrophilic attack was directed
to C2 to produce 8a,b (Scheme 10).
Scheme 7.
It is well known that 9,10-dimethylanthracene is more
reactive in Diels–Alder cycloadditions than anthracene
itself. However, for a stepwise reaction we can expect an-
other model of reactivity: the substituents at C2 and C3
Scheme 9.
Anthrone (2e) was also treated with 1a (Scheme 11) in
of anthracene should not significantly affect the reactivity the presence of a moderate excess of TiCl4 (1.5 equiv.). In
towards donor–acceptor cyclopropanes, whereas substitu- this case, we found that Lewis acid can play two roles. The
tion at C9 and C10 leads to stabilization of the intermediate first one is transformation of anthrone into anthracene in-
carbocation and induces steric repulsions. Both effects termediate C. Another one is catalytic cleavage of cyclopro-
should prevent the formation of both kinds of cycloadducts pane 1a into zwitterionic intermediate A. The interaction
3 and 4. To experimentally test these hypotheses, we studied between A and C leads to the formation of 10-substituted
reactions of donor–acceptor cyclopropanes with tetracene anthrone 9 in high yield.
(2b) as an example of 2,3-disubstituted anthracenes as well
Lewis acid catalyzed formation of Friedel–Crafts adduct
as with 9-methylanthracene (2c) and 9,10-dimethylanthra- was also found in the reaction of 2-phenyl-1,1-cyclopropane
cene (2d).
diester with 1,3-dimethoxybenzene (10; Scheme 12).
Scheme 8.
Eur. J. Org. Chem. 2008, 5329–5335
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5331

O. A. Ivanova et al.
FULL PAPER
Scheme 10.
When the nucleophilicity of the aromatic substituent is low,
[4+3] cycloadducts are formed, but when the aryl group is
sufficiently nucleophilic, electrophilic cyclization onto the
aromatic moiety becomes the main reaction path. The
products of both kinds of cyclization were found in the re-
actions of 2-(2-thienyl)-1,1-cyclopropane diester, wherein
the thienyl group has intermediate reactivity.
Experimental Section
General Remarks: NMR spectra were recorded with a Bruker Av-
ance-400 (400 MHz for 1H and 100 MHz for 13C NMR) spectrom-
eter at room temperature; the chemical shifts (δ) were measured in
1
ppm with respect to the solvent (CDCl3, H: δ = 7.26 ppm, 13C: δ
= 77.13 ppm). MS were recorded with a Bruker Ultraflex MALDI-
TOF mass spectrometer in positive mode (dithranol matrix) or a
Finnigan MAT INCOS 50 (the energy of ionizing electrons was
70 eV, direct input or GCMS). Melting points (mp): Electrothermal
9100 capillary melting point apparatus, values uncorrected. Col-
umn chromatography was performed on silica gel 60 (230–
400 mesh, Merck). TiCl4, SnCl4, Yb(OTf)3, anthracene, benzan-
thracene, 9-methylanthracene, 9,10-dimethylanthracene, anthrone,
and 1,3-dimethoxybenzene are available commercially. 2-Aryl-1,1-
cyclopropane diesters 1 were prepared by published procedures.[14]
All the reactions were carried out by using freshly distilled and dry
solvents from solvent stills.
Scheme 11.
Scheme 12.
General Procedure for the TiCl4 or SnCl4 Catalyzed Reaction of
Diethyl 2-Arylcyclopropane-1,1-dicarboxylates with Anthracenes:
Lewis acid (1.2 mmol) was added to solution of anthracene
(1.2 mmol) in dry CH2Cl2 (20 mL) at –40 °C under an atmosphere
of argon. To the resulting mixture was dropwise added a solution
of cyclopropane (1.0 mmol) in CH2Cl2 (20 mL) over 10–15 min.
The reaction mixture was stirred for 0.5 h at –40 °C, warmed to
room temperature, and stirred for the specified time. The solvent
was evaporated under vacuum, and the final residue was purified
by column chromatography (SiO2; hexane/CHCl3, 1:1) to yield de-
sired product 3, 4, 6–9.
There are only two earlier examples of such reactivity of
donor–acceptor cyclopropanes towards aromatic com-
pounds, namely, annulation of aryl cyclopropyl ketones and
electrophilic substitution in indoles.[13]
Conclusions
2-Aryl-1,1-cyclopropane diesters react with anthracene
derivatives under Lewis acid catalysis through a stepwise
mechanism, which includes cyclopropane ring opening into
1,3-zwitterionic intermediate A, electrophilic attack of this
intermediate onto anthracene with formation of intermedi-
ate B, and finally, transformation of the last intermediate
into the reaction products. Three kinds of products are
formed depending on the substituents in anthracene and
the nature of the aryl group in the donor–acceptor cyclo-
propane. The common Friedel–Crafts products are formed
from 9- and 9,10-substituted anthracenes. For anthracenes
without substituents at C9 and C10, two kinds of products
Diethyl 13-Phenyl-9,10-dihydro-9,10-propanoanthracene-11,11-di-
carboxylate (3a): TiCl4, 4 h. White foam. Yield: 0.37 g (85%). Rf =
1
0.50 (CHCl3). M.p. 135–136 °C. H NMR (400 MHz, CDCl3): δ =
3
1.23 (t, 3J = 7.2 Hz, 3 H, CH3), 1.28 (t, J = 7.2 Hz, 3 H, CH3),
1.62 (dd, 2J = 14.2 Hz, 3J = 12.4 Hz, 1 H, CH2), 2.48 (dd, 2J =
14.2 Hz, 3J = 4.0 Hz, 1 H, CH2), 3.68 (dd, 3J = 4.0 Hz, 3J =
12.4 Hz, 1 H, CHPh), 3.97 (dq, 2J = 10.8 Hz, 3J = 7.2 Hz, 1 H,
CH2O), 4.06 (br. s, 1 H, CH), 4.02–4.19 (m, 2 H, CH2O), 4.27 (dq,
2J = 10.8 Hz, 3J = 7.2 Hz, 1 H, CH2O), 5.02 (br. s, 1 H, CH), 7.13–
7.39 (m, 12 H), 7.82 (br. d, 3J = 7.6 Hz, 1 H) ppm. 13C NMR
resulting from cyclization of intermediate B were isolated. (100 MHz, CDCl3): δ = 14.03 (2ϫCH3), 35.70 (CH2), 42.24
5332
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 5329–5335

Lewis Acid Catalyzed Reactions of Cyclopropanes with Anthracenes
(CHPh), 49.42 (CH), 53.29 (CH), 56.71 (C), 61.13 (CH2O), 61.56
ppm. GC–MS: m/z (%) = 446 (5) [M]+, 268 (2), 222 (5), 178 (100),
(CH2O), 125.33 (CH), 125.76 (CH), 126.45 (CH), 126.67 (CH), 121 (4). C27H26O4S (446.56): calcd. C 72.62, H 5.87; found C 72.55,
126.70 (CH), 127.41 (3ϫCH), 127.61 (CH), 128.19 (CH), 128.65 H 5.64.
(2ϫCH), 129.19 (CH), 138.1 (C), 139.0 (C), 139.6 (C), 146.3 (C),
2-[2,2-Bis(methoxycarbonyl)ethyl]-4-thiapentacyclo-
146.67 (C), 169.8 (CO2Et), 171.1 (CO2Et) ppm. GC–MS: m/z (%)
[6.6.6.03,7.09,14.015,20]icosa-3(7),5,9,11,13,15,17,19-octaene (4d):
= 440 (2) [M]+, 262 (4), 178 (100), 170 (7), 115 (6). C29H28O4
TiCl4, 22 h. Light-yellow oil. Yield: 0.32 g (71 %). Rf = 0.59
(440.53): calcd. C 79.09, H 6.36; found C 79.26, H 6.55.
1
3
(CHCl3). H NMR (400 MHz, CDCl3): δ = 1.34 (t, J = 7.1 Hz, 3
3
2
Diethyl 13-(4-Fluorophenyl)-9,10-dihydro-9,10-propanoanthracene- H, CH3), 1.37 (t, J = 7.1 Hz, 3 H, CH3), 2.22 (ddd, J = 14.4 Hz,
3
2
3
11,11-dicarboxylate (3b): TiCl4, 4 h. White crystals. Yield: 0.33 g
3J = 5.2 Hz, J = 10.1 Hz, 1 H, CH2), 2.37 (ddd, J = 14.4 Hz, J
1
(72%). Rf = 0.80 (CHCl3). M.p. 104–105 °C. H NMR (400 MHz,
= 4.0 Hz, 3J = 10.1 Hz, 1 H, CH2), 3.18–3.25 (m, 1 H, CHTh),
4.01 [dd, J = 5.2 Hz, J = 10.1 Hz, 1 H, CH(CO2Et)2], 3.85–3.96
(m, 2 H, CH2O), 4.25–4.39 (m, 5 H, 2ϫCH2O, CH), 4.91 (s, 1 H,
CH), 6.93 (d, 3J = 5.1 Hz, 1 H, Th), 7.02 (d, 3J = 5.1 Hz, 1 H, Th),
3
3
3
3
CDCl3): δ = 1.23 (t, J = 7.1 Hz, 3 H, CH3), 1.28 (t, J = 7.1 Hz,
2
3
3 H, CH3), 1.54 (dd, J = 14.2 Hz, J = 12.4 Hz, 1 H, CH2), 2.42
2
3
3
(dd, J = 14.2 Hz, J = 4.0 Hz, 1 H, CH2), 3.65 (dd, J = 4.0 Hz,
3J = 12.4 Hz, 1 H, CHPh), 3.95 (dq, J = 10.8 Hz, J = 7.2 Hz, 1 7.10–7.23 (m, 4 H), 7.28–7.41 (m, 4 H) ppm. 13C NMR (100 MHz,
2
3
H, CH2O), 3.98 (br. s, 1 H, CH), 4.06–4.17 (m, 2 H, OCH2), 4.27 CDCl3): δ = 14.16 (CH3), 14.27 (CH3), 35.81 (CH2), 41.36 (CH),
2
3
(dq, J = 10.8 Hz, J = 7.2 Hz, 1 H, OCH2), 4.99 (br. s, 1 H, CH),
48.32 (CH), 48.63 (CH), 50.26 (CH), 61.76 (2 ϫ CH2O), 122.37
(CH), 124.35 (CH), 124.87 (CH), 126.12 (CH), 126.43 (CH), 126.47
(CH), 126.69 (3ϫCH), 128.56 (CH), 136.52 (C), 136.91 (C), 139.56
(C), 139.96 (C), 145.55 (C), 146.67 (C), 169.01 (CO2Et), 169.13
(CO2Et) ppm. GC–MS: m/z (%) = 446 (12) [M]+, 286 (100), 271
3
6.98–7.34 (m, 11 H, Ph), 7.81 (br. d, J = 7.4 Hz, 1 H, Ph) ppm.
13C NMR (100 MHz, CDCl3): δ = 14.00 (2ϫCH3), 35.76 (CH2),
41.41 (CH-p-FPh), 49.27 (CH), 53.35 (CH), 56.65 (C), 61.15
2
(CH2O), 61.60 (CH2O), 115.30 (d, JCF = 21 Hz, 2ϫCH, p-FPh),
125.30 (CH), 125.80 (CH), 126.51 (CH), 126.70 (CH), 127.43 (44), 178 (9). C27H26O4S (446.56): calcd. C 72.62, H 5.87; found C
3
(2ϫCH), 128.13 (CH), 128.74 (d, JCF = 7 Hz, 2ϫCH, p-FPh),
72.52, H 5.91.
129.20 (CH), 137.98 (C), 138.87 (C), 139.26 (C), 142.32 (C), 146.00
Diethyl (2-Chloro-2-phenylethyl)malonate (5a): TiCl4 (0.23 g,
0.13 mL, 1.2 mmol) was added to a solution of cyclopropane 1a
(0.27 g, 1.0 mmol) in dry CH2Cl2 (10 mL) at –25 °C under an atmo-
sphere of argon. The reaction mixture was stirred for 0.5 h at
–25 °C, warmed to room temperature, and stirred for an additional
20 h. The solvent was evaporated under vacuum, and the final resi-
1
(C), 161.60 (d, JCF = 244 Hz, C-F), 169.69 (CO2Et), 171.00
(CO2Et) ppm. GC–MS: m/z (%) = 458 (1) [M]+, 280 (1), 235 (4),
178 (100), 133 (5). C29H27FO4 (458.52): calcd. C 75.96, H 5.94;
found C 75.70, H 5.89.
2-[2,2-Bis(methoxycarbonyl)ethyl]-5,6,7-trimethoxypentacyclo-
[7.6.6.03,8.010,15.016,21]henicosa-3,5,7,10,12,14,16,18,20-nonaene due was purified by column chromatography (SiO2; hexane/CHCl3,
(4c): TiCl4, 18 h. White foam. Yield: 0.35 g (70 %). Rf = 0.20
1:1). Colorless oil. Yield: 0.23 g (77 %). Rf = 0.66 (CHCl3). 1H
(CHCl3). M.p. 72–73 °C. 1H NMR (400 MHz, CDCl3): δ = 2.12 NMR (400 MHz, CDCl3): δ = 1.26 (t, 3J = 7.1 Hz, 3 H, CH3), 1.27
3
3
(m, 1 H, CH2), 2.46 (m, 1 H, CH2), 3.05 (br. d, J = 11.3 Hz, 1 H,
(t, 3J = 7.1 Hz, 3 H, CH3), 2.64 (t, J = 7.4 Hz, 2 H, CH2), 3.62 [t,
CH), 3.79 (s, 3 H, CH3), 3.80 (s, 3 H, CH3), 3.89 (s, 3 H, CH3), 3J = 7.4 Hz, 1 H, CH(CO2Et)2], 4.17–4.26 (m, 4 H, OCH2), 4.98
3.90 (s, 3 H, CH3), 4.00 [dd, 3J = 4.0 Hz, 3J = 11.6 Hz, 1 H,
(t, J = 7.4 Hz, 1 H, CH), 7.30–7.42 (m, 5 H, Ph) ppm. 13C NMR
3
3
CH(CO2Et)2], 4.08 (s, 3 H, CH3), 4.20 (d, J = 11.3 Hz, 1 H, CH),
(100 MHz, CDCl3): δ = 14.02 (2ϫCH3), 38.77 (CH2), 49.76 (CH),
5.63 (s, 1 H, CH), 6.61 (s, 1 H, CH), 7.15–7.50 (m, 8 H) ppm. 13C 60.91 (CH), 61.66 (2ϫCH2), 126.93 (2ϫCH, Ph), 128.64 (CH,
NMR (100 MHz, CDCl3): δ = 36.07 (CH2), 42.59 (CH), 43.66 Ph), 128.77 (2 ϫ CH, Ph), 140.60 (C), 168.53 (CO2Et), 168.68
(CH), 47.83 (CH), 49.89 (CH), 52.76 (2ϫCH3), 55.88 (CH3), 60.80
(CH3), 61.55 (CH3), 111.50 (CH), 124.98 (CH), 125.91 (CH), (6), 160 (100), 143 (11), 140/138 (4/12), 133 (44), 115 (42), 104 (19).
126.16 (CH), 126.26 (CH), 126.39 (CH), 126.55 (CH), 126.80 (CH), C15H19ClO4 (298.76): calcd. C 60.30, H 6.41; found C 60.47, H
(CO2Et) ppm. GC–MS: m/z (%) = 300/298 (3/8) [M]+, 263 (3), 189
127.90 (CH), 133.44 (C), 138.38 (C), 140.40 (2ϫC), 144.67 (C), 6.51.
145.44 (C), 149.29 (C), 151.89 (C), 153.24 (C), 169.69 (CO2Et),
Diethyl 21-Phenylpentacyclo[10.6.3.02,11.04,9.013,18]henicosa-
169.78 (CO2Et) ppm. GC–MS: m/z (%) = 502 (27) [M]+, 370 (8),
324 (25), 281 (11), 265 (13), 207 (32), 178 (100). C30H30O7 (502.56):
calcd. C 71.70, H 6.02; found C 71.50, H 5.91.
2,4,6,8,10,13,15,17-octaene-19,19-dicarboxylate (6): SnCl4, 23 h.
White foam. Yield: 0.30 g (65%). Rf = 0.58 (CHCl3). M.p. 112–
113 °C. 1H NMR (400 MHz, CDCl3, for a mixture of isomers A/B
55:45): δ = 1.64 (dd, 2J = 14.2 Hz, 3J = 12.8 Hz, 1 H, CH2, A),
Diethyl 13-(2-Thienyl)-9,10-dihydro-9,10-propanoanthracene-11,11-
dicarboxylate (3d): TiCl4, 22 h. White crystals. Yield: 63 mg (14%).
2
3
2
1.67 (dd, J = 14.2 Hz, J = 12.8 Hz, 1 H, CH2, B), 2.49 (dd, J =
3
2
3
Rf = 0.75 (CHCl3). M.p. 134–135 °C. 1H NMR (400 MHz, CDCl3): 14.2 Hz, J = 4.0 Hz, 1 H, CH2, A), 2.50 (dd, J = 14.2 Hz, J =
δ = 1.23 (t, 3J = 7.1 Hz, 3 H, CH3), 1.25 (t, 3J = 7.1 Hz, 3 H, CH3), 4.0 Hz, 1 H, CH2, B), 3.57 (s, 3 H, CH3, A), 3.64 (s, 3 H, CH3, B),
1.50 (dd, 2J = 14.0 Hz, 3J = 12.5 Hz, 1 H, CH2), 2.58 (dd, 2J =
3.70 (s, 3 H, CH3, B), 3.73 (s, 3 H, CH3, A), 3.75 (dd, 3J = 12.8 Hz,
14.0 Hz, 3J = 4.2 Hz, 1 H, CH2), 3.93 (dq, 2J = 10.7 Hz, 3J = 3J = 4.0 Hz, 1 H, CH, A), 3.78 (dd, J = 12.8 Hz, J = 4.0 Hz, 1
3
3
7.1 Hz, 1 H, CH2O), 3.98 (dd, 3J = 4.2 Hz, 3J = 12.5 Hz, 1 H,
CHTh), 4.04–4.15 (m, 2 H, CH2O), 4.12 (br. s, 1 H, CH), 4.26 (dq,
H, CH, B), 4.19 (br. s, 1 H, CH, B), 4.23 (br. s, 1 H, CH, A), 5.18
(s, 1 H, CH, A), 5.19 (s, 1 H, CH, B), 7.15–7.54 (m, 10 H, A+11
H, B), 7.45 (s, 1 H, B), 7.73 (s, 1 H, A), 7.75 (s, 1 H, A), 7.81–7.86
(m, 2 H, A+1 H, B), 7.96–7.99 (m, 1 H, A), 8.25 (s, 1 H, B) ppm.
13C NMR (100 MHz, CDCl3, for a mixture of isomers A/B 55:45):
δ = 35.36 (CH2, B), 35.49 (CH2, A), 42.98 (CH, B), 43.32 (CH, A),
49.71 (CH, B), 49.76 (CH, A), 52.12 (2ϫCH), 52.81 (2ϫCH3O),
3
2J = 10.6 Hz, J = 7.1 Hz, 1 H, CH2O), 4.96 (br. s, 1 H, CH), 6.85
3
2
3
(d, J = 3.3 Hz, 1 H, Th), 6.99 (dd, J = 3.3 Hz, J = 5.0 Hz, 1 H,
3
3
Th), 7.13 (t, J = 7.2 Hz, 1 H), 7.18 –7.32 (m, 7 H), 7.73 (br. d, J
= 7.4 Hz, 1 H, Ph) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.99
(2ϫCH3), 36.67 (CH2), 37.83 (CH), 49.13 (CH), 53.87 (CH), 56.84
(C), 61.16 (CH2O), 61.61 (CH2O), 123.09 (CH), 123.25 (CH), 53.45 (CH3O, A), 53.52 (CH3O, B), 57.52 (C, B), 57.67 (C, A),
125.61 (CH), 125.92 (CH), 126.59 (3ϫCH), 127.42 (CH), 127.79 123.39 (CH), 125.57 (CH), 125.68 (CH), 125.73 (CH), 125.92 (CH),
(CH), 128.00 (CH), 128.87 (CH), 137.98 (C), 138.59 (C), 138.67 125.95 (CH), 126.11 (2 ϫ CH), 126.77 (4 ϫ CH), 127.09 (CH),
(C), 145.15 (C), 149.64 (C, Ph), 169.64 (CO2Et), 170.80 (CO2Et)
127.41 (4ϫCH), 127.47 (2ϫCH), 127.59 (CH), 127.76 (2ϫCH),
Eur. J. Org. Chem. 2008, 5329–5335
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5333

O. A. Ivanova et al.
FULL PAPER
127.84 (CH), 127.96 (CH), 128.08 (CH), 128.68 (2ϫCH), 128.72 4.4 Hz, 1 H, CH2), 2.56 (ddd, 2J = 14.0 Hz, 3J = 10.5 Hz, 3J =
(2ϫCH), 129.25 (CH), 132.17 (C, A), 132.53 (C, B), 132.56 (C, B),
132.99 (C, A), 136.12 (C, A), 136.53 (C, B), 137.42 (C, B), 137.62
(C, B), 138.24 (C, A), 139.23 (C, A), 143.44 (C, A), 145.79 (C, B),
3.8 Hz, 1 H, CH2), 3.05 [dd, 3J = 4.4 Hz, 3J = 10.5 Hz, 1 H,
CH(CO2Et)2], 3.12–3.17 (m, 1 H, CHPh), 3.97–4.18 (m, 4 H,
3
3
OCH2), 4.46 (d, J = 3.8 Hz, 1 H, CH), 6.07 (d, J = 7.8 Hz, 2 H,
146.42 (C, B), 146.59 (C, A), 169.92 (CO2Me, B), 170.01 (CO2Me, Ph), 6.91 (t, 3J = 7.8 Hz, 2 H, Ph), 7.08 (t, 3J = 7.8 Hz, 1 H), 7.28–
3
3
A), 171.29 (CO2Me, B), 171.43 (CO2Me, A) ppm. HRMS 7.56 (m, 6 H), 7.92 (d, J = 7.8 Hz, 1 H), 8.02 (d, J = 7.8 Hz, 1
(MALDI-TOF): calcd. for C31H26O4 [M]+ 462.5357; found
462.5362.
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.93 (CH3), 14.06
(CH3), 31.78 (CH2), 49.81 (CH), 50.15 (CH), 54.17 (CH), 61.33
(CH2O), 61.44 (CH2O), 126.44 (CH), 126.73 (CH), 127.12 (CH),
127.33 (CH), 127.43 (CH), 127.68 (2ϫCH), 128.21 (CH), 128.67
(CH), 129.07 (2ϫCH), 131.72 (CH), 132.29 (CH), 133.19 (C),
134.16 (C), 136.15 (C), 140.84 (C), 143.63 (C), 169.06 (CO2Et),
169.18 (CO2Et), 183.78 (CO) ppm. MS (EI): m/z (%) = 263 (45),
208 (32), 193 (37), 189 (24), 165 (43), 115 (62), 57 (100). C29H28O5
(456.53): calcd. C 76.30, H 6.18; found C 76.46, H 6.25.
Diethyl [2-(10-Methyl-9-anthryl)-2-phenylethyl]malonate (7): TiCl4,
3 h, reflux. Yellow crystals. Yield: 0.30 g (67%). Rf = 0.26 (CHCl3).
M.p. 69–70 °C. 1H NMR (400 MHz, CDCl3): δ = 1.06 (t, 3J =
3
3
7.1 Hz, 3 H, CH3), 1.07 (t, J = 7.1 Hz, 3 H, CH3), 2.79 [dd, J =
3
4.5 Hz, J = 10.4 Hz, 1 H, CH(CO2Et)2], 3.18 (s, 3 H, CH3), 3.19–
3.25 (m, 1 H, CH2), 3.43–3.49 (m, 1 H, CH2), 3.85–3.96 (m, 2 H,
CH2O), 4.06–4.30 (m, 2 H, CH2O), 5.82 (dd, 3J = 5.2 Hz, 3J =
10.6 Hz, 1 H, CHPh), 7.14–7.61 (m, 9 H, Ph), 8.20–8.45 (m, 4 H,
Ph) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.79 (2ϫCH3), 14.59
(CH3), 32.34 (CH2), 39.78 (CHPh), 50.14 [CH(CO2Et)2], 61.32
(2 ϫ CH2O), 124.72 (3 ϫ CH), 125.64 (3 ϫ CH), 125.87 (CH),
127.01 (3ϫCH), 128.16 (C), 128.51 (3ϫCH), 128.70 (C), 128.80
(C), 130.03 (C), 130.30 (C), 132.38 (C), 144.60 (C), 169.23 (CO2Et),
169.35 (CO2Et) ppm. GC–MS: m/z (%) = 455 (1) [M + H]+, 365
(8), 281 (29), 207 (100), 191 (10). C30H30O4 (454.21): calcd. C 79.27,
H 6.65; found C 79.40, H 6.70.
Diethyl [2-(2,4-Dimethoxyphenyl)-2-phenylethyl]malonate (11): 1,3-
Dimethoxybenzene (10; 110 mg, 0.8 mmol), 2-phenyl-1,1-dicarboe-
thoxycyclopropane (1a; 210 mg, 0.8 mmol), and Yb(OTf)3 (25 mg,
0.04 mmol) were dissolved in dry chlorobenzene (4 mL) and stirred
with activated 4 Å molecular sieves under an argon atmosphere at
reflux for 6 h. The reaction mixture was filtered, the solvent was
evaporated under vacuum, and the final residue was purified by
column chromatography (SiO2; hexane/CHCl3, 1:1). Colorless li-
quid. Yield: 0.23 g (73%). Rf = 0.20 (CHCl3). 1H NMR (400 MHz,
3
3
CDCl3): δ = 1.26 (t, J = 7.1 Hz, 3 H, CH3), 1.27 (t, J = 7.1 Hz,
3 H, CH3), 2.57–2.73 (m, 2 H, CH2), 3.30 [t, 3J = 7.3 Hz, 1 H,
CH(CO2Et)2], 3.74 (s, 3 H, OCH3), 3.77 (s, 3 H, OCH3), 4.10–4.25
(m, 4 H, OCH2), 4.40 (t, 3J = 8.1 Hz, 1 H, CH), 6.45 (d, 4J =
Diethyl [2-(9,10-Dimethyl-2-anthryl)-2-phenylethyl]malonate (8a):
TiCl4, 24 h. Yellow oil. Yield: 0.24 g (51%). Rf = 0.52 (CHCl3). 1H
NMR (400 MHz, CDCl3): δ = 1.25 (t, 3J = 7.2 Hz, 3 H, CH3), 1.30
3
(t, J = 7.2 Hz, 3 H, CH3), 2.81–2.91 (m, 2 H, CH2), 3.07 (s, 3 H,
3
4
2.4 Hz, 1 H), 6.48 (dd, J = 8.4 Hz, J = 2.4 Hz, 1 H), 7.10–7.35
(m, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 14.08 (2ϫCH3),
33.86 (CH2), 40.59 (CH), 50.51 (CH), 55.24 (CH3O), 55.35
(CH3O), 61.25 (2ϫCH2O), 98.73 (CH, Ph), 104.30 (CH, Ph),
126.11 (CH, Ph), 128.05 (2 ϫ CH, Ph), 128.27 (3 ϫ CH, Ph),
143.98 (C), 158.08 (C), 159.46 (C), 169.41 (CO2Et), 169.60 (CO2Et)
ppm. C23H28O6 (400.46): calcd. C 68.98, H 7.05; found C 68.94, H
7.13.
CH3), 3.12 (s, 3 H, CH3), 3.35–3.42 (m, 1 H, CH), 4.14–4.19 (m, 1
H, CH), 4.20–4.29 (m, 4 H, 2ϫOCH2), 7.02–7.13 (m, 2 H, Ph),
7.20–7.42 (m, 4 H, Ph), 7.48–7.57 (m, 2 H, Ph), 8.21 (br. s, 1 H,
Ph), 8.23–8.37 (m, 3 H, Ph) ppm. 13C NMR (100 MHz, CDCl3): δ
= 14.05 (4ϫCH3), 34.01 (CH2), 49.06 (CH), 50.41 (CH), 61.43
(2 ϫ CH2O), 123.35 (CH), 124.61 (CH), 124.79 (CH), 125.30
(2 ϫ CH), 125.46 (CH), 126.03 (CH), 126.65 (CH), 127.45 (C),
127.99 (C), 128.11 (2ϫCH, Ph), 128.65 (2ϫCH, Ph), 128.90 (C),
129.82 (C), 130.23 (C), 139.11 (C), 143.34 (C), 169.45 (2ϫCO2Et)
ppm. MS (EI): m/z (%) = 305 (28), 263 (22), 209 (94), 152 (57), 115
(62), 105 (100), 77 (68). C31H32O4 (468.58): calcd. C 79.46, H 6.88;
found C 79.26, H 6.53. HRMS (MALDI-TOF): calcd. for
C31H32O4 [M]+ 468.5834; found 468.5842.
[1] a) Z. Rappoport (Ed.), The Chemistry of the Cyclopropyl
Group, Wiley, New York, 1987, vol. 1; b) Z. Rappoport (Ed.),
The Chemistry of the Cyclopropyl Group, Wiley, New York,
1995, vol. 2.
[2] For reviews, see: a) S. Danishefsky, Acc. Chem. Res. 1979, 12,
66–72; b) R. Verhe, N. de Kimpe in The Chemistry of the Cy-
clopropyl Group (Ed.: Z. Rappoport), Wiley, New York, 1987,
vol. 1, pp. 445–564; c) S. Angerer, “Carbocyclic Three- and
Four-membered Ring Compounds” in Houben-Weyl, Methods
of Organic Chemistry E 17c (Ed.: A. de Meijere), Thieme, Stutt-
gart, 1997, pp. 2041–2120.
[3] For examples, see: a) E. Wenkert, Acc. Chem. Res. 1980, 13,
27–31; b) C. Brueckner, H.-U. Reissig, J. Org. Chem. 1988, 53,
2440–2450; c) J. Lee, P. H. Lee, Tetrahedron Lett. 1996, 37,
9305–9306; d) T. Iwama, H. Matsumoto, T. Kataoka, J. Chem.
Soc. Perkin Trans. 1 1997, 835–843.
[4] For reviews on the chemistry of donor–acceptor cyclopropanes,
see: a) H.-U. Reissig, Top. Curr. Chem. 1988, 144, 73–135; b)
H.-U. Reissig, R. Zimmer, Chem. Rev. 2003, 103, 1151–1191;
c) M. Yu, B. L. Pagenkopf, Tetrahedron 2005, 61, 321–347.
[5] a) R. B. Beal, M. A. Dombroski, B. B. Snider, J. Org. Chem.
1986, 51, 4391–4399; b) K. Saigo, S. Shimada, T. Shibasaki,
M. Hasegawa, Chem. Lett. 1990, 1093–1096; c) M. Komatsu,
I. Suehiro, Y. Horiguchi, I. Kuwajima, Synlett 1991, 771–773;
d) Y. Sugita, K. Kawai, H. Hosoya, I. Yokoe, Heterocycles
1999, 51, 2029–2033; e) M. A. Kerr, R. G. Keddy, Tetrahedron
Lett. 1999, 40, 5671–5675; f) Y. Sugita, C. Kimura, I. Yokoe,
Heterocycles 2001, 55, 855–859; g) Y. Sugita, S. Yamadoi, H.
Diethyl [2-(9,10-Dimethyl-2-anthryl)-2-(4-fluorophenyl)ethyl]malon-
ate (8b): TiCl4, 3 h. Orange-red oil. Yield: 0.32 g (66%). Rf = 0.52
1
3
(CHCl3). H NMR (400 MHz, CDCl3): δ = 1.29 (t, J = 7.1 Hz, 3
H, CH3), 1.34 (t, 3J = 7.1 Hz, 3 H, CH3), 2.84–2.99 (m, 2 H, CH2),
3.07 (s, 3 H, CH3), 3.15 (s, 3 H, CH3), 3.41–3.47 (m, 1 H, CH),
4.20–4.24 (m, 1 H, CH), 4.25–4.33 (m, 4 H, CH, 2ϫOCH2), 7.02–
7.13 (m, 2 H), 7.32–7.45 (m, 3 H), 7.50–7.57 (m, 2 H), 8.25 (br. s,
1 H), 8.22–8.39 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
14.17 (4ϫCH3), 34.18 (CH2), 48.38 (CH), 50.41 [CH(CO2Et)2],
61.56 (2ϫCH2O), 115.50 (d, 2JCF = 21 Hz, 2ϫCH, p-FPh), 123.36
(CH), 124.73 (CH), 124.93 (CH), 125.29 (2ϫCH), 125.34 (CH),
3
126.25 (CH), 128.05 (C), 128.38 (C), 128.92 (C), 129.64 (d, JCF
=
8 Hz, 2ϫCH, p-FPh), 129.79 (C), 129.93 (C), 130.30 (C), 138.89
(C), 139.19 (d, 4JCF = 2.9 Hz, C, p-FPh), 161.68 (d, 1JCF = 244 Hz,
C-F, p-FPh), 169.43 (2ϫCO2Et) ppm. C31H31FO4 (486.57): calcd.
C 76.52, H 6.42; found C 76.66, H 6.43.
Diethyl [2-(10-Oxo-9,10-dihydroanthracen-9-yl)-2-phenylethyl]-
malonate (9): TiCl4 (1.5 equiv.), 6 h, reflux. Light-yellow crystals.
Yield: 0.34 g (75%). Rf = 0.35 (CHCl3). M.p. 104–105 °C. 1H NMR
3
3
(400 MHz, CDCl3): δ = 1.14 (t, J = 7.2 Hz, 3 H, CH3), 1.17 (t, J
2
3
3
= 7.2 Hz, 3 H, CH3), 2.31 (ddd, J = 14.0 Hz, J = 12.8 Hz, J =
5334
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 5329–5335

Lewis Acid Catalyzed Reactions of Cyclopropanes with Anthracenes
Hosoya, I. Yokoe, Chem. Pharm. Bull. 2001, 49, 657–658; h)
D. B. England, T. D. O. Kuss, R. G. Keddy, M. Kerr, J. Org.
Chem. 2001, 66, 4704–4709; i) Y. Sugita, C. Kimura, H. Ho-
soya, S. Yamadoi, I. Yokoe, Tetrahedron Lett. 2001, 42, 1095–
1098; j) V. K. Yadav, V. Sriramurthy, Org. Lett. 2004, 6, 4495–
4498; k) C. Venkatesh, P. P. Singh, H. Ila, H. Junjappa, Eur. J.
Org. Chem. 2006, 5378–5386.
a) K. S. Feldman, C. J. Burns, J. Org. Chem. 1991, 56, 4601–
4602; b) M. L. Graziano, M. R. Iesce, F. Cermola, G. Cimmini-
ello, J. Chem. Res. (S) 1992, 4–5; c) V. K. Yadav, V. Sriramur-
thy, Angew. Chem. 2004, 116, 2723–2725; Angew. Chem. Int.
Ed. 2004, 43, 2669–2671.
a) S. Shimada, Y. Hashimoto, A. Sudo, M. Hasegawa, K.
Saigo, J. Org. Chem. 1992, 57, 7126–7133; b) S. Shimada, Y.
Hashimoto, K. Saigo, J. Org. Chem. 1993, 58, 5226–5234; c) S.
Shimada, Y. Hashimoto, T. Nagashima, M. Hasegawa, K.
Saigo, Tetrahedron 1993, 49, 1589–1604; d) P. D. Pohlhaus, J. S.
Johnson, J. Org. Chem. 2005, 70, 1057–1059; e) P. D. Pohlhaus,
J. S. Johnson, J. Am. Chem. Soc. 2005, 127, 16014–16015; f) K.
Fuchibe, Y. Aoki, T. Akiyama, Chem. Lett. 2005, 34, 538–539.
[10] a) M. H. Chang, R. Jain, D. A. Dougherty, J. Am. Chem. Soc.
1984, 106, 4211–4217; b) S. Huenig, M. Schmitt, Tetrahedron
Lett. 1987, 28, 4521–4524; c) M. L. Graziano, M. R. Iesce, F.
Cermola, J. Chem. Res. (S) 1996, 82–83; d) V. S. Korotkov,
O. V. Larionov, A. Hofmeister, J. Magull, A. de Meijere, J. Org.
Chem. 2007, 72, 7504–7510.
[11] a) I. S. Young, M. A. Kerr, Angew. Chem. 2003, 115, 3131–
3134; Angew. Chem. Int. Ed. 2003, 42, 3023–3026; b) M. D.
Ganton, M. A. Kerr, J. Org. Chem. 2004, 69, 8554–8557; c)
I. S. Young, M. A. Kerr, Org. Lett. 2004, 6, 139–141; d) I. S.
Young, J. L. Williams, M. A. Kerr, Org. Lett. 2005, 7, 953–955;
e) F. Cardona, A. Goti, Angew. Chem. 2005, 117, 8042–8045;
Angew. Chem. Int. Ed. 2005, 44, 7832–7835; f) M. P. Sibi, Z.
Ma, C. P. Jasperse, J. Am. Chem. Soc. 2005, 127, 5764–5765;
g) Y.-B. Kang, X.-L. Sun, Y. Tang, Angew. Chem. 2007, 119,
3992–3995; Angew. Chem. Int. Ed. 2007, 46, 3918–3921; h)
C. A. Carson, I. S. Young, M. A. Kerr, Synthesis 2008, 3, 485–
489; i) K. Sapeta, M. A. Kerr, J. Org. Chem. 2007, 72, 8597–
8599; j) A. Karadeolian, M. A. Kerr, J. Org. Chem. 2007, 72,
10251–10253.
[12] O. A. Ivanova, E. M. Budynina, Yu. K. Grishin, I. V. Trushkov,
P. V. Verteletskii, Angew. Chem. 2008, 120, 1123–1126; Angew.
Chem. Int. Ed. 2008, 47, 1107–1110.
[13] a) W. S. Murphy, S. Wattanasin, J. Chem. Soc. Perkin Trans. 1
1982, 1029–1035; b) K. Hantawong, W. S. Murphy, N. Russell,
Tetrahedron Lett. 1984, 25, 999–1000; c) P. Harrington, M. A.
Kerr, Tetrahedron Lett. 1997, 38, 5949–5952.
[14] a) E. J. Corey, M. Chaykovsky, J. Am. Chem. Soc. 1965, 87,
1353–1364; b) W. Fraser, C. J. Suckling, H. C. S. Wood, J.
Chem. Soc. Perkin Trans. 1 1990, 3137–3144.
[6]
[7]
[8] a) M. L. Graziano, M. R. Iesce, J. Chem. Res. (S) 1987, 362–
363; b) K. Saigo, S. Shimada, M. Hasegawa, Chem. Lett. 1990,
905–908; c) M. L. Graziano, G. Cimminiello, J. Chem. Res. (S)
1989, 42–43; d) C. A. Carson, M. A. Kerr, J. Org. Chem. 2005,
70, 8242–8244; e) R. P. Wurz, A. B. Charette, Org. Lett. 2005,
7, 2313–2316; f) Y.-B. Kang, Y. Tang, X.-L. Sun, Org. Biomol.
Chem. 2006, 4, 299–301; g) S. D. R. Christie, R. J. Davoile,
R. S. F. Jones, Org. Biomol. Chem. 2006, 4, 2683–2684.
[9] a) M. Yu, B. L. Pagenkopf, Org. Lett. 2003, 5, 5099–5101; b)
M. Yu, B. L. Pagenkopf, J. Am. Chem. Soc. 2003, 125, 8122–
8123.
Received: June 24, 2008
Published Online: September 30, 2008
Eur. J. Org. Chem. 2008, 5329–5335
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5335