Gold(I)- and Yb(OTf)3-Cocatalyzed rearrangements of epoxy alkynes: Transfer of a carbonyl group in a five-membered carbocycle

Article abstract of DOI:10.1002/chem.200902321

We report here the intramolecular reactions between α,β-epoxy ketones and alkynes cocatalyzed by gold(I) and Yb(OTf)₃. This new catalytic system based on a combination of gold(I) and Yb (OTf)₃ allows facile transformation of epoxy alkynes to give novel indene derivatives in moderate to good yields under mild conditions. Moreover, we describe here the first observation of a transfer of a carbonyl group in a five-membered carbocycle during gold-catalyzed reactions. This proposed mechanism is corroborated by isotope-labeling experiments (D and ¹³C). Furthermore, the probable role of each catalyst in this interesting domino reaction has been examined by ³¹P NMR experiments. The utilization of gold catalysts combined with rareearth metal salts offers a new concept for the design of catalyst combinations for domino or cascade reactions.

Full text of DOI:10.1002/chem.200902321

DOI: 10.1002/chem.200902321
Gold(I)- and YbACHTUNRGTNEUNG(OTf)3-Cocatalyzed Rearrangements of Epoxy Alkynes:
Transfer of a Carbonyl Group in a Five-Membered Carbocycle
Lun-Zhi Dai and Min Shi*[a]
Abstract: We report here the intramo-
lecular reactions between a,b-epoxy
ketones and alkynes cocatalyzed by
first observation of a transfer of a car-
bonyl group in a five-membered carbo-
cycle during gold-catalyzed reactions.
This proposed mechanism is corrobo-
rated by isotope-labeling experiments
(D and 13C). Furthermore, the probable
role of each catalyst in this interesting
domino reaction has been examined by
31P NMR experiments. The utilization
of gold catalysts combined with rare-
earth metal salts offers a new concept
for the design of catalyst combinations
for domino or cascade reactions.
gold(I) and Yb
lytic system based on a combination of
gold(I) and Yb(OTf)3 allows facile
ACHTUNGTRENNUNG(OTf)3. This new cata-
ACHTUNGTRENNUNG
transformation of epoxy alkynes to
give novel indene derivatives in moder-
ate to good yields under mild condi-
tions. Moreover, we describe here the
Keywords: epoxy alkynes · domino
reactions · gold · heterocycles ·
indene derivatives · epoxy ketones
Introduction
catalyzed by a Lewis acid was reported by House and Ryer-
son in the early 1960s;[5a] the products normally consist of a
mixture of 1,2- and 1,3-diketones, which result from either
hydride or acyl migration, respectively. Thus, if 1,3-diketones
are formed from the epoxy alkynes, the resulting 1,3-dike-
tone might react further with alkynes to give more interest-
ing products. In addition to the In-,[6] Pd-,[7] and Zn-cata-
lyzed[8] addition of 1,3-diketones to alkynes, which have
been well described before, Toste[9] and co-workers have re-
ported an efficient gold-catalyzed intramolecular addition of
b-ketoesters to inactivated alkynes, providing the cyclization
products derived from the carbon nucleophiles. More re-
cently, Sawamura et al.[10] reported a similar reaction assist-
ed by holey phosphine to give six- or seven-membered rings
under similar conditions. Moreover, some other groups have
also reported the nucleophilic addition of 1,3-dicarbonyl
compounds to propargyl carboxylates and unactivated ole-
fins catalyzed by gold to give the corresponding adducts in
good yields under mild conditions.[11]
Based on the above results, two reaction models could be
proposed.[12] We envisaged that the ketone-substituted epox-
ides 1 in the presence of acid might undergo isomerization
to give 1,3-diketones 1ꢀ (Scheme 1, step I). Subsequent intra-
molecular cyclization could occur via two pathways: 1) nu-
cleophilic addition of an oxygen atom to the alkyne to give
2 (Scheme 1, step II, path a); 2) cyclization employing a
carbon nucleophile to give 3, in a way similar to that report-
ed by Toste et al. and Sawamura et al. (Scheme 1, step II,
path b).
Gold-catalyzed domino reactions are powerful tools in or-
ganic synthesis to access complex molecular frameworks.[1]
Counter anions present in the AuI solution are very impor-
tant factors with respect to the catalytic activity. The combi-
nation of [LAuHal] (L=ligand, Hal=Cl, Br, etc) with silver
salts is the most common method used to increase the cata-
lytic abilities of gold catalysts.[2] In addition to silver salts,
the Lewis acid BF3·Et2O has also been used to activate the
gold complexes.[3] However, the utilization of rare-earth
metal salts as cocatalysts in gold-catalyzed reactions has
never been reported before as far as we know.
Molecules bearing both an epoxy group and an alkynyl
group can probably be transformed to complex and useful
structures in the presence of suitable catalysts. Although
there is growing interest in the gold-catalyzed domino iso-
merization of epoxy alkynes,[4] successful precedents using
epoxides bearing an electron-withdrawing substituent are
rare. Moreover, the rearrangement of a,b-epoxy ketones
[a] Dr. L. Z. Dai, Prof. M. Shi
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
354 Fenglin Lu, Shanghai 200032 (China)
Fax : (+86)21-64166128
E-mail: mshi@mail.sioc.ac.cn
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200902321.
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Chem. Eur. J. 2010, 16, 2496 – 2502

FULL PAPER
in the presence of [AuACTHNUTRGNE(UGN PMe3)Cl] and AgOTf in nitrome-
thane (CH3NO2) at 508C. We found that an interesting func-
tionalized indene derivative 11a was formed in 59% yield
(Table 1, entry 1). The structure of compound 11a was con-
firmed by X-ray diffraction. Replacing AgOTf (5 mol%)
with Yb
87% yield (Table 1, entry 2). Control experiments indicated
that using Yb(OTf)3 alone as the catalyst gave the 1,2-acyl
transfer product 10a rather than 11a, and that using [Au-
AHCTUNGRTEGNUN(N PMe3)Cl] alone as the catalyst, no reaction occurred
ACHTUNGRTENN(UNG OTf)3 (10 mol%) led to the formation of 11a in
AHCTUNGTRENNUNG
Scheme 1. Hypotheses for the one-pot conversion of epoxy alkynes.
(Table 1, entries 3 and 4). Changing the ligand on the gold
complex to PPh3 resulted in the formation of 11a in 79%
yield (Table 1, entry 5). Using ScACHTNUGTRENNUG(OTf)3 or InACHTUNGTRENNUNG(OTf)3
The substrates 4 and 7 were prepared according to proce-
dures reported previously.[13] A systematic examination of
the reaction outcomes revealed that the type of cyclization
was dependent on the structure of the substrates
(Scheme 2). When substrate 4, which bears four atoms be-
(10 mol%) as a cocatalyst decreased the yield of 11a
(Table 1, entries 6 and 7). Performing the reaction under an
O2 atmosphere did not affect the reaction outcome signifi-
cantly (Table 1, entry 8). Carrying out the reaction in tetra-
hydrofuran (THF) resulted in a sharp decrease of the yield
(Table 1, entry 9). When 1,2-di-
chroloethane (DCE) was used
as a solvent, there was no im-
provement in the yield com-
pared with the result under
identical reaction conditions
when CH3NO2 was used as a
solvent (Table 1, entry 10). Fur-
ther screening of the amount of
cocatalyst Yb
revealed that 5 mol% of Yb-
(OTf)3 was the best choice for
ACHTUNGRTEN(NUNG OTf)3 applied,
AHCTUNGTRENNUNG
the reaction (Table 1, entries 11
and 12). Reducing the tempera-
Scheme 2. Substrate-dependent selective cyclizations.
ture to 308C or elevating the
temperature to 708C did not
tween the epoxy and alkynyl groups, was catalyzed by
improve the reaction outcome, although a clear cut in the
reaction time could be observed at 708C (Table 1, entries 13
and 14). Traces of compound 11a’, an isomer of 11a, could
be observed in all above cases.
Due to the poor solubility of product 11a in many organic
solvents, the characterization of 11a was performed by con-
verting it to 12a by further methylation using iodomethane
in the presence of potassium carbonate (Scheme 3).
5 mol% [Au
ACHTUNGTRENNUNG(PPh3)Cl]/AgOTf, six-membered product 5 was
formed in moderate yield along with by-product
6
(Scheme 2, [Eq. (1)]). However, seven-membered heterocy-
cle 8 was afforded in an efficient one-pot, two-step route
using substrate 7 as the starting material catalyzed by
10 mol% Yb
ACHTUNGTRENNUNG(OTf)3 and then 5 mol% [AuACHTUNGTRNEN(UGN PPh3)Cl]/AgOTf
(Scheme 2, [Eq. (2)]).[12]
In the context of our ongoing efforts to develop cascade
reactions using epoxy alkynes as substrates,[4b,12,14] herein, we
report a novel combination of a gold complex and YbACTHNUTRGNEUNG(OTf)3
that catalyzes the rearrangements of epoxy alkynes 9, af-
fording interesting functionalized indene derivatives in good
yields. The significance of this reaction lies in the first obser-
vation of the transfer of a carbonyl group in the five-mem-
bered carbocycle.
Scheme 3. Methylation of product 11a.
Results and Discussion
Scope of the reaction: Under the optimized conditions, it
was found that when R2 was an alkyl group and R1 was an
aryl group, the reaction proceeded smoothly to give the de-
sired products 12 in moderate yields after two steps
Optimization of the reaction conditions: Preliminary experi-
ments directed towards optimizing the reaction conditions
of the transformation were carried out with epoxy alkyne 9a
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2497

M. Shi and L.-Z. Dai
Table 1. Domino rearrangement of epoxy alkynes.
Table 2. Reaction scope.
Entry R1
R2
Time 1 Time 2 Yield [%][a]
[h]
[h]
ACHTUNGTRNE(NUNG Z/E) 12
1
2
3
4
5
6
7
9a: p-ClC6H5
9b: p-FC6H4
9c: p-BrC6H4
9d: m-BrC6H4
nBu
nBu
nBu
n-hexyl 20
11
n-hexyl 24
nBu 16
n-hexyl 18
11
12
17
8
6
6
7
6
6
6
6.5
6
12a: 70 (10:1)
12b: 60 (3.4:1)
12c: 51 (2.3:1)
12d: 60 (10.5:1)
12e: 52 (1.9:1)
12 f: 46 (1.1:1)
12g: 52 (1.4:1)
12h: 45 (1.1:1)
12i: 67 (1.5:1)
12j: –
Entry Catalyst
(mol%)
Solvent Temp. Time Yield
Yield
11a
[h]
10a
[%][a]
[%][a]
9e: 2-naphthalenyl nBu
1
2
Au
AgOTf (5)
Au(PMe3)Cl (5)/ CH3NO2 50
(OTf)3 (10)
(OTf)3 (10)
(PMe3)Cl (5) CH3NO2 50
Au(PPh3)Cl (5)/ CH3NO2 50
Yb(OTf)3 (10)
Au(PMe3)Cl (5)/ CH3NO2 50
Sc(OTf)3 (10)
Au(PMe3)Cl (5)/ CH3NO2 50
In(OTf)3 (10)
Au(PMe3)Cl (5)/ CH3NO2 50
Yb(OTf)3 (10)
Au(PMe3)Cl (5)/ THF
Yb(OTf)3 (10)
Au(PMe3)Cl (5)/ DCE
Yb(OTf)3 (10)
Au(PMe3)Cl (5)/ CH3NO2 50
Yb(OTf)3 (2.5)
Au(PMe3)Cl (5)/ CH3NO2 50
Yb(OTf)3 (5)
Au(PMe3)Cl (5)/ CH3NO2 50
Yb(OTf)3 (5)
Au(PMe3)Cl (5)/ CH3NO2 70
Yb(OTf)3 (5)
G
22
10
trace
59
9 f: p-MeC6H4
9g: p-MeC6H4
9h: p-MeOC6H4
9i: C6H5
9j: C6H5
9k: Me
8[b]
9
–
87
nBu
C6H5
nBu
18
12
11
10[b]
11
–
5.5
3
4
5
0.5
16
10
75
–
–
–
–
79
12k: 43 (4.4:1)
[a] Isolated overall yields for two steps. [b] The complex product mixture
was obtained.
6
11.5
5
–
–
–
–
–
–
–
–
–
53
64
84
11
76
80
87
76
70
ACHTUNGTRENNUNG
7
ACHTUNGTRENNUNG
8[b]
9
13
64
9
10
11
12[c]
13
14
Scheme 4. Application of the method to the nonaromatic substrate 13.
12
11
23
4
the ring-opening of the cyclopropyl alcohol.[17] Subsequent
nucleophilic addition of the aldehyde oxygen atom gener-
ates intermediate F that undergoes rearrangement with the
assistance of the hydroxyl group to give oxonium G.[18] Intra-
molecular nucleophilic addition of the oxonium by
carbon–gold bond gives epoxy intermediate H, which trans-
forms to product 11 catalyzed by Yb(OTf)3. Interestingly,
a
[a] Isolated yields. [b] Under an O2 atmosphere. [c] The ratio of Z-11a to
E-11a is 2.5:1.
AHCTUNGTRENNUNG
we find that the carbonyl group in intermediate B walks
along a five-membered carbocycle (Scheme 5).
(Table 2, entries 1–9). However, when both R2 and R1 were
aromatic groups, the reaction afforded a complex product
mixture (Table 2, entry 10). Further examination of the sub-
strate 9k (R1 =Me, R2 =nBu) revealed that the desired
indene derivative 12k was formed in 43% yield, indicating a
broad substrate scope (Table 2, entry 11).
Recalling the reaction when [Au
were used as cocatalysts (Table 1, entry 1), we thought that
[Au(PMe3)]OTf acted as a catalyst to promote the rear-
rangement of the epoxide in the absence of Yb
(OTf)3.[19b]
ACHTUNGRTEN(NGNU PMe3)Cl] and AgOTf
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
The remaining silver salt could also be an effective catalyst
The combination of [AuACHTNURTGENNUG(PMe3)Cl] and YbACHTUNGTERN(NUGN OTf)3 was also
during the rearrangement of epoxides.[19b]
applied to nonaromatic substrate 13 under the standard con-
ditions. The product 14 was obtained in 57% yield via an
oxirane rearrangement (Scheme 4).
To verify the proposed reaction mechanism, a series of ex-
periments was carried out. First of all, the process by which
intermediate B was formed from intermediate A via 1,2-acyl
migration was demonstrated by performing a deuterium-la-
beling experiment. Reaction of [D]-9i under the optimized
conditions gave compound 10i, which contains no deuterium
label, in 76% yield (Scheme 6, [Eq. (1)]). This confirms the
occurrence of an intramolecular 1,2-acyl migration and ex-
cludes an 1,2-aryl migration. The resulting active deuterium
on the hydroxyl group was exchanged with the proton
source during the workup process. A subsequent 13C-label-
ing experiment also supported the 1,2-acyl migration with
the observation of a strong signal at d=185.6 ppm in the
Overall reaction mechanism: A tentative reaction mecha-
nism is proposed in Scheme 5. The mechanism initially in-
volves the YbACHTUNGTRENNUNG(OTf)3-catalyzed rearrangement of the epoxy
group to give 1,3-diketone 10 via 1,2-acyl group transfer
from intermediate A. Subsequent five-membered annula-
tion[15] of 10 via intermediate B results in intermediate C.
Gold-assisted nucleophilic addition of a carbonyl group by a
double bond gives the gold(I)-carbenoid intermediate D,[16]
which transforms to intermediate E automatically through
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Gold(I)- and YbACHTUNGTRENNUNG(OTf)3-Cocatalyzed Rearrangements of Epoxy Alkynes
FULL PAPER
also excluded the direct nucleo-
philic attack of an alkyne–gold
complex by an epoxide oxy-
gen.[3a,14b,19]
In line with the situation de-
scribed in Scheme 1, the annu-
lation of 10a probably could
also adopt two pathways.[12] If
the annulation employed an
oxygen nucleophile, a six- or
seven-membered
heterocycle
would be produced as an inter-
mediate. However, the transfor-
mation of the supposed hetero-
cycle to the final product 11a
could not be explained. If the
annulation employed a carbon
nucleophile, in line with the
proposed
mechanism
in
Scheme 5, double transfer of
the carbonyl group in the five-
membered carbocycle might be
involved in the reaction. We
therefore prepared the 13C-la-
beled derivative of 9a to verify
Scheme 5. Proposed mechanism.
the reaction pathway (see the
Supporting Information). Treatment of 13C-9a under the op-
timized conditions resulted in 13C-11a, which subsequently
gave 13C-12a in 60% yield after methylation (13C content
>80%; Scheme 8). This 13C-labeling experiment clearly
demonstrated the involvement of a double transfer of the
carbonyl group in the five-membered carbocycle as shown
in Scheme 5.
Scheme 6. Isotope-labeling experiments using [D]-9i and 13C-9a.
13C NMR spectrum under identical conditions (Scheme 6,
[Eq. (2)], see the Supporting Information).
The isolated product 10a was further subjected to the op-
timized conditions, and it was found that 11a was formed in
80% yield, indicating that 10a might be an intermediate in
this transformation (Scheme 7). Moreover, this experiment
Scheme 8. 13C-labeling studies using 13C-9a.
A direct intramolecular [1,3]-migration of the acyl group
from intermediate C to product 11 via intermediate I, as de-
scribed by Yamamoto et al., could also account for the ob-
servations (Scheme 9).[20]
Roles of the catalysts: The functions of both catalysts were
Scheme 7. A control experiment using 10a.
examined in this cocatalytic system. In Table 1, we described
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2499

M. Shi and L.-Z. Dai
AHCTUNGTRENNUNG
of the AgOTf decomposed when AgOTf was put into the
tube or in CH3NO2, and [Au
Figure 1, b). The 31P NMR spectrum of a sample of [Au-
(PMe3)Cl] (1.0 equiv) and Yb(OTf)3 (1.0 equiv) in CH3NO2
ACHTUNGRTEN(NUNG PMe3)Cl] was still detected;
A
ACHTUNGTRENNUNG
at 508C changes in the presence of substrate 9a (2.0 equiv);
two signals are observed at d=À6.85 and 10.29 ppm
(Figure 1, f). This might be due to the fact that there is an
equilibrium between the intermediate 15a and the inter-
Scheme 9. Intramolecular [1,3]-migration of the acyl moiety.
that using [Au
N
mediate 16a (Scheme 10). When YbACTHNGUTERNNU(G OTf)3 is added, these
occurred, and using YbAHCTUNTGRENNUNG
diketone 10a was obtained in 75% yield. Further examina-
tion of the reaction outcome revealed that no final product
was formed starting from the 1,3-diketone 10a in the pres-
ence of [Au
(PMe3)Cl] was not active enough to activate the alkynyl
bond. Thus, both [Au(PMe3)Cl] and Yb(OTf)3 are necessary
ACHTUNGTRENNUNG(PMe3)Cl], presumably due to the fact that [Au-
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
catalysts for the transformation of the intermediate 10a to
the final product 11a in this reaction. As shown in entry 1 of
Scheme 10. Equilibrium between intermediate 15a and intermediate 16a.
Table 1, using the combination of [Au
afforded 11a in 59% yield, suggesting that [Au
is a real active species in this reaction. The combination of
[Au(PMe3)Cl] and Yb(OTf)3 probably plays a similar role as
that of [Au(PMe3)]OTf, but they are more effective than
[Au(PMe3)]OTf alone under the standard reaction condi-
tions.
Moreover, several 31P NMR experiments were conducted
to test the catalytic roles of [Au(PMe3)Cl] and Yb
(OTf)3.[3b]
The 31P NMR spectrum of a sample of [Au
(PMe3)Cl]
(1.0 equiv) and Yb(OTf)3 (1.0 equiv) in CH3NO2 at 508C
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
two species are in an equilibrium that slightly favors the
later species, and which results in the reaction to form the
indene derivative (Scheme 10). In contrast, the 31P NMR ex-
periment in which 9a (Figure 1, d) is mixed with [Au-
ACHUTNGRENU(NG PMe3)Cl] or that in which 10a is mixed with [AuAHCUTNGTRENN(UGN PMe3)Cl]
(Figure 1, e) under otherwise identical conditions revealed a
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
A
U
sharp signal at d=À7.16 ppm.
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
shows a sharp signal at d=À7.16 ppm (Figure 1, c) that is
almost identical to that of the pure gold complex (a signal at
d=À7.32 ppm; Figure 1, a). The 31P NMR signal for [Au-
Conclusions
A novel combination of [AuACTHNUTRGENNUG(PMe3)Cl] and YbACHUTGNTREN(NUGN OTf)3 cata-
lyzes the domino isomerization of epoxy alkynes to give
functionalized indene derivatives in good yields under mild
conditions.[21] Control experiments demonstrate that both
[Au
transformation of intermediate 10 to the final product 11.
Yb(OTf)3 plays an important role in the reaction by promot-
ACHUTNGTREN(NUG PMe3)Cl] and YbACHTUNTGERN(NUGN OTf)3 are necessary catalysts for the
AHCTUNGTRENNUNG
ing the rearrangement of epoxides, and by activating the
alkyne–gold complex during the reaction.
Double transfer of a carbonyl group in a five-membered
carbocycle or intramolecular [1,3]-migration of an acyl
group might be involved in this process. Although the cleav-
age of carbon–heteroatom and heteroatom–heteroatom
bonds along with a migration of a certain group in the pres-
ence of gold catalysts or platinum catalysts has been report-
ed recently,[20,22] the cleavage of carbon–carbon bonds along
with the migration of a certain group in gold-catalyzed reac-
tions is rare due to the lack of reactivity and is still consid-
ered as a challenging subject. In this reaction, the cleavage
of the carbon–carbon bond along with the migration of a
carbonyl group is involved in the process based on the re-
sults of 13C-labeling experiments.
Figure 1. 31P NMR spectra of experiments to determine the role of the
catalysts: a) [Au
AgOTf (1.0 equiv) in CH3NO2; c) [Au
(OTf)3 (1.0 equiv) in CH3NO2; d) a mixture of [Au
and substrate 9a (2.0 equiv) in CH3NO2; e) a mixture of [Au
(1.0 equiv) and substrate 10a (2.0 equiv) in CH3NO2; f) a mixture of [Au-
(PMe3)Cl] (1.0 equiv), Yb(OTf)3 (1.0 equiv), and substrate 9a (2.0 equiv)
A
ACHTUNGRTEN(NUNG PMe3)Cl] (1.0 equiv) and
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Overall, the alkynyl a,b-epoxy ketones can be easily
transformed to heterocycles and indene derivatives in the
presence of gold complexes. This kind of reaction usually
A
ACHTUNGTRENNUNG
in CH3NO2.
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Gold(I)- and YbACHTUNGTRENNUNG(OTf)3-Cocatalyzed Rearrangements of Epoxy Alkynes
FULL PAPER
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addition of 1,3-dicarbonyl compounds to the alkynyl group
by employing an oxygen or carbon nucleophile. The reaction
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Experimental Section
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General information: Melting points were obtained with a Yanagimoto
micro melting point apparatus and are uncorrected. 1H NMR spectra
were recorded in CDCl3 with tetramethylsilane (TMS) as internal stan-
dard on Bruker AM-300 or AM-400 spectrometers; J values are in Hz.
Mass spectra were recorded with a HP-5989 instrument. All of the com-
pounds reported in this paper gave satisfactory HRMS analytic data.
Commercially obtained reagents were used without further purification.
All reactions were monitored by TLC with Huanghai GF254 silica gel
coated plates. Flash column chromatography was carried out using 300–
400 mesh silica gel at increased pressure.
General procedure for the preparation of 11a: [AuACHTNUGTREN(NUNG PMe3)Cl] (5.1 mg,
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0.015 mmol) and Yb(OTf)3 (9.3 mg, 0.015 mmol) under argon were
ACHTUNGTRENNUNG
added to a solution of 9a (101.4 mg, 0.3 mmol) in freshly distilled nitro-
methane (3.0 mL) at 508C. The reaction mixture was stirred for 11 h and
was monitored by TLC plates. When the reaction was complete, the mix-
ture was diluted with EtOAc, evaporated under reduced pressure, and
the residue was purified by flash column chromatography (silica gel,
EtOAc/PE=1:50). Compound 11a (87.2 mg) was isolated in 87% yield
(containing some impurities). Compound 11a: a yellow solid; IR (NaCl):
n˜ =3061, 2956, 2927, 2858, 1652, 1586, 1557, 1504, 1486, 1456, 1401, 1373,
1293, 1262, 1236, 1203, 1172, 1142, 1088, 1014 cmÀ1; since the product 11a
exists in several forms (11a (Z or E) and 11a’), the 1H NMR and
13C NMR spectra of 11a are very complicated and are not presented
here; MS (EI): m/z (%): 75 [M+À263] (10.6), 111 [M+À227] (30.7), 113
[M+À225] (11.1), 139 [M+À199] (100.0), 141 [M+À197] (34.8), 338 [M]+
(7.8); HRMS: m/z: calcd for C21H19ClO2: 338.1074, found 338.1077.
CCDC-715870 (11a) contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
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We thank the Shanghai Municipal Committee of Science and Technology
(06XD14005, 08dj1400100-2), National Basic Research Program of China
ACHTUNGTRENNUNG(973)-2009CB825300, and the National Natural Science Foundation of
China for financial support (20872162, 20672127, 20821002 and 20732008)
and Jie Sun for performing the X-ray diffraction studies.
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Received: August 22, 2009
Published online: January 14, 2010
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ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2496 – 2502