Highly enantioselective tandem cyclopropanation/Wittig reaction of α,β-unsaturated aldehydes with arsonium ylides catalyzed by recyclable dendritic catalyst

Article abstract of DOI:10.1016/j.tetasy.2008.02.022

A novel tandem cyclopropanation/Wittig reaction of α,β-unsaturated aldehydes with arsonium ylides using a chiral 2-trimethylsilanyloxy-methyl-pyrrolidine-based dendritic catalyst is described. Good yields (up to 86%), and high diastereoselectivities (up to dr = 99:1) and enantioselectivities (up to 99% ee) were obtained under simple and mild reaction conditions. The catalyst can be recycled without any loss in activity.

Full text of DOI:10.1016/j.tetasy.2008.02.022

Available online at www.sciencedirect.com
Tetrahedron: Asymmetry 19 (2008) 701–708
Highly enantioselective tandem cyclopropanation/Wittig reaction
of a,b-unsaturated aldehydes with arsonium ylides catalyzed
by recyclable dendritic catalyst
Yun-Hui Zhao,a,b Chang-Wu Zheng,a Gang Zhaoa,* and Wei-Guo Caob,*
aShanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China
bDepartment of Chemistry, Shanghai University, 99 Shangda Lu, Shanghai 200444, China
Received 19 January 2008; accepted 22 February 2008
Abstract—A novel tandem cyclopropanation/Wittig reaction of a,b-unsaturated aldehydes with arsonium ylides using a chiral 2-trimeth-
ylsilanyloxy-methyl-pyrrolidine-based dendritic catalyst is described. Good yields (up to 86%), and high diastereoselectivities (up to
dr = 99:1) and enantioselectivities (up to 99% ee) were obtained under simple and mild reaction conditions. The catalyst can be recycled
without any loss in activity.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
catalyzed cyclopropanation reaction between halomalo-
nates or 2-halo-b-keto esters and enals.
Cyclopropanes are useful building blocks for the synthesis
of natural and synthetic products due to their unique struc-
tures and reactivities. They are also found as a basic struc-
tural unit in a wide range of biologically active compounds
existing in plants and microorganisms.1 As a result, the
development of efficient methods for the asymmetric syn-
thesis of cyclopropanes has attracted intensive research
interest in recent years. The most important and useful
methods for the preparation of cyclopropanes include the
combination of ylides and electron-deficient olefins with
the Michael-initiated ring closure (MIRC) strategy.2 Vari-
ous ylides including sulfonium,3 telluronium,4 ammonium5
and arsonium ylides6 have been successfully applied in the
enantioselective cyclopropanation of electron-deficient ole-
fins. On the other hand, as an important type of electron-
deficient olefins, a,b-unsaturated aldehydes had remained
a challenging target for enantioselective cyclopropanation
until the development of a procedure involving stabilized
sulfonium ylides and chiral amines7 as the catalyst by
MacMillan et al.8 Thereafter, Arvidsson9 developed (S)-
(ꢀ)-indoline-2-yl-1H-tetrazole and novel aryl sulfonamides
The studies of polymer-supported catalysts have attracted
much attention over the past two decades.12 Dendrimers
as well-defined macromolecules with controllable struc-
tures have triggered increasing attention on their applica-
tions in catalysis, since dendritic catalysts have the
advantages of good solubility and can be analyzed with
routine spectroscopic techniques.13 Moreover, the globular
shapes of higher generation dendritic catalysts are suitable
for either membrane filtration14 or selective precipitation
under specific conditions.15 Recently, we reported the syn-
thesis of a series of new dendritic catalysts and their appli-
cation in catalytic asymmetric reactions.16 As part of our
ongoing research projects with regard to dendritic cata-
lysts, we herein report a highly enantio- and diastereoselec-
tive cyclopropanation/Wittig reaction of a,b-unsaturated
aldehydes with arsonium ylides using the polyether
dendritic chiral 2-trimethylsilanyloxy-methyl-pyrrolidine
derivative 3b as a catalyst.
derived from L-proline as catalysts for this transformation,
11
while Wang10 and Cordova reported that chiral amine
2. Results and discussion
´
Recently, we accomplished a highly enantioselective cyclo-
propanation of a,b-unsaturated aldehydes with arsonium
ylides via MIRC using diphenylprolinol silylether as a
*
Corresponding authors. E-mail addresses: zhaog@mail.sioc.ac.cn;
wgcao@staff.shu.edu.cn
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.02.022

702
Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
CHO
O
O
3a
+
Ph3As
Br
Na2CO3,CHCl3
< 1 equiv
CHO
1a
2a
4a
Ph
O
O
O
O
O
Ph
Ph
N
H
TMSO
Ph
Ph
OTMS
N
H
n=2
O
Ph
n
3a
Dendritic Catalyst 3b
Scheme 1. Organocatalytic asymmetric cyclopropanation of a,b-unsaturated aldehydes with arsonium ylides.
catalyst (Scheme 1).17 During the process of optimizing the
reaction conditions, we isolated new compound 5a as the
major product instead of our desired product 4a when we
increased the amount of arsonium salts to 150 mol % or
200 mol % (Table 1, entries 2 and 3). Preliminary studies
revealed that product 4a could undergo further Wittig type
reactions in the presence of excessive arsonium salt to form
E-5a. Various reaction conditions were studied to optimize
this tandem cyclopropanation/Wittig reaction, and the
results are summarized in Table 1. No product 5 was
Table 1. Optimization of organocatalytic asymmetric tandem cyclopropanation/Wittig reaction of a,b-unsaturated aldehydesa
O
O
Ph
Ph
OTMS
CHO
O
N
H
Ph3As
+
3a
+
Br
CHO
Na2CO3, CHCl3
> 1 eq
O
5a
1a
4a
2a
Entry
Solvent
Arsonium salt (equiv)
Yieldb (%)
drc (E-5a)
eed (%) (4a/E-5a)
4a
E-5a
1e
2f
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
Toluene
DCM
CH3CN
EtOH
DMF
1.0
1.5
2.0
2.5
3.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
54
24
Trace
Trace
—
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
0
20
60
54
45
70
84
65
57
17
16
75
77
41
64
—
30:1
19:1
10:1
7:1
3:1
3:2
99:1
99:1
5:1
96/—
94/95
—/95
—/98
—/98
—/99
—/98
—/90
—/93
—/95
—/94
—/98
—/94
—/95
—/99
3
4g
5h
6
7
8
9
10
11
12
13
14
15
DMSO
THF
n-Hexane
DCE
2:1
5:1
2:1
3:1
DME
8:1
a See Section 4 for detailed conditions.
b Isolated yield.
c Determined by chiral HPLC or 1H NMR analysis.
d Determined by chiral HPLC analysis.
e Na2CO3 0.5 equiv.
f Na2CO3 0.75 equiv.
g Na2CO3 1.25 equiv.
h Na2CO3 1.5 equiv.

Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
703
Table 2. Tandem cyclopropanation of a,b-unsaturated aldehydes catalyzed by dendritic catalysta
O
O
CHO
3b
Ph3AsH
+
Br
Na2CO3,CHCl3
Ph
Ph
1
2
O
E-5a
Entry
Catalyst (mol %)
Concentration
Yieldb (%)
drc
eed (%)
1
2
3
4
5
6
5
1.0
1.0
1.0
1.0
2.0
0.5
31
60
43
30
34
26
99:1
99:1
99:1
99:1
99:1
99:1
97
98
98
98
98
99
10
15
20
10
10
a See Section 4 for detailed conditions.
b Isolated yield.
c Determined by chiral HPLC or 1H NMR analysis.
d Determined by chiral HPLC analysis.
Table 3. Recycling of dendritic catalyst 3ba
observed when 1.0 equiv of arsonium salt was used (Table
1, entry 1). When increasing the amount of arsonium salt,
the amount of product 4a decreased, along with a gradual
increase in the amount of product E-5a. When the amount
of arsonium salt was increased to 2.0 equiv, product 4a dis-
appeared and only product E-5a was isolated in 60% yield
with 95% ee (Table 1, entry 3). Increasing the concentration
of base, the ee values remained almost the same, but the
diastereoselectivity decreased dramatically (Table 1, entries
2–5). A study of the solvent effect revealed that chloroform
was optimal for this tandem process. The reaction
Run
Time (h)
Yieldb (%)
drc
eed (%)
1
2
3
4
24
24
24
24
60
58
58
55
99:1
95:5
96:4
92:8
98
98
96
97
a See Section 4 for detailed conditions.
b Isolated yield.
c Determined by chiral HPLC or 1H NMR analysis.
d Determined by chiral HPLC analysis.
Table 4. Scope of the organocatalytic enantioselective cyclopropanation reaction of a,b-unsaturated aldehydesa
R1
O
O
CHO
3b
R1
Ph3As
+
Br
R1
Na2CO3,CHCl3
R2
R2
O
E-5a
1
2
Entry
R1
R2
Product (E-)
Yieldb (%)
drc
% eed
1
2
3
4
5
6
7
8
9
H
F
Ph
Ph
Ph
Ph
Ph
Ph
5a
5b
5c
5d
5e
5f
60
56
64
70
86
68
60
73
51
61
99:1
91:1
80:20
83:17
93:7
95:5
98:2
74:26
90:10
92:8
98
99
99
93
99
94
92
87
71
80
Cl
Br
Me
MeO
H
Br
H
H
4-MeOC6H4
4-MeOC6H4
Me
5g
5h
5i
10
n-Pr
5j
a See Section 4 for detailed conditions.
b Isolated yield.
c Determined by chiral HPLC or 1H NMR analysis.
d Determined by chiral HPLC analysis.

704
Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
performed with 20 mol % catalyst 3a, 100 mol % cinnamal-
dehyde, 200 mol % arsonium salt, and 100 mol % sodium
carbonate in chloroform gave a good result providing
product E-5a in 60% yield with up to 95% ee and a good
dr value (19:1).
provided the cyclopropane products in moderate to good
yields and excellent ee values. For example, arsonium salts
1 bearing electron-donating groups (EDG) (R1 = EDG)
gave the corresponding cyclopropanes 5 in good yields (en-
tries 5 and 6), while arsonium salts 1 bearing electron-with-
drawing groups (EWG) (R1 = EWG) usually provided
slightly lower yields of cyclopropanes 5 (Table 3, entries
2–4). In addition, as shown in Table 4, the reactions of aro-
matic a,b-unsaturated aldehyde worked well to provide the
corresponding products with high enantioselectivities (93–
99% ee, entries 1–7), while the use of crotonaldehyde as a
substrate resulted in low yield and with moderate enanti-
oselectivity (71% ee, entry 7). The absolute configuration
of 5f is determined unambiguously as E-3-(1R,2R,3R) by
X-ray diffraction (Fig. 1).18
For the sake of comparison, we became interested in the
study of using dendritic catalyst 3b instead of organocata-
lyst 3a. As shown in Table 2, the reactions catalyzed by
dendritic catalyst 3b were more efficient than homogeneous
catalyst 3a with higher stereoselectivities (98–99% ee and
almost single diastereomer) and required less catalyst load-
ing. Most importantly, we only obtained the E-isomer of
5a. These experiments showed that 10 mol % catalyst load-
ing was the optimal amount, which provided products E-5a
in high enantiomeric excess (98%) and excellent diastereo-
meric excess (99:1). Increasing or decreasing the concentra-
tion of the reaction system resulted in low yields (Table 2,
entries 5 and 6). As mentioned above, the most important
advantage of the dendritic catalyst is that it could be recov-
ered easily. After the reaction completed, dry methanol was
added to the reaction mixture. Catalyst 3b precipitated and
was recovered almost quantitatively after filtration. As
shown in Table 3, the recovered catalyst was reused for
at least four times almost without any loss in activity.
In our previous report,17 a reasonable mechanism was pro-
posed for explaining the Wittig type19 cyclopropanation. In
order to confirm that this tandem cyclopropanation prod-
uct 5a was generated from intermediate 4a, several experi-
ments were performed using intermediate 4a as a reactant
(Eqs. 1–4; Scheme 2). Cyclopropyl aldehyde 4a reacted
with an arsonium ylide to afford a mixture of Z and E-iso-
mers 5a in good yields and with high ee values. We believe
that the dendritic catalyst performs some effects on the ste-
reoselectivity of the reaction procedure. While a Wittig
reaction product was not observed in the reaction of cinna-
maldehyde and arsonium ylide. Cyclopropyl aldehyde 4a
can also react with a phosphonium ylide to provide b-
cyclopropyl-a,b-unsaturated ester 8 in excellent yield and
Under the optimized reaction conditions, the scope of this
asymmetric tandem cyclopropanation catalyzed by den-
dritic catalyst 3b was investigated extensively. The results
are summarized in Table 4. Generally, the reactions
O
O
Ph
O
Ph
O
Ph
Ph
As Ph
Ph
CHCl3, rt
O
(Eq 1)
+
+
yield: 80%
Ph
Ph
Ph
Ph
Ph
CHO
98% ee
4a
E-5a
Z/E = 1: 4, ee 80% / 98%
Z-5a
6
O
O
O
CHO
+
O
(Eq 2)
Ph3As
3b, Na2CO3
+
Br
CHO
CHCl3, rt
1 equiv
O
yield 5%, ee 97%
yield 52%, ee 98%
1a
2a
E-5a
4a
O
Ph
O
Ph
DCM, rt
+
Ph3P CHCO2Et
(Eq 3 )
(Eq 4)
yield: 88%
Ph
Z/E = 1: 3, ee 80% / 91%
O
Ph
COOEt
8
7
4a
O
CHO
Ph
CHCl3, rt
As Ph
Ph
No Wittig type reaction product
+
Scheme 2. The Wittig reaction of cyclopropyl aldehydes with arsonium ylides.

Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
705
reduced pressure. Then, H2O (5 mL) was added to the reac-
tion mixture and extracted with DCM (3 ꢁ 10 mL). The
combined organic solution was washed with the saturated
NaCl solution, dried over anhydrous Na2SO4 and concen-
trated at reduced pressure. The crude product was purified
by column chromatography (silica, 12:1 hexane/EtOAc) to
afford the pure product 5.
4.3. (E)-3-((1R,2R,3R)-2-Benzoyl-3-phenylcyclopropyl)-1-
phenylprop-2-en-1-one E-5a
25
White solid, mp 146–147 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ36:0 (c 1.0, CHCl3). IR (film) 3060, 1668, 1608, 1579,
1448, 1372, 1260, 1227, 1177, 1007, 740, 695 cmꢀ1 1H
;
NMR (300 MHz, CDCl3) 8.14 (d, J = 8.7 Hz, 2H), 7.98
(d, J = 8.7 Hz, 2H), 7.70–7.12 (m, 13H), 3.66–3.61 (dd,
J = 6.0, 5.7 Hz, 1H), 3.48 (t, J = 6.0, 9.0 Hz, 1H), 2.68
(ddd, J = 6.0, 6.0, 9.0 Hz, 1H); 13C NMR (75 MHz,
CDCl3) 195.5, 190.5, 145.3, 138.8, 138.0, 137.9, 133.5,
132.8, 129.0, 128.9, 128.8, 128.7, 128.5, 127.6, 127.3,
126.7, 36.9, 36.3, 34.1; MS m/z 353.3 (M++1); Elemental
Anal. Calcd for C25H20O2: C 85.20, H 5.72; Found: C
84.98, H 6.04. The enantiomeric ratio was determined by
HPLC analysis using a Chiracel OD-H column (23 °C,
Figure 1. X-ray crystal structure of E-5f.
with good ee value. These results clearly indicated that 4a
was the intermediate of this reaction to afford product 5a.
3. Conclusion
We have developed a novel tandem cyclopropanation of
a,b-unsaturated aldehydes using a chiral 2-trimethylsilanyl-
oxy-methyl-pyrrolidine-based dendrimer 3b as the catalyst.
The reactions were carried out under mild conditions and
provided the corresponding cyclopropanes E-5 with excel-
lent enantioselectivities. The dendritic catalyst is recover-
able and reusable without any loss in activity. Further
applications of this new process in asymmetric synthesis
are currently in progress.
254 nm, 80:20 hexanes/2-propanol, 1.0 mL/min); tmajor
14.3 min, tminor = 17.0 min.
=
4.4. (Z)-3-((1R,2R,3R)-2-Benzoyl-3-phenylcyclopropyl)-1-
phenylprop-2-en-1-one Z-5a
25
White solid, mp 130–131 °C (EtOAc–hexane), ½aꢂD
¼
þ81:3 (c 1.0, CHCl3). IR (film) 3053, 1655, 1609, 1578,
1448, 1416, 1364, 1335, 1262, 1225, 1172, 1009, 734,
698 cmꢀ1
;
1H NMR (300 MHz, CDCl3) 8.02 (d,
J = 8.7 Hz, 2H), 7.91 (d, J = 8.7 Hz, 2H), 7.54–7.26 (m,
11H), 6.92 (d, J = 12.0 Hz, 1H), 6.53–6.45 (dd, J = 10.5,
11.7 Hz, 1H), 4.22–4.14 (ddd, J = 6.3, 5.7, 9.3 Hz, 1H),
3.49–3.44 (dd, J = 5.7, 9.3 Hz, 1H), 3.32–3.28 (t, J = 5.7,
6.3 Hz, 1H); 13C NMR (75 MHz, CDCl3) 196.7, 191.8,
145.4, 138.9, 138.1, 133.4, 133.0, 128.9, 128.8, 128.6,
128.5, 127.2, 127.0, 124.9, 37.4, 35.3, 33.5; MS m/z 375.2
(M++Na); Elemental Anal. Calcd for C25H20O2: C 85.20,
H 5.72; Found: C 85.04, H 6.08. The enantiomeric ratio
was determined by HPLC analysis using a Chiracel OD
column (23 °C, 254 nm, 80:20 hexanes/2-propanol,
0.75 mL/min); tmajor = 25.4 min, tminor = 37.6 min.
4. Experimental
4.1. General
Analytical TLC was performed on precoated silica gel
plates. Column chromatography was conducted with
300–400 mesh silica gel. NMR spectra were recorded at
400 MHz for 1H NMR using SiMe4 as an internal standard
in CDCl3 and 100 MHz for 13C NMR. Enantiomeric ex-
cesses were determined by chiral HPLC analysis. Optical
rotations were measured on a JASCO 1030 polarimeter.
All solvents were used directly without further purification.
4.5. (E)-3-((1R,2R,3R)-2-(4-Fluorobenzoyl)-3-phenylcyclo-
propyl)-1-(4-fluorophenylprop)-2-en-1-one E-5b
4.2. General procedure for the organocatalytic asymmetric
cyclopropanation
25
White solid, mp 108–110 °C (EtOAc–hexane), ½aꢂD ¼ þ7:7
Dendritic Catalyst (36 mg, 0.02 mmol) was added to a solu-
tion of a,b-unsaturated aldehydes (0.2 mmol) in chloro-
form (CHCl3, 4 mL) and the mixture was stirred for
about 30 min at room temperature. Then, 0.4 mmol of
the arsonium salts and sodium carbonate (21.2 mg,
0.2 mmol) were added to the reaction mixture. The mixture
was stirred at room temperature for 24 h until the starting
material disappeared. The mixture was then treated with
methanol (5 mL) and filtered. The dendritic catalyst was
washed several times with methanol and 31 mg (86%) cat-
alyst was recovered; the filtrate was concentrated at the
(c 1.0, CHCl3). IR (film) 3070, 2926, 1669, 1599, 1507,
1422, 1338, 1262, 1229, 1156, 1009, 753, 698 cmꢀ1 1H
;
NMR (400 MHz, CDCl3) 8.07–8.03 (dd, J = 3.3, 6.6 Hz,
2H), 7.93–7.88 (dd, J = 5.4, 8.7 Hz, 2H), 7.38–6.99 (m,
11H), 3.48–3.43 (dd, J = 6.0, 9.0 Hz, 1H), 3.36–3.32 (t,
J=5.7, 6.0 Hz, 1H), 2.81–2.73 (ddd, J = 5.7, 6.0, 9.0 Hz,
1H); 13C NMR (100 MHz, CDCl3) 193.5, 188.4, 167.2,
164.2, 144.9, 138.4, 134.1, 131.9, 131.1, 130.9, 128.8,
128.7, 127.2, 115.7, 115.5, 115.4, 36.4, 35.9, 33.9; LRMS
(ESI) m/z 389.2 (M++1); HRMS (ESI) 411.1169
[M+Na]+ calcd for C25H18F2O2Na+ 411.1167. The

706
Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
enantiomeric ratio was determined by HPLC analysis using
a Chiracel OD-H column (23 °C, 254 nm, 80:20 hexanes/2-
propanol, 1 mL/min); tmajor = 15.1 min, tminor = 19.8 min.
4.9. (E)-3-((1R,2R,3R)-2-(4-Methoxylbenzoyl)-3-phenylcy-
clopropyl)-1-(methoxylphenylprop)-2-en-1-one E-5f
25
White solid, mp 129–131 °C (EtOAc–hexane), ½aꢂD ¼ 55:2
(c 1.0, CHCl3). IR (film) 3050, 2918, 2848, 1660, 1601,
4.6. (E)-3-((1R,2R,3R)-2-(4-Chlorobenzoyl)-3-phenylcyclo-
propyl)-1-(4-chlorophenylprop)-2-en-1-one 5c
1575, 1506, 1455, 1428, 1339, 1255, 1223, 1169,
1030 cmꢀ1
;
1H NMR (400 MHz, CDCl3) 8.03 (d,
25
J = 8.7 Hz, 2H), 7.90 (d, J = 8.7 Hz, 2H), 7.31–6.84 (m,
11H), 4.16–4.09 (ddd, J = 5.7, 6.0, 9.0 Hz, 1H), 4.07 (s,
3H), 3.85 (s, 3H), 3.42–3.37 (dd, J = 6.0, 9.0 Hz, 1H),
3.28–3.23 (t, J = 5.7, 6.0 Hz, 1H); 13C NMR (100 MHz,
CDCl3) 194.6, 190.3, 171.7, 163.6, 163.3, 144.3, 139.1,
131.6, 131.0, 130.6, 128.6, 126.8, 126.0, 124.6, 114.2,
113.8, 55.5, 55.4, 36.8, 34.6, 32.9; LRMS (ESI) m/z 413.3
(M++1); HRMS (ESI) 435.1556 [M+H]+ calcd for
C27H24O4Na+ 435.1566. The enantiomeric ratio was deter-
mined by HPLC analysis using a Chiracel AD-H column
(23 °C, 254 nm, 60:40 hexanes/2-propanol, 0.7 mL/min);
tmajor = 39.8 min, tminor = 34.6 min.
White solid, mp 140–141 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ21:3 (c 1.0, CHCl3). IR (film) 3071, 2920, 1667, 1606,
1588, 1558, 1424, 1336, 1260, 1229, 1093, 1009, 757,
694 cmꢀ1
;
1H NMR (400 MHz, CDCl3) 7.96 (d,
J = 8.1 Hz, 2H), 7.81 (d, J = 8.1 Hz, 2H), 7.47–6.98 (m,
11H), 3.48–3.43 (dd, J = 6.0, 9.0 Hz, 1H), 3.36–3.32 (t,
J = 5.7, 6.0 Hz, 1H), 2.81–2.73 (ddd, J = 5.7, 6.0, 9.0 Hz,
1H); 13C NMR (100 MHz, CDCl3) 193.9, 188.7, 145.2,
139.8, 139.1, 138.2, 136.1, 130.0, 129.8, 129.1, 129.0,
128.9, 128.8, 127.2, 127.0, 126.4, 36.5, 35.9, 34.8; LRMS
(ESI) m/z 421.2 (M++1); HRMS (ESI) 421.0765 [M+H]+
calcd for C25H18Cl2O2H+ 421.0757. The enantiomeric ratio
was determined by HPLC analysis using a Chiracel OD-H
column (23 °C, 254 nm, 80:20 hexanes/2-propanol, 1 mL/
min); tmajor = 17.4 min, tminor = 35.1 min.
4.10. (E)-3-((1R,2R,3R)-2-Benzoyl-3-(4-methoxylphenyl)-
cyclopropyl)-1-phenylprop-2-en-1-one E-5g
25
4.7. (E)-3-((1R,2R,3R)-2-(4-Bromobenzoyl)-3-phenylcyclo-
propyl)-1-(4-bromophenylprop)-2-en-1-one E-5d
White solid, mp 128–130 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ10:2 (c 1.0, CHCl3). IR (film) 3031, 2919, 2852, 1661,
1608, 1568, 1557, 1423, 1373, 1337, 1264, 1228, 1175,
25
1009, 733, 698 cmꢀ1 1H NMR (400 MHz, CDCl3) 8.01
;
White solid, mp 158–160 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ31:2 (c 1.0, CHCl3). IR (film) 3068, 2921, 1666, 1605,
(d, J = 8.7 Hz, 2H), 7.86 (d, J = 8.7 Hz, 2H), 7.84–6.86
(m, 12H), 3.80 (s, 1H), 3.47–3.42 (dd, J = 6.0, 9.0 Hz,
1H), 3.33–3.29 (t, J = 5.7, 6.0 Hz, 1H), 2.75–2.67 (ddd,
J = 5.7, 6.0, 9.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
195.3, 190.3, 158.8, 145.3, 137.8, 133.2, 132.5, 130.6,
130.1, 128.8, 128.5, 128.4, 128.2, 127.6, 127.3, 114.2, 55.4,
36.5, 35.9, 33.5; LRMS (ESI) m/z 383.2 (M++1); HRMS
(ESI) 383.1645 [M+H]+ calcd for C26H22O3H+ 383.1642.
The enantiomeric ratio was determined by HPLC analysis
using a Chiracel OD-H column (23 °C, 254 nm, 80:20 hex-
1583, 1505, 1418, 1259, 1228, 1176, 1071, 1007, 755,
694 cmꢀ1 1H NMR (400 MHz, CDCl3) 7.89–7.86 (d,
;
J = 8.7 Hz, 2H), 7.75–7.72 (d, J = 8.7 Hz, 2H), 7.63–6.97
(m, 11H), 3.47–3.42 (dd, J = 6.0, 9.0 Hz, 1H), 3.36–3.32
(t, J = 5.7, 6.0 Hz, 1H), 2.81–2.73 (ddd, J = 5.7, 6.0,
9.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) 194.2, 188.9,
145.2, 138.2, 136.5, 136.4, 132.2, 132.0, 131.8, 130.1,
129.7, 128.8, 127.7, 127.2, 127.0, 126.4, 36.6, 35.9, 34.2;
LRMS (ESI) m/z 511.2 (M++1); HRMS (ESI) 508.9739
[M+H]+ calcd for C25H18Br2O2H+ 508.9746. The enantio-
meric ratio was determined by HPLC analysis using a
Chiracel AD column (23 °C, 254 nm, 80:20 hexanes/2-pro-
panol, 1 mL/min); tmajor = 63.5 min, tminor = 54.9 min.
anes/2-propanol, 1 mL/min); tmajor = 14.8 min, tminor
=
16.2 min.
4.11. (E)-3-((1R,2R,3R)-2-(4-Bromobenzoyl)-3-(4-meth-
oxylphenyl)-cyclopropyl)-1-(4-bromo-phenylprop)-2-en-1-
one E-5h
4.8. (E)-3-((1R,2R,3R)-2-(4-Methylbenzoyl)-3-phenylcyclo-
propyl)-1-(4-methylphenylprop)-2-en-1-one E-5e
25
25
White solid, mp 129–130 °C (EtOAc–hexane), ½aꢂD
¼
White solid, mp 135–136 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ10:2 (c 1.0, CHCl3). IR (film) 3031, 2919, 2852, 1661,
ꢀ29:7 (c 1.0, CHCl3). IR (film) 3060, 2926, 2819, 1665,
1608, 1568, 1557, 1423, 1373, 1337, 1264, 1228, 1175,
1604, 1583, 1514, 1446, 1335, 1260, 1222, 1175, 1071,
1009, 733, 698 cmꢀ1
;
1H NMR (400 MHz, CDCl3) 7.93
1005, 657 cmꢀ1 1H NMR (400 MHz, CDCl3) 7.88 (d,
;
(d, J = 8.1 Hz, 2H), 7.77 (d, J = 8.1 Hz, 2H), 7.36–6.98
(m, 11H), 3.50–3.45 (dd, J = 6.0, 9.0 Hz, 1H), 3.35–3.32
(t, J = 5.7, 6.0 Hz, 1H), 2.77–2.69 (ddd, J = 5.7, 6.0,
9.0 Hz, 1H), 2.40 (s, 1H), 2.39 (s, 1H); 13C NMR
(100 MHz, CDCl3) 194.6, 189.8, 144.6, 144.1, 143.3,
138.8, 135.3, 129.5, 129.3, 129.0, 128.7, 128.6, 128.4,
127.4, 127.0, 126.5, 36.5, 35.9, 33.6, 21.6; LRMS (ESI)
m/z 381.2 (M++1); HRMS (ESI) 381.1853 [M+H]+ calcd
for C27H24O2H+ 381.1849. The enantiomeric ratio was
determined by HPLC analysis using a Chiracel AD column
(23 °C, 254 nm, 80:20 hexanes/2-propanol, 1 mL/min);
tmajor = 55.2 min, tminor = 38.2 min.
J = 8.4 Hz, 2H), 7.74 (d, J = 8.4, Hz, 2H), 7.63–7.56 (dd,
J = 9.0, 11.4 Hz, 4H), 7.26–6.86 (m, 6H), 3.80 (s, 1H),
3.40–3.35 (dd, J = 6.0, 9.0 Hz, 1H), 3.31–3.27 (t, J = 5.7,
6.0 Hz, 1H), 2.75–2.67 (ddd, J = 5.7, 6.0, 9.0 Hz, 1H);
13C NMR (100 MHz, CDCl3) 194.3, 189.0, 158.9, 145.5,
136.5, 136.4, 132.0, 131.8, 130.2, 130.1, 129.7, 128.5,
127.7, 127.6, 126.9, 114.2, 55.4, 36.5, 35.9, 33.8; LRMS
(ESI) m/z 541.1 (M++1); HRMS (ESI) 538.9848 [M+H]+
calcd for C26H20Br2O3H+ 538.9852. The enantiomeric
ratio was determined by HPLC analysis using a Chiracel
OD-H column (23 °C, 254 nm, 80:20 hexanes/2-propanol,
0.7 mL/min); tmajor = 20.1 min, tminor = 33.2 min.

Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
707
4.12. (E)-3-((1R,2R,3R)-2-Benzoyl-3-methyl-cyclopropyl)-1-
phenylprop-2-en-1-one 5i
138.5, 137.7, 133.2, 128.7, 128.6, 128.2, 127.0, 126.4,
122.7, 60.3, 35.9, 35.5, 33.6, 14.2; LRMS (ESI) m/z 321.1
(M++1); HRMS (EI) exact mass calcd for (C21H20O3) re-
quires m/z 320.1412, found m/z 320.1402. The enantio-
meric ratio was determined by HPLC analysis using a
Chiracel OD column (23 °C, 254 nm, 80:20 hexanes/2-pro-
panol, 0.75 mL/min); tmajor = 28.5 min, tminor = 23.9 min.
25
White solid, mp 114–115 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ22:2 (c 1.0, CHCl3). IR (film) 3060, 2961, 2924, 2852,
1665, 1605, 1578, 1514, 1449, 1375, 1333, 1263, 1228,
1169, 993, 688 cmꢀ1 1H NMR (400 MHz, CDCl3) 7.96
;
(d, J = 8.7 Hz, 2H), 7.83 (d, J = 8.7 Hz, 2H), 7.58–7.39
(m, 6H), 6.97–6.94 (m, 2H), 2.94 (t, J = 6.6, 7.2 Hz, 1H),
2.25–2.21 (m, 1H), 1.31 (d, J = 5.4 Hz); 13C NMR
(100 MHz, CDCl3) 196.3, 190.5, 146.6, 138.1, 133.5,
132.9, 132.4, 128.8, 128.6, 128.4, 128.3, 126.9, 36.3, 35.9,
25.2, 17.5; LRMS (ESI) m/z 291.2 (M++1); HRMS (ESI)
313.1202 [M+Na]+ calcd for C20H18O2Na+ 313.1199.
The enantiomeric ratio was determined by HPLC analysis
using a Chiracel AD column (23 °C, 254 nm, 80:20 hex-
4.16. Ethyl (Z)-3-(1R,2R,3R)-2-benzoyl-3-phenyl-cyclo-
propyl acrylate Z-8b
25
White solid, mp 96–98 °C (EtOAc–hexane), ½aꢂD ¼ þ44:4
(c 1.0, CHCl3). IR (film) 2924, 2853, 1718, 1670, 1648,
1642, 1588, 1570, 1449, 1371, 1252, 1227, 1185, 1136,
1035, 737, 696 cmꢀ1 1H NMR (300 MHz, CDCl3) 8.05
;
(d, J = 7.2 Hz, 2H), 7.65–7.29 (m, 8H), 6.49–6.40 (dd,
J = 10.8, 15.6 Hz, 1H), 6.07 (d, J = 15.6 Hz, 1H), 4.16–
4.09 (dd, J = 6.6, 14.1 Hz, 2H), 3.41–3.34 (m, 2H), 2.81–
2.73 (ddd, J = 4.5, 10.5, 13.8 Hz, 1H), 1.23 (t, J = 7.2,
14.7 Hz, 1H); 13C NMR (75 MHz, CDCl3) 197.0, 165.9,
145.1, 137.3, 135.3, 133.4, 128.9, 128.7, 128.6, 128.1,
127.3, 122.7, 60.2, 35.6, 34.1, 32.3, 14.2; LRMS (ESI) m/z
321.1 (M++1); HRMS (EI) exact mass calcd for
(C21H20O3) requires m/z 320.1412, found m/z 320.1402.
The enantiomeric ratio was determined by HPLC analysis
using a Chiracel OD column (23 °C, 254 nm, 80:20
hexanes/2-propanol, 0.75 mL/min); tmajor = 21.8 min,
tminor = 18.1 min.
anes/2-propanol, 1 mL/min); tmajor = 17.9 min, tminor
=
21.9 min.
4.13. (E)-3-((1R,2R,3R)-2-Benzoyl-3-propyl-cyclopropyl)-1-
phenylprop-2-en-1-one E-5j
25
White solid, mp 140–141 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ33:2 (c 1.0, CHCl3). IR (film) 3063, 2954, 2923, 2872,
1686, 1664, 1603, 1578, 1554, 1449, 1374, 1267, 1223,
1014, 996, 686 cmꢀ1 1H NMR (400 MHz, CDCl3) 7.99
;
(d, J = 7.2 Hz, 2H), 7.83 (d, J = 7.2, Hz, 2H), 7.56–7.39
(m, 6H), 6.99–6.90 (m, 2H), 2.99–2.94 (dd, J = 6.6,
8.7 Hz, 1H), 2.28–2.22 (m, 2H), 1.54–1.48 (m, 4H), 0.95
(t, J = 6.6, 7.2 Hz); 13C NMR (100 MHz, CDCl3) 196.3,
190.5, 146.7, 138.1, 137.9, 132.9, 132.4, 128.6, 128.4,
128.1, 126.8, 35.3, 34.9, 34.4, 30.7, 22.0, 13.8; LRMS
(ESI) m/z 319.2 (M++1); HRMS (ESI) 341.1510
[M+Na]+ calcd for C22H22O2Na+ 341.1512. The enantio-
meric ratio was determined by HPLC analysis using a
Chiracel AD column (23 °C, 254 nm, 80:20 hexanes/2-pro-
panol, 1 mL/min); tmajor = 32.6 min, tminor = 23.7 min.
Acknowledgements
The authors acknowledge the generous financial support
from the National Natural Science Foundation of China
(Nos. 20532040, 20672135 and 20472047), QT Programme,
Excellent Young Scholars Foundation of NSFC
(20525208).
4.14. Preparation of ethyl 3-(1R,2R,3R)-2-benzoyl-3-phenyl-
cyclopropyl acrylate 8
References
Phosphonium ylide 7 (0.12 mmol) was added to a solution
of cycloproyl aldehyde 4a (0.1 mmol) in DCM (1 mL) and
the mixture was stirred for 4 h at room temperature. The
reaction was monitored by TLC. After completion, the
solution was concentrated at the reduced pressure. The
crude product was purified by column chromatography
(silica, 12:1 hexane/EtOAc) to give product 8a (in 66%
yield) and 8b (in 22% yield).
1. (a) Goldschmidt, Z.; Crammer, B. Chem. Soc. Rev. 1988, 17,
229; Wong, H. N. C.; Hon, M.-Y.; Tse, C.-W.; Yip, Y.-C.;
Tanko, J.; Hudlicky, T. Chem. Rev. 1989, 89, 165; Lebel, H.;
Marcoux, J.-F.; Molinaro, C.; Charette, A. B. Chem. Rev.
2003, 103, 977; Reissig, H.-U.; Zimmer, R. Chem. Rev. 2003,
103, 1151; (b) Tsuji, T.; Nishida, S. In The Chemistry of the
Cyclopropyl Group; Patai, S., Ed.; Wiley: New York, 1987; (c)
Taber, D. F. In Comprehensive Organic Synthesis; Trost, B.
M., Fleming, I., Eds.; Pergamon: New York, 1991; Vol. 3, p
1045; (d) Davis, H. M. L. Tetrahedron 1993, 49, 5203; (e)
Carbocyclic Three- and Four-Membered Ring Compounds.
In Houben–Weyl—Methods of Organic Chemistry; de Mei-
jere, A., Ed.; Thieme: Stuttgart, 1997; Vol. E17a,b, (f) Small
Ring Compounds in Organic Synthesis VI. In Topics in
Current Chemistry; de Meijere, A., Ed.; Springer: New York,
2000; Vol. 207.
2. (a) Corey, E. J.; Chaykovsky, M. J. Am. Chem. Soc. 1962, 84,
867; (b) Gustafsson, J.; Sterner, O. Tetrahedron 1995, 51,
3865; (c) Haly, B.; Bharadwaj, R.; Sanghv, Y. S. Synlett 1996,
687; (d) Doyle, M. P.; Zhou, Q.-L.; Simonsen, S. H.; Lynch,
V. Synlett 1996, 697; (e) Krysiak, J.; Kato, T.; Gornitzka, H.;
Baceiredo, A.; Mikolajczyk, M.; Bertrand, G. J. Org. Chem.
2001, 66, 8240; (f) Hu, W.-H.; Timmons, J.; Doyle, M. P.
4.15. Ethyl (E)-3-(1R,2R,3R)-2-benzoyl-3-phenyl-cyclo-
propyl acrylate E-8a
25
White solid, mp 102–104 °C (EtOAc–hexane), ½aꢂD
¼
ꢀ38:5 (c 1.0, CHCl3). IR (film) 2918, 1710, 1671, 1648,
1641, 1597, 1449, 1367, 1251, 1227, 1172, 1133, 1035,
696 cmꢀ1
;
1H NMR (300 MHz, CDCl3) 8.01 (d,
J = 7.8 Hz, 2H), 7.58–6.99 (m, 9H), 6.05–5.99 (d,
J = 15.9 Hz, 1H), 4.17–4.12 (m, 2H), 3.46–3.41 (dd,
J = 6.0, 8.7 Hz, 1H), 3,28 (t, J = 5.7, 6.3 Hz, 1H), 2.66–
2.63 (dd, J = 5.4, 9.0 Hz, 1H), 1.26 (t, J = 7.2, 14.4 Hz,
3H); 13C NMR (75 MHz, CDCl3) 195.4, 165.9, 144.1,

708
Y.-H. Zhao et al. / Tetrahedron: Asymmetry 19 (2008) 701–708
Org. Lett. 2002, 4, 901; (g) Brunel, J. M.; Legrand, O.;
Reymond, S.; Buono, G. J. Am. Chem. Soc. 1999, 121, 5807;
Angew. Chem., Int. Ed. 2007, 46, 6882; (t) Bertelsen, S.;
Nielsen, M.; Jørgensen, K. A. Angew. Chem., Int. Ed. 2007,
46, 7356; (u) de Figueiredo, R. M.; Christmann, M. Eur. J.
Org. Chem. 2007, 2575; (v) Ibrahem, I.; Rios, R.; Vesely, J.;
`
(h) Calo, V.; Nacci, A.; Lopez, L.; Lerario, L. V. Tetrahedron
Lett. 2000, 41, 8977; (i) Iwasa, S.; Takezawa, F.; Tuchiya, Y.;
Nishiyama, H. Chem. Commun. 2001, 59; (j) Huang, L.-Y.;
Chen, Y.; Gao, G.-Y.; Zhang, X. P. J. Org. Chem. 2003, 68,
8179.
´
Hammar, P.; Eriksson, L.; Himo, F.; Cordova, A. Angew.
Chem., Int. Ed. 2007, 46, 4507.
8. Kunz, R. K.; MacMillan, D. W. C. J. Am. Chem. Soc. 2005,
127, 3240.
3. (a) Corey, E. J.; Chaykovsky, M. J. Am. Chem. Soc. 1965, 87,
1353; (b) Corey, E. J.; Jantelat, M. J. Am. Chem. Soc. 1967,
89, 3912; (c) Aggarwal, V. K.; Thompson, A.; Jones, R. V.
H.; Standen, M. C. H. J. Org. Chem. 1996, 61, 8368; (d)
Aggarwal, V. K.; Thompson, A.; Jones, R. V. H. Chem.
Commun. 1997, 1785; (e) Aggarwal, V. K.; Alsono, E.; Fang,
G.; Ferrara, M.; Hynd, G.; Porcelloni, M. Angew. Chem., Int.
Ed. 2001, 40, 1433.
9. (a) Hartikka, A.; Arvidsson, P. I. J. Org. Chem. 2007, 72,
´
´
5874; (b) Hartikka, A.; Slosarczyk, A. T.; Arvidsson, P. I.
Tetrahedron: Asymmetry 2007, 18, 1403.
10. Xie, H.; Zu, L.; Li, H.; Wang, J.; Wang, W. J. Am. Chem.
Soc. 2007, 129, 10886.
11. Rios, R.; Sunden, H.; Vesely, J.; Zhao, G. L.; Dziedzic, P.;
´
Cordova, A. Adv. Synth. Catal. 2007, 349, 1028.
4. (a) Ye, S.; Huang, Z. Z.; Xia, C. A.; Tang, Y.; Dai, L. X. J.
Am. Chem. Soc. 2002, 124, 2432; (b) Liao, W. W.; Li, K.;
Tang, Y. J. Am. Chem. Soc. 2003, 125, 13030.
5. (a) Papageorgiou, C. D.; Ley, S. V.; Gaunt, M. J. Angew.
Chem., Int. Ed. 2003, 42, 828; (b) Papageorgiou, C. D.;
Cubillo de Dios, M. A.; Ley, S. V.; Gaunt, M. J. Angew.
Chem., Int. Ed. 2004, 43, 4641.
6. (a) Huang, Y.-Z.; Shen, Y. Adv. Organomet. Chem. 1982, 20,
115; (b) Ding, W.-Y.; Han, Z.-H.; Chen, Y.-L.; Zou, Y.-J.;
Liu, X. Chem. Res. Chin. Univ. 1996, 12, 50; (c) Pu, J.-Q.;
Jiang, H.-Z.; Chen, X.; Qiu, M.-Y.; Ding, W.-Y. Hecheng
Huaxue 2000, 8, 356; (d) Ren, Z.-J.; Ding, W.-Y.; Cao, W.-
G.; Wang, S.- H.; Huang, Z.-J. Synth. Commun. 2002, 32,
3143; (e) Ren, Z.-J.; Cao, W.-G.; Ding, W.-Y.; Wang, Y.;
Wang, L.-L. Synth. Commun. 2004, 34, 3785.
12. (a) Hartley, F. R. In Supported Metal Complexes; Ugo, R.,
James, B. R., Eds.; Reidel: New York, 1985; (b) Shuttle-
worth, S. J.; Allin, S. M.; Sharma, P. K. Synthesis 1997, 1217.
13. For recent reviews on dendritic catalysts, see: (a) Oosterom,
G. E.; Reek, J. N. H.; Kamer, P. C. J.; van Leeuwen, P. W. N.
M. Angew. Chem., Int. Ed. 2001, 40, 1828; (b) Astruc, D.;
Chardac, F. Chem. Rev. 2001, 101, 2991; (c) Crooks, R. M.;
Zhao, M.; Sun, L.; Chechik, V.; Yueng, L. K. Acc. Chem.
Res. 2001, 34, 181; (d) Twyman, L. J.; King, A. S. H.; Martin,
I. K. Chem. Soc. Rev. 2002, 31, 69; (e) van Heerbeek, R.;
Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H.
Chem. Rev. 2002, 102, 3717; (f) Fan, Q.-H.; Li, Y.-M.; Chan,
A. S. C. Chem. Rev. 2002, 102, 3385; (g) Caminade, A. M.;
Maraval, V.; Laurent, R.; Majoral, J. P. Curr. Org. Chem.
2002, 6, 739.
7. (a) Hayashi, Y.; Gotoh, H.; Hayashi, T.; Shoji, M. Angew.
Chem., Int. Ed. 2005, 44, 4212; (b) Marigo, M.; Franzen, J.;
Poulsen, T. B.; Zhuang, W.; Jørgensen, K. A. J. Am. Chem.
Soc. 2005, 127, 6964; (c) Marigo, M.; Wabnitz, T. C.;
Fielenbach, D.; Jørgensen, K. A. Angew. Chem., Int. Ed.
2005, 44, 794; (d) Yang, J. W.; Hechavarria Fonseca, M. T.;
Vignola, N.; List, B. Angew. Chem., Int. Ed. 2005, 44, 108; (e)
Wang, W.; Li, H.; Wang, J.; Zu, L. S. J. Am. Chem. Soc.
2006, 128, 10354; (f) Marigo, M.; Bertelsen, S.; Landa, A.;
Jørgensen, K. A. J. Am. Chem. Soc. 2006, 128, 5475; (g)
Brandau, S.; Landa, A.; Franzen, J.; Marigo, M.; Jørgensen,
K. A. Angew. Chem., Int. Ed. 2006, 45, 4305; (h) Palomo, C.;
Mielgo, A. Angew. Chem., Int. Ed. 2006, 45, 7876; (i) Carlone,
A.; Marrigo, M.; North, C.; Landa, A.; Jørgensen, K. A.
Chem. Commun. 2006, 4928; (j) McCooey, S. H.; McCabe, T.;
Connon, S. J. J. Org. Chem. 2006, 71, 7494; (k) Zu, L. S.; Li,
H.; Xie, H. X.; Wang, J.; Jiang, W.; Tang, Y.; Wang, W.
Angew. Chem., Int. Ed. 2007, 46, 3732; (l) Li, H.; Wang, J.;
Xie, H. X.; Zu, L. S.; Jiang, W.; Wang, W. Org. Lett. 2007, 9,
965; (m) Vesely, J.; Imbrahem, I.; Zhao, G. L.; Rios, R.;
14. Dijkstra, H. P.; van Klink, G. P. M.; van Koten, G. Acc.
Chem. Res. 2002, 35, 798.
15. (a) Reetz, M. T.; Lohmer, G.; Schwickardi, R. Angew. Chem.,
Int. Ed. 1997, 36, 1526; (b) Petrucci-Samija, M.; Guillemette,
V.; Dasgupta, M.; Kakkar, A. K. J. Am. Chem. Soc. 1999,
121, 1968; (c) Hu, Q. S.; Pugh, V.; Sabat, M.; Pu, L. J. Org.
Chem. 1999, 64, 7528; (d) Fan, Q. H.; Chen, Y. M.; Chen, X.
M.; Jiang, D. Z.; Xi, F.; Chan, A. S. C. Chem. Commun. 2000,
789; (e) Maraval, V.; Laurent, R.; Caminade, A. M.; Majoral,
J. P. Organometallics 2000, 19, 4025.
16. (a) Liu, X. Y.; Wu, X. Y.; Chai, Z.; Wu, Y. Y.; Zhao, G.;
Zhu, S. Z. J. Org. Chem. 2005, 70, 7432; (b) Wang, G. Y.;
Liu, X. Y.; Zhao, G. Synlett 2006, 1150; (c) Liu, X. Y.; Li, Y.
W.; Wang, G. Y.; Chai, Z.; Wu, Y. Y.; Zhao, G. Tetrahedron:
Asymmetry 2006, 17, 750; (d) Li, Y. W.; Liu, X. Y.; Zhao, G.
Tetrahedron: Asymmetry 2006, 17, 750; (e) Chai, Z.; Liu, X.
Y.; Zhang, J. K.; Zhao, G. Tetrahedron: Asymmetry 2007, 18,
2034.
17. Zhao, Y. H.; Zhao, G.; Cao, W. G. Tetrahedron: Asymmetry
2007, 18, 2462.
˚
´
Cordava, A. Angew. Chem., Int. Ed. 2007, 46, 778; (n) Yang,
18. Cell parameters: a 8.7595(6), b 5.8500(3), c 42.699(2) A, space
J. W.; Stadler, M.; List, B. Angew. Chem., Int. Ed. 2007, 46,
group P21/n. CCDC 669269 (for E-5f) contains the supple-
mentary crystallographic data. These data can be obtained
free of charge from the Cambridge Crystallographic Data
centre via www.ccdc.cam.ac.uk/data_request/cif.
´
609; (o) Vicario, J. L.; Reboredo, S.; Badıa, D.; Carrillo, L.
Angew. Chem., Int. Ed. 2007, 46, 5168; (p) Hayashi, Y.;
Okano, T.; Aratake, S.; Hazelard, D. Angew. Chem., Int. Ed.
2007, 46, 4922; (q) Enders, D.; Narine, A. A.; Benninghaus,
T. R.; Raabe, G. Synlett 2007, 1667; (r) Enders, D.; Bonten,
M. H.; Raabe, G. Synlett 2007, 885; (s) Tiecco, M.; Carlone,
A.; Sternativo, S.; Marini, F.; Bartoli, G.; Melchiorre, P.
19. (a) Herry, M. C.; Wittig, G. J. J. Am. Chem. Soc. 1960, 82,
563; (b) Johnson, A. W. J. Org. Chem. 1960, 25, 183; (c)
Johnson, A. W.; Schubert, H. J. Org. Chem. 1970, 35, 2678;
(d) Paul, F. Acta Chem. Scand. 1971, 25, 2541.