Asymmetric Cyclopropanation Catalyzed by a Series of Copper-(Schiff-Base) Complexes with Two Chiral Centers

Article abstract of DOI:10.1080/10242430215705

A series of copper-(Schiff-base) complexes with two chiral centers derived from 1,2-diphenyl-2-amino-ethnaol were synthesized and applied to catalyze the asymmetric cyclopropanation of ethenes with diazoacetates. A mechanism that can explain the observed

Full text of DOI:10.1080/10242430215705

This article was downloaded by: [Chulalongkorn University]
On: 08 January 2015, At: 04:19
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Enantiomer: A Journal of Sterochemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/gena20
Asymmetric Cyclopropanation Catalyzed by a Series
of Copper-(Schiff-Base) Complexes with Two Chiral
Centers
Changsheng Jiang a , Zhang Ming a , Qitao Tan a , Dai Qian a & Tianpa You a
a Department of Chemistry , University of Science and Technology of China , Hefei, 230026,
People's Republic of China
Published online: 17 Sep 2010.
To cite this article: Changsheng Jiang , Zhang Ming , Qitao Tan , Dai Qian & Tianpa You (2002) Asymmetric Cyclopropanation
Catalyzed by a Series of Copper-(Schiff-Base) Complexes with Two Chiral Centers, Enantiomer: A Journal of Sterochemistry,
7:6, 287-293, DOI: 10.1080/10242430215705
To link to this article: http://dx.doi.org/10.1080/10242430215705
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Enantiomer, Vol. 7, pp. 287–293
c
Copyright 2002 Taylor & Francis
1024-2430/02 $12.00 + .00
DOI: 10.1080/10242430290015881
Asymmetric Cyclopropanation Catalyzed
by a Series of Copper-(Schiff-Base)
Complexes with Two Chiral Centers
Changsheng Jiang,
Zhang Ming, Qitao Tan,
Dai Qian, and Tianpa You
Department of Chemistry,
University of Science and
Technology of China,
ABSTRACT A series of copper-(Schiff-base) complexes with two chi-
ral centers derived from 1,2-diphenyl-2-amino-ethanol were synthesized
and applied to catalyze the asymmetric cyclopropanation of ethenes with
diazoacetates. A mechanism that can explain the observed results was pro-
posed. Some of these complexes were also efficient catalysts for asym-
metric cyclopropanation of 1,1-diphenylethene with ethyl diazoacetate,
affording high e.e. of up to 98.6%. An e.e. of 80.7% was achieved when
no solvent was used.
Hefei 230026,
People’s Republic of China
KEYWORDS asymmetric cyclopropanation chiral, copper-(Schiff-base), diazo-
acetates, diastereoselectivity
INTRODUCTION
Catalytic asymmetric cyclopropanation of diazoacetates with ethens
has attracted much attention [1,2]. Certain transition metal complexes
have been applied to catalyze the decomposition of diazocompounds
[3,4]. The first catalytic asymmetric cyclopropanation reaction was re-
ported in 1966 when Nozaki et al showed that the cyclopropane com-
pound was attained by the effect of a copper(II) complex 1 bearing a
salicyladimine ligand, though with a low e.e. of 6% [5]. This report initi-
ated activities that resulted in the discovery of the Aratani’ catalyst with
dramatic improvements in optical yields for selected intermoleculor cy-
clopropanation reaction [6,7]. Some other other efficient copper-(Schiff-
base) complexes were reported by Zhengling Li [8] and Cai et al [9]
recently which were prepared by modification of Aratani’s catalyst 2.
However, the mechanism of the asymmetric cyclopropanation cat-
alyzed by this kind of Schiff-base complex is still not very clear. Aratani
has proposed a mechanism [7] to explain the mode of chirality trans-
fer. Although this explanation predicts the observed predominant cyclo-
propane configuration, it does not adequately account for the prefer-
ential diastereoselectivity of (E)-product that is observed in most cases.
Therefore it will be helpful to know the mechanism more thoroughly
Received November 20, 2001;
accepted January 12, 2002.
Address correspondence to
Tianpa You. Tel: +86-551-3606944;
E-mail: ytp@ustc.edu.cn
287

TABLE 1 Asymmetric cyclopropanation of styene 4 catalyzed by using 1 mol% of 3a
Entry
3
5
Yield (%)b
Ratio 6:7c
%ee 6d
%7d
1
2
3
4
5
6
7
8
9
a
b
c
d
e
a
b
c
d
e
a
a
a
a
a
b
b
b
b
b
63
65
54
57
75
54
59
60
51
70
30/70
31/69
27/73
27/73
39/61
21/79
22/78
15/85
18/82
27/73
63.2(1S, 2R)
60.6(1R, 2S)
12.1(1S, 2R)
12.9(1R, 2S)
58.8(1S, 2R)
65.4(1S, 2R)
63.9(1R, 2S)
11.3(1S, 2R)
11.4(1R, 2S)
60.1(1S, 2R)
32.8(1S, 2S)
32.3(1R, 2R)
23.4(1S, 2S)
22.7(1R, 2R)
30.5(1S, 2S)
55.3(1S, 2S)
56.7(1R, 2R)
17.2(1S, 2S)
17.8(1R, 2R)
35.0(1S, 2S)
10
a
All reactions were carried out at 40 C in benzene.
b
c
Isolated yields of purified 6 and 7.
Determined by GC (Column: PE-5, length: 20.00 M, ID: 0.18 mm, film thickness: 0.18 um, column temp.: 250 C).
For entry 1–5 the %e.e. was determined by HPLC (Chiracel OD column, elution with hexane/isopropanol 9.75:0.25, 0.4 ml/min; for entry 6–10
d
the %e.e. was determined by GC (Column: PE-5, length: 20.00 M, ID:0.18 mm, film thickness: 0.18 um, column temp.: 250 C). The configuration
in parentheses is of the excess enatiomer, which was established on the basis of the sign of the specific rotation of the corresponding acid [10].
for developing novel efficient catalyst. Up to now,
all the copper(Schiff-base) complexes that have been
applied to catalyze this reaction have only one chi-
ral center the carbon attached to the nitrogen atom.
If the carbon attached to the oxygen is also a chiral
center, how does it affect the enantioselectivity and
which of the two chiral centers has the main effect? To
explore these possibilities and to obtain more details
about the catalytic mechanism, four stereoisomers
of a copper-(Schiff-base) complex with double chi-
ral centers 3a–d and their analogue 3e, which with
a bulky group at the ortho-position to the phenolic
hydroxyl of the complex, were synthesized and ap-
plied to catalyze the asymmetric cyclopropanation
of ethenes with diazoesters in this paper.
the configuration of C2 in complex 3 dominates the
configurations of cyclopropanes in 6a–b and 7a–b.
It is noteworthy that the degree of enantioselectivi-
ties for 3c and 3d are much lower than that for 3a
and 3b. This suggests that the configuration of C1
in complexes 3a–d affect mainly the degree of enan-
tioselectivity. A similar behavior was observed when
complexes 3a–d were used to catalyze the asymmet-
ric cyclopropanation of 1,1-diphenylethylene 8 with
ethyl diazoacetate (Table 2).
TABLE 2 Asymmetric cyclopropanation of 1,1-diphenyl-
ethene 8 with ethyl diazoacetate catalyzed by using 1 mol%
of 3a
RESULTS AND DISCUSSION
Entry
3
Yield (%)b
%eec
Initially, the complexes 3a–e were applied to cat-
alyze the reaction of styrene 4 with diazoesters 5
(Table 1). In the cases of using 3a or 3c as catalyst,
the 1S, 2R for 6a–b and the 1S, 2S for 7a–b are the
major enantiomers, respectively, though the config-
uration of C1 in 3a and 3c are different. When using
3b or 3d as a catalyst, the 1R, 2S for 6a–b and 1R, 2R
for 7a–b turn out to be the major enantiomers, re-
spectively, in spite of the configurations of C1 in 3b
and 3d are different, too. These results indicated that
1
2
3
4
5
a
a
b
c
d
e
53
54
58
51
63
90.1(S)
91.8(R)
13.4(S)
13.1(R)
87.7(S)
All reactions were carried out at 40 C in benzene.
Isolated yields.
b
c
The %e.e. of 10 was determined by HPLC (Chiracel OD column, elu-
tion with hexane/isopropanol 9.75:0.25, 0.4 ml/min, the configuration
in parentheses is of the excess enatiomer, which was established on
the basis of the sign of the specific rotation of the corresponding acid
[4].
288
C. JIANG ET AL.

Comparing the results obtained by using 3a and
3e as the catalysts (Table 1: entry 1, 5, 6, 10; Table 2:
entry 1, 5) both the enantioselectivity and the di-
astereoselectivity (leading to the E) product are some-
what diminished when the 3e is used. This suggests
that a bulky group at the ortho-position to the phe-
nolic hydroxyl of the complex is disadvantageous to
the asymmetric reaction.
lowing discussions. There has been strong evidence
indicating that the actual catalyst responsible for
the asymmetric induction is a mononuclear cuprous
complex such as 10 and 11, in which copper is sup-
posed to have a tetrahedral configuration and one
of the four coordination sites is left vacant [7]. In
the case of 10, two phenyl goups in the catalyst are
syn, and the alkyldiazoacetate will take the vacant site
from the less hindered front side to give 12. The car-
bene carbon bears sp2 hybridization and the outside
orientation of the alkoxycarbonyl group is selected
A possible mechanism (Scheme 1) is proposed to
explain these results. Reactions employing the cata-
lysts 3a and 3c are considered throughout the fol-
SCHEME 1
A SERIES OF COPPER-(SCHIFF-BASE) COMPLEXES WITH TWO CHIRAL CENTERS
289

TABLE 3 Effect of temperature, solvent and amount of catalyst on asymmetric cyclopropanation of 1,1-diphenylethylene with
ethyl diazoacetate catalyzed by 3b
Amt of cat.
(mol%)
Temp.
( C)
Yield
(%)a
E.e
(%)b
Entry
Solvent
Config.c
1
2
3
4
5
6
7
8
9
10
11
12
13d
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Dioxane
THF
1
1
1
1
1
1
0.5
0.1
1
1
1
1
1
80
60
40
30
20
0
40
40
40
40
40
40
40
81
73
53
48
45
38
69
61
50
23
65
59
68
68.2
84.1
91.8
94.1
97.3
98.6
78.5
53.7
67.8
35.6
88.5
89.2
80.7
R
R
R
R
R
R
R
R
R
R
R
R
R
CH2Cl2
Toluene
—
a
Isolated yields.
b
The %e.e. was determined by HPLC (Chiracel OD column, elution with hexane/isopropanol 9.75:0.25, 0.4 ml/min.).
Established on the basis of the sign of the specific rotation of the corresponding acid [4].
No solvent was used.
c
d
to minimize steric replusion. The ethenes will ap-
proach the carbene from the less hindered a side and
the metallacyclobutanes 14 is the main product. The
copper atom forms a bond with the -carbon atom of
the alkene rather than the -carbon atom because the
carbonium ion at the -position is more stable than
that of the -position. Collapse of the metallacycles
14 into the products 16 regenerates the true catalyst
10 to complete a catalysis cycle. In the case of 11, the
difference of the steric repulsion from rear or front
is not obvious. Alkyldiazoacetate can approach the
copper either from rear or front, thus 13 and 130 are
given. Intermediate 13 is somewhat predominant for
C2 is positioned a little closer to the alkoxycarbonyl
group of carbene than C1. The ethens will attack 13
or 130 in the similar manner as that of 10 to give
16 and 17 (16 somewhat predominant). This model
explains most of the results we derived. The configu-
ration of C2 of the catalyst dominates the configura-
tion of predominant cyclopropanes by governing the
side the alkyldiazoacetate approaches the catalyst. A
bulky group at C1 is in favor of the enantioselec-
tivity [8]. The enantioselectivity is diminished when
two phenyl goups are anti in the catalyst such as 3c
and 3d, since the difference in the approach of the
diazoacetates to the catalyst from the rear or from
the front is diminished. If R2 is a more bulky group
than R1 and R2 is at the bottom, the approach of the
ethenes to the carbene is easier and the metallacycles
are more stable, this leads to preference of the (E )-
cyclopropane in most cases and a bulky group in the
diazoacetates favors the diastereoselectivity. When
R3 is tert-butyl, the steric repulsion of the a side is in-
creased so the enantioselectivity is diminished. The
diastereoselectivity is also diminished because R3 is
orientated down side.
The complex 3a and 3b have been found to be
efficient catalysts for the asymmetric cyclopropana-
tion of 1,1-diphenylethylene with ethyl diazoacetate.
The effects of temperature, solvent and the amount
of catalyst on this reaction catalyzed by 3b were
also investigated (Table 3). The expected tempera-
ture effects were observed; decreasing of tempera-
ture caused increasing of enantioselectivity. The best
result of 98.6% e.e was obtained at 0 C. However,
the chemical yield decreased at lower temperature.
Among the solvents studied, benzene was the best
one. When reactions were carried out in polar sol-
vent such as dioxane or THF, the enantioselectivity
diminished. This could be a result of the strong coor-
dinating ability of these solvents to the catalyst com-
plex. Interestingly, a relatively high e.e. of 80.7% was
obtained when no solvent was used (Entry 13). The
enantioselectivity decreased when the amount of cat-
alyst was diminished. But an e.e. of 53.7% still could
be obtained when only 0.1 mol% of the catalyst was
used.
MATERIALS AND METHODS
Unless otherwise stated, all reactions were carried
out under an argon atmosphere with dry, freshly
290
C. JIANG ET AL.

distilled solvents under anhydrous conditions. All
solvents were purified according to standard meth-
ods. Ethenes were purchased from Aldrich Ltd.
and freshly distilled before use. NMR spectra were
recorded with a Bruker DRX-500 (500 MHz). IR
spectra were recorded on a RECTOR-22 instrument.
excess of ammonia, collecting, carefully washing with
water and drying; yield 87%, m.p. 143 C; [ ]D25
=
+7 (C = 0.6,C2H5OH). The mother liquor was con-
centrated and the obtained solid was recrystallized
from 50% ethanol for five times until the m.p. reach
to 196 C, yield 39%. The (1R, 2S) enantiomer was
obtained as described above, yield 98% from 4.3 g.
of glutamate. M.p. 143 C; [ ]D25
C2H5OH).
=
7 (C = 0.6,
Preparation of the Racemate
(1S, 2R) and (1R, 2S)-
1,2-diphenyl-2-amino-ethanol
Preparation of (1R, 2R)-
1,2-diphenyl-2-amino-ethanol
This compound was prepared according to the
procedure reported by J. Weijlard et al [11] with some
modifications. A mixture of 13.6 g. of benzoin oxime
(0.06 mol), 112 ml of ethanol containing 2.4 g. of
hydrogen chloride and 1.2 g. of 10% palladium-on-
charcoal was hydrogenated at 1.06E + 05 Pa. pres-
sure. To the reaction mixture was added 100 ml of
water 5 hours later, and the catalyst was removed by
filtration. The filtrate was diluted to 400 ml with wa-
ter, an excess of concd. ammonia liquor was added,
the precipitated base was collected, washed free from
chloride with water and dried at 45–50 C; Yield 90%,
m.p. 161 C. The hydrochloride was prepared by dis-
solving the base in hot alcohol, adding a slight ex-
cess of alcoholic HCl, and precipitating by adding
an equal volume of ether. The hydrochloride was
dissolved in warm water and an excess of concd. am-
monia liquor was added, the precipitated base was
collected, washed and dried, yield 78%, white crys-
tal, m.p. 163 C. 1H NMR (500 MHz, CD3COCD3)
5.0 1(d, J = 7.8 Hz, 1H), 5.35 (d, J = 7.8 Hz,
1H), 6.98–7.35 (m, 10 H); IR (KBr):3440, 3332, 2920,
2887, 1639, 1592, 1454, 698 cm 1. Anal. Calcd for
C14H15NO: C, 78.87; H, 7.04; N, 6.57. Found: C,
78.91; H, 7.10; N, 6.59%.
Prepared from (1S, 2R)-1,2-diphenyl-2-amino-
ethanol in three steps in a similar manner to the
literature [11]. White crystal, m.p. 116 C; [ ]D25
=
1
120 (C = 0.6, C2H5OH). H NMR (500 MHz,
CD3COCD3) 4.17 (d, J = 8.6 Hz, 1H), 4.74 (d,
J = 8.6 Hz, 1H), 7.14–7.33 (10 H, m) IR (KBr): 3500,
3365, 2895, 1644, 1587, 1454, 699 cm 1. Anal. Calcd
for C14H15NO: C, 78.87; H, 7.04; N, 6.57. Found:
C, 78.95; H, 6.96; N, 6.51%.
Preparation of (1S, 2S)-
1,2-diphenyl-2-amino-ethanol
Prepared from (1R, 2S)-1,2-diphenyl-2-amino-
ethanol in three steps in a similar manner to the
literature [11]. White crystal, m.p. 116 C; [ ]D25
=
1
+121 (C = 0.6, C2H5OH). H NMR (500 MHz,
CD3COCD3) 4.18 (d, J = 8.6 Hz, 1H), 4.75 (d,
J = 8.6 Hz 1H), 7.15–7.34 (10 H, m) IR (KBr):3489,
3330, 2826, 1638, 1590, 1454, 691 cm 1. Anal Calcd
for C14H15NO: C, 78.87; H, 7.04; N, 6.57. Found:
C, 78.89; H, 7.05; N, 6.66%.
Preparation of 3-tert-Butyl-
2-hydroxybenzaldehyde
Resolution of the (1S, 2R)/(1R, 2S)-
1,2-diphenyl-2-amino-ethanol [11]
Prepared by a similar method to the literature
1
A mixture of 13.4 g. of the racemate (0.063 mol)
and 0.93 g. of D-glutamic acid (0.063 mol) were
dissolved in 4000 ml of boiling 50% ethanol. Af-
ter storage overnight at room temperature, the fine
needles were collected, washed with ice-cold 50%
ethanol and dried. M.p. 212 C. This solid was re-
crystallized twice from 50% ethanol until the m.p.
reach to 215 C, yield 56%. The (1S, 2R) enantiomer
was obtained by dissolving 6.2 g of the D-glutamate
salt in 100 ml of warm water, precipitating with
procedure [12], yield 40%, yellow oil. H NMR
(500 MHz, CDCl3) 1.43(s, 9H), 6.90–7.80 (m, 3H),
9.89 (s, 1H), 11.80 (s, 1H); IR (KBr): 2959, 2743,
1
1652, 1612, 1484, 1432, 1090 cm
.
Preparation of the Schiff-Bases:
General Procedure
A mixture of methanol (10 ml), amino alco-
hols (5 mmol), and salicyclaldehyde (6 mmol)
A SERIES OF COPPER-(SCHIFF-BASE) COMPLEXES WITH TWO CHIRAL CENTERS
291

were refluxed for 8 hours. Most of the methanol
was removed in vacuo and the residue was puri-
fied by a chromatographic column to give pure
product.
C25H27NO2: C, 80.43; H, 7.24; N, 3.75. Found: C,
80.39; H, 7.18; N, 3.81%.
Preparation of the
Copper-(Schiff-Bases) Complex:
General Procedure
Ligand of complex 3a. Yield 95%, yellow crystal,
m.p. 126 C; [ ]2D5 = +19 (C = 0.6, CHCl3); H
1
NMR (500 MHz, CDCl3), 3.08 (s, br, 1H), 5.58
(d, J = 7.0 Hz, 1H), 5.72 (d, J = 7.0 Hz, 1H), 6.86
(m, 1H), 6.95 (m, 2H), 7.06–7.27 (m, 8H), 7.41 (d,
J = 7.1 Hz, 2H),7.58 (d, J = 8.2 Hz, 1H), 8.61 (s,
1H),14.2 (s, 1H) IR (KBr): 3443, 1629, 1578, 1497,
1425, 1054 cm 1. Anal. Calcd for C21H19NO2: C,
79.50; H, 5.99; N, 4.42. Found: C, 79.54; H, 6.12; N,
4.41%.
Salicylaldimine (1 mmol) and cupric acetate
monohydrate (1 mmol) were dissolved in 75 ml of
ethanol. Aqueous sodioum hydroxide (10%, 3.8 ml)
was added and the mixture was stirred for 1 h. The
solution was diluted with water and extracted three
times with benzene. The benzene extracts were dried
(K2CO3), filtered and concentrated, the complex was
obtained.
Complex 3a. Yield 92%, Anal. Calcd for
C25H25NO2Cu: C, 66.57; H, 4.49; N, 3.70. Found:
C, 66.44; H, 4.31; N, 3.52%.
Complex 3b. Yield 85%, Anal. Calcd for
C25H25NO2Cu: C, 66.57; H, 4.49; N, 3.70. Found:
C, 66.45; H, 4.62; N, 3.63%.
Complex 3c. Yield 89%, Anal. Calcd for
C25H25NO2Cu: C, 66.57; H, 4.49; N, 3.70. Found:
C, 66.37; H, 4.51; N, 3.49%.
Complex 3d. Yield 84%, Anal. Calcd for
C25H25NO2Cu: C, 66.57; H, 4.49; N, 3.70. Found:
C, 66.51; H, 4.68; N, 3.55%.
Complex 3e. Yield 81%, Anal. Calcd for
C25H25NO2Cu: C, 68.89; H, 5.97; N, 3.01. Found:
C, 69.04; H, 5.84; N, 3.21%.
Ligand of complex 3b. Yield 91%, yellow crystal,
m.p. 125–126 C; [ ]D25
=
18 (C = 0.6, CHCl3);
1H NMR (500 MHz, CDCl3) 3.10 (s, br, 1H), 5.59
(d, J = 7.0 Hz, 1H), 5.74 (d, J = 7.0 Hz, 1H), 6.88
(m, 1H), 6.96 (m, 2H), 7.08–7.29 (m, 8H),7.44 (d,
J = 7.1 Hz, 2H), 7.60 (d, J = 8.2 Hz, 1H), 8.62 (s,
1H), 14.3 (s, 1H) IR (KBr): 3445, 1628, 1577, 1499,
1423, 1055 cm 1. Anal. Calcd for C21H19NO2: C,
79.50; H, 5.99; N, 4.42. Found: C, 79.41;H, 6.02; N,
4.35%.
Ligand of complex 3c. Yield 87%, yellow crystal
m.p. 136–137 C; [ ]2D5 = 87 (C = 1, C2H5OH);
1H NMR (500 MHz, CDCl3) 3.33 (s, br, 1H), 5.22
(d, J = 8.0 Hz, 1H), 5.49 (d, J = 8.0 Hz, 1H) 6.83
(m, 1H), 7.05 (d, J = 8.1 Hz, 1H), 7.14 (s, 2H), 7.22–
7.47 (m, 8H), 7.50 (m, 2H), 8.77 (s, 1H) 12.15 (s, 1H)
1
IR (KBr): 3438, 1629, 1584, 1494, 1450, 1044 cm
.
Cyclopropanation: General
Procedure
Anal. Calcd for C21H19NO2: C, 79.50; H, 5.99; N,
4.42. Found: C, 79.42; H, 5.94; N, 4.45%.
Ligand of complex 3d. Yield 85%, yellow crystal,
m.p. 137–138 C; [ ]2D5 = +89 (C = 1, C2H5OH);
1H NMR (500 MHz, CDCl3) 3.31 (s, br, 1H),
5.21 (d, J = 8.0 Hz, 1H), 5.47 (d, J = 8.0 Hz,
1H), 6.81 (m, 1H), 7.04 (d, J = 8.1 Hz, 1H), 7.12
(s, 2H), 7.20–7.45 (m, 8H), 7.49 (m, 2H), 8.75 (s,
1H), 12.13 (s, 1H) IR (KBr): 3436, 1629, 1586, 1497,
1443, 1045 cm 1. Anal. Calcd for C21H19NO2: C,
79.50; H, 5.99; N, 4.42. Found: C, 79.58; H, 6.05; N,
4.39%.
Under an argon atmosphere, a few drops of a so-
lution of 1.0 mmol of diazoacetates in 2.0 ml of
solvent was added to a mixture of 0.01 mmol of
catalyst, 1.0 ml of olefin and 3.0 ml of the sol-
vent at 80 C to initiate the reaction. After the mix-
ture was cooled to 40 C, the rest of the diazoac-
etates solution was added slowly and the mixture
was stirred for another 6 h after all the diazoacetate
was added. The solvent was removed in vacuo and
passed through a silica gel column to obtained a pure
product.
Ligand of complex 3e. Yield 89%, yellow syrup, 1H
NMR (500 MHz, CDCl3) 1.42 (s, 9H), 2.8 (br, 1H),
4.70 (d, J = 5.9 Hz, 1H), 5.14 (d, J = 5.9 Hz, 1H),
6.77 (d, J = 7.6 Hz, 1H),7.12–7.37 (m, 12H), 8.39
(d, J = 4.3 Hz, 1H),14.05 (s, 1H) IR (KBr): 3436,
2956, 1629, 1493, 1433, 1047 cm 1. Anal. Calcd for
ACKNOWLEDGEMENT
This work was supported by the National Science
Foundation of China (No. 29872035).
292
C. JIANG ET AL.

[6] T. Aratani, Y. Yoneyoshi, and T. Nagase, Tetrahedron Lett.
1975, 1707–1710.
REFERENCES
[7] T. Aratani, Pure & Appl. Chem. 1985, 57, 1839–1844.
[8] Li. Zhengning, Z. Zhuo, and C. Huilin, Tetrahedron: Asym-
metry 2000, 11, 1157–1163.
[9] L. Cai, H. Mahmoud, and Y. Han, Tetrahedron: Asymme-
try 1999, 10, 411–427.
[10] T. Aratani, Y. Nakanisi, and H. Nozaki, Tetrahedron 1970,
26, 1675–1684.
[11] J. Weijlard, K. Pfister, and F. S. Edward, J. Am. Chem. Soc.
1951, 73, 1216–1218.
[1] K. S. Vinod and G. S. Arpita, Synthesis 1997, 137–
149.
[2] M. P. Doyle and M. N. Protopopova, Tetrahedron 1998,
54, 7919–7946.
[3] I. Seiji, T. Futoshi, T. Yasunori, and N. Hisao, Chem. Com-
mun. 2001, 59–60.
[4] D. A. Evans, K. A. Woerpel, M. M. Hinman, and
M. M. Faul, J. Am. Chem. Soc. 1991, 113, 726–
728.
[12] H. Masahiko, M. Yasunori, N. Tetsuya, and O. Nobuki,
J. Org. Chem. 1993, 58, 1515–1522.
[5] H. Nozaki, S. Moriuti, and T. Nagase, Tetrahedron Lett.
1966, 5239–5242.
A SERIES OF COPPER-(SCHIFF-BASE) COMPLEXES WITH TWO CHIRAL CENTERS
293