Asymmetric cyclopropanation of styrene catalyzed by Cu-(chiral Schiff-base) complexes

Article abstract of DOI:10.1016/S0040-4020(00)00623-2

Asymmetric cyclopropanation of olefins was carried out with chiral copper-Schiff base complexes derived from copper acetate monohydrate, substituted salicylaldehydes and a chiral amino alcohol. Substituents on salicylaldehyde framework demonstrate a significant effect on the steroselectivities. Those with electron-withdrawing properties enhance the selectivities, whereas bulky sustituents in ortho position to the phenol hydroxy group decrease the selectivities. An ee of more than 98% was achieved for the reaction of styrene with diazoacetate. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00623-2

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 7187–7191
Asymmetric Cyclopropanation of Styrene Catalyzed by
Cu–(Chiral Schiff-Base) Complexes
*
Zhengning Li, Guosheng Liu, Zhuo Zheng and Huilin Chen
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People’s Republic of China
Received 1 March 2000; revised 21 June 2000; accepted 6 July 2000
Abstract—Asymmetric cyclopropanation of olefins was carried out with chiral copper–Schiff base complexes derived from copper acetate
monohydrate, substituted salicylaldehydes and a chiral amino alcohol. Substituents on salicylaldehyde framework demonstrate a significant
effect on the steroselectivities. Those with electron-withdrawing properties enhance the selectivities, whereas bulky sustituents in ortho
position to the phenol hydroxy group decrease the selectivities. An ee of more than 98% was achieved for the reaction of styrene with
diazoacetate. ᭧ 2000 Elsevier Science Ltd. All rights reserved.
Introduction
efficient catalysts with a C2 symmetry developed in the
last decade.11–23
Chiral cyclopropyl esters are very important intermediates
in the synthesis of optically pure molecules, in particular,
biologically active compounds.1,2 Catalytic asymmetric
cyclopropanation of diazoacetate with alkene has been
one of the most efficient synthetic methods for this kind of
compound. Among the efficient catalysts which have been
developed, copper–Schiff base complexes derived from
chiral amino alcohols are of particular significance because
they are effective for the intermolecular cyclopropanation of
various substituted olefins including mono-, di-, and tri-
substituted olefins, as well as for intramolecular cyclo-
propanation.3–8 The successful industrial application of
this kind of catalysts in the synthesis of chiral 2,2-dimethyl-
cyclopropanecarboxylic acid makes it a significant achieve-
ment in asymmetric catalysis.9 Even though it has received
so much attention, to our knowledge, modification of this
kind of catalyst to obtain higher enantioselectivity had only
focused on the modification of chiral amino alcohols until
1999, Cai reported that copper–Schiff base complexes
derived from 2-hydroxyl-5-methyl-1,3-benzenebisaldehyde
were used as the catalyst.10 However, other modifications of
salicylaldehyde to achieve high ee has not been reported so
far. Here we report our results of ee higher than 98% for the
cyclopropanation of styrene with copper–Schiff base
catalysts modified on the framework of the benzene ring
of salicylaldehyde. This is the highest ee for the reaction
of styrene with a copper–(Schiff base) complex as the
catalyst. It is also the first catalyst without C2 symmetry
giving ee’s comparable to those obtained with the most
Results and Discussion
According to the proposed mechanism of asymmetric cyclo-
propanation,6 metal-carbenes (A1 and A2) (Scheme 1) are
involved as the intermediates. Approach of the alkene to the
metal-carbene occurs from the less hindered side, giving
rise to the enantioselectivity. The decision to study the
electronic and steric effects of substituents on the salicyl-
aldehyde framework was based on the hypothesis that
substituents R1 and R2 may affect the stability of the
metal-carbene and the metallacyclobutane (B1, B2, B3
and B4), key intermediates of this reaction, thus altering
the enantioselectivity. We therefore attempted to replace
some hydrogen atoms on the salicylaldehyde framework
with other substituents. The positions of substitution were
para or ortho, para to the hydroxy group of salicylaldehyde,
and the substituents include t-butyl, chloro, and nitro groups
as a consequence of their ready synthesis and their different
steric and electronic properties. Structures of these catalysts
are shown in Scheme 2. They were synthesized according to
the route in Scheme 3.
The results of asymmetric cyclopropanation of styrene are
shown in Table 1. Firstly, it is noteworthy that this kind of
catalyst is different from the previous chiral copper catalysts
in that the ee’s for the cis isomer are higher than those for
the trans isomer for the cyclopropanation of styrene.2
Similar phenomena were reported by Doyle9 and Cai10
with Rh(II)–carboxamide and Cu–Schiff base as the
catalyst, respectively, even though Cai’s catalysts afford
the opposite result in most cases. Secondly, substituents
on salicylaldehyde ring show a significant influence upon
Keywords: asymmetric cyclopropanation; styrene; Schiff base.
* Corresponding author. Fax: ϩ86-411-4684746;
e-mail: lizn@ms.dicp.ac.cn
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00623-2

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Z. Li et al. / Tetrahedron 56 (2000) 7187–7191
Scheme 1. Some intermediates in asymmetric cyclopropanation.
Scheme 2. Structures of catalysts 1a–1g.
the yields and enantioselectivities of the products. With
catalyst 1a derived from salicylaldehyde and a chiral
amino alcohol, an ee around 80% was obtained for the
reaction of styrene with ethyl diazoacetate. Only low to
moderate ee were obtained with catalysts 1b and 1c bearing
a t-butyl group, a sterically demanding and electron-
donating group (entries 2–5). Substitution of the para-
hydrogen atom in catalyst 1a with electron-withdrawing
substituents, such as a nitro group or a chlorine atom,
resulted in an increase of the yield and ee of both trans
and cis isomers (entries 6, 8 and 10). Catalyst 1e with one
more chlorine atom, gave rise to a higher ee of the cyclo-
propyl esters than catalyst 1d. Thus, reducing the electron
density on salicylaldehyde favors the enantioselectivity.
The best results were obtained with catalyst 1f when ethyl
diazoacetate was used (entries 10 and 11). However, intro-
duction of two nitro groups resulted in a decrease of the ee
(entry 10 vs. entry 12), even though it decreased the electron
density on the salicylaldehyde ring. The results reveal the
complexity of the substituents on the salicylaldehyde ring
upon the reaction. The negative effect of the second nitro
group can be explained more reasonably as a steric effect
because the introduction of a nitro group, which is larger
than hydrogen and chlorine atoms, to the ortho position of
Scheme 3. Synthesis of catalysts 1a–1g. Arˆ2-n-butoxyl-5-butylphenyl: (a) i: Mg, 1,2-dimethoxyethane; ii: methyl alaninate hydrochloride; (b) substituted
salicylaldehyde; (c) copper acetate monohydrate, NaOH.

Z. Li et al. / Tetrahedron 56 (2000) 7187–7191
7189
Table 1. Asymmetric cyclopropanation of styrene
Entry
Cat.
R in RDAa
Yield (%)b
cis/transc
ee % of cisc,d
ee% of transc,e
71.6
1
2
3
4
5
6
7
8
1a
1b
1b
1c
1c
1d
1d
1e
1e
1f
Et
Et
i-Bu
Et
i-Bu
Et
i-Bu
Et
i-Bu
Et
i-Bu
Et
i-Bu
53
52
45
65
36
47
44
85
48
92
50
59
53
33.5:55.5
37.7:62.3
31.1:68.9
33.8:66.2
28.6:71.4
38.1:61.9
31.0:69.0
41.4:58.6
32.0:68.0
46.9:53.1
33.6:66.4
44.3:55.7
34.4:65.6
79.3
75.6
78.7
56.9
38.8
80.1
Ͼ98.0
89.6
89.9
89.2
59.5
56.9
38.8
18.6
67.7
68.9
77.0
70.6
82.8
73.9
68.5
60.7
9
10
11
12
13
1f
1g
1g
Ͼ98.0
80.5
78.6
Reaction conditions: 1 mmol of alkyl diazoacetate, 1.0 mL of styrene, 1 mol% of catalyst (based on diazoacetate), 3.0 mL of dichloroethane, 40ЊC.
a Alkyl diazoacetate.
b Based on alkyl diazoacetate and determined by GC analysis with diethyl adipate as the internal standard.
c Determined by GC analysis (b-cyclodextrin chiral capillary column, 30 m×0.25 mm ID, 0.25 mm film, column temp. 130ЊC); configurations of the
products were determined by the comparison of GC elution order of the enantiomers with authentic samples prepared according to the literature.10
d 1R,2S as the major enantiomer.
e 1R,2R as the major enantiomer.
Table 2. Cyclopropanation of other olefins
Olefin
trans/cis
ee of cis isomers
ee of trans isomers
1,1-Diphenylethene
5,5,5-Trichloro-2-methyl-2-pentene
2,5-Dimethyl-2,4-hexadiene
92.7
55.1
35.0
34.9:65.1
71.8:28.2
26.1
74.0
Reaction conditions: 1f was used as the catalyst, 0.114 g of ethyl diazoacetate when 1,1-diphenylethene or 5,5,5-trichloro-2-methyl-2-pentene was used as
olefin, and 0.224 g of l-menthyl diazoacetate was used for the reaction of 2,5-dimethyl-2,4-hexadiene, 1.0 mL of olefin, 4.0 mL of 1,2-dichloroethane, 40ЊC.
the hydroxylate in the phenol framework of the catalyst,
leads to a steric repulsion. The enantioselectivity is very
sensitive to the size of the subsituent in the ortho position
of the phenol phenoxide of the catalyst since it is very close
to and has a steric repulsion with the ester groups in B1 and
B2, which yield the major isomers of the products. A bulky
substituent will therefore decrease the ee.
chlorine atom. This rarely occurs when other kinds of
catalyst were used in cyclopropanation. It is generally
known that the ee will increase when a diazoacetate with
a bulkier alkyl is used. The interaction between the alkyl
group in RDA and the substituent at the ortho position to
hydroxylate in the salicylaldehyde ring will inhibit the
formation of B1 and B2 as shown in Scheme 1, which
yield the predominant isomers of cis and trans isomers,
respectively. The ee of the product will decrease by the
steric repulsion between the alkyl in RDA and the group
in the ortho position. A dramatic decrease in the ee was
observed with the catalyst derived from o,p-di(t-butyl)sali-
cylaldehyde when i-butyl diazoacetate was used instead of
ethyl diazoacetate, whereas only a small (or no) decrease
was found with the catalyst derived from o,p-dichloro and
dinitro-salicylaldehyde.
From Table 1, the conclusion can be drawn that an electron-
withdrawing substituent on the salicylaldehyde group of the
catalyst favors the ee of both trans and cis products, which is
different to the case when Co–Salen catalyzes cyclopropa-
nation.17 A bulky substituent at the ortho-position to the
phenol hydroxy group, however, decreases the ee.
The use of i-butyl diazoacetate instead of ethyl diazoacetate
results in an increase in ee for the cis isomer and a decrease
in ee for the trans isomer when there is a para-substituent
instead of a hydrogen atom on the salicylaldehyde. Values
of ee higher than 98% were obtained when i-butyl diazo-
acetate was used in the presence of catalyst 1d or 1f.
These results are comparable to the results with the most
efficient catalysts reported to date, including Cu–semi-
corrin, Cu–bisoxazoline, Cu–bipyridine, etc.10–19 Further-
more, when one or two chlorine atoms or nitro groups are
introduced, the ligands formed are easy to purify due to their
high melting points. A recrystallization is sufficient to purify
them. However, the ee of both cis and trans isomers
decreases with the use of i-butyl diazoacetate instead of
ethyl diazoacetate when there are substituents in both the
ortho and para positions, even when the subtstituent is a
This kind of catalyst is effective for the asymmetric cyclo-
propanation of various substituted olefins. Some results are
summarized in Table 2. High stereoselectivities are
obtained for disubstituted and trisubstituted olefins.
Experimental
Unless otherwise noted, all reactions were carried out under
an argon atmosphere. Substituted salicylaldehydes were
synthesized according to literature methods.24–26 Optical
rotations were measured on a SEPA-200 high sensitive
polarimeter. NMR spectra were recorded on a Bruker
DRX-400NMR spectrometer with tetramethyl silane as an

7190
Z. Li et al. / Tetrahedron 56 (2000) 7187–7191
internal standard (d value in CDCl3). The yields and ee
values of cyclopropyl derivatives were determined by GC
analyses with a chiral capillary column (30 m×0.25 mm
permethyl cyclopdextrin, ID, 0.25 mm film) at 130ЊC. The
configurations of phenylcyclopropanecarboxylate were
determined using GC by comparison of GC elution order
of the enantiomers with authentic samples prepared accord-
ing to the literature.
1283, 1268, 1243, 1140, 1075, 1030, 970, 910, 811, 758,
1
700 cmϪ1; H NMR: 13.51 (s, br, 1H, OH), 8.12 (s, 1H),
7.64 (s, 2H), 7.17–7.09 (m, 3H), 7.01–7.00 (m, 2H), 6.77–
6.56 (m, 2H), 5.14 (s, 1H), 3.68 (m, 2H), 3.60 (t, Jˆ7.1 Hz,
2H), 1.41–1.37 (m, 7H), 1.30 (s, 9H), 1.26–1.23 (m, 4H),
1.17 (s, 9H), 0.82 (t, Jˆ7.1 Hz, 6H); 13C NMR: 163.5,
162.4, 153.8, 153.2, 141.9 (2C), 132.7, 132.5, 131.5,
131.0, 125.7 (2C), 124.7, 124.4, 118.7, 117.4, 117.2,
111.9, 111.7, 80.0, 68.0, 67.2, 66.0, 34.2, 34.1, 31.6 (tBu),
31.4 (tBu), 31.0 (2C), 19.1 (2C), 17.2, 13.7 (2C).
(S)-2-Amino-1,1-di(2-n-butoxy-5-t-butylphenyl)propanol.
The hydrochloride salt of methyl l-alaninate (0.90 g,
7.14 mmol) was added to a cooled Grignard solution
derived from 2-n-butoxy-5-t-butyl bromobenzene10,27
(15.5 g, 54.0 mmol) and magnesium (1.44 g, 59.3 mmol)
with vigorous stirring. The mixture was refluxed overnight,
and then cooled to room temperature. Saturated aqueous
solution of ammonium chloride (50 mL) was added to the
cooled mixture, and the organic phase was separated. The
aqueous phase was extracted with chloroform (3×50 mL).
The combined organic solution was washed with aqueous
sodium bicarbonate, saturated brine, dried and concentrated.
The residue was purified with a silica gel column with petro-
leum ether–diethyl ether (8:1 to 1:1) as eluent and gave the
product as a viscous oil (2.40 g, 70%); [Found: C, 77.0%; H,
9.9%; N, 2.8%. C31H49NO3 requires: C, 76.97%; H, 10.21%;
2b. Yellow viscous oil; [Found: C, 78.7%; H, 9.4%; N,
1.97%. C42H61NO4 requires C, 78.34%; H, 9.55 %; N,
2.18%]; [a]Dˆ70.6 (c 0.666, benzene); IR: 3510, 3040
(w), 2960, 2910, 2870, 1640, 1590, 1490, 1465, 1390,
1268, 1242, 1184, 1145, 1075, 1030, 1013, 970, 830, 811,
747 cmϪ1; 1H NMR: 13.40 (s, br, 1H), 8.25 (s, 1H), 7.71 (s,
1H), 7.69 (s, 1H), 7.22 (d, Jˆ8.7 Hz, 1H), 7.18 (d,
Jˆ8.5 Hz, 1H), 7.08–7.06 (m, 2H), 6.76 (d, Jˆ8.7 Hz,
1H), 6.72 (d, Jˆ8.6 Hz, 1H), 6.63 (d, Jˆ8.5 Hz, 1H), 5.20
(s, 1H), 4.86 (m, 1H), 3.72 (t, Jˆ7.3 Hz, 2H), 3.65 (m, 2H),
1.43–1.39 (m, 7H), 1.34 (s, 9H), 1.26 (s, 9H), 1.25 (s, 9H),
1.33–1.22 (m, 4H), 0.86 (t, Jˆ7.3 Hz, 6H); 13C NMR:
164.0, 159.9, 153.8, 153.3, 141.8 (2C), 139.9, 132.2,
129.0 (2C), 127.4, 125.7, 125.6, 124.3 (2C), 118.0, 116.6,
111.9, 111.7, 79.4, 68.0, 67.9, 65.7, 34.1, 34.0, 33.7, 31.6
(tBu), 31.4 (tBu), 31.2 (tBu), 31.0 (2C), 19.1 (2C), 17.1, 13.7
(2C).
1
N, 2.90%]; [a]DˆϪ36.1 (c 1.776, CHCl3); H NMR: 7.67
(s, 1H), 7.65 (s, 1H), 7.14 (d, Jˆ8.3 Hz, 1H), 7.11 (d,
Jˆ6.9 Hz, 1H), 6.69 (d, Jˆ8.5 Hz, 1H), 6.62 (d, Jˆ
8.5 Hz, 1H), 4.20 (br, 3H), 3.77–3.69 (m, 4H), 1.52–1.47
(m, 4H), 1.34 (s, 9H), 1.33 (s, 9H), 1.28 (m, 7H), 0.88 (m,
6H); 13C NMR: 154.1, 153.3, 142.1, 141.8, 132.8, 132.0,
125.6, 125.1, 124.5, 124.1, 112.1, 111.5, 80.0, 68.1, 67.8,
49.7, 34.2 (2C), 31.5 (tBu), 31.4 (tBu), 31.1, 29.9, 19.3 (2C),
16.8, 13.9 (2C).
2c. Yellow viscous oil; [Found: C, 78.7%; H, 10.2%; N,
2.2%. C46H69NO4 requires C, 78.92%; H, 9.93%; N,
2.00%]; [a]Dˆ59.45 (c 0.656, benzene); IR: 3520, 2960,
2870, 1630, 1610, 1500, 1475, 1390, 1362, 1268, 1250,
1
1150, 1075, 1030, 980, 882, 810 cmϪ1; H NMR: 13.96 (s,
br, 1H), 8.24 (s, 1H), 7.79 (s, 1H), 7.71 (s, 1H), 7.27 (s, 1H),
7.18 (d, Jˆ8.50 Hz, 1H), 7.08 (d, Jˆ8.5 Hz, 1H), 6.92 (s,
1H), 6.71 (d, Jˆ8.6 Hz, 1H), 6.63 (d, Jˆ8.6 Hz, 1H), 5.20
(s, 1H), 4.83 (m, 1H), 3.70 (t, Jˆ7.6 Hz, 2H), 3.62 (t,
Jˆ7.3 Hz, 2H), 1.43–1.41 (m, 7H), 1.39 (s, 9H), 1.34 (s,
9H), 1.32 (s, 9H), 1.29 (s, 9H), 1.28–1.22 (m, 4H), 0.86 (t,
Jˆ7.2 Hz, 6H); 13C NMR: 165.1, 158.7, 153.9, 153.4,
142.0, 141.8, 138.9, 136.4, 132.4, 131.8, 126.2, 125.7
(3C), 124.3 (2C), 118.0, 112.9, 112.7, 79.6, 68.0, 67.8,
66.2, 34.9, 34.1 (2C), 33.9, 31.6 (tBu), 31.5 (tBu) 31.3
(tBu), 31.0 (tBu), 29.4, 29.2, 19.1 (2C), 17.5, 13.7 (2C).
Schiff bases. General procedure: (S)-2-amino-1,1-di(2-n-
butoxy-5-t-butylphenyl)propanol (0.102 g, 2.11 mmol) and
2-hydroxy-3,5-dinitrobenzaldehyde (0.0448 g, 2.11 mmol)
were dissolved in ethanol (10 mL) and the mixture was
stirred for 6 h. Most of ethanol was removed in vacuum
and the residue was purified by column chromatography
to afford pure Schiff base 2g (0.094 g, 66%) as a yellow
solid; mp 197–198ЊC; [Found: C, 67.5%; H, 7.4%; N,
6.3%. C38H51N3O8 requires C, 67.33%; H, 7.58%; N,
6.20%]; [a]Dˆ166.8 (c 0.698, benzene); IR: 3480, 3070
(w), 2960, 2870, 1656, 1620, 1557, 1500, 1460, 1362,
1315, 1230, 1172, 1150, 1094, 1032, 980, 935, 904, 810
2d. Yellow viscous oil; [Found: C, 73.5%; H, 8.6%; N,
2.2%. C38H52ClNO4 requires C, 73.35%; H, 8.42%; N,
2.25%]; [a]Dˆ81.5 (c 0.956, benzene); IR: 3520, 3040
(w), 2960, 2872, 1638, 1580, 1500, 1478, 1385, 1282,
1
(m), 752 (w), 710 cmϪ1; H NMR: (CDCl3) d 14.20 (s, br,
1H, OH), 8.88 (d, Jˆ2.9 Hz, H), 8.17 (s, 1H), 7.85 (s, 1H),
7.57 (s, 1H), 7.54 (s, 1H), 7.26 (d, Jˆ7.1 Hz, 1H), 7.14 (d,
Jˆ8.5 Hz, 1H), 6.77 (d, Jˆ8.5 Hz, 1H), 6.73 (d, Jˆ8.5 Hz,
1H), 5.61 (s, 1H), 5.24 (m, 1H), 3.80 (m, 4H), 1.55–1.50 (d,
7H), 1.36 (s, 9H, tBu), 1.28–1.29 (m, 4H), 1.15 (s, 9H, tBu),
0.91 (t, Jˆ7.3 Hz, 6H); 13C NMR: 170.6, 164.6, 153.3,
152.7, 142.9, 142.2, 140.7, 135.9, 130.8, 129.6, 128.9,
128.2, 125.7, 125.5, 125.2, 124.6, 116.5, 112.5, 112.0,
78.9, 68.2, 68.1, 62.1, 34.2, 34.1, 31.5 (tBu), 31.3 (tBu),
30.9, 30.8, 19.1, 19.0, 16.3, 13.7 (2C).
1
1269, 1244, 1143, 1088, 1030, 1013, 970, 825 cmϪ1; H
NMR 13.87 (s, br, 1H), 8.07 (s, 1H), 7.65 (s, 1H), 7.20–
7.18 (m, 2H), 7.09–7.06 (m, 2H), 7.01 (m, 1H), 6.73 (m,
2H), 6.64–6.62 (m, 1H), 5.23 (s, 1H), 4.84 (m, 1H), 3.73 (t,
Jˆ7.9 Hz, 2H), 3.66 (t, Jˆ6.9 Hz, 2H), 1.45–1.42 (m, 7H),
1.35 (s, 9H), 1.34–1.20 (m, 4H), 1.21 (s, 9H), 0.87 (t,
Jˆ7.3 Hz, 3H), 0.86 (t, Jˆ7.3 Hz, 3H); 13C NMR 162.7,
161.4, 153.8, 153.0, 141.9, 141.8, 131.9, 131.7, 130.0,
125.6, 125.4, 124.5 (2C), 121.6, 119.2, 119.0, 111.9,
111.7, 79.3, 68.0, 67.9, 65.6, 34.1, 34.0, 31.5 (tBu), 31.5
(tBu), 31.0 (2C), 19.1 (2C), 16.0, 13.7 (2C).
2a. Yellow viscous oil; [Found: C, 77.4%; H, 9.0%; N,
2.5%. C38H53NO4 requires C, 77.64%; H, 9.09%; N,
2.38%]; [a]Dˆ130.4 (c 2.676, benzene); IR: 3510, 3040,
2960, 2863, 1632, 1620, 1580, 1500, 1460, 1390, 1365,
2e. Yellow solid, mp 110–112ЊC; [Found: C, 69.3; H, 7.9%;

Z. Li et al. / Tetrahedron 56 (2000) 7187–7191
7191
N, 2.1%. C38H51ClNO4 requires C, 69.50%; H, 7.83%; N,
2.13%]; [a]Dˆ144.23 (c 0.936, benzene); IR: 3500, 2960,
2930, 2858, 1640, 1500, 1460, 1378, 1290, 1268, 1242,
removed in vacuum and the residue was passed through a
short silica gel column to remove the catalyst, and was
analyzed by GC (permethyl b-cyclopdextrin chiral capillary
column, 30 m×0.25 mm ID, 0.25 mm film, column temp.
130ЊC) using an internal method with ethyl adipate as a
standard. When ethyl diazoacetate and styrene were used
as reactants, the retention time of the cyclopropyl deriva-
tives is 30.09, 31.37, 35.14, 35.94 min for (1S,2R), (1R,2S),
(1R,2R), (1S,2S) isomers, respectively.
1
1220, 1150, 1105, 990, 860, 814, 750 cmϪ1; H NMR:
14.82 (s, br, 1H), 7.77 (s, 1H), 7.62 (s, 1H), 7.57 (s, 1H),
7.30 (s, 1H), 7.22 (m, 1H), 7.08 (d, Jˆ6.9 Hz, 1H), 6.81 (s,
1H), 6.73 (d, Jˆ8.6 Hz, 1H), 6.65 (d, Jˆ8.6 Hz, 1H), 5.34
(s, 1H), 4.95 (m, 1H), 3.76–3.69 (m, 4H), 1.47 (m, 7H), 1.35
(s, 9H), 1.32–1.26 (m, 4H), 1.17 (s, 9H), 0.89 (t, Jˆ7.3 Hz,
3H), 0.88 (t, Jˆ7.3 Hz, 3H); 13C NMR: 164.2, 162.0, 153.6,
152.8, 142.4, 141.9, 133.1, 131.0, 130.7, 128.8, 125.8,
125.5, 125.2, 124.9 (2C), 118.1, 116.5, 112.0, 111.9, 79.0,
68.0 (2C), 63.2, 34.1, 34.0, 31.5 (tBu), 31.3 (tBu), 31.0, 30.9,
19.1 (2C), 16.9, 13.7 (2C).
References
1. Doyle, M. P.; McKervey, M. A. Chem. Commun. 1997, 983.
2. Singh, V. K.; Gupta, A. D.; Sekar, G. Synthesis 1997, 137.
3. Aratani, T.; Yoneyoshi, Y.; Nagase, T. Tetrahedron Lett. 1975,
1707.
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Tetrahedron Lett. 1990, 31, 4969.
9. Doyle, M. P. In Catalytic Asymmetric Synthesis; Ojima, I. Ed.;
VCH: New York, 1993.
10. Cai, L.; Mahmoud, H.; Han, Y. Tetrahedron: Asymmetry
1999, 10, 411.
11. Fritschi, H.; Leutenegger, U.; Pfaltz, A. Helv. Chim. Acta
1988, 71, 1553.
12. Lowenthal, R. E.; Akio, A.; Masamune, S. Tetrahedron Lett.
1990, 31, 6005.
2f. Yellow solid; [Found: C, 72.3%; H, 8.2%; N, 4.2%.
C38H52N2O6 requires C, 72.12%; H, 8.28%; N, 4.43%];
[a]Dˆ89.6 (c 1.208, benzene); IR: 3500, 2960, 2870,
1650, 1613, 1543, 1500, 1470, 1391, 1364, 1327, 1232,
1
1180, 1146, 1128, 1096, 815 cmϪ1; H NMR: 14.75 (s, br,
1H), 8.03 (s, 1H), 8.01 (s, 1H), 7.82 (s, 1H), 7.62 (s, 1H),
7.56 (m, 1H), 7.22 (m, 1H), 7.10 (m, 1H), 6.75 (d, Jˆ8.6 Hz,
1H), 6.69 (d, Jˆ8.6 Hz, 1H), 6.66 (d, Jˆ9.4 Hz, 1H), 5.50
(s, 1H), 5.09 (s, 1H), 3.79 (t, Jˆ7.4 Hz, 2H), 3.75 (t,
Jˆ7.1 Hz, 2H), 1.52–1.51 (m, 7H), 1.36 (s, 9H), 1.34–
1.30 (m, 4H), 1.16 (s, 9H), 0.90 (t, Jˆ7.3 Hz, 3H), 0.89 (t,
Jˆ7.3 Hz, 3H); 13C NMR: 177.3, 163.6, 153.5, 152.8,
142.6, 142.1, 135.3, 131.0, 130.5, 130.1, 129.2, 125.4,
125.3 (2C), 125.2, 122.7, 113.5, 112.2, 112.0, 79.1, 68.1,
68.0, 62.1, 34.2, 34.1, 31.6 (tBu), 31.3 (tBu), 31.0 (2C), 19.2
(2C), 16.4, 13.8, 13.7.
Catalyst
13. Ito, K.; Yoshitake, M.; Katsuki, T. Heterocycles 1996, 42, 305.
14. Doyle, M. P.; Brandes, B. D.; Kazala, A. P.; Pieters, R. J.;
Jarstfer, M. B.; Watkins, L. M.; Eagle, C. Tetrahedron Lett.
1990, 31, 6160.
15. Nishiyama, H.; Itoh, Y.; Sugawara, Y.; Matsumoto, H.; Aoki,
K.; Itoh, K. Bull. Chem. Soc. Jpn 1995, 68, 1247.
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7175.
17. Tanner, D.; Johansson, F.; Harden, A.; Andersson, P. G.
Tetrahedron 1998, 54, 15731.
18. Fukada, T.; Katsuki, T. Tetrahedron 1997, 53, 7201.
19. Yamada, T.; Ikeno, T.; Sekino, H.; Sato, M. Chem. Lett. 1999,
719, 1345 and references cited therein.
General procedure: Schiff base 2d (0.305 g, 0.491 mmol)
was dissolved in ethanol (30 mL), and copper acetate mono-
hydrate (0.100 g, 5.00 mmol) solution was added to the
above solution. The mixture was stirred and aqueous sodium
hydroxide solution (5%, 2.7 mL) was added to the mixture,
and the stirring was continued for 1 h. Water (50 mL) was
added to the mixture and the mixture was extracted with
benzene (3×10 mL). After washing with water, drying and
removal of benzene in vacuum, the catalyst 1d was obtained
as a violet powder (0.245 g, 73%); [Found: C, 67.1%; H,
7.6%; N, 2.0%. CuC38H50ClNO4 requires C, 66.75%; H,
7.37%; N, 2.05%]; [a]DˆϪ226.13 (c 0.398, benzene); IR:
3030, 2954, 2860, 1641, 1610, 1520, 1493, 1457, 1390,
1376, 1358, 1310, 1260, 1239, 1170, 1105, 1020, 1002,
20. Boulch, R.; Scheurer, A.; Mosset, P.; Saalfrank, R. W.
Tetrahedron Lett. 2000, 41, 1023.
21. Fraile, J. M.; Garia, J. I.; Mayoral, J. A.; Tarnai, T. J. Mol.
Catal. A: Chem. 1999, 144, 85.
900, 826, 807, 719 cmϪ1
.
Cyclopropanation
22. Rios, R.; Liang, J.; Lo, M. M.-C.; Fu, G. C. Chem. Commun.
2000, 378.
Under argon, a few drops of a solution of ethyl diazoacetate
(0.114 g, 1.00 mmol) in 1,2-dichloethane (2.0 mL) was
added to a mixture of the catalyst (6.0 mg, 0.01 mmol),
styrene (1.0 mL) and 1,2-dichloethane (2.0 mL) at 80ЊC to
initiate the reaction. After the mixture was cooled to 40ЊC,
the rest of the diazoacetate solution was added to the
mixture slowly and the mixture was stirred for another 4 h
after all the diazoacetate was added. The solvent was
23. Raza, Z.; Dakovic, S.; Vinkovic, V.; Sunjic, V. Croat. Chem.
Acta 1996, 69, 1545.
24. Peter, H.; Robinson, R. J. Chem. Soc. 1933, 486.
25. James, C. D. J. Chem. Soc. 1941, 547.
26. Casiraghi, G.; Canati, G.; Puglia, G.; Sartori, G.; Terenghi, G.
J. Chem. Soc., Perkin Trans. 1 1980, 1862.
27. Baldwin, J. E.; Carler, C. G. J. Am. Chem. Soc. 1982, 104,
1362.