Telaprevir fragments as organocatalysts in asymmetric direct aldol reactions of aldehydes

Article abstract of DOI:10.1134/S1070363213120414

We have demonstrated that the fragments of Telaprevir can act as organocatalysts for asymmetric aldol reactions between aromatic aldehydes and acetone under mild conditions. The reaction conditions have been optimized in terms of the catalyst nature, choi

Full text of DOI:10.1134/S1070363213120414

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 12, pp. 2447–2452. © Pleiades Publishing, Ltd., 2013.
Telaprevir Fragments as Organocatalysts
in Asymmetric Direct Aldol Reactions of Aldehydes1
Chen Chen Wenga, Xinliang Xub, Xiao Xia Xionga, Xiu Lian Lua, and Yi Feng Zhoua,b
a Zhejiang Provincial Key Laboratory of Biometrology and Inspection & Quarantine, College of Life Sciences,
China Jiliang University, Xiasha, Hangzhou, Zhejiang, 310018 P. R. China
e-mail: xl.xu@apeloajiayuan.com, zhouyifeng@cjlu.edu.cn
b Zhejiang Apeloa Medical Tehnology Co. Ltd., Dongyang, Zhejiang, 322118 P. R. China
Received November 18, 2013
Abstract―We have demonstrated that the fragments of Telaprevir can act as organocatalysts for asymmetric
aldol reactions between aromatic aldehydes and acetone under mild conditions. The reaction conditions have
been optimized in terms of the catalyst nature, choice of temperature, solvent, additive, and the catalyst loading.
Under proper conditions, fairly good yield and enantioselectivity have been achieved.
DOI: 10.1134/S1070363213120414
The aldol reaction is of great importance for the
construction of C–C bonds in organic synthesis, in-
cluding that of complex natural compounds. Therefore,
a variety of synthetic approaches, catalysts, and
reagents have been developed in order to achieve
efficient addition with high stereo- and enantiomeric
selectivity [1].
of ketone needed, and poor results with certain
substrates like unbranched aldehydes [4]; therefore, a
great deal of effort was exerted to the development of
the new catalysts. As proline is very common and
cheap chemical, the new catalysts should reveal
significant improvements, both in terms of selectivity
and reac-tivity, to surpass proline. Many catalysts have
been developed based on proline structure [4]. The
structure modifications majorly aim to increase the
hydro-phobicity and thus to improve solubility in
organic solvents, or to introduce further polar groups
in order to play with the hydrogen bonding properties
[4, 8–16]. Other trends include adding bulky
substituents or stereocenters to enhance the
enantioselectivity [17–22]. The results reported so far
are very promising [23–29].
The first proline-catalyzed enantioselective
intermolecular aldol reaction has been described [2].
Further on, proline has been used as efficient catalyst
in other aldol reactions [3, 4].
The proposed mechanism of L-proline-catalyzed
asymmetric aldol reaction is a typical example of
enamine-based organocatalysis [5] proceeding via
reversible condensation of the catalytic amine with a
ketone to give nucleophilic enamine intermediate. In
the reaction, the carboxylic group of proline plays an
important part in activation and orientation of the
aldehyde acceptor via hydrogen bonding [6]. Based on
the mechanism, the activation energy of the addition
stage should be similar to that of the enamine
formation, indicating that the addition might be a rate-
determining step. Indeed, this has been directly proved
in the recent kinetic study [7].
In this work, we consider Telaprevir intermediates
as possible organocatalysts of aldol reaction.
Telaprevir has become a widely applied drug for
hepatitis C treatment, thus the number of its
intermediates available is also increasing. Moreover,
the smaller fragments of Telaprevir may be formed in
the human body as a result of the drug decay, and it is
important to understand their activity in aldol
reactions.
In spite of proline applicability as aldol reactions
catalyst, it suffers from several drawbacks, such as
slow reaction, high catalyst loadings and large excess
The structures of the catalysts I–V are listed below.
Noteworthily, the catalysts included large chiral
backbone along with the groups acting as hydrogen
bonding donor, thus combining the both promising
approaches of the proline modification mentioned
1
The text was submitted by the authors in English.
2447

2448
CHEN CHEN WENG et al.
above. The catalytic performance of the catalysts was
evaluated in the model direct asymmetric aldol
reaction of 4-nitrobenzaldehyde with acetone; the
catalysts performance is compared in Table 1.
NH2
OH
O
OH
O
NH2
II
I
L-Norvaline
H
(R)-2-Amino-2-cyclohexylacetic acid
O
NH2
O
H
HO
OH
N
H
N
H
NH2
III
(S)-2-Amino-3,3-dimethylbutanoic acid
OH
IV
(S)-2-Amino-N-cyclopropyl- (1R,3a,6aR)-Octahydrocyclopenta[c]pyrrole-1-
O
V
carboxylic acid
2-hydroxypentanamide
As seen from Table 1, II and V efficiently catalyzed
the direct aldol reaction of 4-nitrobenzaldehyde with
acetone, and the products revealed high enantiomeric
excess; in the case of V, the enantioselectivity was
higher as compared with L-proline (reference).
Therefore, the catalyst V was chosen for further
study.
To investigate the effect of the solvent, we tested a
variety of reaction media at different conditions (Table 2).
The solvent affected both the product yield and the
reaction enantioselectivity; a few products were
obtained in alcoholic solutions (entries 5 and 6). All
polar aprotic solvents, such as dimethylacetamide,
dimethylsulfoxide, acetonitrile, dioxane, and tetrahyd-
rofuran showed good results, but dimethylformamide
was the best (entries 1−4, 8, 9). Without the solvent,
the catalyst was not efficient.
Table 1. Model aldol reaction catalyzed with I–Va
O
O
H
+
O2N
OH
O
The catalyst loading was varied to optimize the
reaction conditions (Table 2, entries 1, 12, and 13).
High enantioselectivity (65%) was still obtained even
at relatively low catalyst loading (0.1 equiv., entry 12),
however, the yield was poor (41%) due to low reaction
rate. With the catalyst loading increased to 0.3 equiv.,
the yield was up to 78% at high enantioselectivity
(76%). Therefore, the catalyst loading of 0.3 equiv.
was used in further experiments.
DMSO
Catalyst
O2N
Catalyst
Time, h
ee, %b
53
60
60
60
60
24
24
I
61
II
III
IV
V
45
0
The reaction proceeded with moderate to good
enantioselectivity at 10°C. Decreasing the reaction
temperature did not improve the enantioselectivity
(data not shown). Increasing the reaction temperature
to 30°C or 60°C accelerated the reaction, at the cost of
more of side products formed, and thus decreased yield
and enantioselectivity.
73
L-Proline
58
a
Reactions were carried out with 0.1 mmol of 4-nitrobenz-
aldehyde, 0.2 mL of acetone, 0.03 mmol of catalyst, and 0.8 mL
dimethylsulfoxide at 10°C
b
Enantiomeric excess, as determined by chiral HPLC.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013

TELAPREVIR FRAGMENTS AS ORGANOCATALYSTS
Table 2. The model aldol reaction catalyzed by V under different conditionsa
2449
OH
O
O
O
solvent, V
H
+
temperature
O2N
O2N
Entry
1
Solvent
T, °C
10
10
10
10
10
10
10
10
10
10
10
10
10
30
60
Time, h
48
ee, %b
76
74
76
69
37
35
53
62
68
65
47
65
76
71
69
Yield, %c
Dimethylformamide
Dimethylsulfoxide
Dimethylacetamide
Acetonitrile
78
98
96
97
57
71
64
89
89
91
96
41
60
61
51
2
48
3
48
4
48
5
Ethanol
48
6
Methanol
48
7
Methylbenzene
Tetrahydrofuran
Dioxane
48
8
48
9
48
10
11
12
13
14
15
Dichloroethane
48
No solvent
48
Dimethylformamide d
Dimethylformamide e
Dimethylformamide
Dimethylformamide
48
48
24
24
a
b
c
d
e
Reactions were carried out with 0.1 mmol of 4-nitrobenzaldehyde, 0.4 mL of acetone, 0.03 mmol of V and 1 mL of solvent.
Enantiomeric excess, as determined by chiral HPLC.
Yield in wt % after column chromatography purification.
With 0.1 eq. of V.
With 0.2 equin. of V.
We further studied the effect of different additives
desired products could be obtained with good yields
and excellent enantioselectivity (enantiomeric excess
up to 84%, entries 1–8). However, the reaction of non-
activated aldehydes, such as benzaldehyde and
4-methoxybenzaldehyde, led to moderate yield and
enantioselectivity (entries 9 and 10). The absorption
maximum of some products was shifted from 254 nm;
that should have been taken into account in the course
of HPLC detection.
on the reaction outcome, other conditions being the
same (Table 3). It was found that with weak acids as
additive, the desired product yield was of 67–91%
(entries 2, 3, 8, and 9), and quartz sand showed similar
effect (entry 1). On the contrary, addition of strong
bases usually suppressed the reaction.
The reaction enantioselectivity was significantly
improved with the preserved high yield when certain
salts were introduced into the mixture (entries 11, 13,
15, 17, and 19); the rate of the reaction was increased
as well. However, other salts led to very poor yield and
the purity of the product (entries 12, 16, and 18).
To conclude, we have found that of the Telaprevir
fragments, one is an efficient catalyst of direct
asymmetric aldol reaction. The reaction procedure is
simple and likely scalable, which should allow C–C
bond formation with excellent yield and enantio-
selectivity. Various reaction conditions have been
probed, and the best of them was selected, including
proper choice of temperature, solvent, additive, and the
catalyst loading. In future we plan to study the catalyst
efficiency in other reactions.
To demonstrate the potential of the catalytic system,
the aldol reaction of acetone with differently
substituted aromatic aldehydes was performed with V
as catalyst and in the presence of EDTA (Table 4). The
reaction appeared quite tolerant with respect to the
steric effect of the benzaldehyde substituent, and the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013

2450
CHEN CHEN WENG et al.
Table 3. The model aldol reaction catalyzed by V in the
Table 4. The model aldol reaction of different substrates
catalyzed by V, in the presence of EDTA
presence of different additivesa
O
O
O
O
H
H
+
+
R
O2N
OH
O
OH
O
DMF, V
10°C, additive
DMF, V
R
10°C, EDTA
O2N
Run no. Time, h
Additive
Quartz sand
ee, %b
76
71
68
40
76
69
77
75
76
76
60
32
69
65
77
26
77
31
78
Yield, %c
89
Run no.
R
Product Time, h ee, %a Yield, %b
1
10
10
10
10
8
1
2
3
4-F-Ph
4-Br-Ph
4-Cl-Ph
24
24
24
73
75
73
58
70
50
VIa
VIb
VIc
2
Diatomite
Silica gel
Triethylamined
Imidazoled
Cyclodextrind
EDTAd
Deoxycholic acidd
Ascorbic acidd
NaCle
91
3
67
4
56
4
3.4-Cl2-Ph
4-NO2-Ph
3-NO2-Ph
2-NO2-Ph
4-OMe-Ph
H
24
8
67
78
80
84
72
68
58
97
27
78
88
93
54
53
74
38
VId
VIe
VIf
VIg
VIh
VIi
5
85
5
6
10
8
68
6
8
7
82
7
8
8
8
90
8
32
32
24
32
9
8
85
9
10
11
12
13
14
15
16
17
18
19
8
92
NaBre
LiBre
KIe
86
10
11
2-F
VIj
VIk
8
4-CF3
8
Trace
77
a
Enantiomeric excess, as determined by chiral HPLC.
Yield in wt % after column chromatography purification.
8
b
e
8
Al2O3
93
8
NH4Cle
NH4Bre
87
signals (CDCl3). Chiral High Performance Liquid
Chromatography was performed with Chiralpak® AD
or OJ-H column. The structures of aldol reaction
products were elucidated by comparison with literature
data.
8
Trace
82
e
8
(NH4)2C2O4
e
8
NH4HCO3
Trace
89
8
EDTAe
a
Aldol reaction (general procedure). The typical
aldol reaction procedure can be illustrated by the
following example. Aromatic aldehyde (0.1 mmol)
was added to a solution of the catalyst V (0.03 mmol)
and EDTA (0.03 mmol) in DMF (1 mL). Then, acetone
(0.4 mL) was added, and the reaction mixture was
stirred at 10°C until the reaction was completed
(TLC). The organic products were extracted three
times with ethyl acetate and washed three times with
water. The combined organic extracts were dried over
anhydrous sodium sulfate. The solvent was
evaporated, and the crude product was purified by
flash column chro-matography with various petroleum
ether (60–90°C)–EtOAc mixtures.
Reactions were carried out with 0.1 mmol of 4-nitrobenz-
aldehyde, 0.4 mL of acetone, 0.03 mmol of catalyst, and 1 mL of
DMF at 10°C.
Enantiomeric excess, as determined by chiral HPLC.
Yield in wt% after column chromatography purification.
0.3 equiv. of the addictive.
b
c
d
e
4 equiv. of the addictive.
EXPERIMENTAL
The products were purified by chromatography
using silica gel (200–300 mesh). 1H NMR and 13C
NMR spectra were recorded with a Bruker instrument
(400 MHz and 100 MHz, respectively) and were
internally referenced to residual protonated solvent
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013

TELAPREVIR FRAGMENTS AS ORGANOCATALYSTS
2451
4-(4-Fluorophenyl)-4-hydroxybutan-2-one (VIa).
1H NMR spectrum, δ, ppm: 7.33 d.d (J = 8.3, 5.6 Hz,
2H), 7.04 t (J = 8.6 Hz, 2H), 5.14 d.d (J = 8.7, 3.5 Hz,
1H), 2.83 m (2H), 2.21 s (3H). 13C NMR spectrum, δ,
ppm: 209.20, 163.40, 138.38, 127.36, 127.28, 115.48,
115.26, 69.17, 51.89, 30.78. HPLC (Daicel Chiralpak
AD column, n-hexane–isopropanol 95 : 5, 1 mL/min,
245 nm) ee = 73%.
7.93 d.d (J = 25.1, 8.1Hz, 2H), 7.90 d (J = 7.9 Hz, 1H),
7.67 t (J = 7.6 Hz, 1H), 7.44 t (J = 7.8 Hz, 1H), 5.68 d
(J = 9.4 Hz, 1H), 3.74 d (J = 2.7 Hz, 1H), 3.13 d (J =
17.8 Hz, 1H), 2.73 d.d (J = 17.8, 9.4Hz, 1H), 2.24 s
(3H). 13C NMR spectrum, δ, ppm: 208.93, 147.11,
138.39, 133.88, 128.31, 128.20, 124.48, 65.63, 51.07,
30.48. HPLC (Daicel Chiralpak OJ-H column, n-hexane–
isopropanol 90 : 10, 1 mL/min, 245 nm) ee = 84% .
4-(4-Bromophenyl)-4-hydroxybutan-2-one (VIb).
1H NMR spectrum, δ, ppm: 7.48 d (J = 8.0 Hz, 2H),
7.24 d (J = 8.0 Hz, 2H), 5.12 d.d (J = 7.7, 3.9 Hz, 1H),
2.83 m (2H), 2.20 s (3H). 13C NMR spectrum, δ, ppm:
209.10, 141.66, 131.64, 127.40, 121.45, 69.19, 51.76,
30.82. HPLC (Daicel Chiralpak AD column, n-hexane–
isopropanol 90 : 10, 1 mL/min, 205 nm) ee = 75%.
4-Hydroxy-4-(4-methoxyphenyl)butan-2-one
(VIh). 1H NMR spectrum, δ, ppm: 7.27 d (J = 15.7 Hz,
1H), 6.92 d (J= 8.2 Hz, 2H), 6.82 m (1H), 5.14 d.d (J =
8.9, 3.3 Hz, 1H), 3.82 s (3H), 2.85 q.d (J = 17.7, 6.2
Hz, 2H), 2.20 s (3H). 13C NMR spectrum, δ, ppm:
209.29, 159.80, 144.37, 129.63, 117.86, 113.22, 111.05,
69.76, 55.26, 51.97, 30.83. HPLC (Daicel Chiralpak
AD column, n-hexane–isopropanol 90 : 10, 1 mL/min,
205 nm) ee = 72%.
4-Hydroxy-4-phenylbutan-2-one (VIi). 1H NMR
spectrum, δ, ppm: 7.31 m (6H), 5.16 d.d (J = 9.0, 3.3
Hz, 1H), 2.90 d.d (J = 17.7, 9.0 Hz, 2H), 2.83 d.d (J =
17.7, 3.3 Hz, 1H), 2.21 s (3H). 13C NMR spectrum, δ,
ppm: 209.29, 142.59, 125.61, 127.70, 128.56, 69.80,
51.92, 30.79. HPLC (Daicel Chiralpak AD column,
n-hexane–isopropanol 95 : 5, 1 mL/min, 245 nm)
ee = 68%.
4-(4-Chlorophenyl)-4-hydroxybutan-2-one (VIc).
1H NMR spectrum, δ, ppm: 7.31 (q, J = 8.7 Hz, 5H),
5.13 d.d (J = 8.1, 4.2 Hz, 1H), 2.83 m (2H), 2.21 s
(3H). 13C NMR spectrum, δ, ppm: 209.15, 141.11,
133.34, 128.70, 127.05, 69.16, 51.80, 30.82. HPLC
(Daicel Chiralpak AD column, n-hexane–isopropanol
90 : 10, 1 mL/min, 215 nm) ee = 73% .
4-(3,4-Dichlorophenyl)-4-hydroxybutan-2-one
1
(VId). H NMR spectrum, δ, ppm: 7.45 d.d (J = 23.6,
4.9 Hz, 2H), 7.18 d.d (J = 8.3, 1.6 Hz, 1H), 5.12 t (J =
13
6.1 Hz, 1H), 2.82 d (J = 6.2 Hz, 2H), 2.22 s (3H). C
4-(2-Fluorophenyl)-4-hydroxybutan-2-one (VIj).
1H NMR spectrum, δ, ppm: 7.54 d.d (J = 8.1, 7.0 Hz,
1H), 7.25 m (1H),7.17 t (J = 7.5 Hz, 1H), 7.02 d.d (J =
10.0, 8.8 Hz, 1H), 5.44 d.d (J = 9.2, 2.5Hz, 1H), 2.95
m (2H), 2.83 d.d (J = 17.9, 9.2 Hz, 1H), 2.21 s (3H).
13C spectrum, δ, ppm: 209.35, 160.50, 158.06, 129.01,
128.93, 127.24, 127.20, 124.42, 124.39, 115.28,
115.07, 64.07, 64.05, 50.39, 30.64. HPLC (Daicel
Chiralpak AD column, n-hexane–isopropanol 95 : 5,
1 mL/min, 245 nm) ee = 58%.
NMR spectrum, δ, ppm: 208.75, 142.94, 132.62,
131.44, 130.47, 127.73, 124.99, 68.59, 51.59, 30.74.
HPLC (Daicel Chiralpak AD column, n-hexane–
isopropanol 90 : 10, 1 mL/min, 205 nm) ee = 67%.
4-Hydroxy-4-(4-nitrophenyl)butan-2-one (VIe).
1H NMR spectrum, δ, ppm: 8.21 d (J = 8.6 Hz, 2H),
7.54 d (J = 8.5Hz, 1H), 5.27 m (1H), 3.62 d (J = 2.8
Hz, 1H), 2.86 m (1H), 2.23 s (2H), 1.66 s (0H), 1.25 s
(0H). 13C NMR spectrum, δ, ppm: 208.64, 126.41,
123.79, 68.87, 65.88, 58.48, 51.50, 30.75, 18.42, 15.27.
HPLC (Daicel Chiralpak OJ-H column, n-hexane–
isopropanol 90 : 10, 1 mL/min, 245 nm) ee = 78%.
4-Hydroxy-4-[4-(trifluoromethyl)phenyl]butan-
1
2-one (VIk). H NMR spectrum, δ, ppm: 7.61 d (J =
8.1 Hz, 2H),7.48 d (J = 8.1 Hz, 2H), 5.21 t (J = 7.4 Hz,
1H), 3.54(d, J = 3.2 Hz, 1H), 2.85 m (2H), 2.21 s
(3H).13C NMR spectrum, δ, ppm: 208.77, 146.70,
130.00, 125.94, 125.50, 122.76, 69.22, 51.74, 30.73.
HPLC (Daicel Chiralpak AD column, n-hexane–
isopropanol 90 : 10, 1 mL/min, 215 nm) ee = 97%
4-Hydroxy-4-(3-nitrophenyl)butan-2-one (VIf).
1H NMR spectrum, δ, ppm: 7.48 d (J = 8.4 Hz, 2H),
7.24 d (J =8.3 Hz, 3H), 5.12 d.d (J = 7.8, 4.5 Hz, 1H),
3.39 s (1H), 2.83 m (2H), 2.21 s (3H). 13C NMR
spectrum, δ, ppm: 208.77, 148.33, 144.72, 131.83,
129.53, 122.61, 120.72, 68.75, 51.48, 30.74. HPLC
(Daicel Chiralpak OJ-H column, n-hexane–isopropanol
90 : 10, 1 mL/min, 254 nm) ee = 80%.
ACKNOWLEDGMENTS
The Project of Science Technology Department of
Zhejiang Province (no. 2013C31119) and Zhejiang
Apeloa Medical Technology Co. Ltd are acknowledged
for financial support.
4-Hydroxy-4-(2-nitrophenyl)butan-2-one (VIg).
1H NMR spectrum, δ, ppm: 7.96 d (J = 8.2 Hz, 1H),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013

2452
CHEN CHEN WENG et al.
10. Tsogoeva, S.B., Jagtap, S.B., and Ardemasova, Z.A.,
REFERENCES
Tetrahedron: Asymmetry, 2006, vol. 17, pp. 989–992.
1. (a) Trost, B.M., Fleming, I., and Winterfeldt, E.,
Comprehensive Organic Synthesis: Selectivity, Strategy,
and Efficiency in Modern Organic Chemistry. Vol. 6,
Heteroatom Manipulation, Pergamon, 1991. (b) Palomo, C.,
Oiarbide, M., and García, J.M., Chemical Society
Reviews, 2004, vol. 33, pp. 65–75. (c) Nelson, S.G., Tetra-
hedron: Asymmetry, 1998, no. 9, pp 357–389.
(d) Gröger, H., Vogl, E.M., and Shibasaki, M., Chem.
Weinheim Europ. J., 1998, no. 4, pp. 1137–1141.
(e) Machajewski, T.D. and Wong, C. H., Ang. Chem. Int.
Ed., 2000, vol. 39, pp. 1352–1375. (f) Denmark, S.E.
and Stavenger, R.A., Accounts of Chemical Research,
2000, vol. 33, pp. 432–440.
11. Krattiger, P., Kovasy, R., Revell, J.D., Ivan, S., and
Wennemers, H., Org. Lett., 2005, no. 7, pp. 1101–1103.
12. Tang, Z., Jiang, F., Yu, L.-T., Cui, X., Gong, L.-Z.,
Mi, A.-Q., Jiang, Y.-Z., and Wu, Y.-D., J. Am. Chem.
Soc, 2003, vol. 125, pp. 5262–5263.
13. Fu, Y.-Q., Li, Z.-C., Ding, L.-N., Tao, J.-C., Zhang, S.-H.,
and Tang, M.-S., Tetrahedron: Asymmetry, 2006,
vol. 17, pp. 3351–3357.
14. Betancort, J.M. and Barbas III, C. F., Org. Lett., 2001,
no. 3, pp. 3737–3740.
15. Kurteva, V.B. and Afonso, C.A., Tetrahedron, 2005,
vol. 61, pp. 267–273.
2. List, B., Lerner, R.A., and Barbas, C.F., J. Am. Chem.
Soc., 2000, vol. 122, pp. 2395–-2396
3. Mukherjee, S., Yang, J.W., Hoffmann, S., and List, B.,
16. Yoshitomi, Y., Makino, K., and Hamada, Y., Org. Lett.,
2007, no. 9, pp. 2457–2460.
17. Guillena, G., Hita, M.d.C., and Nájera, C., Tetrahedron:
Asymmetry, 2006, vol. 17, pp. 1493–1497.
Chem. Rev., 2007, vol. 107, p. 5471.
4. (a) Trost, B.M. and Brindle, C.S., Chem. Soc. Rev.,
2010, vol. 39, pp. 1600–1632. (b) Alcaide, B. and
Almendros, P., Ang. Chem. Int. Ed., 2003, vol. 42,
pp. 858–860. (c) Notz, W., Tanaka, F., and Barbas, C.F.,
Acc. Chem. Research, 2004, vol. 37, pp. 580–591.
(d) Guo, Q. and Zhao, J.C.-G., Tetrahedron Lett., 2012,
vol. 53, pp. 1768–1771. (e) List, B., Chem. Comm.,
2006, no. 8, pp. 819–824.
5. (a) List, B., Acc. Chem. Research, 2004, vol. 37,
pp. 548–557. (b) List, B., Pojarliev, P., and Castello, C.,
Org. Lett., 2001, no. 3, pp. 573–575. (c) Alcaide, B.,
Almendros, P., Luna, A., and Martínez del Campo, T.,
J. Org. Chem., 2008, vol. 73, pp. 1635–1638.
(d) Bahmanyar, S., Houk, K., Martin, H. J., and List, B.,
J. Am. Chem. Soc, 2003, vol. 125, pp. 2475–2479.
(e) Fan, J.F., He, L.J., and Sun, Y.P., Chirality, 2008,
vol. 20, pp. 54–61. (f) Yan, J. and Wang, L., Chirality,
2009, vol. 21, pp. 413–420.
18. Puleo, G.L. and Iuliano, A., Tetrahedron: Asymmetry,
2007, vol. 18, pp. 2894–2900.
19. Wang, Y., Wei, S., and Sun, J., Chem. Inform, 2007,
p. 38.
20. Ma, J.A., Ang. Chem. Int. Ed., 2003, vol. 42, pp. 4290–
4299.
21. Inomata, K., Barragué, M., and Paquette, L.A., J. Org.
Chem., 2005, vol. 70, pp. 533–539.
22. Wang, W., Li, H., and Wang, J., Tetrahedron Lett., 2005,
vol. 46, pp. 5077–5079.
23. Limbach, M., Tetrahedron Lett., 2006, vol. 47, pp. 3843–
3847.
24. Ooi, T., Kameda, M., Taniguchi, M., and Maruoka, K.,
J. Am. Chem. Soc, 2004, vol. 126, pp. 9685–9694.
25. Tennyson, R. and Romo, D., J. Org. Chem., 2000, vol. 65,
p. 7248.
6. Robak, M.T., Herbage, M.A., and Ellman, J.A.,
Tetrahedron, 2011, vol. 67, pp. 4412–4416.
7. Sutar, R.L. and Joshi, N.N., Tetrahedron: Asymmetry,
2013, vol. 24, pp. 43–49.
8. Russo, A., Botta, G., and Lattanzi, A., Tetrahedron,
26. Teo, Y.-C., Tetrahedron: Asymmetry, 2007, vol. 18,
pp. 1155–1158.
27. Andreae, M. R. and Davis, A.P., Tetrahedron: Asym-
metry, 2005, vol. 16, pp. 2487–2492.
28. Saito, S. and Yamamoto, H., Acc. Chem. Research,
2007, vol. 63, pp. 11886–11892.
2004, vol. 37, pp. 570–579.
9. Hayashi, Y., Aratake, S., Okano, T., Takahashi, J.,
Sumiya, T., and Shoji, M., Angewandte Chemie, 2006,
vol. 118, pp. 5653–5655.
29. Font, D., Jimeno, C., and Pericàs, M.A., Org. Lett.,
2006, vol. 8, pp. 4653–4655.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013