Stereoselective conjugate addition of carbonyl compounds to maleimides using a diaminomethyleneindenedione organocatalyst

Article abstract of DOI:10.1016/j.tetasy.2016.07.002

A diaminomethyleneindenedione motif can serve as an excellent double hydrogen bonding donor. Bifunctional chiral primary amine 3 bearing a diaminomethyleneindenedione motif is an excellent organocatalyst to promote the asymmetric conjugate additions of va

Full text of DOI:10.1016/j.tetasy.2016.07.002

Tetrahedron: Asymmetry xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Stereoselective conjugate addition of carbonyl compounds to
maleimides using a diaminomethyleneindenedione organocatalyst
Kosuke Nakashima, Masahiro Kawada, Shin-ichi Hirashima, Ayako Kosugi, Mana Kato, Akihiro Yoshida,
⇑
Yuji Koseki, Tsuyoshi Miura
Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A diaminomethyleneindenedione motif can serve as an excellent double hydrogen bonding donor.
Bifunctional chiral primary amine 3 bearing a diaminomethyleneindenedione motif is an excellent
organocatalyst to promote the asymmetric conjugate additions of various carbonyl compounds to malei-
mides in high yields with up to 99% ee.
Received 27 June 2016
Accepted 7 July 2016
Available online xxxx
Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction
been intensively investigated as they exhibit highly efficient cat-
alytic activity in various asymmetric reactions to enantiomeri-
Substituted succinimide derivatives obtained via the stereose-
lective conjugate addition of various nucleophiles to maleimides
are valuable intermediates in the synthesis of natural products
and some clinical drug candidates.1 Organocatalysis, an environ-
mentally benign chemistry, is one of the most effective synthetic
strategies to obtain chiral succinimide derivatives.2 The asym-
metric conjugate additions of 1,3-dicarbonyl compounds to mal-
eimides using natural cinchona alkaloid organocatalysts were
reported in pioneering work by Melchiorre et al.3 Since then,
several research groups have reported on the organocatalytic
conjugate additions of various nucleophilic carbonyl compounds
to maleimides.2,4–6 Thus, the asymmetric conjugate addition of
nucleophilic aldehydes to maleimides using organocatalysts rep-
resents an important synthetic method, and a large number of
articles have been reported on this regard.4 We have also
reported on the asymmetric conjugate additions of aldehydes
to maleimides using thiourea organocatalysts.4e,g To the best of
our knowledge, although conjugate additions of simple linear
and cyclic ketones such as acetone and cyclohexanone to
maleimides are particularly important, they have been
successfully achieved by only three groups.5 Therefore, the
development of an effective and easily prepared organocatalyst
for the conjugate addition of simple ketones to maleimides
remains as an essential research theme in organic chemistry.
cally enriched molecules.7 In addition, modified Takemoto
catalysts, which have shown enhanced acidity due to the intro-
duction of an electron-withdrawing group, have been
developed.8
We have recently developed a diaminomethylenemalononi-
trile motif serving as an excellent double hydrogen donating
functional group in the substitution of thiourea and squara-
mide.9–14 Thus, organocatalyst 1 bearing both a chiral primary
amine group and a diaminomethylenemalononitrile motif was
found to accelerate the asymmetric conjugate additions of alde-
hydes to vinyl sulfone9 and the conjugate additions of malonates
to
a
,b-unsaturated ketones under neat conditions.10 We also
reported that a diaminomethylenemalononitrile organocatalyst
2 bearing a chiral secondary amine is a good catalyst for the
asymmetric conjugate additions of ketones to nitroalkenes11
and stereoselective direct aldol reactions of ketones with aro-
matic
aldehydes.12
In
addition,
we
found
that
a
a
cin-
diaminomethylenemalononitrile organocatalyst bearing
chona alkaloid as a chiral tertiary amine catalyzed the asymmet-
ric conjugate additions of 1,3-diketones to nitroalkenes13 and the
asymmetric hydrophosphonylation of aldehydes with diaryl
phosphonates.14 Very recently, we reported in a preliminary
communication that organocatalyst
3
bearing
a
2-(di-
aminomethylene)-1H-indene-1,3(2H)-dione skeleton promotes
the conjugate additions of acetone or cyclohexanone to malei-
mides yielding the corresponding adducts with excellent stereos-
electivities.15 Herein, we describe the full details of the
asymmetric conjugate additions of various carbonyl compounds
to maleimides using 3 (Fig. 1).
Organocatalysts bearing
hydrogen bonding donor, such as thiourea and squaramide, have
a motif that functions as a double
⇑
Corresponding author. Tel./fax: +81 42 676 4479.
E-mail address: tmiura@toyaku.ac.jp (T. Miura).
http://dx.doi.org/10.1016/j.tetasy.2016.07.002
0957-4166/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

2
K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
NC
CN
NC
CN
F3C
NH2
F3C
F3C
N
H
N
H
N
H
N
H
O
O
HN
NH2
O
O
CF3
7
F3C
CF3
N
H
2
SMe
CF3
1
THF, reflux, 16 h
93%
MeS
SMe
6
8
CF3
O
O
NH2
F3C
N
N
H
H
O
O
NH2
NH2
F3C
9
CF3
N
H
N
3
H
THF, rt, 23 h
67%
NH2
Figure 1. Structure of organocatalysts.
CF3
3
Scheme 1. Preparation of organocatalyts 3.
2. Results and discussion
We first examined diaminomethylenemalononitrile organocat-
alysts 1 and 2 for the asymmetric conjugate addition of acetone
to N-phenylmaleimide 4a as shown in Table 1. Organocatalyst 1
bearing a primary amine group provided the desired product 5a
in low yields and with moderate enantioselectivity (Table 1, entry
1). Organocatalyst 2 bearing a secondary amine group showed no
reactivity (Table 1, entry 2). Although both 1 and 2 were poor cat-
alysts for the Michael reactions of maleimides with acetone,
organocatalysts bearing a primary amine group, such as 1, tend
to be suitable for the conjugate addition. We presumed that the
introduction of a more powerful electron-withdrawing functional-
ity (as compared to the cyano group) is required for the develop-
ment of a more reactive organocatalyst. We selected a carbonyl
group (i.e., acetophenone) with a lower pKa value as compared to
that of acetonitrile (24.7 vs 31.3, DMSO).16 Thus, organocatalyst 3
bearing a diaminomethyleneindenedione skeleton containing car-
bonyl functionalities instead of the cyano groups of 1 was found
to be a good catalyst, which afforded the desired adduct 5a in mod-
erate yields and with high enantioselectivity (Table 1, entry 3).
The studies carried out to find the optimal conditions for the
enantioselective conjugate addition using 3 are summarized in
Table 2. The conjugate addition reactions were conducted with
acetone and 4a as test reactants in the presence of catalytic
amounts of 3 and an additive at room temperature. The reaction
in CH2Cl2 without an additive was very slow (Table 2, entry 1).
The addition of catalytic amounts of benzoic acid enhanced the
reaction rate while improving the enantioselectivity (Table 2, entry
2). Therefore, we studied the reaction in a typical reaction solvent
and in the presence of benzoic acid. The reaction in less polar sol-
vents such as 1,2-dichloroethane, hexane, and ethyl acetate
afforded moderate enantioselectivities (entries 3–5). The stereose-
lectivity was improved using ethereal solvents (entries 6–8). Polar
solvents, such as MeCN, DMF, and MeOH were poor reaction
solvents to give low enantioselectivities (entries 9–11). Aromatic
solvents were good reaction solvents to provide higher stereoselec-
tivities. Among the aromatic solvents examined, p-xylene was
found to be the most suitable showing high enantioselectivities
(Table 2, entries 13–16). Furthermore, effects associated with the
presence of other protic acids in addition to benzoic acid were
tested; however the latter was found to be the most suitable addi-
tive (Table 2, entries 16–27). Changes in the amount of benzoic
acid added (0.2 or 0.05 equiv) resulted in a slight reduction in
the enantioselectivity (Table 2, entries 28 and 29). The enantiose-
lectivity was improved by the reaction under dilute conditions
(Table 2, entry 30). Finally, both high yield and stereoselectivity
were observed when the reaction was conducted at 40 °C and in
the presence of 0.2 equiv of 3 (Table 2, entry 32).
Once the optimal conditions were identified, we investigated
the scope and limitations of the conjugate additions between var-
ious carbonyl compounds and maleimides 4 (Table 3). The reaction
of acetone with N-benzylmaleimide 4b proceeded smoothly to give
the corresponding addition product 5b in high yield and with
excellent enantioselectivity (Table 3, entry 2). Subsequently, we
investigated the substituent effects of the benzene ring during
the conjugate additions of maleimides. Bromo-, chloro-, and
trifluoromethyl-substituents were chosen as representative elec-
tron-withdrawing groups. N-(4-Bromophenyl)maleimide 4c and
N-(4-chlorophenyl)maleimide 4d coupled with acetone to give
the corresponding adducts in high yield and with high enantiose-
Table 1
Selection of organocatalystsa
O
O
O
catalyst
PhCO2H
N
Ph
N
Ph
(0.1 equiv)
(0.1 equiv)
+
O
toluene, rt
(5 equiv)
O
O
5a
Entry
Catalyst
Time (h)
Yieldb (%)
eec (%)
1
2
3
1
2
3
170
170
95
16
57
—
89
N.D.d
59
a
Reaction conditions: 4a (0.20 mmol), acetone (1.0 mmol), and catalyst
(0.020 mmol) in toluene (0.2 mL) were stirred at rt.
b
Isolated yields.
Determined by chiral HPLC analysis.
Not detected.
c
d
As shown in Scheme 1, organocatalyst 3 can be easily prepared
(i.e., two steps) from indenedione derivative 6.17 The substitution
reaction of 6 with 3,5-bis(trifluoromethyl)benzylamine 7 pro-
ceeded smoothly under THF reflux conditions to provide interme-
diate 8 in 93% yield. In a subsequent step, the substitution reaction
of 8 with (1R,2R)-cyclohexane-1,2-diamine 9 in THF afforded the
desired diaminomethyleneindenedione organocatalyst 3 in 63%
yield.
lectivity (Table 3, entries
maleimide 4e bearing
3
and 4, respectively). N-Phenyl-
a
trifluoromethyl group reacted with
moderate yield and high enantioselectivity (Table 3, entry 5). We
selected methyl- and methoxy-substituents as representative
electron-donating groups. The maleimides bearing a methyl sub-
stituent at the para 4f and meta 4g positions were converted into
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
3
Table 2
tivity (Table 3, entry 14). The conjugate addition of 1-methoxypro-
pan-2-one to 4a provided 5o in high yield with low
diastereoselectivity. Unlike the minor diastereomer, the enantiose-
lectivity of the major diastereomer was low (Table 3, entry 15).
Furthermore, we investigated the reactivity of maleimide 4a with
various aldehydes using organocatalyst 3. Isobutyraldehyde
reacted with 4a to provide the corresponding adduct 5p in good
yield and with excellent stereoselectivity (Table 3, entry 16). 2-
Ethylbutanal afforded 5q with low rates and moderate yield and
enantioselectivity in spite of the long reaction time (Table 3, entry
17). Aldehydes bearing a cycloalkane moiety such as cyclopen-
tanecarboxaldehyde and cyclohexanecarboxaldehyde were con-
verted into their corresponding adducts 5r and 5s in high yield
and with high enantioselectivities (Table 3, entries 18 and 19,
respectively). The asymmetric addition of a simple linear aldehyde,
such as propanal, proceeded to the diastereo-mixture 5t with
excellent enantioselectivities (Table 3, entry 20). Dimethyl malo-
nate afforded the adduct 5u in low yield due to the difficult forma-
tion of the enamine by reaction between 3 and dimethyl malonate
(Table 3, entry 21).
Optimization of reaction conditionsa
O
O
O
3
(0.1 equiv)
N
Ph
N
Ph
+
O
(5 equiv)
rt, 48 h
O
O
5a
4a
Entry
Solvent
Additive (equiv)
Yieldb (%)
eec (%)
1d
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30e
31e,f
32e,f,g
CH2Cl2
None
12
32
34
63
59
60
61
66
44
32
37
72
58
63
60
50
59
70
62
65
62
60
42
51
28
9
75
79
79
64
80
83
85
88
36
0
37
49
89
88
88
91
87
89
88
89
88
88
89
88
87
87
—
CH2Cl2
PhCO2H (0.1)
ClCH2CH2Cl
Hexane
AcOEt
PhCO2H (0.1)
PhCO2H (0.1)
PhCO2H (0.1)
Et2O
PhCO2H (0.1)
THF
PhCO2H (0.1)
1,4-Dioxane
MeCN
PhCO2H (0.1)
PhCO2H (0.1)
DMF
PhCO2H (0.1)
MeOH
PhCO2H (0.1)
Neat
PhCO2H (0.1)
Toluene
o-Xylene
m-Xylene
p-Xylene
p-Xylene
P-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
PhCO2H (0.1)
PhCO2H (0.1)
PhCO2H (0.1)
PhCO2H (0.1)
HCO2H (0.1)
MeCO2H (0.1)
EtCO2H (0.1)
n-PrCO2H (0.1)
4-MeOC6H4CO2H (0.1)
4-MeC6H4CO2H (0.1)
4-ClC6H4CO2H (0.1)
4-O2NC6H4CO2H (0.1)
2-O2NC6H4CO2H (0.1)
2,4-(O2N)2C6H3CO2H (0.1)
CF3CO2H (0.1)
PhCO2H (0.2)
We speculate that the conjugate addition of acetone to malei-
mides promoted by diaminomethyleneindenedione-organocata-
lyst 3 follows the reaction mechanism as shown in Scheme 2
that considers the stereochemistry of addition products 5a. The
primary amine group of 3 condenses with acetone to the enamine
intermediate
10.
The
enediamine
protons
of
the
diaminomethyleneindenedione skeleton acting as hydrogen bond-
ing donors then capture one of the carbonyl oxygens of the malei-
mide. Furthermore, the carbonyl group is activated by the
hydrogen bonding to enhance the reactivity of the b-position.
These interactions can control the approach direction (Si face
attack) of the enamine intermediates to the maleimides as shown
in transition state A. This ultimately affords the corresponding
addition products with excellent enantioselectivities. After the
addition of the enamine to the maleimide, iminium intermediate
11 is obtained. Finally, iminium 11 is hydrolyzed to afford adduct
5a and organocatalyst 3. Information supporting the presence of
the enamine intermediate and the transition state could not be
obtained by NMR measurement. However, the enamine intermedi-
ate 10 was detected by mass spectrometry.
Trace
48
66
57
68
81
85
88
93
90
92
PhCO2H (0.05)
PhCO2H (0.05)
PhCO2H (0.1)
PhCO2H (0.1)
a
Reaction conditions (unless otherwise noted): 4a (0.20 mmol), acetone
(1.0 mmol), and catalyst 3 (0.020 mmol) in solvent (0.2 mL) were stirred at rt for
48 h.
b
Isolated yields.
Determined by chiral HPLC analysis.
The reaction was carried out for 65 h.
p-Xylene (0.4 mL) was used.
The reaction was carried out at 40 °C.
Catalyst 3 (0.2 equiv) was used.
c
d
e
3. Conclusion
f
g
In conclusion, the diaminomethyleneindenedione-organocata-
lyst 3 can be readily synthesized from 6 in only two steps. Catalyst
3 efficiently promoted the conjugate additions of various carbonyl
compounds to maleimides 4 to afford the corresponding addition
products 5 in good to high yields with high stereoselectivities
(up to 99% ee). We have demonstrated that a diaminomethylenein-
denedione skeleton is a more efficient double hydrogen bond
donor than diaminomethylenemalononitrile for the conjugate
additions to maleimides. The application of organocatalysts
with diaminomethyleneindenedione motifs to other types of
asymmetric reactions as well as the development of novel
diaminomethyleneindenedione-organocatalysts are currently
underway in our laboratory.
the corresponding addition products 5f and 5g with high enantios-
electivities (Table 3, entries 6 and 7, respectively). The maleimide
bearing a methoxy group at the para-position 4h afforded 5h in
lower yields but with high enantioselectivity (Table 3, entry 8).
Next, we examined the reactivity of maleimides with various
ketones. Maleimide 4a readily reacted with a cyclic ketone, such
as cyclohexanone, to provide the corresponding adduct 5i in excel-
lent yield without diastereoselectivity and with the highest enan-
tioselectivities (each >99% ee) (Table 3, entry 9). Cyclohexanone
bearing a protective acetal group added to 4a afforded adduct 5j
in high yield, excellent enantioselectivities, and no diastereoselec-
tivity (Table 3, entry 10). Cyclopentanone was added to 4a to give
adduct 5k with moderate diastereoselectivity (Table 3, entry 11).
Long-chain aliphatic ketones, such as pentan-3-one and heptan-
4-one, were found to be poor substrates because of their steric hin-
drance. Thus, low to moderate yields and no diastereoselectivities
were obtained in spite of longer reaction times. However, products
5l and 5m were obtained with high enantioselectivities (Table 3,
entries 12 and 13). The reaction of pentane-2,4-dione with 4a
afforded adduct 5n in good yield and with moderate enantioselec-
4. Experimental
4.1. General
1H NMR and 13C NMR spectra were measured with a Bruker
DPX 400 spectrometer (400 MHz for 1H NMR and 100 MHz for
13C NMR). Chemical shifts are expressed in ppm downfield from
tetramethylsilane (d = 0.00) as an internal standard. Mass
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

4
K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
Table 3
Michael reactions of various maleimides with carbonyl compounds in the presence of organocatalyts 3
O
O
F3C
N
H
N
H
O
PhCO2H
(0.1 equiv)
NH2
Carbonyl
R1
+
compounds
N
(0.2 equiv)
p-xylene, 40 o
3
CF3
Products
(5 equiv)
O
C
5
4
Diastereo
Time (h) Yielda (%)
eec (%)
92
Entry
1
Maleimide 4
Product 5
Carbonyl compound
O
ratiob
O
O
48
81
N
Ph
N
Ph
Bn
O
O
O
O
O
5a
4a
O
O
O
2
3
4
N
48
48
48
92
86
79
95
90
86
N
Bn
O
O
5b
4b
O
O
N
Br
N
Br
O
O
O
O
O
O
4c
4d
5c
5d
Cl
Cl
O
N
N
O
O
O
O
CF3
CF3
O
O
5d
48
65
51
92
89
N
N
O
O
O
O
O
O
4e
4f
5e
5f
N
CH3
6
N
CH3
140
O
O
O
O
CH3
CH3
O
N
N
7
8
48
48
80
55
86
85
O
O
O
O
5g
4g
O
O
O
N
OCH3
N
O
OCH3
O
O
4h
5h
O
O
99 (99)e
N
Ph
51:49
48
95
9
N
Ph
O
O
4a
5i
O
O
O
O
O
O
96 (99)e
N
Ph
55:45
24
88
10
N
Ph
5j
O
O
O
O
4a
O
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
5
Diastereo
ratiob
Time (h) Yielda (%)
eec (%)
87(62)e
Entry
11
Maleimide 4
Product 5
Carbonyl compound
O
O
O
N
Ph
24
67
65
73:27
51:49
N
Ph
5k
O
O
4a
O
O
CH3
O
O
O
CH3
96 (88)e
90 (82)e
12
13
160
N
N
O
O
4g
O
5l
O
O
N
Ph
140
168
14
75
53:47
N
Ph
O
O
4a
5m
O
O
O
O
O
O
O
N
Ph
40
14
N
Ph
O
O
O
O
4a
5n
O
O
OMe
OMe
N
Ph
29 (73)e
N
Ph
15
24
87
57:43
O
O
5o
4a
O
O
H
H
O
O
N
Ph
N
Ph
48
168
48
74
62
95
94
76
16
17
O
H
H
O
O
O
O
5p
4a
N
Ph
N
Ph
O
O
O
O
O
O
5q
4a
O
H
H
N
Ph
N
Ph
H
H
18
91
O
O
O
O
4a
5r
O
N
Ph
N
Ph
4a
19
20
O
48
24
84
83
94
O
O
5s
O
O
H
O
57:43
95 (92)e
N
Ph
N
Ph
O
H
O
O
5t
4a
MeO
MeO
O
O
O
O
O
96
18
3
21
N
Ph
N
Ph
MeO
OMe
O
O
O
5u
4a
a Isolated yields.
b Determined by1H NMR.
c Determined by HPLC analysis.
d The reaction was carried out at rt.
e Enantiomeric excess of the major isomer. Enantiomeric excess of the minor isomer in parentheses.
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

6
K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
O
O
O
O
F3C
O
Ph
N
H+
N
H
N
H
NH2
5a
O
CF3
3
H2O
O
O
O
O
F3C
F3C
N
H
N
H
N
H
N
NH
H
N
H
CF3
CF3
O
10
O
Ph
N
N
Ph
O
11
O
O
4a
H+
O
F3C
N
H
N
H
NH
O
CF3
NPh
O
A
Si face attack
Scheme 2. Proposed reaction mechanism for asymmetric conjugate addition.
spectra were recorded by an electrospray ionization-time of flight
(ESI-TOF) mass spectrometer (Micromass LCT). For thin layer chro-
matographic (TLC) analyses, Merck precoated TLC plates (silica gel
60 F254) were used. Flash column chromatography was performed
lized two times from CHCl3 and hexane to afford pure 3 (1.49 g,
67%). Yellow powder; mp 179–180 °C; [
a
]
D
29 = À10.9 (c 1.0, CH2Cl2);
1H NMR (400 MHz, CDCl3): d = 9.61 (br s, 1H), 9.02 (d, J = 9.8 Hz,
1H), 7.87 (s, 3H), 7.61–7.57 (m, 2H), 7.53–7.49 (m, 2H), 5.13 (dd,
J = 6.0, 16.3 Hz, 1H) 4.88 (dd, J = 6.5, 16.3 Hz, 1H), 3.15–3.06 (m,
1H), 2.82–2.76 (m, 1H), 1.89–0.87 (m, 10H); 13C NMR (100 MHz,
on neutral silica gel (40–50 lm).
2
4.2. Preparation of the organocatalyst
CDCl3): d = 192.4, 161.5, 140.3, 138.6, 132.4 (q, JC–F = 33.7 Hz),
1
132.3, 127.1, 123.1 (q, JC–F = 273 Hz), 121.9, 120.5, 93.7, 61.3,
4.2.1. 2-({[3,5-Bis(trifluoromethyl)benzyl]amino}(methylsul-
fanyl)methylidene)-2,3-dihydro-1H-indene-1,3-dione 8
55.7, 47.7, 34.1, 33.2, 24.8, 24.2; Anal. Calcd for C25H23F6N3O2: C,
58.71; H, 4.53; N, 8.22. Found: C, 58.62; H, 4.52; N, 8.22.
To a stirred solution of compound 617 (1.6 g, 6.5 mmol) in THF
(22 mL) was added 3,5-bis(trifluoromethyl)benzylamine 7 (1.6 g,
6.5 mmol). The mixture was stirred at reflux for 16 h. TLC indicated
the reaction was completed, the reaction mixture was cooled to
room temperature. The solvent was removed under reduced pres-
sure and the residue was crystallized from CHCl3 and hexane to
afford compound 8 (2.7 g, 93%). Yellow powder; mp 183–184 °C;
1H NMR (400 MHz, CDCl3): d = 11.12 (br s, 1H), 7.86 (s, 1H), 7.77
(s, 2H), 7.74–7.72 (m, 2H), 7.62–7.60 (m, 2H), 5.01 (d, J = 6.3 Hz,
2H), 2.72 (s, 3H); 13C NMR (100 MHz, CDCl3): d = 171.6, 139.3,
4.3. Typical procedure for
organocatalyst 3 (Table 2)
a
conjugate addition using
To a solution of N-phenylmaleimide 4a (34.6 mg, 0.200 mmol)
and acetone (73.4 L, 1.00 mmol) in p-xylene (0.4 mL) were added
l
organocatalyst 3 (20.5 mg, 0.040 mmol) and benzoic acid (2.5 mg,
0.020 mmol) at room temperature. After stirring in a closed tube
at 40 °C for 48 h, the reaction mixture was directly purified by flash
column chromatography on silica gel with a 3:2–1:1 mixture of
hexane and AcOEt to afford 5a (37.3 mg, 81%) as a white powder.
2
1
133.3, 132.5 (q, JC–F = 33.7 Hz), 127.5, 123.0 (q, JC–F = 273 Hz),
3
122.1 (q, JC–F = 3.7 Hz), 121.6, 104.8, 47.9, 19.1; HRMS (ESI-TOF):
calcd for C20H14F6NO2S (M+H)+: 446.0644, found: 446.0647.
4.3.1. (S)-3-(2-Oxopropyl)-1-phenylpyrrolidine-2,5-dione 5a5c
[a]
27 = +10.0 (c 1.0, CH2Cl2). 92% ee; Enantiomeric excess was
D
4.2.2. 2-({[(1R,2R)-2-Aminocyclohexyl]amino}{[3,5-bis(trifluo-
romethyl)benzyl]amino}methylidene)-2,3-dihydro-1H-indene-
1,3-dione 3
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 75:25), flow rate = 0.5 mL/min; k = 220 nm; tmajor = 57.8 -
min, tminor = 72.3 min.
To a stirred solution of compound 8 (2.0 g, 4.5 mmol) in THF
(15 mL) was added (1R,2R)-cyclohexane-1,2-diamine 9 (512.7 mg,
4.5 mmol). The mixture was stirred at room temperature for 23 h.
The solvent was removed under reduced pressure and the residue
was purified by flash column chromatography on silica gel with a
mixture of CHCl3 and MeOH. Afforded compound 3 was recrystal-
4.3.2. (S)-1-Benzyl-3-(2-oxopropyl)pyrrolidine-2,5-dione 5b5c
[
a]
D
27 = À2.0 (c 1.0, CH2Cl2). 95% ee; Enantiomeric excess was
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 18.6 -
min, tminor = 28.5 min.
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
7
4.3.3. (S)-1-(4-Bromophenyl)-3-(2-oxopropyl)pyrrolidine-2,5-
diastereomer (syn-isomer); The ratio of diastereomers was deter-
mined 73:27 (anti:syn) by the integral of their signals. Enan-
tiomeric excess was determined by HPLC with ChiralPak IB
column (hexane/2-propanol = 80:20), flow rate = 0.5 mL/min;
k = 210 nm; major diastereomer (anti-isomer): tmajor = 51.2 min,
tminor = 48.7 min. minor diastereomer (syn-isomer): tmajor = 66.7 -
min, tminor = 58.8 min.
dione 5c5c
[a]
27 = +5.5 (c 1.0, CH2Cl2). 90% ee; Enantiomeric excess was
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 26.2 -
min, tminor = 45.3 min.
4.3.4. (S)-1-(3-Chlorophenyl)-3-(2-oxopropyl)pyrrolidine-2,5-
dione 5d5a
4.3.12. 3-(3-Oxopentan-2-yl)-1-(m-tolyl)pyrrolidine-2,5-dione 5l5a
27 = +9.2 (c 1.0, CH2Cl2). 86% ee; Enantiomeric excess was
[a]
D
20 = À27.0 (c 1.0, CH2Cl2). 96% ee for major diastereomer;
[a]
D
D
[a
]
20 = +32.5 (c 1.0, CH2Cl2). 88% ee for minor diastereomer; The
determined by HPLC with ChiralPak AD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 18.8 -
min, tminor = 17.4 min.
ratio of diastereomers was determined 51:49 by the integral of
their signals. Enantiomeric excess was determined by HPLC with
ChiralPak AS-H column (hexane/2-propanol = 70:30), flow
rate = 0.6 mL/min; k = 240 nm; major diastereomer: tmajor = 21.5 -
min, tminor = 24.3 min. minor diastereomer: tmajor = 19.3 min,
tminor = 18.3 min.
4.3.5. (S)-3-(2-Oxopropyl)-1-[3-(trifluoromethyl)phenyl]pyrroli-
dine-2,5-dione 5e5a
[a]
25 = +7.3 (c 1.0, CH2Cl2). 92% ee; Enantiomeric excess was
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 15.4 -
min, tminor = 20.7 min.
4.3.13. 3-(4-Oxoheptan-3-yl)-1-phenylpyrrolidine-2,5-dione 5m5a
Compound 5m was obtained as an inseparable mixture. The
ratio of diastereomers is determined 53:47 by the integral of their
signals. Enantiomeric excess was determined by HPLC with Chi-
ralPak AD-H column (hexane/2- propanol = 75:25), flow
rate = 0.5 mL/min; k = 240 nm; major diastereomer: tmajor = 25.7 -
min, tminor = 22.3 min. minor diastereomer: tmajor = 25.7 min,
tminor = 22.3 min.
4.3.6. (S)-1-(4-Methylphenyl)-3-(2-oxopropyl)pyrrolidine-2,5-
dione 5f5a
[a]
25 = +11.7 (c 1.0, CH2Cl2). 89% ee; Enantiomeric excess was
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 23.1 -
min, tminor = 31.8 min.
4.3.7. (S)-1-(3-Methylphenyl)-3-(2-oxopropyl)pyrrolidine-2,5-
4.3.14. 3-(2,4-Dioxopentan-3-yl)-1-phenylpyrrolidine-2,5-dione
5n6o
dione 5g5a
27 = +13.1 (c 1.75, CH2Cl2). 86% ee; Enantiomeric excess was
[a]
20 = À46.8 (c 1.0, CHCl3). 47% ee; Enantiomeric excess was
[a]
D
D
determined by HPLC with ChiralPak AD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 20.5 -
min, tminor = 16.8 min.
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 85:15), flow rate = 1.0 mL/min; k = 210 nm; tmajor = 66.2 -
min, tminor = 52.7 min
4.3.8. (S)-1-(4-Methoxyphenyl)-3-(2-oxopropyl)pyrrolidine-2,5-
4.3.15. 3-(1-Methoxy-2-oxopropyl)-1-phenylpyrrolidine-2,5-
dione 5o5c
dione 5h5a
[a]
25 = +11.9 (c 1.0, CH2Cl2). 85% ee; Enantiomeric excess was
[
a]
20 = À0.1 (c 1.0, CH2Cl2). 29% ee for anti-isomer; [
a]
D
20 = +59.1
D
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 220 nm; tmajor = 38.0 -
min, tminor = 68.4 min.
(c 1.0, CH2Cl2). 73% ee for syn-isomer; The ratio of diastereomers
was determined syn:anti = 43:57 by the integral of their signals.
Enantiomeric excess was determined by HPLC with ChiralPak IC
column (hexane/2-propanol = 85:15), flow rate = 1.0 mL/min;
k = 220 nm; major diastereomer (anti-isomer): tmajor = 46.7 min,
tminor = 29.0 min. minor diastereomer (syn-isomer): tmajor = 53.0 -
min, tminor = 40.9 min.
4.3.9. 3-(2-Oxocyclohexyl)-1-phenylpyrrolidine-2,5-dione 5i5b,c
Compound 5i was obtained as an inseparable mixture. The sig-
nal of 1H NMR for anti-isomer is 3.23–3.35 ppm and the signal for
syn-isomer is 3.18–3.22 ppm.5b The ratio of diastereomers was
determined syn:anti = 51:49 by the integral of their signals.
Enantiomeric excess of each diastereomers was determined by
HPLC with ChiralCel OD-H column (hexane/2-propanol = 70:30),
flow rate = 0.5 mL/min; k = 220 nm; tmajor (anti) = 28.3 min, tminor
(anti) = n.d. tmajor (syn) = 34.4 min, tminor (syn) = n.d. (>99% ee for syn
diastereomer, >99% ee for anti diastereomer).
4.3.16. (R)-2-(2,5-Dioxo-1-phenylpyrrolidin-3-yl)-2-methylpro-
panal 5p4c,5c
[a]
27 = +1.8 (c 1.0, CH2Cl2). 94% ee; Enantiomeric excess was
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 75:25), flow rate = 0.9 mL/min; k = 220 nm; tmajor = 22.2 -
min, tminor = 17.9 min.
4.3.10. 3-(8-Oxo-1,4-dioxaspiro[4.5]decan-7-yl)-1-phenylpyrro-
lidine-2,5-dione 5j5b
4.3.17. (R)-2-(2,5-Dioxo-1-phenylpyrrolidin-3-yl)-2-ethylbutanal
5q4c
Compound 5j was obtained as an inseparable mixture. The ratio
of diastereomers is determined 55:45 by the integral of their sig-
nals. Enantiomeric excess was determined by HPLC with ChiralCel
OJ-H column (hexane/2-propanol = 60:40), flow rate = 0.5 mL/min;
k = 254 nm; major diastereomer: tmajor = 76.5 min, tminor = 144.0 -
min. minor diastereomer: tmajor = 86.6 min, tminor = 119.4 min.
(96% ee for major diastereomer, 99% ee for minor diastereomer).
[a]
19 = +2.9 (c 1.0, CHCl3); 76% ee; Enantiomeric excess was
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 80:20), flow rate = 1.0 mL/min; k = 240 nm; tmajor = 31.7 -
min, tminor = 18.5 min.
4.3.18. (R)-1-(2,5-Dioxo-1-phenylpyrrolidin-3-yl)cyclopentane-
1-carbaldehyde 5r4b
[
a
]
19 = À12.7 (c 1.0, CHCl3). 91% ee; Enantiomeric excess was
4.3.11. (R)-3-[(S)-2-Oxocyclopentyl]-1-phenylpyrrolidine-2,5-
D
dione 5k5c
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 75:25), flow rate = 0.5 mL/min; k = 210 nm; tmajor = 50.6 -
min, tminor = 35.9 min.
[a]
20 = +97.9 (c 0.5, CH2Cl2). 87% ee for major diastereomer
D
(anti-isomer); [
a]
20 = À22.9 (c 0.5, CH2Cl2). 62% ee for minor
D
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002

8
K. Nakashima et al. / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
Xu, L.-W. Chem. Asian J. 2013, 8, 1182; (l) Durmaz, M.; Sirit, A. Tetrahedron:
Asymmetry 2013, 24, 1443; (m) Avila, A.; Chinchilla, R.; Gómez-Bengoa, E.;
Nájera, C. Tetrahedron: Asymmetry 2013, 24, 1531; (n) Kokotos, C. G. Org. Lett.
2013, 15, 2406; (o) Qiao, Y.; Headley, A. D. Green Chem. 2013, 15, 2690; (p)
Orlandi, S.; Pozzi, G.; Ghisetti, M.; Benaglia, M. New J. Chem. 2013, 37, 4140; (q)
Avila, A.; Chinchilla, R.; Gómez-Bengoa, E.; Nájera, C. Eur. J. Org. Chem. 2013,
5085; (r) Song, Z.-T.; Zhang, T.; Du, H.-L.; Ma, Z.-W.; Zhang, C.-H.; Tao, J.-C.
Chirality 2014, 26, 121; (s) Flores-Ferrándiz, J.; Chinchilla, R. Tetrahedron:
Asymmetry 2014, 25, 1091; (t) Flores-Ferrándiz, J.; Fiser, B.; Gómez-Bengoa, E.;
Chinchilla, R. Eur. J. Org. Chem. 2015, 1218; (u) Vizcaino-Milla, P.; Sansano, J. M.;
Nájera, C.; Fiser, B.; Gómez-Bengoa, E. Synthesis 2015, 47, 2199; (v) Fernandes,
T. A.; Vizcaíno-Milla, P.; Ravasco, J. M. J. M.; Ortega-Martínez, A.; Sansano, J. M.;
Nájera, C.; Costa, P. R. R.; Fiser, B.; Gómez-Bengoa, E. Tetrahedron: Asymmetry
2016, 27, 118.
4.3.19. (R)-1-(2,5-Dioxo-1-phenylpyrrolidin-3-yl)cyclohexane-
1-carbaldehyde 5s4b,c
[a]
20 = +1.8 (c 1.0, CHCl3). 94% ee; Enantiomeric excess was
D
determined by HPLC with ChiralCel OD-H column (hexane/2-pro-
panol = 75:25), flow rate = 0.5 mL/min; k = 210 nm; tmajor = 46.6 -
min, tminor = 36.4 min.
4.3.20. (R)-2-[(R)-2,5-Dioxo-1-phenylpyrrolidin-3-yl]propanal 5t4b
Compound 5t was obtained as an inseparable diastereo mix-
ture. The ratio of diastereomers is determined 57:43 by the integral
of their signals. Enantiomeric excess was determined by HPLC with
ChiralPak AD-H column (hexane/2-propanol = 80:20), flow
rate = 0.5 mL/min; k = 210 nm; major diastereomer: tmajor = 46.7 -
min, tminor = 40.9 min. minor diastereomer: tmajor = 61.8 min,
tminor = 36.2 min. (95% ee for major diastereomer, 92% ee for minor
diastereomer).
5. (a) Yu, F.; Sun, X.; Jin, Z.; Wen, S.; Liang, X.; Ye, J. Chem. Commun. 2010, 4589;
(b) Wang, J.; Zhang, M.-M.; Zhang, S.; Xu, Z.-A.; Li, H.; Yu, X.-H.; Wang, W.
Synlett 2011, 473; (c) Muramulla, S.; Ma, J.-A.; Zhao, J. C.-G. Adv. Synth. Catal.
2013, 355, 1260.
6. The reactions of maleimide with other nucleophile, see: (a) Shen, J.; Nguyen, T.
T.; Goh, Y.-P.; Ye, W.; Fu, X.; Xu, J.; Tan, C.-H. J. Am. Chem. Soc. 2006, 128, 13692;
(b) Zu, L.; Xie, H.; Li, H.; Wang, J.; Jiang, W.; Wang, W. Adv. Synth. Catal. 1882,
2007, 349; (c) Ye, W.; Jiang, Z.; Zhao, Y.; Goh, S. L. M.; Leow, D.; Soh, Y.-T.; Tan,
C.-H. Adv. Synth. Catal. 2007, 349, 2454; (d) Lu, J.; Zhou, W. J.; Liu, F.; Loh, T.-P.
Adv. Synth. Catal. 2008, 350, 1796; (e) Jiang, Z.; Ye, W.; Yang, Y.; Tan, C.-H. Adv.
Synth. Catal. 2008, 350, 2345; (f) Jiang, Z.; Pan, Y.; Zhao, Y.; Ma, T.; Lee, R.; Yang,
Y.; Huang, K.-W.; Wong, M. W.; Tan, C.-H. Angew. Chem., Int. Ed. 2009, 48, 3627;
(g) Zea, A.; Valero, G.; Alba, A.-N. R.; Moyano, A.; Rios, R. Adv. Synth. Catal. 2010,
352, 1102; (h) Liao, Y.-H.; Liu, X.-L.; Wu, Z.-J.; Cun, L.-F.; Zhang, X.-M.; Yuan,
W.-C. Org. Lett. 2010, 12, 2896; (i) Alba, A.-N. R.; Valero, G.; Calbet, T.; Font-
Bard, M.; Moyano, A.; Rios, R. Chem. Eur. J. 2010, 16, 9884; (j) Wang, J.-J.; Dong,
X.-J.; Wei, W.-T.; Yan, M. Tetrahedron: Asymmetry 2011, 22, 690; (k) Liao, Y.-H.;
Liu, X.-L.; Wu, Z.-J.; Du, X.-L.; Zhang, X.-M.; Yuan, W.-C. Adv. Synth. Catal. 2011,
353, 1720; (l) Gómez-Torres, E.; Alonso, D. A.; Gómez-Bengoa, E.; Nájera, C. Org.
Lett. 2011, 13, 6106; (m) Shirakawa, S.; Terao, S. J.; He, R.; Maruoka, K. Chem.
Commun. 2011, 10557; (n) Ma, Z.-W.; Wu, Y.; Sun, B.; Du, H.-L.; Shi, W.-M.; Tao,
J.-C. Tetrahedron: Asymmetry 2013, 24, 7; (o) Gómez-Torres, E.; Alonso, D. A.;
Gómez-Bengoa, E.; Nájera, C. Eur. J. Org. Chem. 2013, 1434; (p) Zhao, M.-X.; Ji,
F.-H.; Wei, D.-K.; Shi, M. Tetrahedron 2013, 69, 10763.
4.3.21. Dimethyl 2-(2,5-Dioxo-1-phenylpyrrolidin-3-yl)propane-
dioate 5u6o
[a]
19 = +0.1 (c 0.3, CHCl3). 3% ee; Enantiomeric excess was
D
determined by HPLC with ChiralPak AD-H column (hexane/2-pro-
panol = 92:8), flow rate = 1.0 mL/min; k = 230 nm; tmajor = 102.1 -
min, tminor = 53.9 min.
Acknowledgements
This work was supported by JSPS KAKENHI Grant Number
16K08178. The authors would like to thank Enago (www.enago.
jp) for the English language review.
7. For reviews, see: (a) Miyabe, H.; Takemoto, Y. Bull. Chem. Soc. Jpn. 2008, 81, 785;
(b) Connon, S. J. Chem. Commun. 2008, 2499; (c) Connon, S. J. Synlett 2009, 354;
(d) Takemoto, Y. Chem. Pharm. Bull. 2010, 58, 593; (e) Alemán, J.; Parra, A.; Jiang,
H.; Jørgensen, K. A. Chem. Eur. J. 2011, 17, 6890; (f) Bhadury, P. S.; Li, H. Synlett
2012, 1108; (g) Serdyuk, O. V.; Heckel, C. M.; Tsogoeva, S. B. Org. Biomol. Chem.
2013, 11, 7051; (h) Tsakos, M.; Kokotos, C. G. Tetrahedron 2013, 69, 10199.
8. Modified Takemoto’s catalyst: (a) Robak, M. T.; Trincado, M.; Ellman, J. A. J. Am.
Chem. Soc. 2007, 129, 15110; (b) Kimmel, K. L.; Robak, M. T.; Ellman, J. A. J. Am.
Chem. Soc. 2009, 131, 8754; (c) Inokuma, T.; Furukawa, M.; Uno, T.; Suzuki, Y.;
Yoshida, K.; Yano, Y.; Matsuzaki, K.; Takemoto, Y. Chem. Eur. J. 2011, 17, 10470;
(d) Kimmel, K. L.; Weaver, J. D.; Lee, M.; Ellman, J. A. J. Am. Chem. Soc. 2012, 134,
9058; (e) Kobayashi, Y.; Taniguchi, Y.; Hayama, N.; Inokuma, T.; Takemoto, Y.
Angew. Chem., Int. Ed. 2013, 52, 11114.
9. Kanada, Y.; Yuasa, H.; Nakashima, K.; Murahashi, M.; Tada, N.; Itoh, A.; Koseki,
Y.; Miura, T. Tetrahedron Lett. 2013, 54, 4896.
10. Hirashima, S.; Sakai, T.; Nakashima, K.; Watanabe, N.; Koseki, Y.; Mukai, K.;
Kanada, Y.; Tada, N.; Itoh, A.; Miura, T. Tetrahedron Lett. 2014, 55, 4334.
11. Nakashima, K.; Hirashima, S.; Kawada, M.; Koseki, Y.; Tada, N.; Itoh, A.; Miura,
T. Tetrahedron Lett. 2014, 55, 2703.
12. Nakashima, K.; Hirashima, S.; Akutsu, H.; Koseki, Y.; Tada, N.; Itoh, A.; Miura, T.
Tetrahedron Lett. 2015, 56, 558.
13. Hirashima, S.; Nakashima, K.; Fujino, Y.; Arai, R.; Sakai, T.; Kawada, M.; Koseki,
Y.; Murahashi, M.; Tada, N.; Itoh, A.; Miura, T. Tetrahedron Lett. 2014, 55, 4619.
14. Hirashima, S.; Arai, R.; Nakashima, K.; Kawai, N.; Kondo, J.; Koseki, Y.; Miura, T.
Adv. Synth. Catal. 2015, 357, 3863.
15. Nakashima, K.; Kawada, M.; Hirashima, S.; Kato, M.; Koseki, Y.; Miura, T. Synlett
2015, 1248.
16. Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456.
References and notes
1. (a) Fredenhagen, A.; Tamura, S. Y.; Kenny, P. T. M.; Komura, H.; Naya, Y.;
Nakanishi, K.; Nishiyama, K.; Sugiura, M.; Kita, H. J. Am. Chem. Soc. 1987, 109,
4409; (b) Malochet-Grivois, C.; Roussakis, C.; Robillard, N.; Biard, J. F.; Riou, D.;
Debitus, C.; Verbist, J. F. Anticancer Drug Des. 1992, 7, 493; (c) Ando, Y.; Fuse, E.;
Figg, W. D. Clin. Cancer Res. 1964, 2002, 8; (d) Freiberg, C.; Brunner, N. A.;
Schiffer, G.; Lampe, T.; Pohlmann, J.; Brands, M.; Raabe, M.; Haebich, D.;
Ziegelbauer, K. J. Biol. Chem. 2004, 279, 26066; (e) Isaka, M.; Rugseree, N.;
Maithip, P.; Kongsaeree, P.; Prabpai, S.; Thebtaranonth, Y. Tetrahedron 2005, 61,
5577; (f) Uddin, J.; Ueda, K.; Siwu, E. R. O.; Kita, M.; Uemura, D. Bioorg. Med.
Chem. 2006, 14, 6954; (g) Aboul-Enein, M. N.; El-Azzouny, A. A.; Saleh, O. A.;
Maklad, Y. A. Mini-Rev. Med. Chem. 2012, 12, 671.
2. For reviews, see: Chauhan, P.; Kaur, J.; Chimni, S. S. Chem. Asian J. 2013, 8, 328.
3. Bartoli, G.; Bosco, M.; Carlone, A.; Cavalli, A.; Locatelli, M.; Mazzanti, A.; Ricci,
P.; Sambri, L.; Melchiorre, P. Angew. Chem., Int. Ed. 2006, 45, 4966.
4. (a) Zhao, G.-L.; Xu, Y.; Sundén, H.; Eriksson, L.; Sayah, M.; Córdova, A. Chem.
Commun. 2007, 734; (b) Xue, F.; Liu, L.; Zhang, S.; Duan, W.; Wang, W. Chem.
Eur. J. 2010, 16, 7979; (c) Yu, F.; Jin, Z.; Huang, H.; Ye, T.; Liang, X.; Ye, J. Org.
Biomol. Chem. 2010, 8, 4767; (d) Bai, J.-F.; Peng, L.; Wang, L.-L.; Wang, L.-X.; Xu,
X.-Y. Tetrahedron 2010, 66, 8928; (e) Miura, T.; Masuda, A.; Ina, M.; Nakashima,
K.; Nishida, S.; Tada, N.; Itoh, A. Tetrahedron: Asymmetry 2011, 22, 1605; (f) Ma,
Z.-W.; Liu, Y.-X.; Li, P.-L.; Ren, H.; Zhu, Y.; Tao, J.-C. Tetrahedron: Asymmetry
2011, 22, 1740; (g) Miura, T.; Nishida, S.; Masuda, A.; Tada, N.; Itoh, A.
Tetrahedron Lett. 2011, 52, 4158; (h) Ma, Z.-W.; Liu, Y.-X.; Zhang, W.-J.; Tao, Y.;
Zhu, Y.; Tao, J.-C.; Tang, M.-S. Eur. J. Org. Chem. 2011, 6747; (i) Avila, A.;
Chinchilla, R.; Nájera, C. Tetrahedron: Asymmetry 2012, 23, 1625; (j) Nugent, T.
C.; Sadiq, A.; Bibi, A.; Heine, T.; Zeonjuk, L. L.; Vankova, N.; Bassil, B. S. Chem.
Eur. J. 2012, 18, 4088; (k) Yang, W.; Jiang, K.-Z.; Lu, X.; Yang, H.-M.; Li, L.; Lu, Y.;
17. Verma, R. K.; Ila, H.; Singh, M. S. Tetrahedron 2010, 66, 7389.
Please cite this article in press as: Nakashima, K.; et al. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.tetasy.2016.07.002