Bis(imidazolidine)pyridine-CoCl2: A Novel, Catalytically Active Neutral Complex for Asymmetric Michael Reaction of 1,3-Carbonyl Compounds with Nitroalkenes

Article abstract of DOI:10.1002/adsc.201900421

A neutral bis(imidazolidine)pyridine (PyBidine)-CoCl₂ complex showed catalytic activity for the Michael reaction of malonates with nitroalkenes. The results indicated that a weak amine base aided enolate formation from the neutral complex, in w

Full text of DOI:10.1002/adsc.201900421

Title: Bis(imidazolidine)pyridine-CoCl₂: A Novel,
Catalytically Active Neutral Complex for Asymmetric Michael
Reaction of 1,3-Carbonyl Compounds with Nitroalkenes
Authors: Takayoshi Arai, Yuko Iimori, Mayu Shirasugi, Ryota
Shinohara, Yuri Takagi, Takumi Suzuki, Junma Ma, Satoru
Kuwano, and Hyuma Masu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Adv. Synth. Catal. 10.1002/adsc.201900421
Link to VoR: http://dx.doi.org/10.1002/adsc.201900421

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Bis(imidazolidine)pyridine-CoCl2: A Novel, Catalytically Active
Neutral Complex for Asymmetric Michael Reaction of 1,3-
Carbonyl Compounds with Nitroalkenes
Takayoshi Arai,a* Yuko Iimori,a Mayu Shirasugi,a Ryota Shinohara,a Yuri Takagi,a
Takumi Suzuki,a Junma Ma,a Satoru Kuwanoa and Hyuma Masub
a
Soft Molecular Activation Research Center (SMARC), Chiba Iodine Research Innovation Center (CIRIC), and
Department of Chemistry, Graduate School of Science, Chiba University1-33 Yayoi, Inage, Chiba 263-8522, Japan
[Phone and fax number: +81-43-290-2889, E-mail: tarai@faculty.chiba-u.jp]
Center for Analytical Instrumentation, Chiba University1-33 Yayoi, Inage, Chiba 263-8522, Japan
b
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.
In the bis(oxazoline)-Lewis acid catalysis, non-
Abstract. A neutral bis(imidazolidine)pyridine (PyBidine)-
CoCl2 complex showed catalytic activity for the Michael coordinating anions (e.g., OTf− and tetrakis[3,5-
bis(trifluoromethyl)phenyl]borate: [BArF ]−) are used
reaction of malonates with nitroalkenes. The results
4
indicated that a weak amine base aided enolate formation
from the neutral complex, in which the N-H proton of the
imidazolidine ligand played a significant role.
for making cationic metal complexes with an
unsaturated coordination sphere (Scheme 1a).[2] For
basic catalysts, the counter anion acts as the
conjugate base for eliminating an acidic proton from
the substrate (Scheme 1b).[3] The combination of a
Lewis acidic metal center with the basic anion is also
interesting, and Evans’ bis(oxazoline)-Cu(OAc)2-
catalyzed nitroaldol (Henry) reaction[4] is a good
example.[4d] In this case, a weakly Lewis acidic
copper center increases the acidity of the coordinating
nitroalkanes, which allows the generation of copper
nitronate using the moderately basic acetate anion as
a prelude to the nitroaldol reaction.
These studies can explain the stability of the metal-
halide complex as well (Scheme 1c). Because the
halide strongly connects to the metal center, the
metal-halide complex, referred to as the “neutral
complex,” only shows low Lewis acidity. In addition,
because the halide anion cannot provide meaningful
basicity for promoting catalysis, typically the metal-
halide complex is stable and catalytically inactive.
However, in 2013, a unique asymmetric reaction
catalyzed by a neutral pincer NCN-palladium-Cl
complex (Scheme 2) was reported.[5]
Keywords: Asymmetric catalysis; Michael addition;
Cobalt; Enolates; Imidazolidine
Chiral metal complexes have been applied
extensively in acid- or base-promoted asymmetric
chemical
transformations.
Some
pivotal
bis(oxazoline)-metal catalyses are representative
examples (Scheme 1).[1]
Scheme 1. Classification of bis(oxazoline)-metal catalyses.
Scheme 2. Neutral pincer bis(imidazolidine)-derived
NCN-PdCl complex for Michael addition of malononitrile
with nitroalkenes.
1
This article is protected by copyright. All rights reserved.

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
The
bis(imidazolidine)-derived
NCN-PdCl
at 0 °C using iPr2NEt was found to be the best set of
conditions. Under the optimized conditions, the scope
and limitations were examined, and the results are
shown in Table 2. Not only simply substituted
nitrostyrenes, but also 1-naphthyl nitroalkene, 2-
thienyl nitroalkene, and aliphatic nitroalkenes were
successfully used to give enantioselective products.
When 298 mg (2 mmol) of 2a was used, 504 mg of
3a was obtained in 90% yield with 85% ee.
complex showed catalyst activity in Michael addition
of malononitrile with nitroalkenes to give products in
good yields with up to 92% ee.[5a The comparable
]
catalytic activity of the neutral catalyst with the cationic
form of this catalyst is remarkable. For example, using
the neutral NCN-PdCl catalyst gave the product in 82%
yield and 80% ee, while the cationic NCN-PdOTf
catalysis resulted in 75% yield with 77% ee. Although
focus has been on activation mode using a hydrogen-
bond managed by the NH-proton of imidazolidine
ligand on the metal complex, the origin of the catalytic
activity observed in the neutral complex was unknown.
Prompted by discovery of the catalytically active
bis(imidazolidine)-derived NCN-PdCl complex, a
detailed study was conducted on the catalytic activity
Table 2. Catalytic enantioselective Michael reaction.
of
a
metal
chloride
complex
using
bis(imidazolidine)pyridine ligand (PyBidine), which
easily forms a complex with a wide range of metal
salts.[6] Results from screening asymmetric catalyses
using the PyBidine-metal chloride complexes
revealed that the PyBidine-CuCl2 and PyBidine-
CoCl2 complexes possessed catalyst activity in the
Michael reaction using malonate (Table 1, entries 2
and 4).[7]
Entry
R
Time
(h)
Yield Ee
(%)
(%)
1
2
3
4
5
6
Ph (3a)
24
24
28
54
30
30
53
24
48
>99
66
48
60
52
67
31
33
90
91
90
79
91
74
78
93
89
85
p-ClC6H4 (3b)
p-MeC6H4 (3c)
m-NO2C6H4 (3d)
1-naphthyl (3e)
2-thienyl (3f)
PhCH=CH- (3g)
iPr (3h)
7
Table 1. Catalytic activity of PyBidine-metal salt
complexes.
8a)
9b)
Ph (3a)
a) At rt. b) 2 mmol scale.
To determine the reason for the catalytic activity, a
single crystal of the PyBidine-CoCl2 complex was
obtained from PyBidine with CoCl2-6H2O. X-ray
crystallographic analysis revealed that the tridentate
PyBidine ligand was coordinated meridionally to the
cobalt center in a trigonal bipyramidal configuration,
and no H2O was coordinated to the cobalt center,
even when the complex was prepared from CoCl2-
6H2O (Figure 1).[8] This clearly indicates that the
Lewis acidity of PyBidine-CoCl2 complex is
extremely low. Note that the PyBidine-CoCl2
complex prepared from CoCl2-6H2O was catalytically
active and gave the Michael adduct in 63% yield with
86% ee (Table 1, entry 8).
Entry Ligand
Metal salt
Yield (%) Ee (%)e)
1
2
3
4
PyBidine Cu(OTf)2
PyBidine CuCl2
PyBidine Co(ClO4)2
PyBidine CoCl2
PyBidine CoCl2
PyBidine CoCl2
PyBidine CoCl2
93
64
88
95
>99
>99
6
63
trace
trace
81
53
83
87
89
91
89
86
-
a)
5b)
6b,c)
7d)
8
a)
PyBidine CoCl2
9
CoCl2
L1
10
iPr-pybox CoCl2
-
a) Hexahydrate, b) iPr2NEt was used instead of NEt3. c) At
0 °C. d) Without base. e) Absolute configuration was
determined by ref. 7a and 7e.
When 5 mol % PyBidine-CoCl2 complex was
applied to a mixture of dimethylmalonate with
nitrostyrene in THF, the reaction accelerated
smoothly with the aid of Et3N (10 mol %) to give the
product in 95% yield with 87% ee. The results were
comparable using the cationic PyBidine-Co(ClO4)2
complex (88% yield, 83% ee, entry 3). For the
PyBidine-CoCl2-catalyzed Michael reaction, reaction
Figure 1. X-ray structure of the PyBidine-CoCl2 complex
(CCDC 1906366). Solvent was omitted to clarify (See
details in SI).
2
This article is protected by copyright. All rights reserved.

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
Formation of the cobalt-enolate complex
Scheme 3. For the PyBidine-CoCl2 complex, the N-H
proton of the imidazolidine ligand should be acidic
and easily deprotonated by a weak base of iPr2NEt to
enhance release of chloride anion from the cobalt
center. Although generation of the PyBidine-CoCl
intermediate (A) was unclear in formation of cobalt
enolate B from the dimethyl malonate, the N-H
proton would regenerate on the imidazolidine ligand
(i.e., these processes can be explained as a type of
anion exchange). In the subsequent Michael addition,
the recovered N-H proton would act as a Brønsted
acid for enhancing the reactivity of nitrostyrene. The
proposed TS model in Scheme 3, which can be
generated by an analogy of previously reported TS
for the PyBidine-Cu catalyzed [3+2] cyclization of
iminoester with nitrostyrene,[6f] explains the
production of (S)-enriched Michael adduct using
PyBidine-CoCl2 was examined using ESI-MS (Figure
2), which provided a peak at 797.2676 corresponding
to [PyBidine-CoCl]+ (calcd. for C49H45 ClCoN5:
797.2690). When the PyBidine-CoCl2 was mixed
with dimethyl malonate, no obvious change was
observed. However, addition of 1 mol eq. of TEA to
the PyBidine-CoCl2-dimethyl malonate mixture
resulted in detection of a new peak at 893.3338,
which was assigned to the cobalt-enolate of
[PyBidine-Co-MeO2CCHCO2Me]+
(calcd.
for
C54H52CoN5O4: 893.3351). Although the same ESI-
MS study was conducted on the pybox-CoCl2
complex, no peak was observed, suggesting enolate
formation. Importantly, N,N-dimethyl pybidine-
CoCl2 complex and pybox-CoCl2 and could not
promote the Michael reaction, even in the presence of
iPr2NEt (Table 1, entry 9 and 10).
(S,S)-diphenylethylenediamine-derived
PyBidine-
CoCl2 complex.
The PyBidine-CoCl2 catalyst system was applied
to sequential reactions. In Scheme 4, a sequential
Michael/Michael reaction was examined using γ,δ-
unsaturated -ketoesters.[9] PyBidine-CoCl2 the
catalyst prepared from CoCl2-6H2O, smoothly
catalyzed the first step of Michael reaction (reaction
optimization detailed in Supporting Information).
Based on a protocol developed by Takemoto[10] and
Feng,[11] subsequent treatment with 1,1,3,3-
tetramethylguanidine (TMG) gave the penta-
substituted cyclohexenes with enantioselectivity,
although the stereoselectivities were somewhat lower
than those found for the reaction using malonate
(Scheme 4A).
Figure 2. ESI-MS analysis of PyBidine-Co-enolate
formation.
Scheme 3. Proposed reaction mechanism of PyBidine-
CoCl2-catalyzed asymmetric Michael reaction.
Scheme 4. Catalytic asymmetric Michael/Michael reaction
using the PyBidine-CoCl2 catalyst. The diastereomeric
ratio of products were determined by 1H-NMR.
These mechanistic studies demonstrated that
enolate formation from PyBidine-CoCl2 was much
easier than that from pybox-CoCl2 as explained in
3
This article is protected by copyright. All rights reserved.

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
However, when the first Michael product was
new function of N-H protons, in addition to their
action as a hydrogen-bonding donor.
isolated, it was 81% ee, which was confirmed after
conversion to the cyclohexene 3j using TMG
(Scheme 4B). These results suggest that the
PyBidine-CoCl2 catalyst also promoted the second
Michael cyclization, although the resolution was
negative.
Experimental Section
General procedure of asymmetric Michael addition
reaction
The PyBidine-CoCl2 catalyst was also applied to
the Michael/protonation reaction.[12] Use of the
substrate with an electron-withdrawing group at the
-position resulted in a high yield of product.
Because the diastereoselectivity should be determined
in the protonation step, the reaction conditions were
re-investigated by focusing on the proton source, and
the addition of H2O improved the diastereoselectivity.
The results of catalytic Michael/protonation reaction
PyBidine (0.011 mmol) and CoCl2 (0.010 mmol) were
added to a two-necked round flask containing a stir bar
under Air. THF (1.00 ml) was added to the flask and the
mixture was stirred overnight. To the resulting mixture,
dialkylmalonate (0.24 mmol) and i-Pr2NEt (0.010 mmol)
were added subsequently at room temperature, and then
nitroalkene (0.20 mmol) was added at 0 °C. After being
stirred for appropriate time, the reaction mixture was
quenched by adding aqueous HCl. The aqueous layer was
extracted with dichloromethane, and the combined organic
layers were dried over Na2SO4. After removing the solvent
under reduced pressure, the resulting residue was purified
by silica gel column chromatography to afford product.
The enantiomeric excesses of the products were
determined by chiral stationary phase HPLC.
using
(E)-3-nitro-3-substituted
acrylate
is
summarized in Scheme 5.
General procedure of asymmetric sequential Michael
addition reaction
PyBidine (0.011 mmol) and CoCl2 ∙6H2O (0.010 mmol)
were added to a two-necked round flask containing a stir
bar under Ar. THF (1.00 ml) was added to the flask and the
mixture was stirred for six hours. After removal the solvent
under reduced pressure, dichloromethane (1.00 ml) was
added. To the resulting solution, γ,δ-unsaturated-β-
ketoester (0.10 mmol) and NEt3 (0.010 mmol) were added
subsequently at room temperature, and then nitroalkene
(0.12 mmol) were added at 0 °C. After being stirred for 21
hours, tetramethyl guanidine (0.10 mmol) was added. After
being stirred for additional three hours, reaction mixture
was quenched by adding water. The aqueous layer was
extracted with dichloromethane, and the combined organic
layers were dried over Na2SO4. After removing the solvent
under reduced pressure, the resulting residue was purified
by silica gel column chromatography to afford product.
The enantiomeric excesses of the products were
determined by chiral stationary phase HPLC.
Scheme 5. Catalytic asymmetric Michael/protonation
reaction using PyBidine-CoCl2 catalyst. The
diastereomeric ratio of products were determined by H-
NMR.
General procedure of asymmetric sequential Michael
addition reaction
1
PyBidine (0.011 mmol) and CoCl2 (0.010 mmol) were
added to a two-necked round bottom flask containing a stir
bar under Air. Solvent mixture (THF:H2O = 1000:3.6, 1.00
ml) was added to the flask and the mixture was stirred
overnight. To the resulting mixture, dialkylmalonate (0.24
mmol), NEt3 (0.010 mmol) and nitroalkene (0.20 mmol)
were added subsequently at room temperature. After being
stirred for appropriate time, the reaction mixture was
quenched by adding aqueous HCl. The aqueous layer was
extracted with dichloromethane, and the combined organic
layers were dried over Na2SO4. After removing the solvent
under reduced pressure, the resulting residue was purified
by silica gel column chromatography to afford product.
The enantiomeric excesses of the products were
determined by chiral stationary phase HPLC.
Stereochemistry of the major diastereomer was
determined after converting the cyclic compounds
(Scheme 6).
Acknowledgements
Scheme 6. Chemical transformation of 3p.
This research is supported by JSPS KAKENHI Grant Number
JP16H01004 and JP18H04237 in Precisely Designed Catalysts
with Customized Scaffolding.
In conclusion, neutral PyBidine-CoCl2 catalyst
possessed activity in reaction to produce PyBidine-
Co-enolate. This enolate formation was dramatically
accelerated by an imidazolidine ligand, which is a
References
4
This article is protected by copyright. All rights reserved.

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
[1] For
reviews,
see:
a)
[7] Representative examples of catalytic asymmetric
Michael reaction of malonate with nitroalkenes: a) D.
M. Barnes, J. Ji, M. G. Fickes, M. A. Fitzgerald, S. A.
King, H. E. Morton, F. A. Plagge, M. Preskill, S. H.
Wagaw, S. J. Wittenberger, J. Zhang, J. Am. Chem. Soc.
2002, 124, 13097; b) V. Annamalai, E. F. DiMauro, P.
J. Carroll, M. C. Kozlowski, J. Org. Chem. 2003, 68,
1973; c) H. Li, Y. Wang, L. Tang, L. Deng, J. Am.
Chem. Soc. 2004, 126, 9906; d) M. Watanabe, A.
Ikagawa, H. Wang, K. Murata, T. Ikariya, J. Am. Chem.
Soc. 2004, 126, 11148; e) D. A. Evans, D. Seidel, J. Am.
Chem. Soc. 2005, 127, 9958; f) T. Okino, Y. Hoashi, T.
Furukawa, X. Xu, Y. Takemoto, J. Am. Chem. Soc.
2005, 127, 119; g) S. H. McCooey, S. J. Connon,
Angew. Chem., Int. Ed. 2005, 44, 6367; h) J. Ye, D. J.
Dixon, P. S. Hynes, Chem. Comm. 2005, 4481; i) M.
Terada, H. Ube, Y. Yaguchi, J. Am. Chem. Soc. 2006,
128, 1454; j) F.-Z. Peng, Z.-H. Shao, B.-M. Fan, H.
Song, G.-P. Li, H.-B. Zhang, J. Org. Chem. 2008, 73,
5202; k) Q. Zhu, H. Huang, D. Shi, Z. Shen, C. Xia,
Org. Lett. 2009, 11, 4536; l) D. Almasi, D. A. Alonso,
E. Gomez-Bengoa, C. Najera, J. Org. Chem. 2009, 74,
6163; m) L. Zhang, M.-M. Lee, S.-M. Lee, J. Lee, M.
Cheng, B.-S. Jeong, H. Park, S. Jew, Adv. Synth. Catal.
2009, 351, 3063; n) H. Y. Bae, S. Some, J. S. Oh, Y. S.
Lee, C. E. Song, Chem. Commun. 2011, 47, 9621; o) R.
Jin, K. Liu, D. Xia, Q. Qian, G. Liu, H. Li, Adv. Synth.
Catal. 2012, 354, 3265; p) H. Y. Bae, C. E. Song, ACS
Catalysis 2015, 5, 3613; q) B. A. F. Le Bailly, L. Byrne,
J. Clayden, Angew. Chem., Int. Ed. 2016, 55, 2132; r) S.
K. Ghosh, C. Ganzmann, N. Bhuvanesh, J. A. Gladysz,
Angew. Chem., Int. Ed. 2016, 55, 4356; s) D. Bissessar,
T. Achard, S. Bellemin-Laponnaz, Adv. Synth. Catal.
2016, 358, 1982; t) E. I. Jimenez, W. E. Vallejo
Narvaez, C. A. Roman-Chavarria, J. Vazquez-Chavez,
T. Rocha-Rinza, M. Hernandez-Rodriguez, J. Org.
Chem. 2016, 81, 7419; u) R. S. Tukhvatshin, A. S.
Kucherenko, Y. V. Nelyubina, S. G. Zlotin, ACS
Catalysis 2017, 7, 2981; v) D. Becart, V. Diemer, A.
Salaun, M. Oiarbide, Y. R. Nelli, B. Kauffmann, L.
Fischer, C. Palomo, G. Guichard, J. Am. Chem. Soc.
2017, 139, 12524; and also see ref 3c.
A.K. Ghosh, P. Mathivanan, J. Cappiello, Tetrahedron:
Asymmetry 1998, 9, 1; b) H. A. McManus, P. J. Guiry,
Chem.
G. Desimoni, G. Faita, K.
Rev. 2006, 106, 3561; d) S. Dagorne, S. Bellemin-
Rev. 2004,
104,
4151;
c)
Chem.
A. Jørgensen,
Laponnaz, A. Maisse-François,
Chem. 2007, 913.
Eur.
J.
Inorg.
[2] a) W. Beck, K. Suenkel, Chem. Rev. 1988, 88, 1405; b)
M. Bochmann, Angew. Chem., Int. Ed. Engl. 1992, 31,
1181; c) S. H. Strauss, Chem. Rev. 1993, 93, 927; d) I.
Krossing, I. Raabe, Angew. Chem., Int. Ed. 2004, 43,
2066; e) S. Antoniotti, V. Dalla, E. Duꢀach, Angew.
Chem., Int. Ed. 2010, 49, 7860; f) T. A. Engesser, M. R.
Lichtenthaler, M. Schleep, I. Krossing, Chem. Soc. Rev.
2016, 45, 789.
[3] a) S. Kobayashi, Y. Yamashita, Acc. Chem. Res. 2011,
44, 58; b) S. Saito, T. Tsubogo, S. Kobayashi, J. Am.
Chem. Soc. 2007, 129, 5364; c) T. Tsubogo, Y.
Yamashita, S. Kobayashi, Angew. Chem., Int. Ed. 2009,
48, 9117; d) T. Tsubogo, Y. Kano, Y. Yamashita, S.
Kobayashi, Chem. Asian J. 2010, 5, 1974.
[4] Selected examples of catalytic enantioselective Henry
reaction, see: a) H. Sasai, T. Suzuki, S. Arai, T. Arai, M.
Shibasaki, J. Am. Chem. Soc. 1992, 114, 4418; b) C.
Christensen, K. Juhl, K. A. Jϕrgensen, Chem. Commun.
2001, 2222; c) B. M. Trost, V. S. C. Yeh, Angew.
Chem., Int. Ed. 2002, 41, 861; d) D. A. Evans, D.
Seidel, M. Rueping, H. W. Lam, J. T. Shaw, C. W.
Downey, J. Am. Chem. Soc. 2003, 125, 12692; e) C.
Palomo, M. Oiarbide, A. Laso, Angew. Chem., Int. Ed.
2005, 44, 3881; f) B. M. Choudary, K. V. S. Ranganath,
U. Pal, M. L. Kantam, B. Sreedhar, J. Am. Chem. Soc.
2005, 127, 13167; g) T. Marcelli, R. N. S. van der Haas,
J. H. van Maarseveen, H. Hiemstra, Angew. Chem., Int.
Ed. 2006, 45, 929; h) T. Arai, M. Watanabe, A.
Fujiwara, N. Yokoyama, A. Yanagisawa, Angew.
Chem., Int. Ed. 2006, 45, 5978; i) T. Arai, N.
Yokoyama, A. Yanagisawa, Chem.–Eur. J. 2008, 14,
2052; j) D. Scharnagel, F. Prause, J. Kaldun, R. G.
Haase, M. Breuning, Chem. Commun. 2014, 50, 6623.
[8] CCDC 1906366 contains the supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge
[5] a) T. Arai, I. Oka, T. Morihata, A. Awata, H. Masu,
Chem.–Eur. J. 2013, 19, 1554; b) T. Arai, T.
Moribatake, H. Masu, Chem.–Eur. J. 2015, 21, 10671;
c) T. Arai, J. Kakino, Angew. Chem. Int.
Ed. 2016, 55, 15263.
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/data_request/cif.
[9] Ref. for catalytic asymmetric Michael/Michael
[6] a) T. Arai, A. Mishiro, N. Yokoyama, K. Suzuki, H.
Sato, J. Am. Chem. Soc. 2010, 132, 5338; b) T. Arai, A.
Mishiro, E. Matsumura, A. Awata, M. Shirasugi,
Chem.–Eur. J. 2012, 18, 11219; c) T. Arai, S. Kajikawa,
E. Matsumura, Synlett 2013, 24, 2045; d) T. Arai, E.
Matsumura, Synlett 2014, 25, 1776; e) A. Awata, T.
Arai, Angew. Chem. Int. Ed. 2014, 53, 10462; f) T. Arai,
H. Ogawa, A. Awata, M. Sato, M. Watabe, M.
Yamanaka, Angew. Chem. Int. Ed. 2015, 54,1595; g) T.
Arai, K. Tsuchiya, E. Matsumura, Org. Lett. 2015, 17,
2416; h) T. Arai, T. Miyazaki, H. Ogawa, H. Masu,
Org. Lett. 2016, 18, 5824.
reaction: a) M. Ihara, K. Fukumoto, Angew. Chem., Int.
Ed.
1993,
32,
1010;
b) R.
B.
Grossman, Synlett. 2001, 13.
[10] a) Y. Hoashi, T. Yabuta, Y. Takemoto, Tetrahedron
Lett. 2004, 45, 9185; b) Y. Hoashi, T. Yabuta, R, P.
Yuan, H. Miyabe, Y. Takemoto, Tetrahedron 2006, 62,
365.
[11] P. He, X. Liu, J. Shi, L. Lin, X. Feng, Org. Lett. 2011,
13, 936.
[12] Ref. for catalytic asymmetric Michael/protonation
reaction: a) E. Emori, T. Arai, H. Sasai, M. Shibasaki, J.
Am. Chem. Soc. 1998, 120, 4043; b) K. Nishimura, M.
5
This article is protected by copyright. All rights reserved.

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
Ono, Y. Nagaoka, K. Tomioka, Angew. Chem., Int. Ed.
Int. Ed. 2008, 47, 5641; e) S. Lin, D. Leow, K.-W.
Huang, C.-H. Tan, Chem.–Asian. J. 2009, 4, 1741; f) N.
K. Rana, V. K. Singh, Org. Lett. 2011, 13, 6520; g) L.
Dai, H. Yang, J. Niu, F. Chen, Synlett 2012, 314.
2001, 40, 440; c) B.-J. Li, L. Jiang, M. Liu, Y.-C. Chen,
L.-S. Ding, Y. Wu, Synlett 2005, 603; d) D. Leow, S.
Lin, S. K. Chittimalla, X. Fu, C. H. Tan, Angew. Chem.,
6
This article is protected by copyright. All rights reserved.

10.1002/adsc.201900421
Advanced Synthesis & Catalysis
COMMUNICATION
Bis(imidazolidine)pyridine-CoCl2: A Novel,
Catalytically Active Neutral Complex for
Asymmetric Michael Reaction of 1,3-Carbonyl
Compounds with Nitroalkenes
Adv. Synth. Catal. Year, Volume, Page – Page
Takayoshi Arai,* Yuko Iimori, Mayu Shirasugi,
Ryota Shinohara, Yuri Takagi, Takumi Suzuki,
Junma Ma, Satoru Kuwano and Hyuma Masu
7
This article is protected by copyright. All rights reserved.