Application of asymmetric Henry reaction by copper(II) complexes containing (R,R)-1,2-diaminocyclohexane with naphthyl and thiophenyl substituents

Article abstract of DOI:10.1016/j.ica.2021.120492

A series of Cu(II) complexes containing C₁-symmetric thiophene derivatives of (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclohexane-1,2-diamine, namely L¹, L² and L³ were synthesized and characterized. These complexes h

Full text of DOI:10.1016/j.ica.2021.120492

Inorganica Chimica Acta 525 (2021) 120492
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Application of asymmetric Henry reaction by copper(II) complexes
containing (R,R)-1,2-diaminocyclohexane with naphthyl and
thiophenyl substituents
,
,
Juhyun Choa, Jong Hwa Jeonga *, Hyosun Leea *, Jungkyu K. Leea, Saira Nayabb
a Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, 80 Daehakro, Bukgu, Daegu 41566, Republic of Korea
b Department of Chemistry, Shaheed Benazir Bhutto University, Sheringal Dir (U), Khyber Pakhtunkhwa, Pakistan
A R T I C L E I N F O
A B S T R A C T
Keywords:
A series of Cu(II) complexes containing C1-symmetric thiophene derivatives of (1R,2R)-N1-(naphthalen-2-
ylmethyl)cyclohexane-1,2-diamine, namely L1, L2 and L3 were synthesized and characterized. These complexes
had distorted square-planar geometries around the Cu(II) center. High yield (99%) and excellent enantiose-
lectivity (>99%) for (S)-1-nitro-4-phenylbutan-2-ol from the reaction of 3-phenylpropanal and nitromethane was
obtained using [L1Cu(OAc)2] or [L3Cu(OAc)2] with 10 mol% of diisopropylethylamine (DIPEA) within 24 h.
The catalytic systems also demonstrated good activity and moderate to high enantioselectivity for aliphatic
aldehydes.
Unsymmetrical chiral diamine ligands
Copper(II) complexes
Asymmetric Henry reaction
β-Nitroalcohols
1. Introduction
Arai and co-workers demonstrated that C1-symmetric chiral imidazoli-
dine-pyridine[36] and (R,R)-1,2-diphenylethylenediamine derived Cu
–
C
The asymmetric Henry reaction proved to be an important C
(OAc)2 complexes [25] proved to be efficient catalyst for the Henry
reaction, giving the various nitroaldols with high yields and over 90%
ee. More recently, Panov and Novakova groups independently studied
Cu(II) initiators supported with C1-symmetric 2-(pyridin-2-yl)imidazo-
lidin-4-one[37] and 2-(pyridine-2-yl)imidazolidine-4-thione [38] li-
gands, respectively, which demonstrated moderate to high yields and
enantioselectivities in asymmetric Henry reaction. Similarly, we
recently reported the generation of Cu(II) complexes based on the C1-
symmetric (1R,2R)-N-benzylcyclohexane-1,2-diamine motif that resul-
ted in high product yields and superior enantioselectivities (>99%)
[39]. The nature of the ligand framework and attached substituents is a
pivotal factor governing the efficiency of catalysts in the asymmetric
Henry reaction. The utility of thiophene-based ligands in this reaction
has been investigated by several groups. Mansawat et al. showed that
homochiral amino alcohols carrying the N-2-thienyl methyl substituent
provided moderate yields and good enantioselectivities [40], and Ban-
dini et al. used a C2-symmetric diamino ligand with oligothienyl groups
[41]. We recently explored the influence of the methylthiophenyl moi-
ety on the level of asymmetric induction (enantiomeric excess [ee] up to
92%) in the Henry reaction. Therein, we introduced an unsymmetrical
scaffold by incorporating thiophenyl moieties in the (1R,2R)-N1-
bond formation reaction resulting in enantiomerically enriched β-nitro
alcohols, which are valuable intermediates in the synthesis of biologi-
cally interesting molecules [1,2]. Notably, the resulting nitroaldol
products can be reduced to vicinal amino alcohols, a common structural
motif found in many pharmaceuticals and long-chain lipids [3–7]. Since
the pioneering work of Shibasaki in 1992 [8], several studies have
focused on the development of chiral C2-symmetric ligands for the Cu-
catalyzed asymmetric Henry reaction; these ligands have excellent
asymmetric-induction ability [9–15]. For example, high activities and
moderate to high enantioselectivities have been obtained using salan-
type [16–18], BOX-type [9,10,19], diamine [12–15,20,21], amino-
sulfonamide [22,23] and bistetracarboline amides [24]-based C2-sym-
metric frameworks in the asymmetric Henry reaction. More recently,
chiral C1-symmetric ligands based on unsymmetrical substitutions of
these above-mentioned scaffolds [25-29] and several new synthetic
systems [6,30–34] have also been investigated in the copper-catalyzed
Henry reaction. However many of these catalytic systems display poor
enantioselectivity together with low product yields when using aliphatic
aldehydes as substrates [29,35]. Thus, the development of effective
catalytic systems is still desired for this class of substrate. In this regard
* Corresponding authors.
E-mail addresses: jeongjh@knu.ac.kr (J.H. Jeong), hyosunlee@knu.ac.kr (H. Lee).
https://doi.org/10.1016/j.ica.2021.120492
Received 26 March 2021; Received in revised form 10 May 2021; Accepted 1 June 2021
Available online 4 June 2021
0020-1693/© 2021 Elsevier B.V. All rights reserved.

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
(naphthalylcyclohexane)-1,2-diamine fragment [42]. The synthesis, X-
ray structures, and application in the asymmetric Henry reaction of Cu
(II) complexes supported with these unsymmetrical thiophenyl de-
rivatives of (1R,2R)-N1-naphthalylcyclohexane-1,2-diamine are dis-
cussed herein.
Cy-CH2), 1.92–1.87 (m, 1H, Cy-CH), 1.77–1.67 (m, 2H, Cy-CH2), 1.62
(br, 3H, NH), 1.34–1.18 (m, 2H, Cy-CH2), 1.14–1.01 (m, 2H, Cy-CH2)
ppm. 13C NMR (CDCl3, 125 MHz, 298 K): δ 137.7, 132.5, 131.6, 126.9,
126.6, 126.6, 125.7, 125.3, 124.8, 124.4 (1C, 2naph-C), 62.4 (1C, Cy-C),
54.4 (1C, NH-CH2), 50.2, 35.1, 30.5, 24.5, 24.3 (1C, Cy-C); FTIR (liquid
neat; cmꢀ 1):
ν
(N-H) 3349 (w);
ν
(sp3 C-H) 2922 w;
ν
(C C) 1632 m;
–
–
3
–
–
–
2. Experimental
ν
(C
–
C)antisym and
ν
(C
C)sym 1599(w) and1447(w); δ(-C-H sp )
2
–
–
1361 m;
ν
(N C) 1225 m; δ(C H sp ) 855 w.
2.1. Materials and methods
2.3. Synthesis protocols
All manipulations involved in the synthesis of ligands (L1–L3) and
their corresponding Cu(II) complexes, [LnCuCl2] (Ln = L1–L3), were
performed using bench-top techniques in air unless otherwise specified.
(R,R)-1,2-Diaminoniumcyclohexane mono-(L)-(+)-tartrate salt, 2-naph-
thylaldehyde, 2-naphthylaldehyde, 2-thiophenecarboxaldehyde, 3-thi-
ophenecarboxaldehyde, 5-methyl-2-thiophenecarboxaldehyde, copper
(II) chloride dihydrate (CuCl2⋅2H2O), benzaldehyde, 3-phenylpropional-
dehyde, butyraldehyde, 3-methylbutanal, and diisopropylethylamine
(DIPEA) were obtained from Sigma–Aldrich. Solvents for nuclear mag-
netic resonance (NMR) measurements were purchased from Sigma-
–Aldrich and stored over 3-Å molecular sieves. Various solvents, such as
methanol (MeOH), dichloromethane (CH2Cl2), diethyl ether, ethanol, n-
hexane (n-hex), and ethyl acetate (EtOAc), were purchased from high-
grade commercial suppliers and used as received.
2.3.1. Synthesis of L1
2-Thiophenecarboxaldehyde (0.8 g, 7.0 mmol) was added to a so-
lution of CMN (1.8 g, 7.0 mmol) in MeOH (95%, 50 mL). The reaction
mixture was refluxed for 4 days. The solvent was removed to obtain a
yellow oil as the imine product (2.4 g, 6.8 mmol, yield 98%). The imine
product was reduced by dissolving in MeOH (95%, 50 mL) followed by
the addition of NaBH4 (0.6 g, 17.0 mmol). After stirring for 12 h, the
solvent was evaporated and the resulting crude solid was treated with
distilled water (10 mL). The organic layer was extracted with CH2Cl2
(30 mL). The solvent was evaporated to obtain a light-yellow oil as the
final product (2.40 g, yield 98%). Analysis calculated for C22H26Cl2N2S
1
(%): C, 75.38; H, 7.48; N, 7.99. Found: C, 75.35; H, 7.47; N, 7.95. H
NMR (CDCl3, 500 MHz, 298 K): δ = 7.83–7.76 (m, 4H, Naph-CH),
7.50–7.43 (m, 3H, Naph-CH), 7.21–7.19 (m, 1H, Thiophen-CH), 6.95
(m, 1H, Thiophen-CH), 6.91 (m, 1H, Thiophen-CH), 4.13 (d, J = 14 Hz,
1H, CHACHB), 4.09 (d, J = 13.4 Hz, 1H, CHcCHd), 3.89 (d, J = 14 Hz, 1H,
CHACHB), 3.85 (d, J = 13.4 Hz, 1H, CHcCHd), 2.38–2.26 (m, 2H, Cy-H),
Proton (1H; operating at 500 MHz) and carbon-13 (13C; operating at
125 MHz) NMR spectra were recorded on a Bruker Avance Digital 500-
NMR spectrometer (Bruker, Billerica, MA). Chemical shifts are reported
in δ units relative to residual 1H in the deuterated solvent (CDCl3, δ =
7.26 ppm). Coupling constants are reported in Hertz (Hz). Data are re-
ported as m = multiplet, br = broad, s = singlet, d = doublet, t = triplet,
and q = quartet. Fourier transform-infrared (FTIR) spectra of neat
samples were recorded on a Bruker FT/IR-Alpha instrument, and the
data are reported in cmꢀ 1. Elemental analyses were determined using
the EA 1108 Elemental Analyzer at the Chemical Analysis Laboratory of
the Center for Scientific Instruments of Kyungpook National University.
Enantiomeric excess was determined by HPLC using Chiralcel OD-H and
Chiralpak AD-H columns with various proportions of HPLC-grade iso-
propanol (IPA) and n-hexane as eluting solvents. The ligands designed in
the current study are the thiophene derivatives of (1R,2R)-N1-(naph-
thalen-2-ylmethyl)cyclohexane-1,2-diamine: (1R,2R)-N1-(naphthalen-
2-ylmethyl)–N2-(thiophen-2-ylmethyl)cyclohexane-1,2-diamine (L1),
(1R,2R)-N1-((5-methylthiophen-2-yl)methyl)–N2-(naphthalen-2-
ylmethyl)cyclohexane-1,2-diamine (L2), and (1R,2R)-N1-(naphthalen-
2-ylmethyl)–N2-(thiophen-3-ylmethyl)cyclohexane-1,2-diamine (L3).
–
2.24–2.13 (m, 2H, Cy-H), 1.93 (br, 2H, N H), 1.74 (m, 2H, Cy-H),
1.27–1.21 (m, 2H, Cy-H), 1.13–0.99 (m, 2H, Cy-H) ppm. 13C NMR
(CDCl3, 125 MHz, 298 K): δ = 145.3, 138.5, 133.5, 132.6, 127.9, 127.7,
127.6, 126.7, 126.5, 126.26, 125.9, 125.4, 124.3, 124.2, 60.7, 60.6,
50.9, 45.6, 31.6, 25.06, 24.9. IR (liquid neat; cmꢀ 1):
ν(N-H) 3299 (w);
(sp3 C-H) 2925 w;
ν(C C) 1654 m; ν(C C)antisym and (C C)sym
– –
– –
–
ν
–
ν
1508 w and1447 w; δ(-C-H sp3) 1359 m;
ν
2
– –
(N C) 1211 m; δ(C H sp )
815 w.
2.3.2. Synthesis of L2
An analogous method to that described for L1 was adopted for the
synthesis of L2 except using CMN (1.8 g, 7.0 mmol) and 5-methylthio-
phene-2-carboxaldehyde (0.90 g, 7.0 mmol). The imine product (2.5
g, 6.8 mmol) was treated with NaBH4 (0.6 g, 17 mmol) to obtain the
amine product as a yellow oil (2.5 g, 6.8 mmol, yield 98%). Analysis
calculated for C23H28N2S (%): C, 75.78; H, 7.74; N, 7.68. Found: C,
75.77; H, 7.73; N, 7.65. 1H NMR (CDCl3, 500 MHz, 298 K): δ =
7.84–7.79 (m, 4H, Naph-CH), 7.52–7.43 (m, 3H, Naph-CH), 6.87–6.68
(m, 1H, Thiophene-CH), 6.66–6.57 (m, 1H, Thiophene-CH), 4.09 (d, J =
13.4 Hz, 1H, CHACHB), 4.04 (d, J = 14 Hz, 1H, CHcCHd), 3.84 (d, J =
13.4 Hz, 1H, CHACHB), 3.81 (d, J = 14 Hz, 1H, CHcCHd), 2.44 (s, 3H,
Thiophene-CH3), 2.37–2.32 (m, 1H, Cy-H), 2.30–2.25 (m, 1H, Cy-H),
2.2. Synthesis of CMN [(1R,2R)-N1-(naphthalen-2-ylmethyl)
cyclohexane-1,2-diamine]
2-Naphthaldehyde (7.02 g, 45.0 mmol) solution in CH2Cl2 (200 mL)
was added dropwise into (1R,2R)-(+)-1,2-cyclohexanediamine L-
Tartrate (12.0 g, 45.0 mmol) solution of 2 N NaOH (30 mL). After being
stirred for 3 days, the organic layer was extracted and over MgSO4. The
solution was concentrated to get imine product as ivory solid (10.3 g,
40.9 mmol). For reduction of imine moiety, the above mentioned ivory
solid (10.3 g, 40.9 mmol) was dissolved in MeOH (95%, 100 mL) fol-
lowed by the addition of NaBH4 (2.32 g, 61.3 mmol) slowly and stirred
for 12 h. The solvent as removed and the resultant residue was treated
with distilled water (10 mL) to get rid of any excess NaBH4. The product
was extracted with CH2Cl2 (30 mL) and the organic layer was dried over
MgSO4. The solvent was removed to get crude yellow oil which was
purified by column (EA: MeOH, 3:1, Rf = 0.28 (mono-sub), 0.57 (di-
sub)) to provide pure (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclohexane-
1,2-diamine. (Yellow oil, 4.68 g, 18.4 mmol, 40% yield). 1H NMR
(CDCl3, 500 MHz, 298 K): δ = 7.83–7.75 (m, 4H, naph-CH), 7.48–7.43
(m, 3H, naph-CH), 4.11 (d, J = 13.1 Hz, 1H, NHCHaHb), 3.87 (d, J =
13.4 Hz, 1H, NHCHaHb), 2.44–2.39 (m, 1H, Cy-CH), 2.22–2.11 (m, 2H,
–
2.23–2.19 (m, 1H, Cy-H), 2.16–2.13 (m, 1H, Cy-H), 1.96 (br, 2H, N H),
1.75–1.72 (m, 2H, Cy-H), 1.27–1.21 (m, 2H, Cy-H), 1.14–1.00 (m, 2H,
Cy-H). 13C NMR (CDCl3, 125 MHz, 298 K): δ = 142.7, 138.6, 138.5,
133.4, 127.9, 127.6, 126.6, 126.2, 125.82, 125.4, 125.3, 124.7, 124.4,
124.1, 60.7, 60.3, 52.6, 50.91, 45.9, 31.5, 25.0, 15.5, 15.3. IR (liquid
neat; cmꢀ 1):
ν
(N-H) 3305 (w);
ν
(sp3 C-H) 2925 w;
ν
(C C) 1627 m;
–
–
3
–
–
–
ν
(C C)antisym and
ν
(C C)sym 1525 w and 1448 w; δ(-C-H sp ) 1357
–
2
– –
m;
ν(N C) 1226 m; δ(C H sp ) 854 w.
2.3.3. Synthesis of L3
An analogous method to that described for L1 was followed to syn-
thesize L3 except using CMN (1.8 g, 7.0 mmol) and 3-thiophenecarbox-
aldehyde (0.8 g, 7.0 mmol) to obtain the imine product (2.4 g, 6.8 mmol,
yield 98%). Further reduction of the imine product (2.4 g, 6.8 mmol)
with NaBH4 (0.6 g, 17 mmol) was done to obtain the final product as a
yellow oil (2.40 g, yield 98%). Analysis calculated for C22H26N2 (%): C,
2

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
75.38; H, 7.48; N, 7.99. Found: C, 75.37; H, 7.45; N, 7.97. 1H NMR
(CDCl3, 500 MHz, 298 K): δ = 7.84–7.76 (m, 4H, Naph-CH), 7.49–7.44
(m, 3H, Naph-CH), 7.28–7.26 (m, 1H, Thiophen-CH), 7.13–7.12 (m, 1H,
Thiophen-CH), 7.06–7.05 (m, 1H, Thiophen-CH), 4.08 (d, J = 13.4 Hz,
1H, NCHaHb), 3.94 (d, J = 13.0 Hz, 1H, NCHcHd), 3.84 (d, J = 13.3 Hz,
1H, NCHaHb), 3.70 (d, J = 13.4 Hz, 1H, NCHcHd), 2.32–2.29 (m, 2H, Cy-
CH2), 2.24–2.20 (m, 1H, Cy-CH), 2.17–2.13 (m, 1H, Cy-CH), 1.97 (br,
2H, NH), 1.77–1.72 (m, 2H, Cy-CH2), 1.28–1.22 (m, 2H, Cy-CH2),
1.11–1.01 (m, 2H, Cy-CH2). 13C NMR (CDCl3, 125 MHz, 298 K): δ =
141.9, 138.4, 133.4, 132.6, 127.9, 127.6, 127.6, 127.5, 126.6, 126.2,
except the disordered atoms and all hydrogen atoms were positioned
geometrically using the riding model with fixed isotropic thermal fac-
tors. The crystallographic data and refinements of the complexes are
summarized in Table S1.
2.5. Asymmetric Henry reaction
A 25-mL flask was charged with 10 mol% of a dichloro Cu(II) com-
plex [LnCuCl2] (Ln = L1–L3) in 10 mL of IPA and treated with silver
acetate to generate the diacetato Cu(II) complex in situ; the resulting
solution was applied to the Henry reaction. Then, nitromethane (0.53
mL, 10 mmol) and aldehyde (5.0 mmol) were added, followed by
addition of 10.0 mol% of DIPEA as co-catalyst due to its good activity at
–20 ◦C [30,46]. After stirring for a specified time, reactions were
quenched with 1.0 mL of 1 N HCl solution and then evaporated to
dryness. The products were extracted by CH2Cl2 (3 × 20 mL), dried over
anhydrous MgSO4, and concentrated under reduced pressure. The crude
products were purified by column chromatography. Yields of isolated
products (β-nitroalcohols) are based on weight obtained. The purity of
isolated product were assessed by 1H NMR spectroscopy. The enantio-
meric excess was determined by chiral HPLC analysis using Chiralpak
AD-H and Chiralcel OD-H columns.
125.9, 125.6, 125.4, 121.1, 60.8, 60.7, 50.9, 45.8, 31.5, 31.3, 24.9, 24.9.
IR (liquid neat; cmꢀ 1):
ν
(N-H) 3298 (w);
ν
(sp3 C-H) 2925 w;
ν
(C C)
–
–
–
–
–
1667 m;
ν
(C C)antisym and
ν
(C C)sym 1508 w and 1448 w; δ(-C-H
–
sp3) 1336 m;
ν
2
– –
(N C) 1243 m; δ(C H sp ) 814 w.
2.3.4. Synthesis of [L1CuCl2]
A solution of L1 (1.0 g, 2.8 mmol) in CH2Cl2 (10 mL) was treated with
a solution of CuCl2⋅2H2O (0.5 g, 2.8 mmol) in CH2Cl2 and stirred for 12 h
at ambient temperature. The blue-green precipitate was isolated by
filtration and oven-dried at 60 ◦C to obtain a crystalline solid as the final
product (98% yield). Single crystals suitable for X-ray diffraction anal-
ysis were grown by slow evaporation of MeOH solution of [L1CuCl2].
Analysis calculated for C22H26Cl2CuN2S (%): C, 54.48; H, 5.40; N, 5.78.
Found: C, 54.38; H, 5.42; N, 5.79. IR (liquid neat; cmꢀ 1):
ν(N-H) 3216
2.5.1. (S)-1-phenyl-2-nitroethanol
–
ν
–
(w);
ν
(sp3 C-H) 2933 w;
ν(C C) 1630 m; ν(C C)antisym and (C C)
– –
– –
The crude products were purified by column chromatography (30%
EtOAc/n-hexane) to provide (S)-1-phenyl-2-nitroethanol as a colorless
sym 1518 w and 1448 w; δ(-C-H sp3) 1365 m;
ν
(N C) 1282 m; δ(C
–
–
H
sp2) 823 w;
ν(Mꢀ N) 655 s.
1
oil [20]. H NMR (500 Hz, CDCl3): δ 7.30 (5H, m, Ph), 5.38 (1H, dd,
–CH), 4.51(1H, dd, –CH2), 4.41 (1H, dd, –CH2), 2.89 (1H, br s, –OH)
ppm. The enantiomeric excess was determined using HPLC on a Chir-
alcel OD-H column (n-hex:IPA 95:5; flow rate 1.5 mL/min; λ = 215 nm);
R enantiomer tr = 17.1 min, S enantiomer tr = 21.5 min.
2.3.5. Synthesis of [L2CuCl2]
An analogous method to that described for [L1CuCl2] was adopted
for the synthesis of [L2CuCl2], except using L2 and CuCl2⋅2H2O (0.5 g,
2.8 mmol) to obtain a blue-green solid as the final product (98% yield).
Single crystals suitable for X-ray diffraction analysis were grown by slow
evaporation of MeOH solution of [L2CuCl2]. Analysis calculated for
2.5.2. (S)-1-nitro-4-phenylbutan-2-ol
The crude products were purified by column chromatography (10%
EtOAc/n-hexane) to provide (S)-1-nitro-4-phenylbutan-2-ol as a color-
less oil [23,39,47]. 1H NMR (500 Hz, CDCl3): δ 7.30 (5H, m, Ar–H), 5.38
(1H, dd, –CH), 4.51(1H, dd, –CH2), 4.41 (1H, dd, –CH2), 2.89 (1H, br, s,
–OH) ppm. The enantiomeric excess was determined using HPLC on
Chiralcel OD-H column (n-hex:IPA 90:10; flow rate 1.0 mL/min; λ =
254 nm); R enantiomer tR (minor) = 11.8 min, S enantiomer tR (major)
= 14.8 min.
C
23H28Cl2CuN2S (%): C, 55.36; H, 5.66; N, 5.61. Found: C, 55.33; H,
5.65; N, 5.59. IR (liquid neat; cmꢀ 1):
ν
(N-H) 3212 (w);
ν
(sp3 C-H) 2935
–
–
–
–
w; ν(C C) 1600 m; ν(C C)antisym and ν(C C)sym 1518 w and 1444
– –
w; δ(-C-H sp3) 1365 m;
ν
(N C) 1268 m; δ(C H sp ) 865 w; ν(Mꢀ N)
2
– –
698 s.
2.3.6. Synthesis of [L3CuCl2]
An analogous method to that described for [L1CuCl2] was adopted
for the synthesis of [L3CuCl2], except using L3 and CuCl2⋅2H2O (0.5 g,
2.8 mmol) to obtain a blue-green solid as the final product (98% yield).
Single crystals suitable for X-ray diffraction analysis were grown by slow
evaporation of MeOH solution of [L3CuCl2]. Analysis calculated for
2.5.3. (S)-1-nitropentan-2-ol
The crude products were purified by column chromatography (5%
EtOAc/n-hexane) to provide (S)-1-nitropentan-2-ol as a light yellow oil
[48]. 1H NMR (CDCl3): 0.98 (3H, t, J = 6.9 Hz), 1.50–1.59 (4H, m), 2.53
(1H, br s), 4.35–4.46 (3H, m) ppm. HPLC analysis: Chiralpak AD-H
column (n-hexane:IPA 98:2), flow rate 1.0 mL/min, 215 nm); R enan-
tiomer tR (minor) = 63.7 min, S enantiomer tR (major) = 103.3 min.
C
22H26Cl2CuN2S (%): C, 54.48; H, 5.40; N, 5.78. Found: C, 54.45; H,
5.42; N, 5.81. IR (liquid neat; cmꢀ 1):
ν
(N-H) 3157 (w);
ν
(sp3 C-H) 2937
–
–
–
–
w; ν(C C) 1600 m; ν(C C)antisym and ν(C C)sym 1509 w and 1448
– –
w; δ(-C-H sp3) 1365 m;
ν
(N C) 1264 m; δ(C H sp ) 859 w; ν(Mꢀ N)
2
– –
699 s.
2.5.4. (S)-4-methyl-1-nitropentan-2-ol
The crude products were purified by column chromatography (5%
EtOAc/n-hexane) to provide (S)-4-methyl-1-nitropentan-2-ol as a light
yellow oil [49]. 1H NMR (CDCl3): 0.95–1.01 (m, 6H, –CH(CH3)2),
1.21–1.30 (m, 1H, –CH2–), 1.50–1.56 (m, 1H, –CH2–), 1.81–1.91 (m, 1H,
–CH–), 2.50 (brs, 1H, –OH), 4.37–4.45 (m, 3H, –CH2NO2, –CHOH–)
ppm. HPLC analysis: Chiralpak AD-H column (n-hexane:IPA 95:5, flow
rate 0.5 mL/min, λ = 210 nm); R enantiomer tR (minor) = 27.42 min, S
enantiomer tR (major) = 37.22 min.
2.4. X-ray crystallographic studies
X-ray-quality single crystals were mounted in thin-walled glass
capillaries on an Enraf-Noius CAD-4 diffractometer with Mo Kα radia-
tion (λ = 0.71073 Å). Unit cell parameters were determined by least-
squares analysis of 25 reflections. Intensity data were collected in the
ω
/2θ scan mode, and three standard reflections were monitored every
hour during data collection. Empirical absorption corrections with
-scans were performed on the data using the ABSCALC program [43].
ψ
3. Results and discussion
The structures were solved using direct methods and refined by full-
matrix least-squares techniques on F2 using the SHELXL-97 and
SHELXS-97 program packages [44,45]. Absolute structures were
confirmed using anomalous dispersion effects with Friedel pairs, which
were not merged. All non-hydrogen atoms were refined anisotropically,
3.1. Synthetic methods and physical properties
The C1-symmetric derivatives served as an important building block
and provided metal complexes of variable coordination geometries and
3

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
nuclearities. Scheme 1 illustrates the synthesis of ligands via the
condensation reaction of (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclo-
hexane-1,2-diamine[42] with 2- or 3-thiophenecarboxyaldehyde and 5-
methyl-2-thiophenecarboxyaldehyde. Treatment of the imine with a
stoichiometric amount of reducing agent in MeOH yielded the corre-
sponding diamines (Scheme 1). The structures of the resulting ligands
were characterized by 1H and 13C NMR, and elemental analysis. The
(–CH2–) unit of the thiophene ring and amine moiety appeared as a set of
four doublets at 4.13–3.85 for L1, 4.09–3.81 for L2, and 4.08–3.70 ppm
for L3 (Fig. S1–S3). The 1H NMR spectrum of L2 clearly indicated a
singlet at 2.44 ppm corresponding to the methyl protons attached to the
thiophene ring. Similarly, the 13C NMR spectra (Fig. S4–S6) of the li-
gands showed peaks that were consistent with the ligand formulation.
The direct coordination of these ligands to CuCl2⋅2H2O at the 1:1 M
ratio furnished the corresponding dichloro Cu(II) complexes [LnCuCl2]
(Ln = L1–L3) in high yield (98%) (Scheme 2). The FTIR spectra of the
ligands (Ln = L1–L3) were compared with those of the corresponding Cu
(II) complexes (Figs. S7–S12). Characteristic bands assigned to the sp3
and could be stored for months at room temperature without appre-
ciable degradation.
3.2. Single-crystal X-ray studies
Single-crystal X-ray crystallographic analysis were carried out to
determine the geometries of the obtained Cu(II) complexes. Slow
evaporation of MeOH solutions of the complexes provided crystals
suitable for X-ray analysis. The ORTEP diagrams of [L1CuCl2],
[L2CuCl2], and [L3CuCl2] are presented in Figs. 1–3, and the bond
lengths and angles of the complexes are provided in Table 1. The
[LnCuCl2]⋅CH3OH (Ln = L1 – L3) complexes crystallized in the ortho-
rhombic crystal system with P212121 space group.
The central metal atom in [LnCuCl2] (Ln = L1–L3) was tetra-
coordinated and adopted a square-planar geometry. The Cu–Namine
bond lengths were in the range of 2.032(2)–2.0652(1) Å [20,21]. There
was a slight difference between the Cu–N(1) and Cu–N(2) lengths, which
might be due to the different substituents attached to the nitrogen atoms
of the (R,R)-1,2-diaminocyclohexane backbone. However, these geo-
metric parameters are within the acceptable range reported for similar
Cu(II) complexes [20,21,39,51]. The Cu–N(2) bond length increased by
approximately 0.013 Å in the order [L3CuCl2] < [L1CuCl2] <
[L2CuCl2]. These results are in agreement with our previously reported
Cu(II) complex [52], in which the presence of methyl substituents at the
thiophene moieties affected the bond lengths. The average Cu–Cl bond
length was 2.3290 Å, which is consistent with structural data obtained
for similar Cu(II) complexes [53].
–
–
(N H) and ν(C C) bond stretching vibrations were observed at
–
ν
2865–2949 and 1638–1663 cmꢀ 1, respectively, in [LnCuCl2] (Ln
=
1
3
–
L –L ). The symmetric and antisymmetric v(C C) stretching vibration
–
–
–
–
bands, νsym(C C) and νasym(C C), of the thiophene ring appeared at
–
1456, 1467, and 1510 cmꢀ 1. The
ν
–
(N H) bands assigned to the amine
moieties were shifted to lower wavenumbers in the spectra of the Cu(II)-
complexes compared with the corresponding ligands, which suggested
back-donation and the participation of nitrogen atoms in bonding [50].
3
2
–
Similarly, the typical sp and sp v(C H) stretching bands appeared at
the frequencies reported in the literature. The presence of these ab-
sorption bands confirmed the involvement of amine nitrogens in
chelating the Cu(II) center. Additionally, elemental analysis data for the
synthesized Cu(II) complexes were consistent with the structures pro-
posed in Scheme 2. The synthesized Cu(II) complexes were stable in air
However, these lengths are slightly shorter than the Cu–Clterminal
lengths reported for Cu(II) complexes bearing C2-symmetric ligands,
such as N,N′-di(methoxybenzyl)-(R,R)-1,2-diaminocyclohexane Cu(II)
dichloride [20], (R,R)-N,N′-(bis)methyl-naphthalenylmethyl-1,2-dia-
minocyclohexanes [52], and bis(5-methylthiophene-2-ylmethyl)
Scheme 1. Synthetic route of thiophene derived ligands (Ln = L1–L3) based on (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclohexane-1,2-diamine framework.
4

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
Scheme 2. Synthesis of C1-symmetric Cu(II)-complexes, [LnCuCl2] (Ln = L1 – L3), based on thiophene derivatives of (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclo-
hexane-1,2-diamine.
Fig. 2. An ORTEP drawing of [L2CuCl2] with thermal ellipsoids at 50%
probability.
Fig. 1. An ORTEP drawing of [L1CuCl2] with thermal ellipsoids at 50%
probability.
cyclohexane-1,2-diamine Cu(II) dichloride [21]. The data in Table 1
indicate that the Cu–Cl(2) bond length is longer in [L2CuCl2] than in its
[L1CuCl2] analog. This discrepancy is attributed to the methyl sub-
stituents attached to the thiophene moiety in [L2CuCl2].
The N(2)–Cu(1)–N(1) and N(3)–Cu(1)–N(2) bond angles in
[LnCuCl2] (Ln = L1–L3) ranged from 78.89(2)◦ to 82.08(2)◦ and were
affected by the substitution of the five-membered chelate ring [39,53].
The Cu center was attached to the (R,R)-1,2-diaminocyclohexane
backbone derivative in a bidentate fashion and resulted in the formation
of a five-membered chelate ring.
The average Namine–Cu–Namine bond angles for [LnCuCl2] (Ln
=
L1–L3) were in the range of 83.92(2)–84.31(6)◦ and hence deviated
slightly from the 90◦ angle of an ideal square-planar geometry. Simi-
larly, the Namine–Cu–Clterminal angles were 97.49(11)◦ for [L1CuCl2],
97.40(6)◦ for [L2CuCl2], and 96.02(7)◦ for [L3CuCl2], which are
reminiscent of similar square-planar tetra-coordinated Cu(II) complexes
Fig. 3. An ORTEP drawing of [L3CuCl2] with thermal ellipsoids at 50%
probability.
5

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
3.3. Catalytic activities of Cu(II) complexes in the Henry reaction
Table 1
Selected bond lengths (Å) and angles (◦) of [LnCuCl2] (Ln = L1–L3).
[L1CuCl2].CH3OH
[L2CuCl2].CH3OH
[L3CuCl2].CH3OH
Our current work is targeted toward the C1-symmetric Cu(II)-
catalyzed asymmetric Henry reaction because of the diverse structural
properties of asymmetrical ligand frameworks [54,55]. The catalytic
activity of the diacetato derivatives, generated in situ, of the synthesized
Cu(II) complexes in the asymmetric Henry reaction between nitro-
methane and various aldehydes with 10 mol% of DIPEA as base additive
in IPA at –20 ◦C was examined (Scheme 3, Table 2). The use of DIPEA as
a base for the asymmetric Henry reaction is well documented, and
negligible product was observed when the reaction proceeded in the
absence of DIPEA. It has been suggested that transition metal complexes
(acting as Lewis acids) are not powerful enough to form bonds through
the single activation of nucleophiles; thus, deprotonation of a nucleo-
phile precursor with an amine base is needed to activate the reaction
[56]. We previously reported that 10 mol% of DIPEA as promoter
ensured the best results in term of yields and enantioselectivities of the
corresponding β-nitroalcohol with copper acetate complexes [LnCu
(OAc)2] (Ln = L1–L3).21
Bond Lengths (Å)
Cu-N1
2.026(5)
2.034(5)
2.228(4)
2.2273(1)
1.493(7)
1.481(7)
1.484(8)
1.481(7)
2.013(4)
2.038(4)
2.2284(15)
2.2304(15)
1.511(6)
1.478(5)
1.481(6)
1.485(5)
2.009(4)
2.025(4)
2.2226(17)
2.2240(16)
1.487(6)
1.491(6)
1.491(6)
1.488(6)
Cu-N2
Cu-Cl1
Cu-Cl2
N1-C1
N2-C2
N1-C7
N2-C18
Bond Angles (◦)
N1-Cu1-N2
N2-Cu1-Cl2
N2-Cu1-Cl1
N1-Cu1-Cl2
N1-Cu1-Cl1
Cl2-Cu1-Cl1
C7-N1-Cu1
83.91(19)
93.60(14)
150.77(17)
159.09(17)
97.72(17)
97.49(11)
115.2(5)
84.04(15)
93.56(11)
157.70(11)
157.66(11)
92.82(11)
97.40(6)
84.31(15)
94.06(11)
154.96(13)
159.31(13)
93.94(12)
96.02(7)
115.8(3)
116.3(3)
C18-N2-Cu1
118.0(4)
116.6(3)
114.7(4)
The screening of complexes toward benzaldehyde and nitromethane
revealed lower yields of the resulting 2-nitro-1-phenylethanol, with
activity increasing in the order [L1Cu(OAc)2] < [L2Cu(OAc)2] <
[L3Cu(OAc)2], whereas the enantioselectivities increased in the order
[L2Cu(OAc)2] < [L1Cu(OAc)2] < [L3Cu(OAc)]. No significant change
in yield (>98%) of the resulting β-nitroalcohols was observed with
[LnCu(OAc)2] (Ln = L1–L3) when 3-phenylpropanal was used as a
substrate, with [L3Cu(OAc)2] showing superior enantioselectivity
(>99%) (Table 2) (Figs. S13–S24). These results are consistent with our
[53]. Additionally, the complexation of the metal to the ligand frame-
work with the stereogenic centers RC, RC derived from a (R,R)-1,2dia-
minocyclohexane backbone resulted in hindering nitrogen atom
inversion and thus induced chirality therein. [LnCuCl2] (Ln = L1–L3)
were obtained as enantiopure complexes in which both nitrogens have
the RN configuration. The hydrogen atoms of the stereogenic carbons
and nitrogens in [LnCuCl2] (Ln = L1–L3) were in the head-to-tail
conformation.
Scheme 3. Henry reaction of different aldehydes with CH3NO2 catalysed by [LnCu(OAc)2] (Ln = L1–L3) at –20 ◦C in the presence of 10 mol% of DIPEA.
6

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
Table 2
Screening diacetato Cu(II) complexes supported with (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclohexane-1,2-diamine derivatives in asymmetric Henry reaction.
Catalyst
Entry
Aldehydes
Time (days)
Yields (%)b
ee(%)c
Config.d
Blank
e1
e2
f3
Me-NO2
Me-NO2
Me-NO2
Ph-(CH2)2C(O)H
Ph-(CH2)2C(O)H
Ph-(CH2)2C(O)H
4
1
1
60
80
82
–
–
–
–
–
–
1
2
3
4
5
6
7
Me-NO2
Me-NO2
Me-NO2
Me-NO2
Ph-C(O)H
4
1
1
1
62
98
99
93
84
99
83
74
S
S
S
S
Ph-(CH2)2C(O)H
CH3(CH2)2C(O)H
(CH3)2CHCH2C(O)H
8
Me-NO2
Me-NO2
Me-NO2
Me-NO2
Ph-C(O)H
4
1
1
1
68
98
99
94
77
90
88
88
S
S
S
S
9
Ph-(CH2)2C(O)H
CH3(CH2)2C(O)H
(CH3)2CHCH2C(O)H
10
11
12
13
14
15
Me-NO2
Me-NO2
Me-NO2
Me-NO2
Ph-C(O)H
4
1
1
1
90
99
99
99
85
S
S
S
S
Ph-(CH2)2C(O)H
CH3(CH2)2C(O)H
(CH3)2CHCH2C(O)H
>99
82
83
a 1 = [L1Cu(OAc)2], 2 = [L2Cu(OAc)2], 3 = [L3Cu(OAc)2], 0.50 mmol of Cu(II)-initiator, 5.0 mmol aldehyde, 10.0 mmol of CH3NO2,10 mol% of DIPEA, solvent IPA
c
(10 mL), temperature ꢀ 20 ◦C.b Yields defined as weight of isolated β-nitro alcohols. Enantiomeric excess (ee) was determined by chiral HPLC analysis using a
Chiralcel OD-H and Chiralpak AD-H columns as per the reported protocol [20,23,47–49].d S enantiomer was the major product [59–61].e Experiments conducted in the
absence of catalysts (blank reaction), 5.0 mmol aldehyde, 10.0 mmol of CH3NO2,10 mol% of DIPEA, solvent IPA (10 mL), temperature ꢀ 20 ◦C . f Reaction performed in
the absence of base DIPEA produced nitroalcohols with 82% yields with very low enantiomeric excess.
previous findings that unsymmetrical naphthyl derivatives of the (R,R)-
1,2-diaminocyclohexane backbone showed excellent activity (99% in
24 h) and unusually high enantioselectivity (>99%) for the reaction
between 3-phenylpropanal and nitromethane yielding (S)-1-nitro-4-
phenylbutan-2-ol [39]. Longer reaction times and inferior enantiose-
lectivities were anticipated for the dichloro Cu(II) complexes compared
to their diacetato counterparts, based on our previous reports. Conse-
quently, the dichloro complexes were not explored for the Henry reac-
tion in our current study [39,53]. A blank reaction of nitromethane and
benzaldehyde/3-phenylpropanal performed in the absence of the C1-
symmetric chiral Cu(II) complexes resulted in mild activity with negli-
gible enantioselectivity (Table 2 entries 1 and 2). Additionally, experi-
ment conducted in the absence of DIPEA produced (S)-1-nitro-4-
phenylbutan-2-ol (Table 2 entry 3) in 88% yield with very low enan-
tiomeric excess, consistent with reported studies [57].
stereo-directing for both butyraldehyde and 3-methyl-butanal (Table 2
entries 10 and 11).
Interestingly, the Henry reaction catalyzed by these Cu(II) catalytic
species resulted in the corresponding β-nitroalcohols with an (S)-
configuration at the stereogenic center. This configuration may be due
to the favorable orientation of the phenyl group of the aldehydes and the
aromatic moieties of the ligand architecture [12,58–60]. The stereo-
chemical outcomes (S)-enantiomer of the Henry reaction with these
diacetato Cu(II) complexes are in agreement with the previous studies
[5,12,25,39,61]. In this mechanism, the carbonyl oxygen atom is coor-
dinated at one of the equatorial positions and the oxygen atom of
nitromethane approaches the metal center from the axial side. The Re
face (A) of the carbonyl group of the aldehyde is much more accessible
to a nucleophilic group (nitromethane) than the Si face. This positioning
of the reactants seems to be the most favorable orientation, taking into
account steric and electronic considerations of neighboring coordination
sites. Additionally, the attacking group will strongly increase repulsion
between the aldehyde moiety and ligand substituents, as illustrated in
transition state B of Fig. S25 [39]. The illustrated transition states for
These results clearly indicate that [L3Cu(OAc)2] is better stereo-
directing compared with complexes bearing 2-thiophenyl and 5-
methyl-2-thiophene pendant groups for both benzaldehyde and 3-phe-
nypropanal (Table 2, entries 12 and 13). Using [L3Cu(OAc)2] as a
catalyst for 3-phenylpropanal brought excellent activity (99%) and
selectivity (>99%) compared with benzaldehyde under identical
experimental protocols [39]. Compared with our previously studied C2-
symmetric (R,R)-N,N--bis(5-methylthiophen- 2-ylmethyl) cyclohexane-
1,2-diamine based Cu(OAc)2 complex which resulted in 70% yield of
β-nitroalcohol with 92% enantioselectivity from reaction of nitro-
methane and benzaldehyde in the presence of 3 mol% DIPEA as a pro-
moter [21], [L3Cu(OAc)2] with C1-symmetric ligand architecture
exhibited 90% yields for corresponding β-nitroalcohol with 87% ee
(Table 2 entry 12).
Henry reaction are also proposed to be supported by π-π interactions
between the thiophenyl and phenyl moieties of ligand (Figure S25 A),
which is additionally assisted by a charge-assisted hydrogen bonding
(CAHB), as reported previously [62].
Compared with the chiral Cu(II)-complexes bearing L-proline[63]
and core-chiral-bispidine ligands (88% yield; ee 97% in 48 h for 3-phe-
nylpropanal) [64], the [L3Cu(OAc)2] complex displayed superior ac-
tivity, providing (S)-1-nitro-4-phenylbutan-2-ol with excellent
enantioselectivity (99% yield; >99% (S) ee in 24 h; Table 2 entry 13).
Interestingly, [LnCu(OAc)2] (Ln = L1–L3) performed less selectively
toward benzaldehyde; consistent with the reported studies that chiral
catalyst bearing cyclohexane-1,2-diamine ligands exhibits better enan-
tioselectivity with aliphatic aldehydes compared with aromatic ones
[65]. The C1-symmetric Cu(II)-acetate complex bearing the pyridyl de-
rivative of 1,2-diaminocyclohexane studied as an aliphatic aldehyde
demonstrated lower activity and good enantioselectivity; the aldehyde
with the n-butyl alkyl chain provided the corresponding β-nitroalcohol
in 88% yield, 98% ee in 60 h, compared with our current system (94%
yield, 88% ee in 24 h, Table 2 entry 11) [66]. Compared with (1R,2R)-
N1-(4-methylpentan-2-yl)cyclohexane-1,2-diamine/Cu(OAc)2⋅2H2O/
Et3N for aliphatic aldehydes, the corresponding β-nitroalcohols were
obtained in the (S)-configuration in low yields (38–53%) and enantio-
selectivities (75–86%) compared with our studied catalysts [29].
Based on the conditions investigated, the catalytic protocol was
extended to aliphatic aldehydes. The aliphatic aldehydes smoothly
converted into their corresponding β-nitroalcohols with good to excel-
lent yields. The length of the alkyl chain of the aldehyde moiety influ-
enced the activity and enantioselectivity. In aliphatic aldehydes, a
decrease in activity and enantioselectivity was observed with increasing
aldehyde chain length. This contrasts with other findings in which the
enantioselectivity increased with increasing aldehyde chain length [35].
These preliminary results reveal that the electron-donating methyl
substituent in the pendant thiophenyl moiety in the L2 complex signif-
icantly influenced the enantioselectivity of the 4-methyl-1-nitropentan-
2-ol product compared with its analogs lacking methyl substituents in
their respective thiophene moieties. Thus, [L2Cu(OAc)2] was better
7

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
[4] A. Roy, L.A. Reddy, N. Dwivedi, J. Naram, R. Swapna, G.C. Malakondaiah,
M. Ravikumar, D. Bhalerao, T.P. Pratap, P.P. Reddy, Tetrahedron Lett. 52 (2011)
6968–6970.
Similarly, compared with the in situ-generated Cu(II)-triflate complex of
(1S,2R)-2-((5-methylthiophen-2-yl)methylamino-1-phenylpropanol
[35] for aliphatic aldehydes, our current system gave superior results.
Further investigation is being carried out on the catalytic applications of
these complexes for the diastereoselective Henry reaction and other
asymmetric reactions.
[5] Z.L. Guo, Y.Q. Deng, S. Zhong, G. Lu, Tetrahedron Asymmetry 22 (2011)
1395–1399.
[6] Y. Zhou, J. Dong, F. Zhang, Y. Gong, J. Org. Chem. 76 (2011) 588–600.
[7] K. Xu, G. Lai, Z. Zha, S. Pan, H. Chen, Z. Wang, Chem. Eur. J. 18 (2012)
12357–12362.
[8] H. Sasai, T. Suzuki, S. Arai, T. Arai, M. Shibasaki, J. Am. Chem. Soc. 114 (1992)
4418–4420.
4. Conclusions
[9] D.A. Evans, D. Seidel, M. Rueping, H.W. Lam, J.T. Shawand, C.W. Downey, J. Am.
Chem. Soc. 125 (2003) 12692–12693.
We synthesized Cu(II) complexes containing thiophene derivatives of
the (1R,2R)-N1-naphthalylcyclohexane-1,2-diamine framework. The
diacetato complexes were used in the asymmetric Henry reaction of
aromatic and aliphatic aldehydes with nitromethane in the presence of
10 mol% of DIPEA to yield the corresponding β-nitroalcohols. All the
studied C1-symmetric [LnCu(OAc)2] (Ln = L1–L3) complexes proved to
be efficient enantioselective catalysts for the asymmetric Henry reaction
between 3-phenylpropanal and nitromethane, resulting in (S)-1-nitro-4-
phenylbutan-2-ol in high yield (99%), with [L3Cu(OAc)2] being pro-
duced β-nitroalcohols with highest ee (>99%). These results compare
well with the best reported enantioselective Cu(II) catalysts of the Henry
reaction between 3-phenylpropanal and nitromethane. Furthermore,
the screening of [LnCu(OAc)2] (Ln = L1–L3) for aliphatic aldehydes
provided the corresponding β-nitroalcohols in excellent yields (up to
99%) and moderate to high enantioselectivities (up to 88%). With
respect to ee, the best results were obtained with [L2Cu(OAc)2] for
aliphatic aldehydes. This finding is attributed to the electron-donating
effect of the methyl substituent.
[10] S.K. Ginotra, V.K. Singh, Org. Biomol. Chem. 5 (2007) 3932–3937.
[11] H. Mei, X. Xiao, X. Zhao, B. Fang, X. Liu, L. Lin, X. Feng, J. Org. Chem. 80 (2015)
2272–2280.
[12] R. Kowalczyk, L. Sidorowicz, J. Skarzewski, Tetrahedron: Asymmetry 19 (2008)
2310–2315.
[13] N. Sanjeevakumar, M. Periasamy, Tetrahedron: Asymmetry 20 (2009) 1842–1847.
[14] Z. Chunhong, F. Liu, S. Gou, Tetrahedron: Asymmetry 25 (2014) 278–283.
[15] S.V. Malhotra, H.C. Brown, RSC Adv. 4 (2014) 14264–14269.
[16] Y. Xiong, F. Wang, X. Huang, Y. Wen, X. Feng, Chem. Eur. J. 13 (2007) 829–833.
[17] J.D. White, S. Shaw, Org. Lett. 14 (2012) 6270–6273.
[18] M. Kannan, T. Punniyamurthy, Tetrahedron: Asymmetry 25 (2014) 1331–1339.
´
[19] H. Cruz, G. Aguirre, D. Madrigal, D. Chavez, R. Somanathan, Tetrahedron:
Asymmetry 27 (2016) 1217–1221.
[20] S.E. Song, Q.T. Nguyen, J.J. Yu, H.-I. Lee, J.H. Jeong, Polyhedron 67 (2014)
264–269.
[21] J. Cho, G.H. Lee, S. Nayab, J.H. Jeong, Polyhedron 99 (2015) 198–203.
[22] W. Jin, X. Li, Y. Huang, F. Wu, B. Wan, Chem. Eur. J. 16 (2010) 8259–8261.
[23] W. Jin, X. Li, B. Wan, J. Org. Chem. 76 (2011) 484–491.
[24] J.-L. Li, L. Liu, Y.-N. Pei, H.-J. Zhu, Tetrahedron 70 (2014) 9077–9083.
[25] T. Arai, M. Watanabe, A. Yanagisawa, Org. Lett. 9 (2007) 3595–3597.
[26] T. Arai, R. Takash-ita, Y. Endo, M. Watanabe, A. Yanagisawa, J. Org. Chem. 73
(2008) 4903–4906.
¨
¨
[27] A. Chougnet, G. Zhang, K. Liu, D. Haussinger, A. Kagi, T. Allmendinger, W.-
D. Woggon, Adv. Synth. Catal. 353 (2011) 1797–1806.
[28] F. Liu, S. Gou, L. Li, P. Yana, C. Zhao, J. Mol. Catal. A 379 (2013) 163–168.
[29] F. Liu, S. Gou, L. Li, Appl. Organomet. Chem. 28 (2014) 186–193.
[30] G. Blay, E. Climent, I. Fernandez, V. Hernandez-Olmos, J.R. Pedro, Tetrahedron
Asymmetry 18 (2007) 1603–1612.
CRediT authorship contribution statement
Juhyun Cho: Conceptualization, Data curation, Formal analysis.
Jong Hwa Jeong: Funding acquisition, Investigation, Methodology,
Project administration. Hyosun Lee: Validation, Visualization, Writing -
original draft. Jungkyu K. Lee: Resources, Software, Supervision. Saira
Nayab: Writing - review & editing.
[31] T. Arai, R. Takashita, Y. Endo, M. Watanabe, A. Yanagisawa, J. Org. Chem. 73
(2008) 4903–4906.
[32] G. Qi, Y.Q. Ji, Z.M.A. Judeh, Tetrahedron 66 (2010) 4195–4205.
[33] L. Filippova, Y. Sten-strøm, T.V. Hansen, Molecules 20 (2015) 6224–6236.
[34] A. Noole, K. Lippur, A. Metsala, M. Lopp, T. Kanger, J. Org. Chem. 75 (2010)
1313–1316.
[35] A.E. Aydin, Appl. Organometal. Chem. 27 (2013) 283–289.
[36] T. Arai, K. Suzuki, Syn. Lett. (2009) 3167–3170.
Declaration of Competing Interest
[37] I. Panov, P. Drabina, Z. Padelkova, P. Simune, M. Sedlak, J. Org. Chem. 78 (2011)
4787–4793.
´
´
´
´
[38] G. Novakova, P. Drabina, B. Frumarova, M. Sedlak, Adv. Synth. Catal. 358 (2016)
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
2541–2552.
[39] M.K. Chun, S. Nayab, J.H. Jeong, Appl. Organometal. Chem. 33 (2019), e4955.
[40] W. Mansawat, I. Saengswang, P. Uprasitwong, W. Banthumnavin, T. Vilaivan,
Tetrahedron Lett. 48 (2007) 4235–4238.
[41] M. Bandini, E. Cabiddu, P. Olivelli, R. Sinisi, A. Umani-Ronchi, M. Usai, Chirality
21 (2009) 239–244.
Acknowledgments
[42] J. Cho, J.H. Jeong, H.J. Shin, K.S. Min, Polyhedron 187 (2020), 114643.
[43] P. McArdle, P. Daly, ABSCALC, National University of Ireland, Galway, Ireland,
1999.
This research was supported by the National Research Foundation
(NRF) of Republic of Korea, funded by the Ministry of the Education,
Science, and Technology (MEST) (Grant No. 2019R1A2C1088654). This
work also was supported by the Technology Innovation Program (TIP #
20011123, Development of Cyclic Olefin Polymer(COP) with High Heat
Resistance and High Transmittance) funded by the Korea Evaluation
Institute of Industrial Technology (KEIT) and the Ministry of Trade,
Industry & Energy (MOTIE, Republic of Korea). This work has also been
supported by National Research Programme for Universities (NRPU)
Grant No. 6840-KP, funded by the Higher Education Commission (HEC),
Islamic Republic of Pakistan.
[44] G.M. Sheldrick, Acta Crystallogr. Sect. A 64 (2008) 112–122.
[45] G.M. Sheldrick, Acta Crystallogr. Sect. C 71 (2015) 3–8.
[46] B. Qin, X. Xiao, X. Liu, J. Huang, Y. Wen, X. Feng, J. Org. Chem. 72 (2007)
9323–9328.
[47] G. Lai, F. Guo, Y. Zheng, Y. Fang, H. Song, K. Xu, S. Wang, Z. Zha, Z. Wang, Chem.
Eur. J. 17 (2011) 1114–1117.
[48] Y.Q. Ji, G. Qi, Z.M.A. Judeh, Tetrahedron Asymmetry 22 (2011) 929–935.
[49] Y. Shi, Y. Li, J. Sun, Q. Lai, C. Wei, Z. Gong, Q. Gu, Z. Song, Appl. Organometal.
Chem. 29 (2015) 661–667.
[50] N.M. Hosny, Synth. React. Inorg Met.-Org. Nano-Metal Chem. 41 (2011) 736–742.
[51] Q.T. Nguyen, J.H. Jeong, Polyhedron 27 (2008) 3227–3230.
[52] K.S. Kwon, J. Cho, S. Nayab, J.H. Jeong, Inorg. Chem. Commun. 55 (2015) 36–38.
[53] S.H. Ahn, M.K. Chun, E. Kim, J.H. Jeong, S. Nayab, H. Lee, Polyhedron 127 (2017)
51–58.
Appendix A. Supplementary data
[54] P. Kocovský, S. Vyskocil, M. Smrcina, Chem. Rev. 103 (2003) 3213–3246.
´
[55] S. Castillon, C. Claver, Y. Díaz, Chem. Soc. Rev. 34 (2005) 702–713.
[56] S. Kanemasa, K. Ito, Eur. J. Org. Chem. 2004 (2004) 4741–4753.
[57] G. Blay, E. Climent, I. Fernandez, V. Hernandez-Olmos, J.R. Pedro, Tetrahedrons
Asymmetry 17 (2006) 2046–2049.
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.ica.2021.120492.
[58] M.C. Christensen, K. Juhl, R.G. Hazell, K.A. Jorgensen, J. Org. Chem. 67 (2002)
4875–4881.
References
[59] A. Dixit, P. Kumar, G.D. Yadav, S. Singh, Inorg. Chim. Acta 479 (2018) 240–246.
[60] Z.L. Guo, S. Zhong, Y.B. Li, G. Lu, Tetrahedron Asymmetry 22 (2011) 238–245.
[61] K. Kodama, K. Sugawara, T. Hirose, Chem. Eur. J. 17 (2011) 13584–13592.
[1] N. Ono, The Nitrogroup in Organic Synthesis, Wiley-VCH, New York, USA, 2001.
[2] F.A. Luzzio, Tetrahedron 57 (2001) 915–945.
´
[62] K.T. Mahmudov, A.V. Gurbanov, F.I. Guseinov, M. Fatima, C.G. da Silv, Coord.
[3] H. Sasai, T. Suzuki, S. Arai, M. Shibasaki, J. Am. Chem. Soc. 114 (1992)
4418–4420.
Chem. Rev. 387 (2019) 32–46.
8

J. Cho et al.
Inorganica Chimica Acta 525 (2021) 120492
´
[63] D. Xu, Q. Sun, Z. Quan, W. Sun, X. Wang, Tetrahedron Asymmetry 28 (2017)
954–963.
[65] L. Androvic, P. Drabina, I. Panov, B. Frumarova, M. Sedlak, Tetrahedron
Asymmetry 25 (2014) 775–780.
[64] D. Scharnagel, A. Miller, F. Prause, M. Eck, J. Goller, W. Milius, M. Breuning,
Chem. Eur. J. 21 (2015) 12488–12500.
[66] G. Zhang, E. Yashima, W.-D. Woggon, Adv. Synth. Catal. 351 (2009) 1255–1262.
9