Crystal structure studies towards the synthesis and applications of n-heterocyclic carbene-metal complexes derived from [2.2]paracyclophane

Article abstract of DOI:10.1071/CH15002

The crystal structures of six planar chiral N-heterocyclic carbene (NHC) precursors and one NHC-Rh complex derived from [2.2]paracyclophane were described. The NHC-metal complexes were prepared to examine their catalytic activities toward the Rh-catalyzed

Full text of DOI:10.1071/CH15002

CSIRO PUBLISHING
Aust. J. Chem. 2015, 68, 1472–1478
Full Paper
http://dx.doi.org/10.1071/CH15002
Crystal Structure Studies towards the Synthesis and
Applications of N-heterocyclic Carbene–Metal Complexes
Derived from [2.2]Paracyclophane
A C
,
B D
,
A
A
Wenzeng Duan,
Yudao Ma,
Yanmin Huo, and Qingxia Yao
A
School of Chemistry and Chemical Engineering, Liaocheng University,
Hunan Road No. 1, Liaocheng 252000, China.
B
School of Chemistry and Chemical Engineering, Shandong University,
Shanda South Road No. 27, Jinan 250100, China.
C
School of Chemistry and Chemical Engineering, Taishan University,
Tai’an 271021, China.
D
Corresponding author. Email: ydma@sdu.edu.cn
The crystal structures of six planar chiral N-heterocyclic carbene (NHC) precursors and one NHC–Rh complex derived
from [2.2]paracyclophane were described. The NHC–metal complexes were prepared to examine their catalytic activities
toward the Rh-catalyzed asymmetric addition of phenylboronic acid to 1-naphthaldehyde. The results were correlated to
the single-crystal crystallographic studies. The novel NHC precursor 5 can achieve high catalytic activity in the
asymmetric addition of phenylboronic acid to 1-naphthaldehyde.
Manuscript received: 13 January 2015.
Manuscript accepted: 9 March 2015.
Published online: 8 May 2015.
Introduction
Results and Discussion
Since chiral N-heterocyclic carbenes (NHCs) were first reported
by Herrmann et al. and Enders et al.,[1] much research has
focussed on the isolation of novel NHC precursors and their
applications as ligands in transition metal catalysis.[2] Planar
chiral NHC precursors, such as substituted [2.2]paracyclophane
derivatives, play an important role in asymmetric catalysis.[3]
These planar chiral NHCs as well as their metal complexes have
been prepared and applied in asymmetric catalytic reactions
with good yields and enantioselectivities.[4,5] However, there is
still a lack of systemic structural studies in this area.
The study of the structures and chemical reactivities of NHCs
has become an active research area after Arduengo et al.
reported the synthesis and isolation of stable imidazol-2-ylidene
carbenes for the firt time in 1991.[6] Despite the isolation and
characterization of a vast array of NHC precursors and NHC–
metal complexes,[7] there are few reports on the systematic
structural studies regarding the stability and reactivity of NHCs
in catalysis systems. In the previous studies, our group has
employed dozens of planar chiral NHC precursors and their
complexes based on optically pure [2.2]paracyclophane. These
NHCs demonstrated high catalytic activities toward the
1,2-addition of arylboronic acids to aldehydes and b-boration
of acyclic enones,[5] which may be due to the NHC structure and
the basicity of the ligands. In this study, we present the single-
crystal crystallographic studies of six [2.2]paracyclophanyl
NHC precursors and one NHC–Rh complex 1–7 (Fig. 1) to
explore the relationships between the structure of ligands and
their complexes.
We designed and synthesized six planar chiral NHC precursors
and one NHC–Rh complex based on the [2.2]paracyclophane
skeleton. The NHC precursors 1, 2, 3, 4, 6, and NHC–Rh 7 could
be obtained following our published procedure.[5] (Rp)-12-
Amino-4-fluoro[2.2]paracyclophane 10 was readily prepared in
highyield from (Rp)-4-bromo-12-fluoro[2.2]paracyclophane 8[8]
by amination with benzhydrylideneamine, followed by imine
9 hydrolysis under acidic conditions (Scheme 1). The compound
10 was converted into corresponding diimine by treatment with
aqueous glyoxal in THF. Then, the imidazolium triflate was
obtained by using Glorius process with silver triflate and chlor-
omethyl pivalate. At last, the reaction of imidazolium triflate and
saturated KBr aqueous solution resulted in the formation of
N,N0-bis[(Rp)-(ꢀ)-12-fluoro-4-[2.2]paracyclophanyl] imidazo-
lium bromide 5 in moderate yield (Scheme 2). The structures of
these planar chiral NHC precursors 1–6 and the NHC–Rh com-
plex 7 were all determined by X-ray diffraction (Fig. 2).
It is known that the free NHCs can be obtained from the
imidazolium or imidazolinium salts using standard deprotonat-
ing agents such as t-BuOK (potassium tert-butoxide), KHMDS
(potassium bis(trimethylsilyl)amide), or NaH. However, present
attempts to prepare the free NHCs from the [2.2]paracyclopha-
nyl-NHC precursors using standard deprotonating agents failed.
These results indicate that it may not always be safe to assume
carbene-C bonding in the imidazolium and imidazolinium salts
when preparing NHC complexes in situ.[9] Deprotonation using
silver oxide as base has been widely used to synthesize NHC–Ag
complexes that can transfer the carbene ligands to a variety of
Journal compilation Ó CSIRO 2015
www.publish.csiro.au/journals/ajc

Crystal Studies of [2.2]Paracyclophane Derivatives
1473
in the imidazolinium 1. However, when the less bulky imida-
zolinium salt 11 was used to generate NHC–Ag complexes
under the same conditions, the hydrolysis product was also
observed (Scheme 3). The hydrolysis reaction of the imida-
zolinium salts 1 and 11 with Ag2O may be due to the sensitivity
of the structure and high basicity of the NHCs.
N
N
N
N
ꢁ
ꢁ
OTfꢀ
BF4ꢀ
Br
Br
Generally, the NCN bond angles of NHC precursors have a
dramatic effect on basicity.[13] From the crystal structure data of
the imidazolinium salt 1 (Table 1), the NCN bond angle is
114.09(18)8 which is quite large compared with other bond
angles in the imidazolinium salts.[14] As a result, the pKa value
of this precursor could be higher than that of other ligands.[13]
1
2
Ph
N
ꢁ
N
O
OTfꢀ
N
N
OTfꢀ
ꢁ
N
Br
Br
1
As evidenced, the H NMR data (298 K, CDCl3, N–CH–N of
NHC precursor) are consistent with the basicity of the imida-
zolinium salt 1. On the other hand, it is well known that the ring
strain results from a combination of angle strain, conforma-
tional strain, and transannular strain that can substantially
weaken the C–N bonds of the ring. Compared with the crystal
structures of 1,3-bis(2-methylnaphthalen-1-yl)-imidazolinium
tetrafluoroborate (SI2MeNapꢁHBF4), 1,3-bis(2,4,6-trimethyl-
phenyl)imidazolidin-2-ylidene (SIMes), SIMesAgCl, 1,3-bis
(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), and
SIPrAgCl (Table 1), the C–N bond lengths of the NCN moiety
in compound 1 are shorter.[14] This suggests that the angle strain
of the imidazolinium salt 1 should not lead to ring-opening.
Gu¨nay et al. and Kantchev et al. have concluded that the ring-
opening reaction of the imidazolinium salts is attributed to the
lower acidity.[15] Therefore, the high basicity of the imidazoli-
nium salt 1 might be the main reason for the hydrolysis.
3
4
O
N
Nꢁ
N
N
N
ꢁ
Brꢀ
Ph
Clꢀ
F
F
5
6
Cl
Rh
N
N
7
Fig. 1. Planar chiral NHC precursors and NHC–Rh complex.
On the other hand, the conformational environment around
the imidazolinium ring may also affect the stability of com-
pound 1. The conformations of compounds 1–7 are dependent
on the orientation of the phenyl rings relative to the heterocyclic
core, shown in Chart 1 as A, B, and C.[13]
Br
N ꢂ CPh2
(Ph)2CN ꢂ NH
Pd-dppf
t-BuONa
F
F
The dihedral angles in Table 2 can predict the conformations
of compounds 1–7. For clarity in describing the conformations,
structure A is the highest energy conformation and structure C is
the lowest energy one among the three conformations. The
conformation of compound 1 resembles that of the C2 symmetric
structure C, in which one phenyl ring is orthogonal to the
imidazoline core, while the other phenyl ring and imidazoline
ring is twisted, with the dihedral angle being 22.78. As in other
reported imidazolinium salts,[14] the two phenyl rings are almost
orthogonal to the imidazoline core that also belong to structure
C. The structure C has the least conformational strain. As such,
the conformational strain of imidazolinium salt 1 should not
result in the ring-openingreaction. It is worth mentioning that the
imidazolium salts 3 and 5 and NHC–Rh 7 all belong to structure
C with the least conformational strain. The conformation of
compound 2 corresponds to the structure B, which exhibits a
propeller-type arrangement. Compounds 4 and 6 only have one
[2.2]paracyclophane, in which the closest phenyl ring of the [2.2]
paracyclophane unit is twisted to heterocyclic ring, while the
other closest six-membered ring and heterocyclic ring is almost
planar. The structures of these NHC precursors 1–6 and NHC–
Rh 7 are conformationally stable.
8
9
NH2
THF
HCl
F
10
Scheme 1. Synthesis of Rp-4-amino-12-fluoro[2.2]paracyclophane.
N
N
NH2
ꢁ
1. (CHO)2/THF
Brꢀ
2. AgOTf
F
F
ClCH2OOCC(CH3)3
F
3. KBr
10
5
Scheme 2. Synthesis of imidazolium bromide.
other metals.[10] Following this strategy, the imidazolinium salt
1 and imidazolium salts 2–4 were treated with an excess of Ag2O
in anhydrous CH2Cl2, but no reaction occurred. The anion
exchange of the imidazolinium salt 1 with NaBr in the presence
of Ag2O in anhydrous CH2Cl2[ 11] resulted in the hydrolysis of the
imidazolinium salt 1 and generated N-formylethylenedia-
mines.[12] It seems to be the effect of the bulky naphthyl group
These results prompted us to further investigate the reactivity
of NHC precursors 2–6 with Ag2O. Under the same reaction
conditions,[11] imidazolium salts 2 and 3 reacted with Ag2O and
NaBr in anhydrous CH2Cl2 at room temperature for 3 days; the
yields were moderate (37 % and 68 %, respectively). When the
reaction was carried out with compound 4, however, 91 %
conversion was observed after ,12 h. In the absence of NaBr,

1474
W. Duan et al.
Br
S
B
F
F
N
C
H
N
C
H
O
1
2
Br
N
C
H
S
F
O
S
F
O
C
H
N
3
4
Br
C
Cl
C
H
O
N
H
N
CL
F
5
6
Rh
Cl
O
H
N
C
7
Fig. 2. NHC precursors and NHC–Rh crystal structures. Hydrogen atoms and solvent molecules are omitted for clarity.
N
N
NH
O
N
H
ꢁ
NaBr
CH2Cl2
Ag2O
BFꢀ4
11
Scheme 3. Hydrolysis of imidazolinium tetrafluoroborate.
12

Crystal Studies of [2.2]Paracyclophane Derivatives
1475
Table 1. NCN bond angles and 1H NMR chemical shifts of N–CH–N for NHC precursors and NHC–Rh complex
1H NMR d of N–CH–N [ppm]
˚
Bond lengths of N–C and C–N in N–C–N [A]
Compound
Bond angles of N–C–N [8]
1
114.09(18)
114.1(3)
111.3(6)
113.1(3)
108.51(17)
109.6(7)
108.4(4)
108.6(6)
106.8(6)
108.6(3)
107.4(3)
103.7(4)
8.05–8.06
1.291(3) 1.298(3)
1.307(4) 1.309(4)
1.320(7) 1.314(7)
1.311(3) 1.311(3)
1.332(16) 1.332(16)
1.308(12) 1.329(12)
1.317(6) 1.337(6)
1.326(7) 1.356(7)
1.334(7) 1.366(7)
1.316(5) 1.332(4)
1.318(4) 1.334(5)
1.357(6) 1.361(6)
SIMes
–
SIPr
–
SI2MeNapꢁHBF4
9.47
SIMesAgCl
–
SIPrAgCl
–
9.50
2
3
4
5
6
7
10.01–10.08
9.97
9.70
11.14
–
of the heterocyclic rings in the imidazolium salts 2–5 and the
(a)
(b)
ꢁ
ꢁ
˚
triazolium salt 6 ranged from 0.0031 to 0.0222 A. In the case of
the NHC–Rh complex 7, the mean deviation from plane of the
N
N
N
N
˚
imidazole ring in NHC–Rh complex is 0.0068 A. Based on
the NCN bond angle (103.7(4)8) and the mean deviation from
the plane of NHC–Rh complex, the structures of the imidazo-
lium salts 2–5 and the triazolium salt 6 are more suitable for the
preparation of NHC–metal complexes.
(c)
ꢁ
N
N
Because we found that the synthesis of NHC–Ag complexes
was affected by the structure of these NHC precursors, we
further investigated the impact of structure on catalytic activity.
With the imidazolium salts 2, 3, 4, and 5, the imidazolinium
salt 1, the triazolium salt 6, and the NHC–Rh complex 7 in hand,
we preliminarily examined their application in Rh-catalyzed
asymmetric addition of phenylboronic acid to 1-naphthaldehyde.
We began our experiment under identical conditions used in
our previous study of Rh-catalyzed asymmetric arylation of
aromatic aldehydes.[5d] The reaction of phenylboronic acid and
1-naphthaldehyde was performed with 3.0 mol-% of catalyst
generated in situ from NHCprecursor and [Rh(OAc)2]2 (rhodium
acetate) in t-butanol/methanol (t-BuOH/MeOH) (5 : 1) at 808C
for 7 h. Compared with our previous work,[5d] the enantioselec-
tivity of the reaction was improved by the use of ligand 5.
Because of the high basicity and prompt hydrolysis, the
imidazolinium salt 1 was almost ineffective as a ligand for the
reaction (Table 3, entry 1). The carbene precursors 2 and 3,
possessing electron-deficient substituents, resulted in low yields
(36 % and 45%, respectively) and low enantioselectivities (23 %
and 38% ee, respectively). Ligands 4 and 6 were found to be less
efficient in this reaction in terms of either reactivity or enantios-
electivity (Table 3, entries 4 and 6). Ligand 5, bearing a fluoro
substituent on the 12-position of the [2.2]paracyclophane,
showed good catalytic properties in the reaction (92 % yield,
54% ee). This result suggested that the fluoro moiety[16] in ligand
5 could play an important role in the Rh-catalyzed asymmetric
addition reaction. However, the NHC–Rh complex 7 yielded the
desired product with low enantiomeric excess (Table 3, entry 7).
Chart 1.
Table 2. Dihedral angles for compounds 1–7
Compound
Angle between heterocyclic
ring and closest left-hand
phenyl ring [8]
Angle between heterocyclic
ring and closest right-hand
phenyl ring [8]
1
2
3
4
5
6
7
87.3
142.1
34.1
22.7
35.2
32.4
37.8
133.5
3.3
178.3
126.9
41.8
52.9
72.5
the imidazolium salt 5, as an ion exchange product of its triflate
analogue, and the triazolium salt 6 could react with Ag2O
directly to give 91 % and 97 % yields, respectively, after 12 h.
It is also observed that the reactions of NHC precursors 2–6 with
Ag2O do not lead to ring-opening. These results reveal that the
reactivity of NHC precursors with an excess of Ag2O in
anhydrous CH2Cl2 is related to their structure and acidity. From
the crystal structures of the NHC precursors 2–6 (Table 1), the
NCN bond angles are between 106.88 and 108.68, and the pKa
value[13] is suitable for reaction with Ag2O. The 1H NMR data
(298 K, CDCl3, N–CH–N of NHC precursors) are also consis-
tent with the basicity of the NHC precursors. As a rule of thumb,
the greater the chemical shift of proton, the higher the acidity of
the NHC precursors. Therefore, the acidity is too weak for the
imidazolinium salt 1 to form corresponding NHC–Ag complex
(Table 1). On the other hand, the mean deviation from plane of
Conclusions
The crystal structures of six planar chiral NHC precursors and
one NHC–Rh complex derived from [2.2]paracyclophane were
described. The NHC–metal complexes were prepared and eval-
uated as ligands in the Rh-catalyzed asymmetric addition of
phenyl boronic acid to 1-naphthaldehyde. The results were cor-
related to the single-crystal crystallographic studies. This work has
˚
the imidazolinium ring is 0.2399 A in imidazolinium salt 1.
Unlike the imidazolinium salt 1, the mean deviations from plane

1476
W. Duan et al.
Table 3. Evaluation of ligands and NHC–RhA
(2.0 mL) were stirred at 1158C for ,8 h under a slight positive
pressure of nitrogen. After completion of the reaction as
indicated by TLC, the mixture was cooled to the room tem-
perature; water (5.0 mL) was added and the solution of water
and reaction mixture was filtered. The solution was extracted
using dichloromethane (5.0 mL ꢂ 3), and the solvent was
removed using a rotary evaporator. The residue was purified by
chromatography on silica gel (petroleum ether/ethyl acetate ¼
20 : 1), and pure product (Rp)-4-benzhydrylideneamino-12-
fluoro[2.2]paracyclophane (9) was obtained (430 mg, 77.4 %).
To the solution of (Rp)-4-benzhydrylideneamino-12-fluoro
[2.2]paracyclophane (9) (430 mg, 1.06 mmol) in THF (4.0 mL)
was added concentrated HCl (12.0 M, 0.25 mL, 3.0 mmol), and
the mixture was stirred at room temperature for 4 h. After the
yellow colour of the mixture disappeared, the white precipitate
was collected by filtration. The precipitate was washed with
ether (3 ꢂ 5.0 mL), and dried under vacuum. The remaining
solid was dissolved in ethanol (4.0 mL), and saturated NaOH
was added dropwise until the stirred mixture was basic (pH 9).
The solvent was removed, and the residue was purified by
chromatography on silica gel (petroleum ether/ethyl acetate ¼
10 : 1). The target compound 10 was obtained as a white solid
(243.2 mg, 95.1 %), mp 178–1808C. [a]2D0 ꢀ167.78 (c 0.13 in
CH2Cl2). dH (CDCl3, 300 MHz) 6.78 (1H, dd, J 11.8, 1.6), 6.54
(1H, t, J 8.1), 6.31 (1H, s), 6.28 (1H, s), 6.04 (1H, dd, J 7.7, 1.7),
5.88 (1H, dd, J 3.1, 1.8), 3.53 (2H, s), 3.37–3.25 (1H, m),
3.14–2.97 (3H, m), 2.97–2.79 (2H, m), 2.69–2.54 (2H, m). dC
(CDCl3,75 MHz) 162.21, 158.98, 144.57, 142.36, 142.26,
141.16, 134.99, 134.89, 134.81, 127.75, 127.71, 124.71,
124.47, 123.47, 122.48, 117.73, 115.47, 115.17, 33.26, 32.03,
32.01, 31.46, 29.54. m/z (HRMS ESI) 242.1339; [M þ H]þ
requires 242.1345.
HO
CHO
B(OH)2
∗
Ligand (3 mol-%)
[Rh(OAc)2]2 (3 mol-%)
t-BuOK
t-BuOK/MeOH ꢂ 5:1
Entry
Metal source
Ligand
Yield [%]B
ee [%]C
1
2
3
4
5
6
7
[Rh(OAc)2]2
[Rh(OAc)2]2
[Rh(OAc)2]2
[Rh(OAc)2]2
[Rh(OAc)2]2
[Rh(OAc)2]2
–
1
2
3
4
5
6
7
10
36
45
42
92
47
84
3 (R)
23 (S)
38 (S)
7 (S)
54 (S)
5 (S)
12 (R)
AReaction conditions: [Rh(OAc)2]2 (3 mol-%), ligand (3 mol-%), t-BuOK
(1 equiv.), phenylboronic acid (2 equiv.), 1-naphthaldehyde (1 equiv.), N2,
808C, 7 h.
BIsolated yield.
CDetermined by chiral HPLC (CHIRALPAK IA Column) analysis.
established that the planar chiral NHC precursors do not always
give normal NHCs on metalation, implying that the chemistry of
this ligand system can be more complex than currently thought.
Further studies to synthesize the [2.2]paracyclophane-based
carbene complexes as well as investigating their applications in
asymmetric catalysis are in progress in our group.
Experimental
Material
Commercially available reagents were used without further
purification unless otherwise noted. Solvents were reagent grade
and purified by standard techniques. N,N0-bis[(4Sp,13Rp)-(ꢀ)-13-
(1-naphthyl)-4-[2.2]paracyclophanyl]-4,5-dihydroimidazolium
tetrafluoroborate (1), N,N0-bis[(Sp)-(þ)-12-bromo-4-[2.2]para-
cyclophanyl]imidazolium triflate (2), N,N0-bis[(4Rp,13Sp)-
13-bromo-4-[2.2]paracyclophanyl]imidazolium triflate (3),
(R,4Sp,13Rp)-3-{13-(4-phenyloxazolin-2-yl)[2.2]paracyclophane-
4-yl}imidazo[1,5-a]pyridinium triflate (4), triazolium salt
(R,Rp)-6, chloro(Z2,Z2-1,5-cyclo-octadiene)-[N,N0-bis[(Rp)-
(þ)-4- [2.2]paracyclophanyl]imidazole-2-ylidene]rhodium (7),
and Rp-4-bromo-12-fluoro[2.2]paracyclophane (8) were prepared
according to published procedures.[5,9] Melting points were
recordedona melting point apparatus and are uncorrected. 1H and
13C NMR spectra were recorded on a Bruker Avance 400 MHz
and 300 MHz spectrometers. High-Resolution mass spectrometry
(HRMS) patternswererecordedonanAgilent Technologies6510
Q-Tof LC/MS. Enantiomeric excess was determinedusing HPLC
on a Chiralpak IA chiral column. Optical rotations were deter-
mined on a polarimeter with a wavelength of 589 nm. The con-
centration ‘c’ has units of g per 100 mL (or 10 mgmLꢀ1) unless
otherwise noted.
General Procedures for the Synthesis of
Imidazolium Bromide (5)
Rp-4-Amino-12-fluoro[2.2]paracyclophane (10) (243 mg,
1.0 mmol) and 40 % glyoxal (174.0 mg, 1.2 mmol) in 1.0 mL
THF were stirred at room temperature for 5 h, during which time
the colour of the reaction mixture turned yellow and a yellow
precipitate appeared. After completion of the reaction, as indi-
cated by TLC, the yellow precipitate was collected by filtration
and washed with 2.0 mL water. The desired diimine was isolated
as a yellow solid (251 mg, 99.5 %).
A solution of AgOTf (0.165 g, 0.65 mmol, where AgOTf ¼
silver triflate) and chloromethyl pivalate (0.08 mL, 0.55 mmol)
in THF was stirred in a sealed tube in the dark at room
temperature for 10 min until a white precipitate appeared. Then,
a solution of the diimine (251 mg, 0.5 mmol) in CH2Cl2 (2.0 mL)
was added to the above suspension. The solution was stirred in a
sealed tube in the dark at 408C for 8 h. After the solution was
cooled to room temperature, the solvent was removed under
vacuum. The resulting oil was chromatographed on silica gel
(CH2Cl2/ethanol (EtOH) ¼ 50 : 1–10 : 1) to afford the pure prod-
uct (186.5 mg, 56 %).
The pure product N,N0-bis[(Rp)-(ꢀ)-12-fluoro-4-[2.2]para-
cyclophanyl]-imidazolium triflate (186.5 mg, 0.28 mmol) was
dissolved in CH2Cl2 (5.0 mL), saturated KBr aqueous solution
(5.0 mL) was added, and the mixture was stirred vigorously.
After 12 h, saturated KBr aqueous solution was removed. The
product was collected by filtration. Compound 5 was obtained
as a white solid (80.3 mg, 48 %), mp . 2508C. [a]2D0 ꢀ212.38
(c 0.15 in CH2Cl2). dH (CDCl3, 300 MHz) 9.70 (1H, s),
Synthesis of Rp-4-Amino-12-fluoro[2.2]paracyclophane (10)
(Rp)-4-Bromo-12-fluoro[2.2]paracyclophane (8) (418.0 mg,
1.37 mmol), 4,12-bis(benzhydrylideneamino) [2.2]para-
cyclophane (3.9 mg, 0.0069 mmol), benzhydrylideneamine
(372.4 mg, 2.06 mmol), sodium t-butoxide (198.0 mg,
2.06 mmol), and Pd(dppf)Cl2 (10.3 mg, 0.014 mmol, where
dppf ¼ 1,10-bis-(dipheny1phosphino) ferrocene) in toluene

Crystal Studies of [2.2]Paracyclophane Derivatives
1477
7.99 (2H, s), 7.17 (2H, s), 6.81 (2H, d, J 8.0), 6.70 (2H, t, J 7.8),
6.62 (4H, dd, J 11.7, 8.3), 6.25 (2H, d, J 9.8), 3.46 (2H, ddd, J
13.6, 10.0, 4.0), 3.40–3.05 (10H, m), 2.95–2.75 (4H, m). dC
(CDCl3, 75 MHz) 161.73, 158.50, 143.34, 143.30, 143.26,
141.80, 136.35, 135.96, 134.66, 134.49, 134.41, 133.69,
132.72, 128.93, 125.41, 125.28, 125.18, 123.77, 123.17,
121.51, 117.18, 116.89, 76.94, 76.72, 76.52, 76.09, 34.05,
33.03, 30.97, 28.43. m/z (HRMS ESI) 517.2452; [M – Br]þ
requires 517.2455.
(d) D. Enders, H. Gielen, K. Breuer, Tetrahedron: Asymmetry 1997, 8,
3571. doi:10.1016/S0957-4166(97)00519-3
[2] (a) Y. D. Ma, C. Song, C. Ma, Z. Sun, Q. Chai, M. B. Andrus, Angew.
Chem., Int. Ed. 2003, 42, 5871. doi:10.1002/ANIE.200352679
(b) M. Fructos, T. R. Belderrain, C. Nicasio, S. P. Nolan, H. Kaur,
M. M. D´ıaz-Requejo, P. J. Pe´rez, J. Am. Chem. Soc. 2004, 126, 10846.
doi:10.1021/JA047284Y
(c) D. Martin, S. Kehrli, M. d’Augustin, H. Clavier, M. Mauduit,
A. Alexakis, J.Am. Chem. Soc.2006, 128, 8416. doi:10.1021/JA0629920
(d) K. B. Selim, Y. Matsumoto, K. Yamada, K. Tomioka, Angew.
Chem., Int. Ed. 2009, 48, 8733. doi:10.1002/ANIE.200904676
(e) S. D´ıez-Gonza´lez, N. Marion, S. P. Nolan, Chem. Rev. 2009, 109,
3612. doi:10.1021/CR900074M
General Procedure for the Synthesis of
N-Formylethylenediamine (12)[10]
(f) T. L. May, J. A. Dabrowski, A. H. Hoveyda, J. Am. Chem. Soc.
A dry Schlenk tube was charged with N,N0-bis[4-[2.2]para-
cyclophanyl]imidazolinium tetrafluoroborate[2a] (11) (57 mg,
0.1 mmol), NaBr (51 mg, 0.5 mmol), Ag2O (14 mg, 0.06 mmol),
and CH2Cl2 (3.0 mL). The mixture was stirred in the absence of
light for 48 h at room temperature. The resulting off-white
precipitate was filtered and the solvent was removed under
vacuum to afford the crude product. The crude product was
purified by column chromatography on silica gel (CH2Cl2); the
target compound 12 was obtained as a white solid (32.5 mg,
65 %). dH (CDCl3, 400 MHz) 8.65 (1H, s), 6.78 (1H, dd, J 7.7,
1.7), 6.71–6.46 (7H, m), 6.36–6.26 (4H, m), 6.20 (1H, d, J 7.6),
6.02 (1H, d, J 7.6), 5.12 (1H, s), 4.59 (1H, ddd, J 13.5, 7.8, 5.5),
4.07 (1H, s), 3.46 (1H, dt, J 13.6, 5.5), 3.19–2.73 (16H, m), 2.59
(1H, dt, J 3.9, 8.1).
2011, 133, 736. doi:10.1021/JA110054Q
(g) F. J. Wang, L. J. Liu, W. F. Wang, S. K. Li, M. Shi, Coord. Chem.
Rev. 2012, 256, 804. doi:10.1016/J.CCR.2011.11.013
(h) L. Han, P. Xing, B. Jiang, Org. Lett. 2014, 16, 3428. doi:10.1021/
OL501353Q
(i) Y. R. Chen, J. J. Feng, W. L. Duan, Tetrahedron Lett. 2014, 55, 595.
doi:10.1016/J.TETLET.2013.10.158
[3] (a) V. Rozenberg, E. Sergeeva, H. Hopf, in Modern Cyclophane
Chemistry (Eds R. Gleiter, H. Hopf) 2004, pp. 435–462 (Wiley-
VCH: Weinheim, Germany)
(b) T. Focken, J. Rudolph, C. Bolm, Synthesis 2005, 3, 429.
(c) D. X. Wang, Y. D. Ma, F. Y. He, W. Z. Duan, L. Zhao, C. Song,
Synth. Commun. 2013, 43, 810. doi:10.1080/00397911.2011.610548
[4] (a) S. E. Gibson, J. C. Knight, Org. Biomol. Chem. 2003, 1, 1256.
doi:10.1039/B300717K
(b) T. Focken, G. Raabe, C. Bolm, Tetrahedron: Asymmetry 2004, 15,
1693. doi:10.1016/J.TETASY.2004.03.047
Details of X-Ray Data Collection and Refinement
(c) C. Song, C. Q. Ma, Y. D. Ma, W. H. Feng, S. T. Ma, Q. Chai,
M. B. Andrus, Tetrahedron Lett. 2005, 46, 3241. doi:10.1016/J.TET
LET.2005.03.026
The crystallographic data of 1–7 were collected on a Bruker
Smart APEX CCD area-detector diffractometer with MoKa
˚
[5] (a) W. Z. Duan, Y. D. Ma, H. Q. Xia, X. Y. Liu, Q. S. Ma, J. S. Sun,
J. Org. Chem. 2008, 73, 4330. doi:10.1021/JO800468X
(b) Q. S. Ma, Y. D. Ma, X. Liu, W. Z. Duan, B. Qu, C. Song, Tetra-
hedron: Asymmetry 2010, 21, 292. doi:10.1016/J.TETASY.2010.01.025
(c) B. Hong, Y. D. Ma, L. Zhao, W. Z. Duan, F. Y. He, C. Song,
Tetrahedron: Asymmetry 2011, 22, 1055. doi:10.1016/J.TETASY.
2011.06.023
radiation (l 0.71073 A). The crystal data were solved by the
direct method and refined by a full-matrix least-squares method
on F2 using the SHELXL-97 crystallographic software pack-
age.[17] The SQUEEZE/PLATON program[18] was used to model
some disordered guest water molecules in compound 4.
Supplementary Material
(d) W. Z. Duan, Y. D. Ma, B. Qu, L. Zhao, J. Q. Chen, C. Song,
Tetrahedron: Asymmetry 2012, 23, 1369. doi:10.1016/J.TETASY.
2012.09.001
(e) L. Zhao, Y. D. Ma, F. Y. He, W. Z. Duan, J. Q. Chen, C. Song,
J. Org. Chem. 2013, 78, 1677. doi:10.1021/JO302694D
(f) W. Z. Duan, Y. D. Ma, F. Y. He, L. Zhao, J. Q. Chen, C. Song,
Tetrahedron: Asymmetry 2013, 24, 241. doi:10.1016/J.TETASY.2013.
01.017
The experimental materials details, methods and spectral data
for products are available on the Journal’s website. Crystallo-
graphic data (excluding structure factors) for 1, 2, 3,[19] 4, 5,[20]
6, and 7 have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication numbers
CCDC 1023337, CCDC 753625, CCDC 1015372, CCDC
821397, CCDC 1017723, CCDC 1017741, and CCDC 903887,
respectively. Copies of the data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html; fax: þ44 1223 336
033; email: deposit@ccdc.cam.ac.uk.
[6] A. J. Arduengo III, R. L. Harlow, M. Kline, J. Am. Chem. Soc. 1991,
113, 361. doi:10.1021/JA00001A054
[7] (a) T. M. Trnka, R. H. Grubbs, Acc. Chem. Res. 2001, 34, 18.
doi:10.1021/AR000114F
(b) W. A. Herrmann, Angew. Chem., Int. Ed. 2002, 41, 1290.
doi:10.1002/1521-3773(20020415)41:8,1290::AID-ANIE1290.3.0.
CO;2-Y
Acknowledgements
(c) B. Liu, Q. Q. Xia, W. Z. Chen, Angew. Chem., Int. Ed. 2009, 121,
5621. doi:10.1002/ANGE.200901850
(d) M. Poyatos, J. A. Mata, E. Peris, Chem. Rev. 2009, 109, 3677.
doi:10.1021/CR800501S
Financial support from the National Natural Science Foundation of China
(Grant No. 21372144), Shandong Province Natural Science Foundation
(ZR2012BL08 and ZR2011BM013), and the Liaocheng University Funds
for Young Scientists (31805) is gratefully acknowledged.
(e) C. Samojłowicz, M. Bieniek, K. Grela, Chem. Rev. 2009, 109,
3708. doi:10.1021/CR800524F
(f) G. C. Vougioukalakis, R. H. Grubbs, Chem. Rev. 2010, 110, 1746.
doi:10.1021/CR9002424
(g) M. Jahnke, F. E. Hahn, Top. Organomet. Chem. 2010, 30, 95.
doi:10.1007/978-3-642-04722-0_4
(h) K. Riener, S. Haslinger, A. Raba, M. P. Ho¨gerl, M. Cokoja,
W. A. Herrmann, F. Ku¨hn, Chem. Rev. 2014, 114, 5215. doi:10.1021/
CR4006439
References
[1] (a) W. A. Herrmann, L. J. Goossen, C. Ko¨cher, G. R. J. Artus, Angew.
Chem., Int. Ed. Engl. 1996, 35, 2805. doi:10.1002/ANIE.199628051
(b) D. Enders, H. Gielen, G. Raabe, J. Runsink, J. H. Teles, Chem. Ber.
1996, 129, 1483. doi:10.1002/CBER.19961291213
(c) W. A. Herrmann, L. J. Goossen, G. R. J. Artus, C. Ko¨cher, Orga-
nometallics 1997, 16, 2472. doi:10.1021/OM960784I

1478
W. Duan et al.
[8] F. Y. He, Y. D. Ma, L. Zhao, W. Z. Duan, J. Q. Chen, C. Song, Org.
Lett. 2012, 14, 5436. doi:10.1021/OL302510T
[9] O. Schuster, L. R. Yang, H. G. Raubenheimer, M. Albrecht, Chem.
Rev. 2009, 109, 3445. doi:10.1021/CR8005087
(d) A. Berkessel, S. Elfert, V. R. Yatham, J. M. Neudo¨rfl, N. E.
Schlo¨rer, J. H. Teles, Angew. Chem., Int. Ed. 2012, 51, 12370.
doi:10.1002/ANIE.201205878
¨
[15] (a) M. E. Gu¨nay, N. Ozdemir, M. Ulusoy, M. Uc¸ak, M. Dinc¸er,
[10] (a) H. M. J. Wang, I. J. B. Lin, Organometallics 1998, 17, 972.
doi:10.1021/OM9709704
B. C¸ etinkaya, J. Organomet. Chem. 2009, 694, 2179. doi:10.1016/
J.JORGANCHEM.2009.02.023
(b) A. M. Magill, D. S. McGuinness, K. J. Cavell, G. J. P. Britovsek,
V. C. Gibson, A. J. P. White, D. J. Williams, A. H. White, B. W. Skelton,
J. Organomet. Chem. 2001, 617–618, 546. doi:10.1016/S0022-328X(00)
00720-8
(b) E. A. B. Kantchev, J. Y. Ying, Organometallics 2009, 28, 289.
doi:10.1021/OM8008475
[16] (a) T. Nishimura, H. Kumamoto, M. Nagaosa, T. Hayashi, Chem.
Commun. 2009, 5713. doi:10.1039/B911118B
(c) J. C. Garrison, W. J. Youngs, Chem. Rev. 2005, 105, 3978.
doi:10.1021/CR050004S
(b) S. Morikawa, K. Michigami, H. Amii, Org. Lett. 2010, 12, 2520.
doi:10.1021/OL100697A
(d) X. Wang, S. Liu, G. X. Jin, Organometallics 2004, 23, 6002.
doi:10.1021/OM049467Z
(e) M. Alcarazo, S. J. Roseblade, A. R. Cowley, R. Fernandez,
J. M. Brown, J. M. Lassaletta, J. Am. Chem. Soc. 2005, 127, 3290.
doi:10.1021/JA0423769
[17] (a) G. M. Sheldrick, SHELXL97, Program for Crystal Structure
Refinement 1997 (University of Go¨ttingen: Go¨ttingen, Germany)
(b) G. M. Sheldrick, SHELXS97, Program for Crystal Structure
Solution 1997 (University of Go¨ttingen: Go¨ttingen, Germany).
[18] P. van der Sluis, A. L. Spek, Acta Crystallogr., Sect. A 1990, 46, 194.
doi:10.1107/S0108767389011189
(f) J. A. Mata, A. R. Chianese, J. R. Miecznikowski, M. Poyatos,
E. Peris, J. W. Faller, R. H. Crabtree, Organometallics 2004, 23, 1253.
doi:10.1021/OM034240þ
[19] Crystal data for compound 3: C36H31Br2F3N2O3S, M 788.51, colour-
less block, orthorhombic, space group P 21 21 21, a 10.932(2),
3
˚
˚
(g) A. Prades, M. Viciano, M. Sanau, E. Peris, Organometallics 2008,
27, 4254. doi:10.1021/OM800377M
(h) K. P. McGrath, A. H. Hoveyda, Angew. Chem., Int. Ed. 2014, 53,
b
12.123(2),
c
25.594(5) A,
b
908,
V
3391.9(11) A ,
Z
4,
Dc 1.544 Mg mꢀ3, F000 1592, MoKa radiation, m 2.507 mmꢀ1, T
296 K. 16581 data measured, of which 7446 unique (Rint 0.0954),
ymax 27.508, ymin 1.868. Refinement of 7446 reflections (424 para-
meters) with I . 2s(I) converged at final R1 0.0562 (R1 all data
0.2021), wR2 0.0973 (wR2 all data 0.1224), GoF 1.001. The structure
was solved by the direct method and refined by the full-matrix least-
squares method on F2 using the SHELXTL 97 crystallographic soft-
ware package.
1910. doi:10.1002/ANIE.201309456
[11] M. Iglesias, D. J. Beetstra, J. C. Knight, L. L. Ooi, A. Stasch, S. Coles,
L. Male, M. B. Hursthouse, K. J. Cavell, A. Dervisi, I. A. Fallis,
Organometallics 2008, 27, 3279. doi:10.1021/OM800179T
[12] K.-A. Green, P. T. Maragh, K. Abdur-Rashid, A. J. Lough, T. P.
Dasgupta, Tetrahedron Lett. 2014, 55, 5085. doi:10.1016/J.TETLET.
2014.07.044
[20] Crystal data for compound 5: C36H32BrCl3F2N2, M 714.08, colour-
[13] A. M. Magill, K. J. Cavell, B. F. Yates, J. Am. Chem. Soc. 2004, 126,
8717. doi:10.1021/JA038973X
less block, orthorhombic, space group P 2(1) 2(1) 2(1), a 11.703(5),
3
˚
˚
b
11.958(5),
c
23.535(10) A, b ¼ 908, V ¼ 3294(2) A ,
Z 28,
[14] (a) P. de Fre´mont, N. M. Scott, E. D. Stevens, T. Ramnial, O. C.
Lightbody, C. L. B. Macdonald, J. A. C. Clyburne, C. D. Abernethy,
S. P. Nolan, Organometallics 2005, 24, 6301. doi:10.1021/OM050735I
(b) X. J. Luan, R. Mariz, M. Gatti, C. Costabile, A. Poater, L. Cavallo,
A. Linden, R. Dorta, J. Am. Chem. Soc. 2008, 130, 6848. doi:10.1021/
JA800861P
Dc 1.446 Mg mꢀ3, F000 1464, MoKa radiation, m 1.532 mmꢀ1, T
273 K. 16468 data measured, of which 5808 unique (Rint 0.0489),
ymax 25.028, ymin 1.918. Refinement of 5808 reflections (397 para-
meters) with I . 2s(I) converged at final R1 0.0421 (R1 all data
0.0780), wR2 0.0843 (wR2 all data 0.0962), GoF 0.990. The structure
was solved by the direct method and refined by the full-matrix least-
squares method on F2 using the SHELXTL 97 crystallographic
software package.
(c) B. F. Straub, M. Wrede, K. Schmid, F. Rominger, Eur. J. Inorg.
Chem. 2010, 1907. doi:10.1002/EJIC.201000197