Synthesis and Characterization of Ferrocene Based Hemicages

Article abstract of DOI:10.1021/acs.joc.8b00146

We present a series of tripodal ligands L1-3, which fold into hemicages C1-3 by using coordination-driven dynamic combinational chemistry. The identities of these hemicages were characterized using ¹H NMR, ¹H-¹H COSY, DOSY, and ESI-TWIM-MS. Free rotation of the ferrocene structural units in the ligands affords an adaptable directionality, which is essential for the construction of these hemicages. Encapsulation of adamantane by C2 indicates the presence of a well-defined inner cavity as the binding pocket.

Full text of DOI:10.1021/acs.joc.8b00146

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Synthesis and Characterization of Ferrocene Based Hemicages
Nianqiang Jiang, Ziyong Yuan, Tao Li, Yanpeng Zhu, Yu-Sheng
Chen, Liqiong Lin, Jingrui Zhang, Yi-Tsu Chan, and Jiaobing Wang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b00146 • Publication Date (Web): 29 Mar 2018
Downloaded from http://pubs.acs.org on March 30, 2018
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Synthesis and Characterization of Ferrocene Based Hemi-
cages
Nianqiang Jiang,† Ziyong Yuan,† Tao Li,† Yanpeng Zhu,† Yu-Sheng Chen,‡ Liqiong Lin,† Jingrui
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Zhang,† Yi-Tsu Chan,‡ Jiaobing Wang†*
†School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, People’s Republic of China.
‡Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan, Republic of China.
Supporting Information Placeholder
can fold into hemicages C1-3 (Figure 1), in the presence of one
equivalent of iron (Ⅱ) and three equivalents of 2-formylpyridine,
using a coordination-driven dynamic combinational chemistry
(DCC).14,53 To satisfy the spatial arrangement of the octahedral
coordination of iron (Ⅱ) as well as that of the trigonal bottom
panels, the Fc-axle functions as an adaptable structural unit in the
final hemicages C1-3 by manifesting a dihedral angle (DA), rang-
ing from ca. 54˚ to 86˚. This approach is highly modular. Metal-
organic hemicages of varied size and shape can be rationally de-
signed and efficiently assembled. Study on guest encapsulation
indicates a well-defined inner cavity present in the obtained met-
al-organic hemicages.
ABSTRACT: We present a series of tripodal ligands L1-3,
which fold into hemicages C1-3 by using coordination-driven
dynamic combinational chemistry. The identities of these hemi-
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cages were characterized using H NMR, H-1H COSY, DOSY,
and ESI-TWIM-MS. Free rotation of the ferrocene structural units
in the ligands affords an adaptable directionality, which is essen-
tial for the construction of these hemicages. Encapsulation of
adamantane by C2 indicates the presence of a well-defined inner
cavity as the binding pocket.
Metal-organic cages (MOCs) have attracted considerable interests
for their potential utilizations in fields such as molecular recogni-
tion,1-7 catalysis in small space,8-13 and stabilization of reactive
species.14-17 Construction of such discrete MOCs relies on direc-
tional bonding interactions encoded in their building blocks,18-24
and matching of the geometry requirements for different structural
subunits is crucial for the successful delivery of a specific target
MOC.25-27 Metal-organic hemicage is a kind of MOC, which is
prepared by assembling of metal ion with a multidentate ligand,
normally in a 1:1 mole ratio.28 For instance, Raymond and his
coworkers have prepared a series of hemicages by assembling
Fe3+ with the enterobactin or catecholate-based tripodal ligands.29-
Scheme 1. Adaptable directionality of the 1,1ʹ-
disubstituted ferrocene unit.
34
Over the years, various tripodal ligands ，derived from 8-
hydroxyquinoline,35 2-phenylpyridine,36,37 and 2,2ʹ-bipyridine38-43
had been utilized to build metal-organic hemicages. However,
most of these ligands use highly flexible linkers to provide the
desired angularity in favor of cage formation. Therefore, in these
hemicages, it is difficult to generate a well-defined inner cavity,
which is highly important for their applications.
The synthesis and characterization of precursors L1-3 are de-
scribed in the Experimental Section. To demonstrate the feasibil-
ity of this approach, hemicage C1 was synthesized using Nitsch-
ke’s DCC condition (Figure 1).14,53 Upon addition of 1.0 equiva-
lent of iron (Ⅱ) tetrafluoroborate to a mixture of L1 and 2-
formylpyridine (3.0 equivalents), the color of the solution imme-
diately turns from yellow to deep burgundy (Figure 1B, inset),
indicating the formation of an iron complex.
Ferrocene (Fc) has been utilized as a key structural unit in differ-
ent molecular systems for its reversible redox property.44-47 In
addition, free rotation about the Fc axle (Scheme 1) was utilized
to facilitate dynamic response in molecular machines.48-50 Specifi-
cally, the adaptable directionality of the Fc axle was employed for
the construction of metal-organic macrocycles.51 But, to the best
of our knowledge, previous attempt to utilize the adaptable direc-
tionality of the Fc axle for the construction of MOCs was unsuc-
cessful.52
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In the H NMR spectrum, typical resonance signals of the iron
(Ⅱ)–iminopyridine complexes,54 at 5.15 and 5.40 ppm, assigned
to the aromatic protons Hf and Hh (Figure 2A) in the ortho-
position of the imine substituent, were observed. These two pro-
tons undergo a significant upfield shift, due to strong shielding
effect from the adjacent phenyl rings in the octahedral iron (Ⅱ)
coordination unit.54 Moreover, a group of eight well-resolved
resonance signals, assigned to the cyclopentadienyl protons of the
Fc-axle unit, appears in the spectrum.55 This spectral feature is in
sharp contrast to the corresponding tetrad resonance signals for
the Fc-axle unit in precursor L1 (Figure 2A, inset). Apparently,
Herein, we show that adaptable directionality from the Fc units
can be utilized to build metal-organic hemicages with defined
inner cavity. As shown in Figure 1, we designed three tripodal
precursors L1-3 incorporated with the Fc-axles. These precursors
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spectrum (B) of C1. Protons are indicated on a partial stick model of C1. Inset of
restricted rotation of the Fc-unit in C1 results in a magnetic in-
equivalence, which is not observed in L1 with the free-rotating
Fc-unit. All the signals can be assigned using a combination of 1H
(A), the 1H NMR spectrum of the ferrocene part of L1. Inset of (B), the measured
mass spectrum of [C1]2+ and the simulated spectrum.
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NMR, H-1H correlation spectroscopy (COSY) and H-1H rotat-
All signals in the 1H diffusion ordered spectroscopy (DOSY)
share a common diffusion coefficient, which indicates the for-
mation of only one discrete species (Figure 2A, for full DOSY
NMR spectrum, see Figure S6). A hydrodynamic radius of 9.2 Å,
derived from the diffusion coefficient (D, 6.46 × 10-10 m2s-1) in
CD3CN, is consistent with the computed molecular model (Figure
S1). High-resolution electrospray ionization mass spectrometry
(ESI-MS) reveals a clean ionic species of [C1]2+ (HRMS (ESI-
TOF) m/z: [C1]2+ Calcd. for C102H78Fe4N6O6 853.6703; Found
853.6717, Figure 2B and S7). The isotopic pattern matches that of
the theoretical one. All these data support an efficient synthesis of
C1, in which the Fc-axle functions as a ca. 54˚ corner, as indicat-
ed by the molecular model (Figure 1C).
ing-frame Overhauser spectroscopy (ROESY) (Figure S2-5).
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Figure 1. Molecular structures of the tripodal precursors L1-3 (A), representative
preparation of hemicage (B), and the molecular models of C1-3 (C). The octahedral
iron ( )–iminopyridine coordination center, the ferrocene moiety, and the visualized
image of a solution of C1 are shown beside the synthetic scheme (B). Molecular
models are optimized with molecular mechanics using SPARTAN software. Meth-
oxy group or the triethylene glycol monomethyl ether chains, appended on the phe-
nylene edge of the cage, and counterions are omitted for clarity. Note, in C1-3, both
the octahedral vertices and the ferrocene moiety are chiral, and only the low-energy
isomer of each hemicage is presented.
Figure 3. Partial 1H-NMR spectra (300 MHz, CD3CN, 293 K) of C2 (A) and C3 (B).
Protons from the Fc-axle are marked with asterisks (A). ESI-MS data of C2 (C)
(HRMS (ESI-TOF) m/z: [C2]2+ Calcd. for C150H138Fe4N6O15 1243.8826; Found
1243.8822) and C3 (D) (HRMS (ESI-TOF) m/z: [C3]2+ Calcd. for C174H150Fe4N6O15
896.6872; Found 896.6794) are consistent with the theoretical values.
We then tested the modularity of this approach by changing the
size and shape of the target hemicages. As shown in Figure 1A,
the edge of the precursor was extended from two phenylene rings,
in L1, to three phenylene rings in L2. The bottom panel in the
precursor was also extended, concurrently, to meet the structural
requirement. These variations are expected to result in an enlarged
hemicage C2 (Figure 1C). In addition, precursor L3 was de-
signed, which uses triptycene as the bottom panel (Figure 1A).
Molecular modeling study reveals that the Fc-axle would accom-
modate the cage formation by manifesting a DA of around 54˚ for
C2, and 86˚ for C3, respectively (Figure 1C).
Despite a significant change in the structure of the precursor, L2
and L3 assemble into hemicage C2 and C3 in a highly efficient
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manner. In situ H NMR spectra demonstrated that C2 and C3
were formed quantitatively, after subjecting the precursors to a
mixture of iron and 2-formylpyridine (precursor/Fe2+/2-
formylpyridine, 1/1/3, mole ratio). Spectroscopic analysis, using a
combination of 1H NMR, 1H-1H COSY, DOSY, and ESI-MS,
Figure 2. 1H DOSY (300 MHz, CD3CN, 293 K) spectrum (A) and ESI-TOF mass
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confirmed the structure of hemicages C2 (Figure 3A, 3C and S10-
In conclusion, we have demonstrated that Fc-axle could accom-
modate the construction of hemicages C1-3 by providing adapta-
ble directionality. The structure of the obtained hemicages were
confirmed using 1H NMR, 1H-1H COSY, DOSY, and ESI-TWIM-
MS. Host-guest complexation with adamantane suggests that C2
has a well-defined inner cavity. In principle, Fc-axle can provide
on-demand directionality without inducing structural strains,
greatly expanding the potential combinations of various structural
units for building MOCs with more sophisticated functions, such
as molecular recognition and catalysis in a confined small space.
Moreover, given the pivotal roles that macroscopic axles play in
various dynamic structures, axle units, in the molecular scale, are
expected to be utilized in the construction of MOCs featuring
stimulus responsive structures and properties.
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14) and C3 (Figure 3B, 3D and S17-21). The D value of C1 (6.46
× 10-10 m2s-1) and C3 (6.03 × 10-10 m2s-1) are larger than that of
C2 (4.90 × 10-10 m2s-1), which is consistent with the size of these
hemicages (Figure S1, S9 and S16).
C1-3 were further analyzed using electrospray ionization traveling
wave ion mobility mass spectrometry (ESI-TWIM-MS), in which
the drift time of the sample is dependent on the average collision
cross-section (CCS).56 As shown in Figure 4, the drift times of
these cages were found to be 9.4 (C1), 14.8 (C2), and 10.8 ms
(C3), respectively (Figure S8, S15 and S22). The corresponding
CCS values (C1, 336.2 Å2, C2, 444.2 Å2, C3, 364.7 Å2), derived
from the drift times, are highly consistent with the theoretical ones
(Mobcal TM: 322.1 5.8 Å2, 437.3 15.3 Å2, and 363.0 6.2 Å2
for C1, C2, and C3, respectively, See Table S1-3). We also tried
different conditions to grow single crystals to characterize these
hemicages by X-ray analysis, but unfortunately, these endeavors
were failed.
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EXPERIMENTAL SECTION
All chemicals and solvents were purchased from commercial
sources, and used without further purification unless otherwise
noted. Compounds below were synthesized according to litera-
tures: 1,1ʹ-diiodoferrocene,57 1,1ʹ-dibromoferrocene,57 1-iodo-1ʹ-
(trimethylsilylethynyl)ferrocene (1a),58 triptycene,59 1,3,5-triiodo-
2,4,6-trimethoxybenzene
(5a),60
1-iodo-2-methoxy-4-
nitrobenzene (7a),61 2,7,14-triiodotriptycene (1c),62 triethy-
leneglycol monomethyl ether tosylate.63 Et2O and THF were puri-
fied by distillation from Na/benzophenone under a nitrogen at-
mosphere. Et3N was dried with KOH powder overnight prior to
use. All reactions were performed using either standard Schlenk
technique or in a glove box with dry solvents under nitrogen at-
mosphere. Column chromatography was carried out using silica
gel (200-300 mesh). 1H NMR (300 MHz), 13C{1H} NMR (75
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MHz), H-1H COSY, 1H-1H ROESY, and H DOSY spectra were
recorded in CDCl3, CD2Cl2 or CD3CN on a Bruker AVANCE III-
300 spectrometer (TOPSPIN 3.2 software version). Chemical
shifts (δ) were given in parts per million (ppm) using the residual
solvent peaks as internal standards: CHCl3 (δ 7.26 ppm) or
Figure 4. ESI-TWIM-MS plot of C1-3 (A-C).
1
CHD2CN (δ 1.94 ppm) for H NMR; CDCl3 (δ 77.16 ppm) or
CD3CN (δ 118.26 ppm) for 13C{1H} NMR. The coupling con-
stants (J) were reported as Hertz (Hz). Splitting patterns are
shown as s (singlet), d (doublet), t (triplet), m (multiplet), dd
(doublet of doublets), and br (broad signal). Melting points (mp)
were measured on a YUHUA X-5 micro-melting point apparatus
without correction.
Diffusion Ordered Spectroscopy (DOSY) Experiments. The DOSY
experiments were acquired using the standard Bruker pulse pro-
gram ledbpgp2s (2D LED experiment using bipolar gradients).
DOSY spectra were processed using the Bruker Topspin software
(version 3.2). Assuming that the cage is a spherical molecule, the
diffusion coefficient D is described using the Stokes-Einstein
equation
Figure 5. (A) Partial 1H NMR spectral changes of C2 (2.0 mM, 500 ꢀL) upon addi-
tion of adamantane from 0 to 16 mM (300 MHz, CD3CN, 293 K). (B) The adaman-
tane resonance signals shift to upfield upon encapsulation, inset: models of adaman-
tane and its complex with C2.
ꢂꢃ
ꢀ ꢁ
6πηrH
where k is the Boltzmann constant, T is the temperature, η is the
viscosity of the solvent and rH is the hydrodynamic radius.
To prove that the hemicage obtained has a well-defined inner
cavity, we carried out an encapsulation study (Figure 5). Molecu-
lar modeling indicates that C2 has an inner cavity which may bind
adamantane, a pseudo-spherical guest (Figure 5B, inset). This
expectation is proven by the experimental observation that the
resonance signals of adamantane undergo an evident shift to high
field, from 1.78 to 1.63 ppm, in the present of 1.4 equivalent C2
(Figure 5B). We attribute this spectral change to a shielding effect
resulting from host-guest encapsulation. An association constant
Ka of 320 30 M-1 is determined by fitting the titration curve
(Figure S24).
Mass Spectrometry and Traveling Wave Ion-Mobility Experi-
ments. Low-resolution electrospray ionization mass spectra
(LRMS-ESI) were obtained using TSQ Quantum Ultra mass spec-
trometer (Thermofisher). Electron ionization (EI) mass spectra
were obtained on a DSQ mass spectrometer (Thermofisher).
High-resolution electrospray ionisation mass spectra (HRMS-ESI)
were obtained on either a Bruker maXis 4G (electrospray ioniza-
tion time-of-flight mass spectrometry, ESI-TOF-MS), or a LTQ
Orbitrap Elite (Thermofisher) spectrometer.
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HR-MS and traveling wave ion-mobility (TWIM) experiments of
(s, 12H), 0.24 (s, 9H). 13C NMR (75 MHz, CDCl3) δ (ppm) 141.8,
135.0, 125.7, 103.8, 91.1, 86.2, 83.8, 73.8, 71.4, 70.5, 69.2, 65.8,
25.0, 0.4. HRMS (ESI-TOF) m/z: [M]+ Calcd. for C27H33BFeO2Si
484.1692; Found 484.1711.
the cages were conducted on a Waters Synapt HDMS G2 with a
LockSpray ESI source, using the same measurement conditions in
the literature.64 The experimental collision cross-sections (CCSs)
and molecular modeling were obtained according to the litera-
ture.64,65
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Synthesis of 4a. A mixture of 3a (2.0 g, 4.13 mmol) and K2CO3
(1.14 g, 8.25 mmol) in THF (20 mL) and MeOH (50 mL) was
stirred at 25 °C overnight. Then the reaction mixture was filtered
through a pad of Celite with CH2Cl2 as eluent, and the filtrate was
concentrated in vacuo. The crude residue was purified by flash
chromatography (silica gel, CH2Cl2/petroleum ether 1/3, v/v, Rf ≈
0.25) to afford 4a (1.29 g, yield 76%) as a yellow solid. mp 126.8
General Procedure for the Suzuki-Miyaura Coupling.66 A mixture
of halogenated reactant, 1.2-1.5 equivalents of the corresponding
boronic acid pinacol ester, Pd catalyst (3-5 mol %) and 3 equiva-
lents of base in toluene/MeOH = 3:1 (v/v) solution was refluxed
for the appropriate time under a nitrogen atmosphere. The reac-
tion was monitored by thin layer chromatography. The reaction
mixture was then allowed to cool to 25 °C and filtered through
Celite with CH2Cl2 as eluent. Then the solvent was removed in
vacuo. The residue was purified by column chromatography on
silica gel.
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– 130.1 °C. H NMR (300 MHz, CDCl3) δ (ppm) 7.75 (d, J = 8.2
Hz, 2H), 7.51 (d, J = 8.3 Hz, 2H), 4.73 – 4.66 (m, 2H), 4.42 –
4.36 (m, 2H), 4.27 – 4.20 (m, 2H), 4.08 – 4.02 (m, 2H), 2.67 (s,
1H), 1.36 (s, 12H). 13C NMR (75 MHz, CDCl3) δ (ppm) 141.5,
135.0, 125.6, 86.1, 83.8, 82.1, 74.2, 73.6, 71.5, 70.7, 68.7, 64.9,
25.0. HRMS (ESI-TOF) m/z: [M]+ Calcd. for C24H25BFeO2
412.1296; Found 412.1304.
General Procedure for the Sonogashira Coupling.67 A mixture of
aryl halide, 1.2-1.5 equivalents of the corresponding terminal
alkyne, Pd catalyst (3-5 mol %), and CuI (6-10 mol %) in Et3N
solution was refluxed for the appropriate time under a nitrogen
atmosphere, and the reaction was monitored by thin layer chroma-
tography. The reaction mixture was then allowed to cool to 25 °C
and filtered through Celite with CH2Cl2 as eluent. Then the sol-
vent was removed in vacuo. The residue was purified by column
chromatography on silica gel.
Synthesis of 6a. Following the general procedure of Sonogashira
coupling, a mixture of 1,3,5-triiodo-2,4,6-trimethoxybenzene 5a
(300 mg, 0.55 mmol), 4a (780 mg, 1.89 mmol), Pd(PPh3)2Cl2
(150 mg, 0.21 mmol), CuI (75 mg, 0.39 mmol), and Et3N (50 mL)
was refluxed for 22 h. The residue was purified by column chro-
matography (silica gel, EtOAc/petroleum ether 1/8, v/v, Rf ≈ 0.2)
to afford 6a (331 mg, yield 43%) as a red-brown solid. mp 113.1
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– 116.0 °C. H NMR (300 MHz, CDCl3) δ (ppm) 7.74 (d, J = 8.2
Synthesis of C1 (Scheme S1).
Hz, 6H), 7.55 (d, J = 8.1 Hz, 6H), 4.75 (pseudo-t, J = 1.9 Hz, 6H),
4.48 (pseudo-t, J = 1.9 Hz, 6H), 4.35 (pseudo-t, J = 1.9 Hz, 6H),
4.13 (s, 9H), 4.11 (pseudo-t, J = 1.9 Hz, 6H), 1.34 (s, 36H). 13C
NMR (75 MHz, CDCl3) δ (ppm) 163.0, 141.9, 135.0, 125.7,
108.5, 96.0, 86.2, 83.8, 77.5, 73.2, 71.7, 71.1, 68.8, 66.4, 61.4,
25.0. HRMS (ESI-TOF) m/z: [M]+ Calcd. for C81H81B3Fe3O9
1398.4241; Found 1398.4227.
Synthesis of 2a.68 In a 100 mL Schlenk flask, a THF (60 mL) solu-
tion of 1a (2.13 g, 5.22 mmol) was stirred at -78 °C for 15 min.
Then n-BuLi (4.3 mL, 6.88 mmol, 1.6 M in n-hexane) was added
and the mixture was stirred for 30 min at -78 °C. After warming
to 0 °C, anhydrous zinc chloride (1.00 g, 7.35 mmol) in 10 mL
THF was added and the solution was stirred at 0 °C for 120 min.
Then the pre-reduced Pd(PPh3)2Cl2 (294 mg, 0.42 mmol) with
DIBAL-H (600 ꢀL, 0.90 mmol, 1.5 M in toluene) in 10 mL THF
and the 1-bromo-4-iodobenzene (1.92 g, 6.78 mmol) in 10 mL
THF were added sequentially. The resulting mixture was stirred at
70 °C for 17 h. The mixture was cooled to 25 °C. Dilute aqueous
NaOH and CH2Cl2 were added and the organic phase was sepa-
rated, washed with water, dried (MgSO4) and concentrated in
vacuo. The crude product was purified by column chromatog-
raphy (silica gel, petroleum ether/ CH2Cl2, 15:1, v/v, Rf ≈ 0.3) to
afford a red-brown solid (1.17 g, yield 51%). mp 102.2 – 104.8
Synthesis of 8a. Following the general procedure of Suzuki-
Miyaura coupling, a mixture of 6a (331 mg, 0.24 mmol), 1-iodo-
2-methoxy-4-nitrobenzene 7a (290 mg, 1.04 mmol), Pd(PPh3)4
(110 mg, 0.095 mmol), K2CO3 (690 mg, 5.00 mmol), toluene (36
mL) and MeOH (12 mL) was refluxed overnight. The residue was
purified by column chromatography (silica gel, CH2Cl2/petroleum
ether 4/1, v/v, Rf ≈ 0.5) to afford 8a (330 mg, yield 95%) as a
brick red solid. mp 117.1 – 118.6 °C. 1H NMR (300 MHz, CDCl3)
δ (ppm) 7.87 (dd, J = 8.4, 2.2 Hz, 3H), 7.77 (d, J = 2.2 Hz, 3H),
7.60 (d, J = 8.3 Hz, 6H), 7.46 (d, J = 8.3 Hz, 6H), 7.40 (d, J = 8.4
Hz, 3H), 4.69 (pseudo-t, J = 1.9 Hz, 6H), 4.45 (pseudo-t, J = 1.9
Hz, 6H), 4.35 (pseudo-t, J = 1.9 Hz, 6H), 4.22 (pseudo-t, J = 1.9
Hz, 6H), 4.06 (s, 9H), 3.88 (s, 9H). 13C NMR (75 MHz, CDCl3) δ
(ppm) 162.7, 156.8, 147.8, 138.7, 137.2, 134.2, 130.8, 129.6,
126.4, 116.3, 108.5, 106.3, 96.1, 86.4, 77.7, 73.3, 71.2, 70.7, 68.9,
66.5, 61.3, 56.2. HRMS (ESI-TOF) m/z: [M]+ Calcd. for
C84H63Fe3N3O12 1473.2464; Found 1473.2478.
1
°C. H NMR (300 MHz, CDCl3): δ (ppm) 7.41 (s, 4H), 4.55 (s,
2H), 4.37 (s, 2H), 4.20 (s, 2H), 4.08 (s, 2H), 0.24 (s, 9H). 13C
NMR (75 MHz, CDCl3) δ (ppm) 137.7, 131.6, 128.0, 119.9,
103.7, 91.3, 85.5, 73.8, 71.3, 70.4, 69.0, 66.0, 0.4. HRMS (ESI-
TOF) m/z: [M]+ Calcd. for C21H21BrFeSi 435.9942 and 437.9920;
Found 435.9946 and 437.9925.
Synthesis of 3a. In a 50 mL Schlenk flask, 2a (1.16 g, 2.65 mmol)
was dissolved in 15 mL THF and the solution was cooled to -78
°C. n-BuLi (2.2 mL, 3.52 mmol, 1.6 M in n-hexane) was added
Synthesis of L1. To a 100 mL Schlenk flask were added 8a (261
mg, 0.176 mmol), SnCl2·2H2O (1.78 g, 7.89 mmol), THF (50 mL)
and MeOH (15 mL). The mixture was stirred at 65 °C for 12 h.
The reaction mixture was neutralized by NaHCO3 (aq) and ex-
tracted with CH2Cl2. The organic layer was dried over anh.
Na2SO4 and concentrated in vacuo. The residue was purified by
column chromatography (silica gel, CH2Cl2/EtOAc 100/3, v/v, Rf
≈ 0.2) to afford L1 (242 mg, yield 99%) as an orange-red solid.
dropwise. After
1 h, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (900 ꢀL, 4.41 mmol) was added. The mixture was
stirred at -78 °C for 4 h, then warmed to 25 °C and further stirred
overnight. The reaction mixture was quenched with water and
filtered through Celite with CH2Cl2 as eluent. The organic layer
was dried over anh. Na2SO4 and evaporated. The residue was
purified by column chromatography (silica gel, CH2Cl2/petroleum
ether 1/5 (Rf ≈ 0.4) to 3/2, v/v) to afford the product (820 mg,
1
mp 115.0 – 117.1 °C. H NMR (300 MHz, CDCl3) δ (ppm) 7.54
(d, J = 8.2 Hz, 6H), 7.43 (d, J = 8.1 Hz, 6H), 7.12 (d, J = 8.0 Hz,
3H), 6.34 (d, J = 8.0 Hz, 3H), 6.31 (s, 3H), 4.67 (s, 6H), 4.42 (s,
6H), 4.37 (s, 6H), 4.18 (s, 6H), 4.10 (s, 9H), 3.77 (s, 9H), 3.70 (s,
6H). 13C NMR (75 MHz, CD2Cl2) δ 163.3, 158.0, 148.1, 137.5,
1
yield 63%) as a yellow solid. mp 91.6 – 94.4 °C. H NMR (300
MHz, CDCl3) δ (ppm) 7.75 (d, J = 7.8 Hz, 2H), 7.52 (d, J = 7.9
Hz, 2H), 4.63 (s, 2H), 4.38 (s, 2H), 4.19 (s, 2H), 4.05 (s, 2H), 1.36
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The Journal of Organic Chemistry
136.3, 131.7, 129.8, 126.5, 120.9, 109.1, 107.8, 99.1, 96.6, 87.7,
C13H18BrIO4K 482.9065 and 484.9045; Found 482.9087 and
78.0, 73.5, 71.5, 71.3, 69.0, 66.6, 61.8, 55.8. HRMS (ESI-TOF)
m/z: [M+H]+ Calcd. for C84H70Fe3N3O6 1384.3317; Found
1384.3220.
484.9068.
1
2
3
4
5
6
7
8
4ʹ-Bromo-2ʹ-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-[1,1ʹ-
biphenyl]-4-amine (4b). Following the general procedure of Su-
zuki-Miyaura coupling, a mixture of 3b (2.33 g, 5.24 mmol), 4-
(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (1.5 g, 6.9
mmol), Pd(PPh3)4 (300 mg, 0.26 mmol), K2CO3 (2.16 g, 15.65
mmol), toluene (80 mL), and MeOH (20 mL) was refluxed over-
night. The residue was purified by column chromatography (silica
gel, CH2Cl2/EtOAc 5/1, v/v, Rf ≈ 0.3) to afford 4b (1.35 g, yield
63%) as a colorless oil. 1H NMR (300 MHz, CDCl3) δ (ppm) 7.35
(d, J = 8.4 Hz, 2H), 7.19 – 7.06 (m, 3H), 6.70 (d, J = 8.5 Hz, 2H),
4.09 (t, J = 4.8 Hz, 2H), 3.78 (t, J = 4.9 Hz, 2H), 3.67 – 3.58 (m,
6H), 3.57 – 3.50 (m, 2H), 3.37 (s, 3H). 13C NMR (75 MHz,
CDCl3) δ (ppm) 156.5, 145.7, 131.5, 130.5, 130.2, 127.7, 124.3,
120.7, 116.5, 114.8, 72.1, 71.0, 70.8, 70.7, 69.7, 68.6, 59.2.
LRMS (ESI-TOF) m/z: [M+H]+ Calcd. 410.1; Found 410.1.
Synthesis of C1. In a 25 mL Schlenk tube, to a CHCl3 solution
(1000 ꢀL) of L1 (21.55 mg, 0.0147 mmol), 2-
pyridinecarboxaldehyde (5.2 mg, 0.0486 mmol) in 460 ꢀL CHCl3
was added. After stirring for 3 minutes, an MeCN solution (1500
ꢀL) of iron (II) tetrafluoroborate hexahydrate (5.75 mg, 0.0170
mmol) was added. The reaction mixture was stirred at 50 °C for 8
h. After cooling to 25 °C, Et2O (30 mL) was added to the reaction
mixture. The resulted flocculent precipitate was collected by cen-
trifugation, washed three times with Et2O (3 × 20 mL) and dried
in vacuo to afford the product (20.0 mg, yield 69%) as a black
brown solid. 1H NMR (300 MHz, CD3CN) δ 9.16 (s, 3H), 8.58 (d,
J = 7.7 Hz, 3H), 8.37 (t, J = 7.7 Hz, 3H), 7.82 (t, J = 6.7 Hz, 3H),
7.69 (d, J = 8.1 Hz, 6H), 7.54 (d, J = 5.6 Hz, 3H), 7.47 (d, J = 8.1
Hz, 6H), 7.23 (d, J = 8.1 Hz, 3H), 5.39 (d, J = 1.9 Hz, 3H), 5.14
(d, J = 7.9 Hz, 3H), 4.76 (s, 3H), 4.74 (s, 3H), 4.59 (s, 3H), 4.47
(s, 3H), 4.43 (s, 3H), 4.37 (s, 3H), 4.22 (s, 3H), 4.17 (s, 9H), 3.95
(s, 3H), 3.38 (s, 9H). HRMS (ESI-TOF) m/z: [M]2+ Calcd. for
C102H78Fe4N6O6 853.6703; Found 853.6717,
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1,1ʹ-Bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)phenyl]ferrocene (5b). In a 100 mL Schlenk flask, 1,1’-di(4-
bromophenyl)ferrocene (2.0 g, 4.03 mmol) was dissolved in 50
mL dry THF, then n-BuLi (4.8 mL, 12 mmol, 2.5 M in n-hexane)
was added dropwise at -78 °C. The solution was stirred at -78 °C
In situ synthesis of C1. To a 4 mL glass bottle, L1 (1.38 mg, 1.00
ꢀmol) and then 2-pyridine-carboxaldehyde (0.33 mg, 3.05 ꢀmol)
in 150 ꢀL CDCl3 were added. After stirring for 3 minutes, a
CD3CN solution (450 ꢀL) of iron (II) tetrafluoroborate hexahy-
drate (0.37 mg, 1.10 ꢀmol) was added. The reaction mixture was
stirred at 25 °C for 10 h. The deep burgundy solution was used for
the NMR experiments.
for
1
h. Then, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (2.7 mL, 13.2 mmol) was added, and the solution
was stirred for additional 4 h at -78 °C. After that, the resulting
mixture was warmed to 25 °C and stirred overnight. The reaction
was quenched with water and filtered through a pad of Celite with
CH2Cl2 as eluent, then extracted with CH2Cl2. The organic layer
was dried over anh. Na2SO4 and evaporated. The residue was
purified by column chromatography (silica gel, CH2Cl2 / petrole-
um ether, 2/3 (Rf ≈ 0.17) to 1/1, v/v) to afford 5b (1.6 g, 67%) as a
brick red solid. mp 163.7 – 165.0 °C. 1H NMR (300 MHz, CDCl3)
δ (ppm) 7.71 (d, J = 8.0 Hz, 4H), 7.37 (d, J = 8.1 Hz, 4H), 4.45
(pseudo-t, J = 1.9 Hz, 4H), 4.20 (pseudo-t, J = 1.9 Hz, 4H), 1.37
(s, 24H). 13C NMR (75 MHz, CDCl3) δ (ppm) 142.1, 134.9,
125.4, 85.5, 83.8, 71.2, 68.6, 25.1. HRMS (ESI-TOF) m/z: [M]+
Calcd. for C34H40B2FeO4 590.2469; Found 590.2500.
Synthesis of C2 (Scheme S2).
5-Bromo-2-iodo-phenol (2b). A 2 M solution of boron tribromide
in CH2Cl2 (9.6 mL, 19.2 mmol) was added dropwise to 4-bromo-
1-iodo-2-methoxybenzene (3.0 g, 9.59 mmol) in CH2Cl2 (100 ml)
at -78 °C. The resulting mixture was stirred at -78 °C for 2 h, then
allowed to warm to 25 °C, and stirred overnight. The reaction was
then quenched by pouring in ice bath with caution. The organic
phase was extracted with water (2 × 200 mL), brine (100 mL),
dried over anh. Na2SO4, and concentrated in vacuum. The residue
was purified by column chromatography (silica gel,
CH2Cl2/petroleum ether 1/5, v/v, Rf ≈ 0.2) to afford 2b (2.15 g,
Synthesis of 6b. Following the general procedure of Suzuki-
Miyaura coupling, a mixture of 4b (957 mg, 2.33 mmol), 5b (2.75
g, 4.66 mmol), Pd(PPh3)4 (135 mg, 0.117 mmol), K2CO3 (1000
mg, 7.25 mmol), toluene (50 mL), and MeOH (18 mL) was re-
fluxed overnight. The residue was purified by column chromatog-
raphy (silica gel, CH2Cl2/EtOAc 4/1, v/v, Rf ≈ 0.4) to afford 6b
1
yield 75%) as a white solid. mp 57.1 – 58.1 °C. H NMR (300
MHz, CDCl3) δ (ppm) 7.50 (d, J = 8.4 Hz, 1H), 7.16 (d, J = 2.2
Hz, 1H), 6.83 (dd, J = 8.4, 2.2 Hz, 1H), 5.32 (s, 1H). 13C NMR
(75 MHz, CDCl3) δ (ppm) 155.7, 139.1, 125.8, 123.6, 118.6, 84.1.
The characterization data were in agreement with the data previ-
ously reported.69
1
(1.0 g, yield 54%) as a brick red oil. H NMR (300 MHz, CDCl3)
δ (ppm) 7.67 (d, J = 7.8 Hz, 2H), 7.47 (d, J = 8.0 Hz, 4H), 7.42 –
7.32 (m, 5H), 7.29 (d, J = 1.6 Hz, 1H), 7.20 (d, J = 1.7 Hz, 1H),
6.75 (d, J = 8.3 Hz, 2H), 4.53 (pseudo-t, J = 1.9 Hz, 2H), 4.49
(pseudo-t, J = 1.8 Hz, 2H), 4.30 – 4.18 (m, 6H), 3.84 (t, J = 4.9
Hz, 2H), 3.72 – 3.60 (m, 6H), 3.57 – 3.49 (m, 2H), 3.37 (s, 3H),
1.34 (s, 12H). 13C NMR (75 MHz, CDCl3) δ (ppm) 156.1, 145.5,
141.8, 140.8, 138.5, 137.5, 134.9, 130.8, 130.6, 130.0, 128.6,
127.0, 126.4, 125.4, 119.9, 114.8, 111.7, 85.8, 85.6, 83.8, 72.1,
71., 71.0, 70.9, 70.9, 70.7, 69.9, 68.5, 68.3, 68.2, 59.2, 25.0.
HRMS (ESI-TOF) m/z: [M]+ Calcd. for C47H52BFeNO6 793.3240;
Found 793.3264.
4-Bromo-1-iodo-2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzene
(3b). A mixture of 5-bromo-2-iodophenol (1.69 g, 5.65 mmol), 2-
(2-(2-methoxyethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (5.4
g, 16.98 mmol), K2CO3 (2.34 g, 16.96 mmol), NaI (117 mg, 0.78
mmol), and butanone (50 mL) was refluxed for 17 h. The reaction
mixture was filtered through a pad of Celite with CH2Cl2 as eluent
and evaporated to dryness. The residue was purified by column
chromatography (silica gel, CH2Cl2/EtOAc 10/1, v/v, Rf ≈ 0.5) to
1
afford 3b (1.14 g, yield 45%) as a colorless oil. H NMR (300
Synthesis of L2. Following the general procedure of Suzuki-
Miyaura coupling, a mixture of 6b (358 mg, 0.45 mmol), 5a (70
mg, 0.13 mmol), Pd(PPh3)4 (31 mg, 0.026 mmol), K2CO3 (108
mg, 0.78 mmol), toluene (18 mL), and MeOH (6 mL) was re-
fluxed overnight. The residue was purified by column chromatog-
raphy (silica gel, CH2Cl2/MeOH 80/1, v/v, Rf ≈ 0.2) to afford L2
(110 mg, yield 39%) as an orange-red solid. mp 75.1 – 75.9 °C.
1H NMR (300 MHz, CDCl3) δ (ppm) 7.56 – 7.40 (m, 30H), 7.38
MHz, CDCl3) δ (ppm) 7.59 (d, J = 8.3 Hz, 1H), 6.96 (d, J = 2.0
Hz, 1H), 6.85 (dd, J = 8.3, 2.0 Hz, 1H), 4.21 – 4.10 (m, 2H), 3.97
– 3.86 (m, 2H), 3.84 – 3.76 (m, 2H), 3.71 – 3.62 (m, 4H), 3.58 –
3.50 (m, 2H), 3.37 (s, 3H). 13C NMR (75 MHz, CDCl3) δ (ppm)
158.4, 140.3, 125.9, 122.9, 116.0, 85.0, 72.1, 71.4, 70.9, 70.7,
69.6, 69.5, 59.2. HRMS (ESI-TOF) m/z: [M+K]+ Calcd. for
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 8
(d, J = 7.9 Hz, 3H), 7.30 – 7.24 (m, 3H), 7.20 (d, J =1.7 Hz, 3H),
CDCl3) δ (ppm) 156.8, 147.8, 144.6, 144.0, 138.4, 137.2, 134.0,
130.7, 129.5, 128.8, 126.6, 126.2, 123.7, 121.1, 116.2, 106.3,
87.2, 86.5, 86.2, 73.1, 71.1, 70.5, 68.6, 66.8, 56.2, 53.5, 53.5.
HRMS (ESI-TOF) m/z: [M]+ Calcd. for C95H65Fe3N3O9
1560.2799; Found 1560.2833.
6.73 (d, J = 8.4 Hz, 6H), 4.54 (pseudo-t, J = 1.9 Hz, 6H), 4.49
(pseudo-t, J = 1.9 Hz, 6H), 4.29 – 4.16 (m, 18H), 3.81 (t, J = 4.9
Hz, 6H), 3.72 – 3.58 (m, 18H), 3.56 – 3.47 (m, 6H), 3.36 (s, 9H),
3.22 (s, 9H). 13C NMR (75 MHz, CDCl3) δ (ppm) 156.2, 156.0,
145.5, 140.7, 138.6, 138.1, 137.4, 132.1, 130.9, 130.7, 130.7,
130.1, 128.5, 127.0, 126.6, 126.0, 125.7, 119.9, 114.8, 111.8,
85.9, 85.7, 72.1, 71.1, 71.1, 71.0, 70.9, 70.7, 69.9, 68.6, 68.4,
68.3, 60.7, 59.2. HRMS (ESI-TOF) m/z: [M+2Na]3+ Calcd. for
C132H129Fe3N3O15Na2 736.9097; Found 736.9107.
1
2
3
4
5
6
7
8
Synthesis of L3. A mixture of 3c (347 mg, 0.22 mmol),
SnCl2·2H2O (2.8 g, 12.4 mmol), THF (60 mL), and MeOH (20
mL) was stirred at 65 °C for 12 h. After the reaction mixture had
been neutralized by NaHCO3 (aq) and extracted with CH2Cl2, the
organic layer was dried over anh. Na2SO4 and concentrated in
vacuo. The residue was purified by column chromatography (sili-
ca gel, CH2Cl2/EtOAc 100/3 to 100/10, v/v, Rf ≈ 0.3) to afford L3
9
Synthesis of C2. In a 25 mL Schlenk tube, to a CHCl3 solution
(1500 ꢀL) of L2 (30.40 mg, 0.014 mmol), 2-
pyridinecarboxaldehyde (4.96 mg, 0.046 mmol) in 500 ꢀL CHCl3
was added. After stirring for 3 minutes, an MeCN solution (2000
ꢀL) of iron (II) tetrafluoroborate hexahydrate (6.16 mg, 0.018
mmol) was added. The reaction mixture was stirred at 50 °C for 8
h. After cooling to 25 °C, Et2O (30 mL) was added to the reaction
mixture. The resulted flocculent precipitate was collected by cen-
trifugation, washed three times with Et2O (3 × 20 mL) and dried
in vacuo to afford the product (26.6 mg, yield 73%) as a black
brown solid. 1H NMR (300 MHz, CD3CN) δ 8.95 (s, 3H), 8.56 (d,
J = 7.7 Hz, 3H), 8.41 (t, J = 7.9 Hz, 3H), 7.77 (t, J = 6.6 Hz, 3H),
7.62 – 7.26 (m, 42H), 5.41 (d, J = 8.0 Hz, 6H), 4.49 (s, 12H), 4.38
(s, 6H), 4.25 (s, 6H), 4.15 (s, 6H), 3.66 (s, 6H), 3.46 – 3.17 (m,
33H), 3.12 (s, 9H). HRMS (ESI-TOF) m/z: [M]2+ Calcd. for
C150H138Fe4N6O15 1243.8826; Found 1243.8822.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
(300 mg, yield 92%) as a yellow solid. mp 152.7 – 154.5 °C. H
NMR (300 MHz, CDCl3) δ (ppm) 7.53 (d, J = 8.5 Hz, 6H), 7.44
(d, J = 8.5 Hz, 6H), 7.41 (d, J = 1.3 Hz, 3H), 7.31 (d, J = 7.6 Hz,
3H), 7.18 – 7.08 (m, 6H), 6.36 – 6.28 (m, 6H), 5.39 (s, 1H), 5.16
(s, 1H), 4.66 (pseudo-t, J = 1.9 Hz, 6H), 4.37 (pseudo-t, J = 1.9
Hz, 6H), 4.32 (pseudo-t, J = 1.9 Hz, 6H), 4.16 (pseudo-t, J = 1.9
Hz, 6H), 3.76 (s, 9H), 3.51 – 3.94 (br, 6H). 13C NMR (75 MHz,
CDCl3) δ (ppm) 157.6, 147.3, 144.7, 144.1, 136.7, 135.8, 131.5,
129.4, 128.8, 126.9, 126.1, 123.7, 121.1, 121.0, 107.7, 99.0, 87.4,
87.2, 86.5, 73.2, 70.8, 70.5, 68.6, 66.4, 55.6, 53.7, 53.3. HRMS
(ESI-TOF) m/z: [M]+ Calcd. for C95H71Fe3N3O3 1470.3573;
Found 1470.3613.
Synthesis of C3. In a 10 mL Schlenk tube, to a CHCl3 solution
(800 ꢀL) of L3 (16.10 mg, 0.011 mmol), 2-
pyridinecarboxaldehyde (3.88 mg, 0.036 mmol) in 335 ꢀL CHCl3
was added. After stirring for 3 minutes, an MeCN solution (1150
ꢀL) of iron (II) tetrafluoroborate hexahydrate (4.80 mg, 0.014
mmol) was added. The reaction mixture was stirred at 50 °C for 8
h. After cooling to 25 °C, Et2O (30 mL) was added to the reaction
mixture. The resulted flocculent precipitate was collected by cen-
trifugation, washed three times with Et2O (3 × 20 mL) and dried
in vacuo to afford the product (15.3 mg, yield 74%) as a black
brown solid. 1H NMR (300 MHz, CD3CN) δ 9.03 (s, 3H), 8.55 (d,
J = 7.4 Hz, 3H), 8.41 (t, J = 7.7 Hz, 3H), 7.91 – 7.56 (m, 18H),
7.55 – 7.37 (m, 9H), 7.23 (d, J = 7.6 Hz, 3H), 5.86 (s, 1H), 5.74
(s, 1H), 5.63 (d, J = 8.7 Hz, 6H), 4.60 – 4.28 (m, 18H), 4.05 (s,
3H), 3.96 (s, 3H), 3.63 (s, 9H). HRMS (ESI-TOF) m/z: [M]2+
Calcd. for C174H150Fe4N6O15 896.6872; Found 896.6794.
In situ synthesis of C2. To a 4 mL glass bottle, L2 (2.16 mg, 1.00
ꢀmol), and 2-pyridine-carboxaldehyde (0.33 mg, 3.05 ꢀmol) in
150 ꢀL CDCl3 were added. After stirring for 3 minutes, a CD3CN
solution (450 ꢀL) of iron (II) tetrafluoroborate hexahydrate (0.37
mg, 1.10 ꢀmol) was added. The reaction mixture was stirred at 25
°C for 10 h. The deep burgundy solution was used for the NMR
experiments.
Synthesis of C3 (Scheme S3).
Synthesis of 2c. Following the general procedure of Sonogashira
coupling, a mixture of 4a (990 mg, 2.40 mmol), 2,7,14-
triiodotriptycene 1c (430 mg, 0.68 mmol), Pd(PPh3)2Cl2 (180 mg,
0.26 mmol), CuI (90 mg, 0.47 mmol), and Et3N (60 mL) was
refluxed for 18 h. The residue was purified by column chromatog-
raphy (silica gel, CH2Cl2/petroleum ether 3/2, v/v, Rf ≈ 0.4) to
afford 2c (820 mg, yield 84%) as a red-brown solid. mp 169.6 –
In situ synthesis of C3. To a 4 mL glass bottle, L3 (1.75 mg, 1.2
ꢀmol) and then 2-pyridine-carboxaldehyde (0.39 mg, 3.66 ꢀmol)
in 165 ꢀL CDCl3 were added. After stirring for 3 minutes, a
CD3CN solution (435 ꢀL) of iron (II) tetrafluoroborate hexahy-
drate (0.44 mg, 1.32 ꢀmol) was added. The reaction mixture was
stirred at 25 °C for 10 h. The deep burgundy solution was used for
the NMR experiments.
1
172.3 °C. H NMR (300 MHz, CDCl3) δ (ppm) 7.75 (d, J = 7.7
Hz, 6H), 7.59 (s, 3H), 7.52 (d, J = 7.9 Hz, 6H), 7.37 (d, J = 7.6
Hz, 3H), 7.15 (d, J = 7.6 Hz, 3H), 5.51 (s, 1H), 5.44 (s, 1H), 4.67
(s, 6H), 4.39 (s, 6H), 4.24 (s, 6H), 4.08 (s, 6H), 1.37 (s, 36H). 13C
NMR (75 MHz, CDCl3) δ (ppm) 144.8, 144.1, 141.9, 135.0,
128.8, 127.0, 125.6, 123.8, 121.1, 87.3, 86.4, 86.0, 83.9, 73.4,
71.5, 70.7, 68.9, 66.3, 53.8, 53.3, 25.1. HRMS (ESI-TOF) m/z:
[M]+ Calcd. for C92H83B3Fe3O6 1484.4554; Found 1484.4543.
ASSOCIATED CONTENT
Supporting Information
Synthesis of 3c. Following the general procedure of Suzuki-
Miyaura coupling, a mixture of 2c (445 mg, 0.31 mmol), 1-iodo-
2-methoxy-4-nitrobenzene 7a (312 mg, 1.12 mmol), Pd(PPh3)4
(72 mg, 0.06 mmol), K2CO3 (445 mg, 3.22 mmol), toluene (30
mL) and MeOH (10 mL) was refluxed overnight. The residue was
purified by column chromatography (silica gel, CH2Cl2/petroleum
ether 2/1, v/v, Rf ≈ 0.4) to afford 3c (434 mg, yield 90%) as a red-
brown solid. mp 142.6 – 145.3 °C. 1H NMR (300 MHz, CDCl3) δ
(ppm) 7.80 – 7.75 (m, 6H), 7.55 (d, J = 8.6 Hz, 6H), 7.41 (d, J =
8.5 Hz, 9H), 7.29 – 7.22 (m, 6H), 7.08 (dd, J = 7.6, 1.6 Hz, 3H),
5.34 (s, 1H), 5.23 (s, 1H), 4.68 (pseudo-t, J = 1.9 Hz, 6H), 4.41
(pseudo-t, J = 1.9 Hz, 6H), 4.32 (pseudo-t, J = 1.9 Hz, 6H), 4.17
(pseudo-t, J = 1.9 Hz, 6H), 3.85 (s, 9H). 13C NMR (75 MHz,
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.
Synthetic routes, molecular models, and characterizations of C1-3,
1H NMR titration experiment, spectroscopic data (1H NMR and
13C NMR) of new compounds and cartesian coordinates of the
optimized hemicages.
AUTHOR INFORMATION
Corresponding Author
*Email: wangjb5@mail.sysu.edu.cn.
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENT
This research was supported by the National Natural Science
Foundation of China (Grant Nos. 21372264), the Foundation of
Guangzhou Science and Technology (201504010021), and the
Program for Changjiang Scholars and Innovative Research Team
in University of China (IRT1298).
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