Construction of rotacatenanes using rotaxane and catenane frameworks

Article abstract of DOI:10.1039/c4ob00602j

The construction of novel mechanically interlocked structures has become a topic of great current interest due to the requirements of topology and their potential application in molecular machines and devices. Rotaxane and catenane as two basic topological frameworks can be used to construct the fused structures. In the current investigation, a class of novel ammonium backbones were synthesized. The ammonium group incorporated in the linear part of the molecule can be used for templating rotaxane formation while the macrocyclic part of the molecule can be used for templating catenane formation. Accordingly, they were subjected to dynamic covalent chemistry, resulting in a series of [n]rota[n]catenane structures (n = 2, 3, 4). In this process, the N-hetero crown ethers were installed on ammonium template sites of linear and macrocyclic components all at once by a template-directed clipping reaction. The results showed that these novel building blocks could be assembled with high efficiencies. Finally, this investigation provides a foundation for future studies aimed at constructing complicated integrated structures or polymers with multiple topological units. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ob00602j

Organic &
Biomolecular Chemistry
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Construction of rotacatenanes using rotaxane and
catenane frameworks†
Cite this: Org. Biomol. Chem., 2014,
12, 4862
Wen Xue,a Ziyong Li,a Guoxing Liu,a Xiaoqiang Chen,b Tingting Li,c Sheng Hua Liua
and Jun Yin*a
The construction of novel mechanically interlocked structures has become a topic of great current inter-
est due to the requirements of topology and their potential application in molecular machines and
devices. Rotaxane and catenane as two basic topological frameworks can be used to construct the fused
structures. In the current investigation, a class of novel ammonium backbones were synthesized. The
ammonium group incorporated in the linear part of the molecule can be used for templating rotaxane
formation while the macrocyclic part of the molecule can be used for templating catenane formation.
Accordingly, they were subjected to dynamic covalent chemistry, resulting in a series of [n]rota[n]cate-
nane structures (n = 2, 3, 4). In this process, the N-hetero crown ethers were installed on ammonium
template sites of linear and macrocyclic components all at once by a template-directed clipping reaction.
The results showed that these novel building blocks could be assembled with high efficiencies. Finally,
this investigation provides a foundation for future studies aimed at constructing complicated integrated
structures or polymers with multiple topological units.
Received 20th March 2014,
Accepted 15th April 2014
DOI: 10.1039/c4ob00602j
www.rsc.org/obc
construction of main-chain, side-chain, bridged, or pendant
polycatenanes and dendrimers.2a,g,3 Additionally, integrated
Introduction
The mechanical bonds widely existing in numerous molecules architectures such as hetero[n]rotaxanes with different macro-
such as rotaxanes, catenanes, knots and links, have evoked cyclic components or different dumbbell-shaped components
considerable interest in exploring intriguing architectures and are gaining increasing attention.4 Recently, we reported a type
topologies, molecular switches and devices, nanotechnology, of novel dual functional building blocks (A) containing both a
biological functional machines, drug delivery and materials crown ether and an ammonium cation group. They were
science based on mechanically interlocked structures.1 As a employed to construct the novel topological hetero[n]rotaxanes
result, the design and construction of mechanically inter- (in Scheme 1) in which the ammonium unit served as a tem-
locked molecules (MIMs) with novel configurations has plate for incorporating an encircling macrocyclic ring by using
become one of the most popular research projects in supra- template-directed clipping reaction while the crown ether com-
molecular chemistry and self-assembly. Along with the great ponent was then subjected to a threading-followed-by-stopper-
development of MIMs, rotaxanes and catenanes, as the most ing sequence to install a second encircling crown ether ring as
common MIMs, have shown a trend from single and simple part of the new heterorotaxane.5 Similar work was also reported
structures to complicated and polymeric structures over recent by Leung.6 The above integration was constructed only by
decades.1 For example, rotaxanes can be used to construct fusing one type of mechanically interlocked framework.
main-chain or side-chain polyrotaxanes, dendrimers and poly-
[c2]daisy chains,1r,2 while catenanes can be applied in the
aKey Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of
Chemistry, Central China Normal University, Wuhan 430079, PR China.
E-mail: yinj@mail.ccnu.edu.cn
bState Key Laboratory of Materials-Oriented Chemical Engineering, College of
Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing
210009, China
cInstitute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430079, PR China
†Electronic supplementary information (ESI) available: The 1H NMR, 13C NMR
and MS spectra of all the new intermediates and [n]rota[n]catenanes. See DOI:
Scheme 1 Schematic representation of the route for heterorotaxane
10.1039/c4ob00602j
and rotacatenane integration.
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In contrast, the other integration involved in different ammonium (B) involving one ammonium on the linear com-
mechanically interlocked frameworks. As early in 1999, Stod- ponent of the backbone and the second ammonium on the
dart’s group reported a type of novel integration by fusing a macrocyclic component of the backbone as in Scheme 1, the
rotaxane moiety and a catenane moiety which was named as a new building block would be capable of constructing the inte-
rotacatenane.7 Recently, they found this structure had multi- gration (rotacatenane) of rotaxane and catenane. Additionally,
state switchable properties.8 In 2012, the same group reported we have confirmed that the macrocyclic ammoniums could
a flexible donor–acceptor [3]catenane that, through a particular efficiently self-assemble catenane by use of the template-
disposition of its three rings in water, could act as a host for a directed clipping reaction in our previous work.5a According to
chainlike guest, resulting in the formation of a 1 : 1 complex this idea, the bisammonium (B) could be employed to perform
with a hitherto unknown topology that was termed a [2]pseudo- the bis-clipping reaction, constructing the integration of rota-
rota[3]catenane.9 Saito’s group also recently reported
a
catenane in one pot through the congenerous self-assembly of
series of [2]rota[2]catenanes which were synthesized by a cata- two different ammonium templates.
lytic reaction using a macrocyclic phenanthroline–CuI complex
followed by the installation of another ring under the template
Synthesis of ammonium frameworks
effect.10 In view of the structural character described above
The first bis-ammonium 6 was synthesized utilizing the route
and based on the novel building blocks of heterorotaxane inte-
gration, herein we have designed a series of novel ammonium
blocks (B) which incorporate an ammonium on the linear
component of the backbone and another ammonium on the
macrocyclic component of the backbone (in Scheme 1). The
ammonium on the linear component of the backbone was
designed to have the ability to construct the rotaxane while
another ammonium on the macrocyclic component of the
backbone played a role in the construction of the catenane.
The results indicated that these new building blocks could
highly efficiently assemble [n]rota[n]catenanes via the tem-
plate-directed clipping reaction all at once.
shown in Scheme 2. The cyclization of diphenol 2 5a with the
pseudo crown ether 1 5b in the presence of Cs2CO3 produced
the aldehyde-substituted macrocyclic alkylamine. To facilitate
purification, the NH of the free amine was protected using
Boc2O before purification. Subsequently, the Boc-protected
macrocyclic amine 3 was obtained in 20% yield over two steps.
In the presence of anhydrous sodium sulfate, compound 3 as
starting material was treated with 3,5-dimethoxybenzylamine 4
to afford the corresponding dynamic imine, which was then
reduced by NaBH4 in a solution of THF and MeOH to give the
kinetically stable amine. Similarly, the NH of the free amine
was protected with Boc2O. Subsequently, the Boc-protected
macrocyclic compound 5 was obtained in 62% yield over three
steps. The Boc groups were then removed with excess trifluoro-
acetic acid (TFA) in dry dichloromethane. Protonation of the
as-formed amine and subsequent counterion exchange with
saturated NH4PF6 aqueous solution afforded the target
Results and discussion
Design of ammonium blocks and rotacatenanes
As described above, we have developed a series of heterorotax- ammonium 6 in 90% yield over two steps.
anes possessing a novel topological structure by employing a
A similar synthetic strategy was employed to prepare the
host–guest dual-functional building block (A) as shown in tetra-ammonium 8, which contained two ammoniums on the
Scheme 1. Furthermore, numerous researchers have confirmed linear component of the backbone and two ammoniums on
that the template-directed clipping reaction can efficiently self- the macrocyclic component of the backbone (Scheme 3).
assemble rotaxanes.11 Accordingly, if another ammonium was Reductive amination of 3 with 1,6-hexanediamine gave the pre-
introduced into the macrocyclic component to afford bis- cursor of the Boc-protected amino crown ether 7 in 60% yield,
Scheme 2 Synthesis of bis-ammonium 6.
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Scheme 3 Synthesis of tetra-ammonium 8.
produced for the purpose of convenient purification. Boc- (H1, H12 and H13) adjacent to the ammonium residues dis-
deprotection with trifluoroacetic acid (TFA) in dry dichloro- played obvious downfield shifts in comparison to the
methane followed by counterion exchange with saturated ammonium 6 in Fig. 1C, while the corresponding benzene
aqueous NH4PF6 generated the target tetra-ammonium 8. The ring protons (H2 and H3, H10 and H11, H14 and H15) showed
successful construction of building blocks 6 and 8 inspired us significant upfield shifts as a result of shielding effects associ-
to further explore the synthesis of triangular hexa-ammonium ated with the encircling N-hetero crown ethers. For example,
11 (Scheme 4). Accordingly, the star-shaped triamine 9 12 was protons H2 at 7.30 ppm and H3 at 6.97 ppm shifted to 6.75
selected as starting material and treated with 3, affording the and 6.51 ppm, respectively, implying the formation of a
triangular compound 10. Subsequent deprotection and coun- [2]catenane structure. Furthermore, these changes were in
terion exchange gave the hexa-ammonium 11 in a yield of agreement with our previous report.5a Likewise, the resonance
80%. All of the new building blocks were well characterized by of protons (H10 and H11, H14 and H15) on the benzene rings
standard spectroscopic techniques such as NMR spectroscopy, adjacent to the other ammonium residue also displayed
mass spectrometry and elemental analysis (see the ESI†).
upfield shifts in comparison to those in the ammonium 6
(Fig. 1C), suggesting that this moiety was encircled by a crown
ether component. These shifts were in agreement with those
noted in our previous work.5a,13 Another change of resonance
signals on the pyridine components could be observed in
Fig. 1. According to the 1H NMR spectra in Fig. 1A, the protons
(Hl and Hk) were split into two sets of peaks, respectively,
owing to the different chemical environments that the
N-hetero crown ether components were in. These results indi-
cated that the bis-ammonium 6 efficiently assembled the
[2]rota[2]catenane 14a in one pot. Similar investigations were
also performed well in the construction of [2]rota[2]catenane
14b, as presented in Fig. 1. Further proof was provided by
matrix assisted laser desorption ionization (MALDI) mass spec-
trometry in acetonitrile: the peaks at m/z 1705.8 and 2130.4
could be assigned to the [M − PF−6 − HPF6]+ species, in which
M was 14a and 14b (see ESI†).
Rotacatenanes assembly
The poly-ammonium salts 6, 8 and 11 including dialkylammo-
nium recognition sites on the linear component and dialkyl-
ammonium sites on the macrocyclic component were treated
with 12a or 12b and 13 in CH3CN. A light yellow solution was
then observed on account of the formation of the dynamic
imine, which was well in agreement with experimental
phenomena reported in the literature.5,13 Then, the mixture
was treated with BH3·THF to reduce the dynamic imine bonds
to the kinetically stable C–NH bonds, and the pure forms of
[2]rota[2]catenane 14 (Scheme 5), [3]rota[3]catenane 16 (Scheme 6)
and [4]rota[4]catenane 17 (Scheme 7) were obtained by column
chromatography. The process of self-assembly was monitored by
1H NMR spectroscopy. Additionally, for comparison to aid the
spectroscopic analysis, the N-hetero crown ethers 15a and 15b
were synthesized separately in 43–75% yields, as previously
reported.5,13c
Evidence for the formation of 16a and 16b in this process
came from analysis of their 1H NMR spectra. As shown in
Fig. 2A and C, there were also obviously two sets of the charac-
In the 1H NMR spectra, there were obviously two sets of the
characteristic resonance signals of the ammonium NH2
+
+
teristic signals of ammonium NH2 protons as broad peaks in
the kinetically stable [3]rota[3]catenane 16a and 16b. Some
obvious downfield shifts of the resonance for the methylene
protons (H1′ and H12′) were observed while protons (H2′, H3′,
protons as broad peaks in the kinetically stable [2]rota[2]-
catenane 14a (Fig. 1B) and 14b (Fig. 1D). For 14a, as shown in
Fig. 1B, the resonance signals of the two methylene protons
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Scheme 4 Synthesis of hexa-ammonium 11.
Scheme 5 Synthesis of [2]rota[2]catenanes 14a–b.
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Scheme 6 Synthesis of [3]rota[3]catenanes 16a–b.
Scheme 7 Synthesis of [4]rota[4]catenanes 17a–b.
Fig. 1 Partial 1H NMR spectra (600 MHz, CD3CN, 298 K) of 15a (A), [2]rota[2]catenane 14a (B), 6 (C), [2]rota[2]catenane 14b (D), and 15b (E).
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Fig. 2 Partial 1H NMR spectra (600 MHz, CD3CN, 298 K) of [3]rota[3]catenane 16a (A), 8 (B) and [3]rota[3]catenane 16b (C).
H10′ and H11′) on the adjacent benzene rings showed signifi- shifts while the resonance of the protons on the adjacent
cant upfield shifts compared with the tetra-ammonium salt 8 benzene rings (H2″, H3″, H10″, H11″, H14″, H15″, and H16″
)
(in Fig. 2B), suggesting the N-hetero crown ethers 15a and 15b showed upfield shifts, owing to the shielding effect of the
encircled the linear ammonium sites and the macrocyclic encircling crown ether. Therefore, these data supported the
ammonium sites of template 8. As in [2]rota[2]catenane 14a, finding that the N-hetero crown ethers 15a and 15b encircled
two sets of split peaks on the pyridine ring (Hl and Hk) were the linear ammonium sites and macrocyclic ammonium sites
also observed. The results further demonstrated that the tem- of template 11, affording [4]rota[4]catenane 17a and 17b. Simi-
plate-directed clipping reaction was efficiently applied in the larly, additional evidence supporting this conclusion came
synthesis of [n]rota[n]catenane integration. Additional proof from analysis of the MALDI mass spectra (ESI†), which con-
was provided by MALDI mass spectrometry in acetonitrile. As tained a peak at m/z 5007.6 and 6280.6 that corresponded to
can be seen from the ESI,† the peaks at m/z 3192.4 and 4041.2 the [M − PF− − 5HPF6]+ species of [4]rota[4]catenane 17a and
6
can be assigned to the [M − PF− − 3HPF6]+ species, in which 17b, respectively.
6
M was the [3]rota[3]catenanes 16a and 16b.
The final effort focused on the investigation of the star-
shaped structure. Similarly, two sets of the characteristic
Conclusions
+
signals of ammonium NH2 protons as broad peaks were
found in the 1H NMR spectra of kinetically stable [4]rota[4]-
In conclusion, we developed three novel polyfunctional build-
catenane 17a and 17b, as shown in Fig. 3A and C. Compared
with the spectrum of the hexa-ammonium salt 11 (Fig. 3B), the
methylene protons (H1″, H12″ and H13″) displayed downfield
ing blocks possessing different ammonium sites, and the
ammonium group incorporated in the linear part of the mole-
cules 6, 8, 11 can be used for templating rotaxane formation
Fig. 3 Partial 1H NMR spectra (600 MHz, CD3CN, 298 K) of [4]rota[4]catenane 17a (A), 11 (B), and [4]rota[4]catenane 17b (C).
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while the macrocyclic part of the molecules 6, 8, 11 can be 24 h. After removing the solvent, the residue was dissolved in
used for templating catenane formation. Therefore, these new THF (30 mL) and MeOH (30 mL), and then NaBH4 (0.15 g,
frameworks were employed to assemble a series of [n]rota[n]- 4.0 mmol) was added slowly in 10 portions. After stirring over-
catenanes (n = 2, 3, 4) with high efficiencies, and in which the night, the reaction was quenched with the saturated
N-hetero crown ether components were installed on ammonium ammonium chloride (aq). The solvent was removed under
template sites of the linear and macrocyclic components all at vacuum, and the residue was extracted with absolute ethyl
once. The successful construction of [n]rota[n]catenanes pro- ether and then dried over anhydrous sodium sulfate. After
vides a foundation for future studies aimed at constructing a removing the solvent, the residue was dissolved in dry chloro-
complicated integrated structure or supramolecular polymer by form (60 mL), and then Boc2O (0.31 g, 1.44 mmol) and triethyl-
use of multiple mechanically interlocked frameworks.
amine (0.31 mL) were added. The mixture was stirred at room
temperature for 24 h. Removal of solvent under reduced
pressure and purification on a silica gel column using DCM–
ethyl acetate (3 : 1) as the eluent afforded the Boc-protected
amine 5 as a yellow liquid. Yield: 0.42 g, 62%. Compound 5:
1H NMR (600 MHz, CDCl3) δ 7.02 (s, 2H), 6.88 (s, 2H), 6.81 (s,
4H), 6.41 (s, 2H), 6.39–6.30 (m, 4H), 4.33 (s, 4H), 4.24 (s, 4H),
4.13 (s, 4H), 4.05 (s, 4H), 3.85 (s, 8H), 3.76 (s, 6H), 3.74 (s, 8H),
1.47 (d, J = 18 Hz, 18H). 13C NMR (100 MHz, CDCl3) δ 160.8,
160.0, 157.9, 156.0, 140.5, 130.2, 130.0, 129.7, 128.9, 114.6,
106.6, 105.9, 105.7, 105.1, 100.1, 99.1, 80.0, 79.8, 70.9, 69.8,
69.7, 67.4, 67.3, 55.2, 49.4, 49.0, 28.4. ESI-MS m/z = 969.8
[M + Na+], 985.8 [M + K+]; calculated exact mass = 946.5. Anal.
Calcd for C52H70N2O14: C, 65.87; H, 7.38; N, 2.89. Found: C,
65.94; H, 7.45; N, 2.96%.
Experimental
Materials and methods
All manipulations were carried out under an argon atmosphere
by using standard Schlenk techniques, unless otherwise
stated. THF was distilled under nitrogen from sodium–benzo-
phenone. EtOH and MeOH were distilled under a drying pipe
from magnesium–iodine. DMF was dried with magnesium
sulfate and then distilled under vacuum. 1H and 13C NMR
spectra were collected with either a 400 or 600 MHz spectro-
meter. Mass spectra were measured in the ESI mode. Elemen-
tal analyses were performed by investigation of C, H and N.
Synthesis of 3
Synthesis of 6
A mixture of 1 (0.71 g, 1.0 mmol) and 4,4′-(azanediylbis-
(methylene))diphenol 2 (0.23 g, 1.0 mmol) in dry DMF
(400 mL) was added dropwise over a period of 24 h to a stirred
suspension of Cs2CO3 (1.30 g, 4.0 mmol) in DMF (200 mL) at
80 °C under an argon atmosphere. The mixture was then
stirred at 80 °C for a further 48 h. The resulting mixture was
allowed to cool to room temperature, and filtered. After that,
the solvent was removed under vacuum, and the residue was
extracted with ethyl acetate, and then dried over anhydrous
sodium sulfate. After removing the solvent, the residue was
dissolved in dry chloroform (20 mL), and then Boc2O (0.44 g,
2 mmol) and triethylamine (0.43 mL) were added. The mixture
was stirred at room temperature for 24 h. Removal of solvent
under reduced pressure and purification on a silica gel
column using DCM–ethyl acetate (5 : 1) as the eluent gave the
Boc-protected macrocycle 3 as a light yellow liquid. Yield:
To a solution of the Boc-protected amine 5 (0.19 g, 0.2 mmol)
in dry DCM (10 mL), TFA (0.25 mL, 4.0 mmol) was added at
room temperature. After stirring for 2 h under nitrogen atmos-
phere, the solvent was removed under vacuum. The residue
was dissolved in MeOH (1.0 mL), and then saturated NH4PF6
(2.0 mL, aq) was added to yield a brown precipitate. After filter-
ing, washing with H2O and drying under vacuum, the title
compound was obtained as a light yellow gum. Yield: 0.19 g,
1
90%. Compound 6: H NMR (600 MHz, CD3CN) δ 7.29 (d, J =
+
6 Hz, 4H), 7.11 (s, 4H, NH2 ), 6.96 (d, J = 6 Hz, 4H), 6.60 (d, J =
6 Hz, 2H), 6.57 (d, J = 6 Hz, 2H), 6.56 (t, J = 6 Hz, 1H), 6.44 (t,
J = 6 Hz, 1H), 4.17–4.15 (m, 4H), 4.11 (s, 8H), 4.03–3.99 (m,
4H), 3.78 (s, 6H), 3.78–3.76 (m, 4H, CH2), 3.72 (t, J = 6 Hz, 4H,
CH2), 3.61 (m, 8H, CH2); 13C NMR (100 MHz, CD3CN) δ 161.8,
160.8, 160.3, 133.0, 132.3, 123.0, 115.6, 108.9, 108.4, 101.6,
71.0, 69.8, 69.7, 68.2, 55.8, 51.8, 50.8; ESI-MS m/z = 747.5
[M − PF−6 − HPF6]; calculated exact mass = 1038.3; Anal. Calcd
for C42H56F12N2O10P2: C, 48.63; H, 5.52; N, 2.62. Found: C,
48.56; H, 5.43; N, 2.70%.
1
0.14 g, 20%. Compound 3: H NMR (400 MHz, CDCl3) δ 9.85
(s, 1H), 7.00 (s, 4H), 6.88 (s, 2H), 6.80 (s, 4H), 6.76 (s, 1H), 4.32
(s, 2H), 4.23 (s, 2H), 4.13 (s, 8H), 3.85 (s, 8H), 3.74 (s, 8H), 1.46
(s, 9H). 13C NMR (100 MHz, CDCl3) δ 191.7, 160.3, 157.8,
156.0, 138.2, 129.7, 128.8, 114.6, 108.2, 107.8, 79.7, 69.8, 69.5,
67.8, 67.5, 28.4. ESI-MS m/z = 718.5 [M + Na+], 734.5 [M + K+];
calculated exact mass = 695.3. Anal. Calcd for: C38H49NO11: C,
65.65; H, 7.01; N, 2.10. Found: C, 65.59; H, 7.10; N, 2.01%.
Synthesis of [2]rota[2]catenanes 14a and 14b
A mixture of 6 (100 mg, 0.10 mmol), tetraethyleneglycol bis(2-
aminophenyl) ether 13 (75 mg, 0.20 mmol) and dicarboxalde-
hyde 12a (26 mg, 0.20 mmol) or 12b (70 mg, 0.20 mmol) was
stirred for 2 d in dry CH3CN (10 mL) under nitrogen atmos-
phere at room temperature. Then, BH3·THF solution (1.6 mL)
Synthesis of 5
To a solution of 3 (0.50 g, 0.72 mmol) in anhydrous MeOH was added, and the mixture was further stirred overnight. The
(80 mL) was added 3,5-dimethoxybenzylamine 4 (0.18 g, solvents were removed under vacuum, and the residue was
1.08 mmol) with anhydrous sodium sulfate acting as drying purified by column chromatography (silica gel, DCM–MeOH =
agent under argon atmosphere. The mixture was refluxed for 100 : 0–80 : 1) to give [2]rota[2]catenanes 14a and 14b. [2]Rota-
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[2]catenane 14a: white solid, yield: 95 mg, 48%. 1H NMR (s, 4H). 13C NMR (100 MHz, CDCl3) δ 159.9, 157.8, 155.9,
(600 MHz, CD3CN) δ 8.74 (s, 2H), 8.48 (s, 2H), 7.84 (t, J = 141.0, 130.2, 130.0, 129.8, 128.9, 114.5, 106.2, 105.6, 100.0,
6.0 Hz, 1H), 7.71 (t, J = 6.0 Hz, 1H), 7.39 (d, J = 6.0 Hz, 2H), 79.8, 79.4, 70.8, 69.7, 67.4, 67.2, 60.3, 49.4, 46.2, 28.4, 27.9,
7.27 (d, J = 6.0 Hz, 2H), 6.74 (d, J = 12.0 Hz, 4H), 6.66–6.70 (m, 27.7, 26.6, 14.1; MALDI-MS m/z = 1697.8 [M + Na+], 1713.8
8H), 6.63 (d, J = 12.0 Hz, 4H), 6.58 (d, J = 12.0 Hz, 2H), 6.50 (d, [M + K+]; calculated exact mass = 1674.9; Anal. Calcd for
J = 6.0 Hz, 4H), 6.39 (d, J = 6.0 Hz, 2H), 6.27 (s, 1H), 6.26 C92H130N4O24: C, 65.86; H, 7.90; N, 3.27. Found: C, 65.93; H,
(s, 1H), 6.11 (s, 2H), 6.08 (s, 2H), 4.54 (s, 4H), 4.41 (s, 8H), 4.05 7.82; N, 3.34%.
(s, 8H), 4.01 (d, J = 6.0 Hz, 4H), 3.91 (s, 8H), 3.76 (s, 4H), 3.75
(s, 8H), 3.70 (d, J = 6.0 Hz, 8H), 3.67 (d, J = 6.0 Hz, 4H), 3.59 (d,
Synthesis of 8
J = 6.0 Hz, 4H), 3.55 (d, J = 6.0 Hz, 8H), 3.51 (d, J = 6.0 Hz, 4H), To
a solution of the Boc-protected amine 7 (100 mg,
3.41 (s, 6H). 13C NMR (100 MHz, CD3CN) δ 161.3, 160.3, 159.4, 0.06 mmol) in dry DCM (10 mL), TFA (0.16 mL, 2.40 mmol)
159.2, 158.8, 146.9, 138.6, 138.3, 137.3, 137.2, 134.7, 134.3, was added at room temperature. After stirring for 2 h under
130.8, 124.4, 122.6, 122.2, 121.6, 121.5, 120.0, 119.7, 117.5, nitrogen atmosphere, the solvent was removed under vacuum.
115.2, 112.7, 112.6, 110.4, 110.4, 107.2, 107.1, 102.6, 101.2, The residue was dissolved in MeOH (1.0 mL), and then satu-
71.6, 71.4, 71.3, 70.7, 70.6, 69.5, 69.4, 68.1, 67.7, 55.2, 52.9, rated NH4PF6 (2.0 mL, aq) was added to yield a brown precipi-
51.9. MALDI-MS m/z = 1705.8 [M − PF− − HPF6]; calculated tate. After filtering, washing with H2O and drying under a
6
exact mass = 1996.8; Anal. Calcd for C96H122F12N8O20P2: C, vacuum, the title compound 7 was obtained as a light yellow
57.78; H, 6.09; N, 5.55. Found: C, 57.71; H, 6.15; N, 5.61%. gum. Yield: 90 mg, 85%. Compound 7: 1H NMR (600 MHz,
1
[2]Rota[2]catenane 14b: white solid, yield: 100 mg, 42%. 1H CD3CN) H NMR (600 MHz, CD3CN) δ 7.29 (d, J = 6.0 Hz, 8H),
NMR (600 MHz, CD3CN) δ 8.75 (s, 2H), 8.48 (s, 2H), 6.94 (s, 6.96 (d, J = 6.0 Hz, 8H), 6.58 (s, 4H), 6.44 (s, 2H), 4.26 (s, 4H),
4H), 6.77–6.74 (m, 4H), 6.71–6.66 (m, 8H), 6.62 (t, J = 6.0 Hz, 4.17 (s, 8H), 4.10 (s, 8H), 4.04–3.99 (m, 8H), 3.77 (s, 8H),
4H), 6.58 (s, 2H), 6.42 (d, J = 6.0 Hz, 4H), 6.33 (s, 2H), 6.32 (s, 3.75–3.70 (m, 8H), 3.63 (d, J = 6.0 Hz, 8H), 3.60 (d, J = 6.0 Hz,
1H), 6.27 (s, 1H), 6.12 (s, 2H), 6.08 (s, 2H), 4.50 (s, 4H), 4.39 (s, 8H), 2.98 (m, 4H), 1.42 (s, 4H), 1.28 (s, 4H); 13C NMR
4H), 4.10–4.06 (m, 8H), 4.01 (s, 4H), 3.91 (t, J = 6.0 Hz, 8H), (100 MHz, CD3CN) δ 160.8, 160.3, 133.5, 132.3, 123.1, 115.5,
3.73 (s, 8H), 3.70 (s, 8H), 3.61–3.59 (m, 4H), 3.56–3.53 (m, 8H), 108.7, 102.3, 70.9, 69.8, 68.2, 51.8, 50.5, 48.0, 28.1, 25.7;
3.51 (d, J = 4.8 Hz, 4H), 3.42 (s, 6H), 1.28 (s, 48H), 0.89 (m, MALDI-MS m/z = 1275.7, [M − PF− − 3HPF6]; calculated exact
6
10H). 13C NMR (100 MHz, CD3CN) δ 161.8, 160.9, 160.1, 147.4, mass = 1858.6; Anal. Calcd for C72H102F24N4O16P4: C, 46.59; H,
137.7, 131.5, 125.0, 122.2, 115.8, 107.8, 101.7, 72.0, 71.3, 70.0, 5.47; N, 3.10. Found: C, 46.51; H, 5.53; N, 3.01%.
68.7, 68.2, 55.8, 53.5, 52.6, 50.5, 32.5, 30.2, 29.9, 23.2, 14.2.
Synthesis of [3]rota[3]catenanes 16a and 16b
MALDI-MS m/z = 2130.4 [M − PF− − HPF6]; calculated exact
6
mass = 2421.2; Anal. Calcd for C124H178F12N8O22P2: C, 61.40; A mixture of compound 8 (93 mg, 0.05 mmol), tetraethylene-
H, 7.37; N, 4.55. Found: C, 61.47; H, 7.41; N, 4.63%.
glycol bis(2-aminophenyl) ether 13 (75 mg, 0.20 mmol) and
dicarboxaldehyde 12a (26 mg, 0.20 mmol) or 12b (70 mg,
0.20 mmol) was stirred for 4 d in dry CH3CN (10 mL) under
Synthesis of 7
To a solution of 3 (0.50 g, 0.72 mmol) in anhydrous MeOH nitrogen atmosphere at room temperature. Then, BH3·THF
(80 mL) was added 1,6-hexanediamine (42 mg, 0.36 mmol) solution (1.6 mL) was added, and the mixture was further
with anhydrous sodium sulfate acting as drying agent under stirred overnight. The solvents were removed under vacuum,
argon atmosphere. The mixture was refluxed for 24 h. After and the residue was purified by column chromatography
removing the solvent, the residue was dissolved in THF (silica gel, DCM–MeOH = 100 : 0–60 : 1) to give the [3]rota[3]-
(40 mL) and MeOH (20 mL), and then NaBH4 (0.15 g, catenanes 16a and 16b. [3]Rota[3]catenane 16a: white solid,
1
4.0 mmol) was added slowly in 10 portions. After stirring over- yield: 66 mg, 39%. H NMR (600 MHz, CD3CN) δ 8.67 (s, 4H),
night, the reaction was quenched with the saturated 8.50 (s, 4H), 7.84 (t, J = 9.0 Hz, 2H), 7.71 (t, J = 6.0 Hz, 2H),
ammonium chloride (aq). The solvents were removed under 7.38 (d, J = 6.0 Hz, 4H), 7.27 (d, J = 6.0 Hz, 4H), 6.75 (m, 20H),
vacuum, and the residue was extracted with absolute ethyl 6.72–6.65 (m, 16H), 6.50 (d, J = 6.0 Hz, 8H), 6.45 (d, J = 6.0 Hz,
ether and then dried over anhydrous sodium sulfate. After 4H), 6.28 (d, J = 6.0 Hz, 2H), 6.12 (s, 4H), 4.43 (s, 8H), 4.38 (s,
removing the solvent, the residue was dissolved in dry chloro- 4H), 4.07 (d, J = 6.0 Hz, 16H), 3.92 (s, 16H), 3.74 (s, 8H), 3.69
form (60 mL), and then Boc2O (0.31 g, 1.44 mmol) and triethyl- (m, 48H), 3.62 (t, J = 3.9 Hz, 8H), 3.59–3.55 (m, 16H), 3.55–3.48
amine (0.31 mL) were added. The mixture was stirred at room (m, 8H), 3.42 (s, 8H), 2.94 (s, 4H), 1.42 (s, 4H), 1.29 (s, 4H); 13
C
temperature for 24 h. Removal of solvent under reduced NMR (100 MHz, CD3CN) δ 160.9, 160.0, 159.4, 159.3, 147.9,
pressure and purification on a silica gel column using DCM– 147.5, 139.3, 138.9, 137.9, 137.8, 131.4, 125.0, 122.9, 122.7,
ethyl acetate (2 : 1) as the eluent obtained the Boc-protected 122.2, 122.1, 120.5, 115.8, 115.4, 113.7, 113.3, 111.0, 107.6,
1
amine 7. Yield: 0.36 g, 60%. Compound 7: H NMR (600 MHz, 102.8, 72.2, 71.8, 71.3, 71.1, 70.0, 68.5, 68.3, 52.5, 50.8, 50.6,
CDCl3) δ 7.02 (s, 4H, Ar), 6.88 (s, 4H, Ar), 6.80 (s, 8H), 6.39 (s, 49.2; MALDI-MS m/z = 3192.4, [M − PF− − 3HPF6]; calculated
6
4H), 6.35 (s, 2H), 4.33 (s, 8H), 4.24 (s, 4H), 4.13 (s, 8H), 4.05 (s, exact mass = 3375.6. Anal. Calcd for C180H234F24N16O36P4: C,
8H), 3.83 (d, J = 12.0 Hz, 16H), 3.72 (s, 16H), 3.14 (s, 2H), 3.05 57.32; H, 6.18; N, 5.85. Found: C, 57.23; H, 6.24; N, 5.93%.
(s, 2H), 1.44 (d, J = 24.0 Hz, 36H), 1.26 (d, J = 6.0 Hz, 4H), 1.21 [3]Rota[3]catenane 16b: light yellow solid, yield: 81 mg, 35%.
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Organic & Biomolecular Chemistry
1H NMR (600 MHz, CD3CN) δ 8.65 (s, 4H), 8.55 (s, 4H), 6.91 (s, vacuum, the title compound was obtained as a light yellow
8H), 6.79–6.72 (m, 16H), 6.69 (m, 20H), 6.52 (d, J = 6.0 Hz, 8H), gum. Yield: 0.14 g, 80%. Compound 10: 1H NMR (600 MHz,
6.45 (d, J = 6.0 Hz, 4H), 6.31 (d, J = 6.0 Hz, 2H), 6.09 (s, 4H), CD3CN) δ 7.97 (s, 3H), 7.92 (d, J = 12.0 Hz, 6H), 7.60 (d, J = 6.0
4.41 (d, J = 6.0 Hz, 8H), 4.34 (s, 4H), 4.11 (s, 8H), 4.11–4.08 (m, Hz, 6H), 7.29 (d, J = 12.0 Hz, 12H), 6.97 (d, J = 6.0 Hz, 12H),
16H), 4.07 (s, 16H), 3.91 (m, 16H), 3.73 (s, 8H), 3.70 (s, 16H), 6.60 (s, 6H), 6.46 (s, 3H), 4.16 (d, J = 6.0 Hz, 24H), 4.09 (s,
3.66–3.64 (m, 16H), 3.63–3.60 (m, 16H), 3.58–3.54 (m, 16H), 12H), 4.03 (s, 12H), 3.77 (s, 12H), 3.73 (s, 12H), 3.62 (d, J = 6.0
3.52 (t, J = 3.9 Hz, 8H), 2.96 (s, 4H), 1.83–1.74 (m, 8H), 1.48 (m, Hz, 24H). 13C NMR (100 MHz, CD3CN) δ 160.8, 160.3, 141.8,
4H), 1.42 (s, 12H), 1.28 (s, 80H), 0.89 (t, J = 6.0 Hz, 12H); 13C 133.8, 132.0, 131.3, 131.1, 128.3, 125.6, 123.1, 117.8, 115.7,
NMR (100 MHz, CD3CN) δ 167.7, 161.1, 160.9, 160.0, 147.8, 108.7, 102.6, 70.8, 69.7, 68.2, 51.9, 51.5, 50.6; MALDI-MS m/z =
147.5, 138.0, 131.5, 125.1, 122.1, 120.5, 115.8, 114.2, 111.0, 2132.1, [M − PF− − 5HPF6]; calculated exact mass = 3006.9.
6
109.2, 72.1, 71.9, 71.3, 71.2, 71.0, 70.3, 70.1, 70.0, 69.5, 68.6, Anal. Calcd for: C126H156F36N6O24P6: C, 50.21; H, 5.15; N, 2.86.
68.5, 68.3, 52.5, 51.0, 32.5, 30.2, 29.9, 28.5, 26.9, 26.5, 26.4, Found: C, 50.30; H, 5.23; N, 2.79%.
23.2; MALDI-MS m/z = 4041.2, [M − PF− − 3HPF6]; calculated
exact mass = 4624.4. Anal. Calcd for: C236H346F24N16O40P4: C,
6
Synthesis of [4]rota[4]catenanes 17a and 17b
61.33; H, 7.62; N, 4.75. Found: C, 61.26; H, 7.54; N, 4.84%.
A mixture of 11 (100 mg, 0.033 mmol), tetraethyleneglycol bis
(2-aminophenyl) ether 13 (75 mg, 0.20 mmol) and dicarbox-
aldehyde 12a (26 mg, 0.20 mmol) or 12b (70 mg, 0.20 mmol)
was stirred for 6 d in dry CH3CN (10 mL) under nitrogen
atmosphere at room temperature. Then, BH3·THF solution
(1.6 mL) was added, and the mixture was further stirred over-
night. The solvents were removed under vacuum, and the
residue was purified by column chromatography (silica gel,
DCM–MeOH = 100 : 0–40 : 1) to give the [4]rota[4]catenanes 17a
and 17b. [4]Rota[4]catenane 17a: white solid, yield: 72 mg,
Synthesis of 10
To a solution of 3 (0.50 g, 0.72 mmol) in anhydrous MeOH
(80 mL) was added 9 (0.094 g, 0.24 mmol) with anhydrous
sodium sulfate acting as drying agent under argon atmos-
phere. The mixture was refluxed for 48 h. After removing the
solvent, the residue was dissolved in THF (40 mL) and MeOH
(20 mL), and then NaBH4 (0.15 g, 4.0 mmol) was added slowly
in 10 portions. After stirring overnight, the reaction was
quenched with saturated ammonium chloride (aq). The sol-
vents were removed under vacuum, and the residue was
extracted with absolute ethyl ether and then dried over anhy-
drous sodium sulfate. After removing the solvent, the residue
was dissolved in dry chloroform (60 mL), and then Boc2O
(0.31 g, 1.44 mmol) and triethylamine (0.31 mL) were added.
The mixture was stirred at room temperature for 24 h. Removal
of solvent under reduced pressure and purification on a silica
gel column using DCM–ethyl acetate (1 : 1) as the eluent
obtained the Boc-protected amine 10. Yield: 0.35 g, 54%. Com-
1
37%. H NMR (600 MHz, CD3CN) δ 8.96 (s, 6H), 8.49 (s, 6H),
7.77 (t, J = 7.2 Hz, 3H), 7.70 (t, J = 7.8 Hz, 3H), 7.59 (s, 3H),
7.33 (d, J = 7.2 Hz, 6H), 7.27 (d, J = 7.2 Hz, 6H), 7.00 (d, J =
7.8 Hz, 6H), 6.77 (s, 6H), 6.75 (d, J = 8.4 Hz, 12H), 6.68 (t, J =
6.6 Hz, 24H), 6.61 (s, 20H), 6.50 (d, J = 8.4 Hz, 12H), 6.38 (d, J =
7.8 Hz, 8H), 6.27 (d, J = 7.8 Hz, 3H), 6.08 (s, 6H), 4.65 (s, 6H),
4.57 (s, 6H), 4.42 (s, 24H), 4.06 (d, J = 3.2 Hz, 48H), 3.93 (m,
24H), 3.76 (m, 24H), 3.71 (s, 24H), 3.60 (s, 12H), 3.56 (s, 24H),
3.53 (s, 12H); The 13C NMR spectrum was not collected due to
the poor solubility of [4]rota[4]catenane 17a; MALDI-MS m/z =
1
1
5007.6, [M − PF− − 5HPF6]; calculated exact mass = 5882.4.
pound 10: H NMR (600 MHz, CDCl3) H NMR δ 7.77 (s, 3H),
7.67 (s, 6H), 7.35 (d, J = 6.0 Hz, 3H), 7.30 (d, J = 6.0 Hz, 3H),
7.03 (d, J = 6.0 Hz, 6H), 6.89 (d, J = 6.0 Hz, 6H), 6.81 (s, 12H),
6.43 (s, 6H), 6.38 (s, 3H), 4.38 (d, J = 4.8 Hz, 6H), 4.34 (s, 6H),
4.30 (s, 6H), 4.24 (s, 6H), 4.17–4.11 (m, 12H), 4.06 (s, 12H),
3.84 (m, 24H), 3.74 (d, J = 3.0 Hz, 24H), 1.48 (m, 54H). 13C
NMR (100 MHz, CDCl3) δ 160.0, 157.8, 155.9, 141.9, 140.3,
139.9, 137.3, 130.1, 129.7, 128.9, 128.4, 127.9, 127.4, 124.8,
114.6, 106.6, 106.0, 100.3, 80.1, 79.8, 77.3, 77.0, 76.7, 70.8,
69.8, 69.6, 67.5, 67.4, 49.4, 48.9, 29.6, 29.3, 28.4. MALDI-MS
m/z = 2754.2 [M + Na+], 2770.2 [M + K+]; calculated exact mass
= 2731.4. Anal. Calcd for C156H198N6O36: C, 68.62; H, 7.23; N,
3.14. Found: C, 68.55; H, 7.30; N, 3.07%.
6
Anal. Calcd for: C288H354F36N24O54P6: C, 58.70; H, 6.13; N, 5.66.
Found: C, 58.77; H, 6.06; N, 5.71%. [4]Rota[4]catenane 17b:
white solid, yield: 54 mg, 23%. 1H NMR (600 MHz, CD3CN)
δ 8.97 (s, 6H), 8.57 (s, 6H), 7.60 (d, J = 7.8 Hz, 3H), 7.42–7.18 (m,
12H), 6.99 (d, J = 7.8 Hz, 6H), 6.88 (s, 6H), 6.74 (m, 12H),
6.72–6.60 (m, 24H), 6.59 (s, 20H), 6.50 (d, J = 7.8 Hz, 12H),
6.44–6.38 (m, 8H), 6.29 (d, J = 7.8 Hz, 3H), 6.07 (s, 6H), 4.63 (s,
6H), 4.52 (s, 6H), 4.42 (s, 12H), 4.34 (s, 12H), 4.13–3.97 (m, 48H),
3.93 (s, 24H), 3.85–3.69 (m, 48H), 3.69 (s, 24H), 3.58 (d, J = 9.9
Hz, 24H), 3.53 (s, 24H), 1.74 (d, J = 8.7 Hz, 12H), 1.40 (d, J = 6.2
Hz, 12H), 1.26 (s, 120H), 0.86 (s, 18H); The 13C NMR spectrum
was not collected due to the poor solubility of [4]rota[4]catenane
17b; MALDI-MS m/z = 6280.6, [M − PF− − 5HPF6]; calculated
6
Synthesis of 11
exact mass = 7155.6. Anal. Calcd for: C372H522F36N24O60P6: C,
To
a solution of the Boc-protected amine 10 (0.16 g,
62.49; H, 7.27; N, 4.60. Found: C, 62.40; H, 7.35; N, 4.69%.
0.06 mmol) in dry DCM (10 mL), TFA (0.23 mL, 3.60 mmol)
was added at room temperature. After stirring for 2 h under
nitrogen atmosphere, the solvent was removed under vacuum.
The residue was dissolved in MeOH (1.0 mL), and then satu-
Acknowledgements
rated NH4PF6 (2.0 mL, aq) was added to yield a brown precipi- We acknowledge financial support from the National Natural
tate. After filtering, washing with H2O and drying under a Science Foundation of China (21072070, 21272088) and the
4870 | Org. Biomol. Chem., 2014, 12, 4862–4871
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Paper
Program for Academic Leader in Wuhan Municipality
(201271130441). The work was also supported by the Scientific
Research Foundation for Returned Overseas Chinese Scholars,
Ministry of Education, the Natural Science Foundation of
Hubei Province (2013CFB207) and excellent doctoral disser-
tation cultivation grant from Central China Normal University
(CCNU13T04095).
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