Size effects in the alkali metal ion-templated formation of oligo(ethylene glycol)-containing [2]catenanes

DOI: 10.1039/c5ob01956g

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Organic and Biomolecular Chemistry p. 1153 - 1160 (2016)

Update date:2022-08-04

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Lee, Yong-Jay

Ho, Tsung-Hsien

Lai, Chien-Chen

Chiu, Sheng-Hsien

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Article abstract of DOI:10.1039/c5ob01956g

An investigation into the most suitable alkali metal ions for templating the assembly of [2]catenanes from di-, tri-, and tetra(ethylene glycol)-containing guest diamines and isophthalaldehyde has indicated that Na⁺, K⁺, and Rb⁺

Full text of DOI:10.1039/c5ob01956g

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Size eﬀects in the alkali metal ion-templated

formation of oligo(ethylene glycol)-containing

Cite this: DOI: 10.1039/c5ob01956g

[2]catenanes†

Yong-Jay Lee,^aTsung-Hsien Ho,^aChien-Chen Lai^band Sheng-Hsien Chiu*^a

An investigation into the most suitable alkali metal ions for templating the assembly of [2]catenanes from

di-, tri-, and tetra(ethylene glycol)-containing guest diamines and isophthalaldehyde has indicated that

Na⁺, K⁺, and Rb⁺ions are optimal for preparing [2]catenanes containing at least one di(ethylene glycol)

unit, two tri(ethylene glycol) units, and at least one tetra(ethylene glycol) unit [in the absence of a di

(ethylene glycol) unit], respectively.

Received 20th September 2015,

Accepted 26th November 2015

DOI: 10.1039/c5ob01956g

www.rsc.org/obc

however, that eﬃcient alignment of the longer analogues of

the di(ethylene glycol) units would require other alkali metal

Introduction

A template aligns its bound species in a manner that facilitates ions as templates, suggesting the need for a systematic study

the eﬃcient synthesis of a particular product.¹Because of to find the best alkali metal ion for templating each possible

their strong interactions with ligands containing nitrogen, homo- and hetero-[2]catenane assembled in this way. Herein,

oxygen, and sulfur atoms, transition metal ions have, for over we report the results of our investigation into the use of

five decades, been applied to template the syntheses of planar diﬀerent alkali metal ions to template the assembly of [2]cate-

macrocycles containing such heteroatoms.²By aligning two (or nanes from di-, tri-, and tetra(ethylene glycol)-containing guest

more) pyridine-type ligands into a polyhedral configuration, diamines and isophthalaldehyde. We found that Na⁺is the

transition metal ions can also be useful templates for the con- best alkali metal ion to template the assembly of [2]catenanes

struction of aesthetically appealing interlocked molecules and containing di(ethylene glycol) units, with K⁺being the best

molecular knots³(e.g., trefoil knots,⁴Borromean rings,⁵Stars choice only for the construction of a tri(ethylene glycol)-con-

of David⁶). Although alkali metal ions have also been applied taining homo-[2]catenane. When the assembly involved the

for many years to template the syntheses of crown ethers,⁷they tetra(ethylene glycol)-containing diamine 3, but not the di

have rarely been employed as templates to direct the syntheses (ethylene glycol)-containing diamine 1,⁹Rb⁺became the tem-

of interlocked molecules.⁸Recently, we found that the Na⁺ion plating ion providing the most eﬃcient assembly.

can template the orthogonal alignment of two di(ethylene

glycol) chains, allowing the direct construction of a [2]cate-

nane through the assembly of five components [two di(ethyl-

Results and discussion

ene glycol)-containing diamines, two isophthalaldehydes, one

Na⁺ion].⁹To explore the possible applications of [2]catenanes

To investigate the template eﬀects in the syntheses of a variety

of [2]catenanes, we synthesized the diamines 1–3, containing

synthesized using this approach, we wished to investigate its

synthetic flexibility by replacing one (or both) of the Na⁺ion-

central di-, tri-, and tetra(ethylene glycol) motifs, respectively,

by reacting the corresponding oligo(ethylene glycol)s with

aligned di(ethylene glycol) units with a longer analogue, pro-

4-cyanobenzylbromide under basic conditions to give the

nitriles 4–6, respectively, and then reducing them with LiAlH₄

(Scheme 1).

viding hetero-[2]catenanes (two nonequivalent macrocyclic

components) or larger homo-[2]catenanes. We suspected,

First, we examined the syntheses of the homo-[2]catenanes,

^aDepartment of Chemistry and Center for Emerging Material and Advanced Devices,

National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617,

ROC. E-mail: shchiu@ntu.edu.tw

^bInstitute of Molecular Biology, National Chung Hsing University and Department of

Medical Genetics, China Medical University Hospital, Taichung, Taiwan, ROC

†Electronic supplementary information (ESI) available: ¹H and ¹³C NMR spectra

of all new compounds. See DOI: 10.1039/c5ob01956g

because only one possible [2]catenane could be generated in

each solution. Thus, we heated CDCl₃solutions of the di(ethyl-

ene glycol)-containing diamine 1 (20 mM), the dialdehyde 7

(20 mM), and alkali metal ions in the form of tetrakis[3,5-bis

(trifluoromethyl)phenyl]borate (TFPB) salts (10 mM) at 323 K

until the reactions reached equilibrium (generally 24 h)

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the form of their TFPB salts (10 mM), after heating at 323 K

for 24 h, all featured three characteristic upfield-shifted

signals at δ 2.90–3.40, representing the xylene-shielded tri

(ethylene glycol) units in the homo-[2]catenanes [9·M]⁺.

This observation suggested that all of the tested alkali

metal ions were capable of templating the formation of the

homo-[2]catenanes [9·M]⁺, although their eﬃciencies varied

significantly. We estimated the yields of the [2]catenanes

[9·M]⁺assembled using the various alkali metal ions as tem-

plates by comparing the integrated signals of the tri(ethylene

glycol) and/or benzylic protons of each [2]catenane

(δ 2.90–3.40 and 4.21, respectively) with the signal of the TFPB

anions (δ 7.70). The K⁺ion appeared to be the best template

(yield: 75%). The smallest ion (Li⁺, 7%) and the largest (Cs⁺,

25%) were both much less eﬃcient templates for the assembly

of their [2]catenanes [9·M]⁺. This finding suggests that when

the two oligo(ethylene glycol) chains were aligned orthogonally

for the synthesis of the [2]catenanes, the binding pocket that

formed preferred a specifically size-matched template.

Scheme 1 Syntheses of diamines 1–3.

(Scheme 2). Only the mixtures in which Li⁺and Na⁺ions were

present displayed the characteristic xylene-shielded upfield

signals (δ 2.50–3.10)⁹for the protons of the ethylene glycol

units in the ¹H NMR spectra, indicating the formation of their

[2]catenanes [8·Li]⁺and [8·Na]⁺, respectively (Fig. 1A). With

integration of the signal for the TFPB anion at δ 7.70 as a refer-

ence, the yields of the [2]catenanes [8·Na]⁺and [8·Li]⁺were 81

and 55%, respectively (Table 1). Because Na⁺and K⁺ions can

be diﬃcult to diﬀerentiate,¹⁰our observation that the [2]cate-

nane [8·M]⁺can be synthesized eﬃciently when using Na⁺

ions, but not K⁺ions, as templates suggests an alternative

method for discerning between these two metal ions. We

suspect that the inability of K⁺and other larger alkali metal

ions to template the formation of their [2]catenanes [8·M]⁺

arose from the binding pocket formed from the two orthog-

onally aligned di(ethylene glycol) chains being too small to

host these cations appropriately.

Because K⁺was the best alkali metal ion for templating the

assembly of the tri(ethylene glycol)-containing homo-[2]cate-

nane [9·M]⁺, whereas the smaller Na⁺ion was much better at

templating the formation of [8·M]⁺with two shorter di(ethyl-

ene glycol) chains, we suspected that obtaining the [2]catenane

[10·M]⁺, formed from two units of the tetra(ethylene glycol)-

containing diamine 3 and the dialdehyde 7, would prefer an

alkali metal ion larger than K⁺as the template. Fig. 1C pre-

sents the ¹H NMR spectra of the CDCl₃solutions of the

diamine 3 (20 mM), the dialdehyde 7 (20 mM), and alkali

metal ions in the form of TFPB salts (10 mM), recorded after

heating at 323 K for 24 h. The spectra displayed the four

characteristic upfield-shifted signals of the interlocked tetra

Similar to the significantly upfield-shifted signals for the

xylene-shielded di(ethylene glycol) units in the H NMR spec-

trum of the homo-[2]catenane [8·Na]⁺, the spectra of the CDCl₃

solutions of the tri(ethylene glycol)-containing diamine 2

(20 mM), the dialdehyde 7 (20 mM), and alkali metal ions in

Fig. 1 ¹H NMR spectra (400 MHz, CDCl₃, 298 K) of the mixtures of the dialdehyde 2, M⁺TFPB⁻salts, and the diamines (A) 1, (B), 2 and (C) 3, where

the M⁺ions were (a) Li⁺, (b) Na⁺, (c) K⁺, (d) Rb⁺, and (e) Cs⁺.

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(ethylene glycol) units in the [2]catenanes [10·M]⁺only when

we applied K⁺, Rb⁺, and Cs⁺ions as templates. Among them,

the Rb⁺ion is the most eﬃcient template for the synthesis of

the [2]catenanes [10·M]⁺, although the yield of its product

(42%) was significantly lower than those determined similarly

for the formation of the [2]catenanes [8·Na]⁺and [9·K]⁺(81 and

75%, respectively). We suspect that the entropic cost when

organizing the two highly flexible tetra(ethylene glycol) chains

into the complexation geometry as well as the lower enthalpy

when coordinating the oxygen atoms of the tetra(ethylene

glycol) units to the lower-charge-density Rb⁺ion were respon-

sible for the relatively low eﬃciency of this transformation.

The inability of Na⁺ions to template the formation of the rela-

tively large tetra(ethylene glycol)-containing [2]catenane

[10·M]⁺and the inability of K⁺ions to template the formation

of the relatively small di(ethylene glycol)-containing [2]cate-

nane [8·M]⁺suggest an alternative method of diﬀerentiating

between these two alkali metal ions when they are the only

ones present in solution.

Table 1 Estimated yields (from ¹H NMR spectra) of the [2]catenanes

[8·M]⁺–[13·M]⁺assembled from the diamines 1–3 and the dialdehyde 7

when using various alkali metal ions as templates

Template

Diamines

Li⁺

1 + 1

2 + 2

3 + 3

1 + 2

2 + 3

1 + 3

55%

81%

—

Na⁺

K⁺

Rb⁺

Cs⁺

Li⁺

Na⁺

K⁺

64%

75%

57%

28%

—

Rb⁺

Cs⁺

Li⁺

—

Na⁺

K⁺

19%

42%

26%

—

12%

11%

ND^a

13%

Rb⁺

Cs⁺

Li⁺

—

16%

18%

—

11%

ND^a

21%

36%

31%

11%

14%

12%

16%

—

ND^a

19%

ND^a

—

Na⁺

K⁺

—

Rb⁺

Cs⁺

Li⁺

To prove unambiguously that the homo-[2]catenanes

[(8–10)·M]⁺formed in solution, we heated mixtures of the di-

amines 1–3, the dialdehyde 7, and their best templating ions

(as determined above) at 323 K for 24 h and then reduced the

products with NaBH₄. We then methylated (HCHO/HCOOH)

the resulting secondary amino groups to aﬀord the [2]cate-

nanes 14–16.¹¹After chromatography, we isolated the di- and

tri(ethylene glycol)-containing homo-[2]catenanes 14 and 15,

respectively, in moderate yields (58 and 48%, respectively),

confirming that Na⁺and K⁺ions are eﬃcient templates for the

assembly of the imino [2]catenanes [8·Na]⁺and [9·K]⁺. Because

of the lower eﬃciency (42%) of the Rb⁺-templated formation of

the imino [2]catenane [10·M]⁺, the isolated yield of the amino

[2]catenane 16 was only 30% (Table 2). The templating alkali

metal ions were lost at some point during the aqueous extrac-

tion and chromatography processes (possibly because their

complexation to the binding pocket in the [2]catenanes was

ND^a

11%

—

Na⁺

K⁺

Rb⁺

Cs⁺

Li⁺

—

ND^a

Na⁺

K⁺

—

Rb⁺

Cs⁺

—

^aNot determined because no reliable signal was observed.

not particularly strong), as evidenced by the H NMR spectra

of the purified [2]catenanes 14–16 lacking any signals from the

TFPB counter anions.

Having assigned the signals of the homo-[2]catenanes

14–16 in their H NMR spectra, we could identify the signals

of the hetero-[2]catenanes 17–19 in the H NMR spectra of the

structures assembled when mixing two diﬀerent diamines

(chosen from 1–3), the dialdehyde 7, and M·TFPB salts (Fig. 2).

Table 2 Isolated yields of the [2]catenanes 14–19 assembled from the

diamines 1–3 and the dialdehyde 7 when using the most-suitable alkali

metal ion as the template in each case

Template

Diamines

Na⁺

K⁺

1 + 1

2 + 2

3 + 3

1 + 2

2 + 3

1 + 3

58%

—

21%

—

19%

—

48%

—

24%

16%

—

30%

—

26%

—

16%

—

16%

—

Rb⁺

Na⁺

Rb⁺

Na⁺

Scheme 2 Template-directed synthesis of the [2]catenanes [(8–13)·M]⁺

and 14–19.

—

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Fig. 2 ¹H NMR spectra (400 MHz, CDCl₃, 298 K) of the mixtures of the dialdehyde 7, M⁺TFPB⁻salts, and the diamines (A) 1 and 2, (B) 2 and 3, and

(C) 1 and 3, where the M⁺ions were (a) Li⁺, (b) Na⁺, (c) K⁺, (d) Rb⁺, and (e) Cs⁺. Asterisks: signals assigned to the hetero-[2]catenanes.

For example, after heating a mixture of the diamines 1 much from those estimated from the ¹H NMR spectrum of

(10 mM) and 2 (10 mM), the dialdehyde 7 (20 mM), and alkali their imino-[2]catenane precursors [8·Na]⁺(18%), [9·Na]⁺

metal ions in the form of their TFPB salts (10 mM) in CDCl₃at (21%), and [11·Na]⁺(19%), respectively.

323 K for 24 h, the ¹H NMR spectrum of the reaction tem-

The Rb⁺ion is the best template among our tested alkali

plated by Na⁺ions was the only one to feature a reasonably metal ions when assembling the hetero-[2]catenane [12·M]⁺

intense new set of signals corresponding to the hetero-[2]cate- from the tri(ethylene glycol)-containing diamine 2 and the

nane [11·M]⁺. A tiny set of signals, similar to those assigned tetra(ethylene glycol)-containing diamine 3. Although K⁺and

for the hetero-[2]catenane [11·Na]⁺, appeared in the ¹H NMR Cs⁺ions also templated the formation of their same [2]cate-

spectrum when using the K⁺ion as the template, suggesting nanes [12·M]⁺, they more strongly preferred to template the

that the latter ion remained too large to template the for- assembly of their homo-[2]catenanes [9·K]⁺and [10·Cs]⁺,

mation of [11·K]⁺eﬃciently; instead, the predominant inter- respectively. After using NaBH₄to reduce the imino bonds of

locked species in solution was the better-complexed homo-[2]- the hetero-[2]catenane [12·Rb]⁺[generated from a solution of

catenane [9·K]⁺. As expected, Rb⁺and Cs⁺ions, both larger the diamines 2 (10 mM) and 3 (10 mM), the dialdehyde 7

than a K⁺ion, were not capable of templating the formation of (20 mM), and RbTFPB (10 mM) in CDCl₃] and methylating the

their hetero-[2]catenanes [11·M]⁺, giving their tri(ethylene resulting secondary amino groups, we isolated the hetero-[2]

glycol)-containing homo-[2]catenanes [9·M]⁺as the only inter- catenane 18 in 16% yield as well as the homo-[2]catenanes 15

locked products. The smallest ion, Li⁺, which did not template and 16, in yields of 26 and 16%, respectively, confirming that

the formation of the homo-[2]catenane [9·Li]⁺, was again too the Rb⁺ion is a suitable template for the formation of this

small to align one unit of di(ethylene glycol) with one of tri- hetero-[2]catenane.

(ethylene glycol) for the assembly of the hetero-[2]catenane

The formation of the hetero-[2]catenanes [13·M]⁺was the

[11·Li]⁺. Because Na⁺is the best template for the formation of most challenging because the synthesis required a short di

the hetero-[2]catenane [11·M]⁺, we heated a CHCl₃solution of (ethylene glycol) unit and a long tetra(ethylene glycol) unit to

the diamines 1 and 2, the dialdehyde 7, and NaTFPB at 323 K be aligned by a single alkali metal ion, with unavoidable com-

for 24 h, reduced the imino bonds with NaBH₄, and then petition from the formation of the homo-[2]catenanes [8·M]⁺

methylated (HCHO/HCOOH) the resulting secondary amino and [10·M]⁺. The ¹H NMR spectra of the mixtures of the di-

groups in the [2]catenane. After chromatographic purification, amines 1 (10 mM) and 3 (10 mM), the dialdehyde 7 (20 mM),

we isolated the hetero-[2]catenane 17 and the homo-[2]cate- and alkali metal ions in the form of their TFPB salts (10 mM),

nanes 14 and 15 in yields of 16, 21, and 24%, respectively. after heating at 323 K for 24 h, displayed no convincing sets of

Although the various intermediates may have had diﬀerent signals corresponding to the hetero-[2]catenanes [13·M]⁺. The

stabilities under these reduction conditions, the isolated homo-[2]catenane [8·M]⁺was preferred in the presence of the

yields of 14 (21%), 15 (24%), and 17 (16%) did not deviate smaller Li⁺and Na⁺ions, while the homo-[2]catenane [10·M]⁺

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Table 3 Binding constants and thermodynamic data for the interactions between the [2]catenanes 14–19 and their optimal templating alkali metal

ions^a

Host

Metal ion

K [M⁻¹

]

ΔG° [kcal M⁻¹

]

ΔH° [kcal M⁻¹

]

ΔS° [cal K⁻¹M⁻¹

]

18C6

Na⁺

K⁺

(2.6 0.8) × 10⁶

(2.1 0.6) × 10⁶

(3.8 0.9) × 10⁵

(1.7 0.3) × 10⁶

(9.2 1.0) × 10⁵

(3.3 0.6) × 10⁵

(6.8 0.9) × 10⁵

(3.0 0.4) × 10⁵

−8.8 0.2

−8.6 0.2

−7.6 0.2

−8.5 0.1

−8.1 0.1

−7.5 0.1

−8.0 0.1

−7.5 0.1

−2.4 0.1

−7.0 0.1

−4.2 0.1

−6.3 0.1

−8.4 0.1

−4.8 0.1

−7.6 0.1

−4.9 0.1

21.2 3.0

5.2 1.3

11.3 0.9

7.1 1.3

−0.8 0.9

9.1 2.5

1.2 1.1

8.7 1.5

Na⁺

K⁺

Rb⁺

Na⁺

Rb⁺

Na⁺

^aEach value is the average from three independent experiments.

was preferred when applying the larger Rb⁺and Cs⁺ions, con- enthalpically slightly more favorable and entropically slightly

firming that cross alignment of the two diﬀerent amines was less favorable than those for its complexation to the [2]cate-

unfavorable under these conditions. Nevertheless, because the nane 15, implying only slight diﬀerences in their host binding

¹H NMR spectra of the solutions containing Na⁺and K⁺ions pockets. We measured greater enthalpy gains for the complexa-

as templates were relatively complicated, we subjected their tion of the [2]catenanes 14–16 to their optimal templating Na⁺,

mixtures to reduction (NaBH₄) and methylation (HCHO/ K⁺, and Rb⁺ions, respectively, consistent with the fact that the

HCOOH) in the hope that we could isolate the amino hetero- binding of more-sizable cations in larger binding pockets with

[2]catenane 19 to confirm the formation of the imino hetero- higher numbers of oxygen atoms is enthalpically more favor-

[2]catenanes [13·M]⁺in solution. Gratifyingly, we isolated the able. Because higher entropy losses were, however, required to

hetero-[2]catenane 19 in 6% yield from the solution containing organize these longer oligo(ethylene glycol) chains into their

Na⁺as the template; in contrast, the mixture in which K⁺was binding pockets, the binding aﬃnities of the [2]catenanes

the template aﬀorded only a trace amount of the hetero-[2]cate- 14–16 to their optimal templating alkali metal ions did not

nane 18. Thus, the Na⁺ion is the best alkali metal ion for tem- deviate too much. Interestingly, the complexation of Na⁺ions

plating the formation of the di- and tetra(ethylene glycol)- to the di(ethylene glycol)-containing [2]catenanes 14, 17, and

containing hetero-[2]catenane [13·M]⁺.

19 occurred with very similar binding enthalpies and entro-

We used isothermal titration calorimetry (ITC) to determine pies, implying that the sizes and shapes of the binding

the association constants and thermodynamic constants for pockets induced by the Na⁺ions were quite similar, regardless

the interactions of the [2]catenanes 14–19 with their most suit- of the length of the oligo(ethylene glycol) chain in the other

able templating alkali metal ions in a mixture of CH₂Cl₂and macrocyclic component.

CH₃CN (7 : 3). The binding constants of the [2]catenanes 14

and 15 to Na⁺and K⁺ions, respectively, were comparable to

those of [18]crown-6 to these two alkali metal ions under the

same conditions (Table 3). Thus, although the two ortho-

Conclusions

gonally aligned oligo(ethylene glycol) chains in the [2]catenanes We have determined the most suitable alkali metal ions for

14 and 15 are not covalently linked, their interlocking allows templating the assembly of various homo- and hetero-[2]cate-

them to operate cooperatively as very good binders of alkali nanes from the diamines 1–3 and the dialdehyde 7. We con-

metal ions. Also with six oxygen atoms in the binding pocket, clude that Na⁺is the best templating ion among the tested

the [2]catenane 14 is enthalpically more favorable than [18] alkali metal ions for constructing [2]catenanes containing di

crown-6 in the binding of a Na⁺ion, suggesting that the (ethylene glycol) units, namely the homo-[2]catenane [8·M]⁺

orthogonal alignment of the two di(ethylene glycol) units and the hetero-[2]catenanes [11·M]⁺and [13·M]⁺. For [2]cate-

allows the oxygen atoms to better interact with the Na⁺ion nanes featuring tetra(ethylene glycol), but not di(ethylene

than does the planar cyclic arrangement. Nevertheless, the glycol), units, namely the homo-[2]catenane [10·M]⁺and the

structural flexibility of the [2]catenane 14 is greater than that hetero-[2]catenane [12·M]⁺, Rb⁺is the best template among our

of [18]crown-6, resulting in higher entropy loss when organiz- tested alkali metal ions. For construction of the homo-[2]cate-

ing the former’s binding pocket for complexation of the Na⁺nane [9·M]⁺, K⁺is the best template for aligning its two tri

ion; accordingly, the entropy of binding a Na⁺ion to [18] (ethylene glycol) units. Thus, it is possible to assemble a

crown-6 is significantly larger than that to the [2]catenane 14, variety of [2]catenanes from oligo(ethylene glycol)-containing

making the binding aﬃnity of the Na⁺ion to the latter slightly diamines and isophthalaldehyde after judicious selection of a

stronger than that to the former. For the K⁺ion, the best- suitable alkali metal ion as the template. The ability to con-

fitting alkali metal ion to [18]crown-6, the situation is struct such [2]catenanes with diﬀerently sized macrocyclic

diﬀerent. The complexation of a K⁺ion to [18]crown-6 is units should assist in the development of interesting inter-

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locked switches; indeed, we are now investigating the dynamic organic phases were dried (MgSO₄) and concentrated to aﬀord

behavior and switching properties of these [2]catenanes.

a yellow liquid (874 mg, 86%); H NMR (400 MHz, CDCl₃): δ =

3.55–3.60 (m, 4H), 3.60–3.65 (m, 8H), 3.79 (s, 4H), 4.50 (s, 4H),

7.22 (d, J = 8.0 Hz, 4H), 7.26 (d, J = 8.0 Hz, 4H); ¹³C NMR

(100 MHz, CDCl₃): δ = 45.4, 68.6, 69.9, 72.2, 126.3, 127.2,

136.0, 142.0 (one signal was missing, possibly due to a signal

Experimental

General

overlap); HR-MS (ESI): calcd for [M + H]⁺C₂₂H₃₃N₂O₄, m/z

All glassware, stir bars, syringes, and needles were either oven- 389.2440; found 389.2471.

or flame-dried prior to use. All reagents, unless otherwise indi-

Amine 3. LiAlH₄(268 mg, 7.06 mmol) was added to a solu-

cated, were obtained from commercial sources. Reactions were tion of 6 (1.00 g, 2.36 mmol) in THF (47.1 mL) at 0 °C and

conducted under N₂or Ar atmospheres. Thin layer chromato- then the mixture was heated under reflux for 3 h. After cooling

graphy (TLC) was performed on Merck 0.25 mm silica gel to room temperature, H₂O (2 mL) was added dropwise to

(Merck Art. 5715). Column chromatography was performed quench the reaction; the mixture was dried (MgSO₄) and fil-

using Kieselgel 60 (Merck, 70–230 mesh) and Chromatorex NH tered and the filtrate was then concentrated. The residue was

series (Fuji Silysia, MB100-40/75). Melting points were deter- purified chromatographically (SiO₂; MeOH/NEt₃/CH₂Cl₂,

mined using a Fargo MP-2D melting point apparatus. For 5 : 5 : 90). The product isolated was partitioned between

NMR spectroscopy, the deuterated solvent was used as the lock NaOH_(aq.)(10%, 50 mL) and CH₂Cl₂(2 × 50 mL); the combined

and the solvent’s residual protons were employed as the organic phases were dried (MgSO₄) and concentrated to aﬀord

internal standard.

a yellow liquid (0.947 g, 93%); ¹H NMR (400 MHz, CDCl₃):

Benzonitrile 5. NaH (1.34 g, 56.0 mmol) was added to a δ = 3.57–3.61 (m, 4H), 3.62–3.66 (m, 12H), 3.83 (s, 4H), 4.52

solution of tri(ethylene glycol) (3.00 mL, 22.4 mmol) in THF (s, 4H), 7.25 (d, J = 8.0 Hz, 4H), 7.29 (d, J = 8.0 Hz, 4 H);

(224 mL) and then the mixture was stirred at room tempera- ¹³C NMR (100 MHz, CDCl₃): δ = 46.1, 69.2, 70.5, 70.5, 70.5,

ture for 30 min. After the addition of 4-cyanobenzylbromide 72.8, 127.0, 127.9, 136.6, 142.6; HR-MS (ESI): calcd for

(11.0 g, 56.1 mmol), the mixture was heated under reflux for [M + H]⁺C₂₄H₃₇N₂O₅, m/z 433.2702; found 433.2735.

16 h and then cooled to room temperature. The mixture was

[2]Catenane 14. A solution of 1 (165 mg, 0.479 mmol), iso-

filtered through Celite and then the filtrate was evaporated phthalaldehyde (64.1 mg, 0.478 mmol), and NaTFPB (212 mg,

under reduced pressure. The residue was purified chromato- 0.239 mmol) in CHCl₃(23.9 mL) was stirred at 50 °C for 24 h.

graphically (SiO₂; EtOAc/hexanes, 4 : 6) to aﬀord a yellow liquid After cooling to room temperature, the mixture was slowly

(2.37 g, 28%); ¹H NMR (400 MHz, CDCl₃): δ = 3.60–3.71 (m, added to a solution of NaBH₄(726 mg, 19.2 mmol) in MeOH

12H), 4.60 (s, 4H), 7.43 (d, J = 8.4 Hz, 4H), 7.60 (d, J = 8.4 Hz, (95.6 mL) and then the organic solvents were evaporated

4H); ¹³C NMR (100 MHz, CDCl₃): δ = 69.8, 70.3, 70.3, 71.8, under reduced pressure. The residue was partitioned between

110.8, 118.6, 127.4, 131.8, 143.7; HR-MS (ESI): calcd for H₂O (30 mL) and CH₂Cl₂(2 × 30 mL); the combined organic

[M + H]⁺C₂₂H₂₅N₂O₄, m/z 381.1814; found 381.1836.

phases were dried (MgSO₄) and concentrated. The residue was

Benzonitrile 6. NaH (696 mg, 29.0 mmol) was added to a dissolved in DMF (23.9 mL), paraformaldehyde (1.48 g,

solution of tetra(ethylene glycol) (2.00 mL, 11.6 mmol) in THF 47.7 mmol) and formic acid (1.80 mL, 47.7 mmol) were added,

(116 mL) and then the mixture was stirred at room tempera- and then the solution was stirred at 70 °C for 16 h. The

ture for 30 min. After the addition of 4-cyanobenzylbromide organic solvent was evaporated under reduced pressure and

(5.68 g, 29.0 mmol), the mixture was heated under reflux for the residue partitioned between NaOH_(aq.)(10%, 30 mL) and

16 h and then cooled to room temperature. The mixture was CH₂Cl₂(2 × 30 mL). The combined organic phases were dried

filtered through Celite and then the filtrate was evaporated (MgSO₄) and concentrated. The residue was purified chromato-

under reduced pressure. The residue was purified chromato- graphically (NH-silica gel; EtOAc/hexanes, 2 : 8) to aﬀord a

graphically (SiO₂; EtOAc/hexanes, 4 : 6) to aﬀord a yellow liquid colorless oil (132 mg, 58%); ¹H NMR (400 MHz, CDCl₃): δ =

(4.53 g, 92%); ¹H NMR (400 MHz, CDCl₃): δ = 3.61–3.69 (m, 2.21 (s, 12H), 2.77 (t, J = 5.6 Hz, 8H), 2.86 (t, J = 5.6 Hz, 8H),

16H), 4.59 (s, 4H), 7.43 (d, J = 8.0 Hz, 4H), 7.61 (d, J = 8.0 Hz, 3.36 (s, 8H), 3.59 (s, 8H), 3.94 (s, 8H), 6.95 (s, 2H), 6.99 (d, J =

4H); ¹³C NMR (100 MHz, CDCl₃): δ = 70.0, 70.6, 70.6, 70.7, 8.0 Hz, 8H), 7.18 (d, J = 8.0 Hz, 8H), 7.23–7.27 (m, 6H);

72.2, 111.2, 118.8, 127.7, 132.2, 143.9; HR-MS (ESI): calcd for ¹³C NMR (100 MHz, CDCl₃): δ = 42.4, 59.9, 62.3, 68.0, 69.2,

[M + H]⁺C₂₄H₂₉N₂O₅, m/z 425.2076; found 425.2099.

72.3, 126.6, 128.0, 128.6, 128.8, 128.9, 137.2, 137.4, 139.6;

Amine 2. LiAlH₄(299 mg, 7.88 mmol) was added to a solu- HR-MS (ESI): calcd for [M + H]⁺C₆₀H₇₇N₄O₆: m/z 949.5838;

tion of 5 (1.00 g, 2.63 mmol) in THF (52.6 mL) at 0 °C and found 949.5877.

then the mixture was heated under reflux for 3 h. After cooling

[2]Catenane 15. A solution of 2 (187 mg, 0.481 mmol), iso-

to room temperature, H₂O (2 mL) was added dropwise to phthalaldehyde (64.6 mg, 0.482 mmol), and KTFPB (217 mg,

quench the reaction; the mixture was dried (MgSO₄) and fil- 0.240 mmol) in CHCl₃(24.1 mL) was stirred at 50 °C for 24 h.

tered and the filtrate was then concentrated. The residue was After cooling to room temperature, the mixture was slowly

purified chromatographically (SiO₂; MeOH/NEt₃/CH₂Cl₂, added to a solution of NaBH₄(730 mg, 19.3 mmol) in MeOH

5 : 5 : 90). The product isolated was partitioned between (96.4 mL) and then the organic solvents were evaporated

NaOH_(aq.)(10%, 50 mL) and CH₂Cl₂(2 × 50 mL); the combined under reduced pressure. The residue was partitioned between

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H₂O (30 mL) and CH₂Cl₂(2 × 30 mL); the combined organic under reduced pressure and the residue partitioned between

phases were dried (MgSO₄) and concentrated. The residue was NaOH_(aq.)(10%, 50 mL) and CH₂Cl₂(2 × 50 mL). The organic

dissolved in DMF (24.1 mL), paraformaldehyde (1.49 g, phase was dried (MgSO₄) and concentrated. The residue was

48.0 mmol) and formic acid (1.81 mL, 48.0 mmol) were added, purified chromatographically (NH-silica gel; EtOAc/hexanes,

and then the solution was stirred at 70 °C for 16 h. The 3 : 7) to aﬀord 17 (66.8 mg, 16%), 14 (42.8 mg, 21%), and 15

organic solvent was evaporated under reduced pressure and (54.6 mg, 24%), each as a colorless oil; data for 17: ¹H NMR

the residue partitioned between NaOH_(aq.)(10%, 30 mL) and (400 MHz, CDCl₃): δ = 2.10 (s, 6H), 2.20 (s, 6H), 2.78 (s, 4H),

CH₂Cl₂(2 × 30 mL). The combined organic phases were dried 2.87–3.00 (m, 8H), 3.11–3.19 (m, 8H), 3.24 (s, 4H), 3.35 (s, 4H),

(MgSO₄) and concentrated. The residue was purified chromato- 3.40 (s, 4H), 3.48 (s, 4H), 4.04 (s, 4H), 4.16 (s, 4H), 6.90 (d, J =

graphically (NH-silica gel; EtOAc/hexanes, 3 : 7) to aﬀord a 8.0 Hz, 4H), 6.95 (s, 1H), 6.97–7.02 (m, 5H), 7.08 (d, J = 8.0 Hz,

colorless oil (119 mg, 48%); ¹H NMR (400 MHz, CDCl₃): δ = 4H), 7.13–7.30 (m, 10H); ¹³C NMR (100 MHz, CDCl₃): δ = 42.3,

2.14 (s, 12H), 3.06–3.18 (m, 24H), 3.31 (s, 8H), 3.40 (s, 8H), 42.7, 60.0, 60.8, 61.9, 62.0, 68.3, 68.3, 69.3, 69.6, 70.0, 72.7,

4.12 (s, 8H), 6.97 (d, J = 8.0 Hz, 8H), 7.05 (s, 2H), 7.09 (d, J = 72.8, 126.5, 126.9, 127.7, 128.2, 128.2, 128.4, 128.6, 128.7,

8.0 Hz, 8H), 7.21–7.26 (m, 6H); ¹³C NMR (100 MHz, CDCl₃): δ = 128.9, 129.2, 136.4, 137.1, 137.6, 138.2, 139.5 (one signal was

42.5, 60.7, 61.7, 68.7, 69.8, 70.2, 72.7, 126.9, 128.0, 128.5, missing, possibly due to a signal overlap); HR-MS (ESI): calcd

128.7, 136.6, 137.8, 139.4 (one signal was missing, possibly for [M + H]⁺C₆₂H₈₁N₄O₇⁺: m/z 993.6105; found 993.6133.

due to a signal overlap); HR-MS (ESI): calcd for [M + H]⁺

C₆₄H₈₅N₄O₈: m/z 1037.6367; found 1037.6350.

[2]Catenane 18. A solution of 2 (154 mg, 0.396 mmol), 3

(171 mg, 0.395 mmol), isophthalaldehyde (106 mg,

[2]Catenane 16. A solution of 3 (206 mg, 0.476 mmol), iso- 0.790 mmol), and RbTFPB (376 mg, 0.396 mmol) in CHCl₃

phthalaldehyde (63.8 mg, 0.476 mmol), and RbTFPB (226 mg, (39.6 mL) was stirred at 50 °C for 24 h. After cooling to room

0.238 mmol) in CHCl₃(23.8 mL) was stirred at 50 °C for 24 h. temperature, the mixture was slowly added to a solution of

After cooling to room temperature, the mixture was slowly NaBH₄(1.20 g, 31.7 mmol) in MeOH (158 mL) and then the

added to a solution of NaBH₄(722 mg, 19.1 mmol) in MeOH organic solvents were evaporated under reduced pressure. The

(95.3 mL) and then the organic solvents were evaporated residue was partitioned between H₂O (40 mL) and CH₂Cl₂(2 ×

under reduced pressure. The residue was partitioned between 40 mL); the combined organic phases were dried (MgSO₄) and

H₂O (30 mL) and CH₂Cl₂(2 × 30 mL); the combined organic concentrated. The residue was dissolved in DMF (39.6 mL),

phases were dried (MgSO₄) and concentrated. The residue paraformaldehyde (2.46 g, 79.3 mmol) and formic acid

was dissolved in DMF (23.8 mL), paraformaldehyde (1.48 g, (2.99 mL, 79.3 mmol) were added, and then the mixture was

47.7 mmol) and formic acid (1.80 mL, 47.7 mmol) were added, stirred at 70 °C for 16 h. The organic solvent was evaporated

and then the mixture was stirred at 70 °C for 16 h. The organic under reduced pressure and the residue partitioned between

solvent was evaporated under reduced pressure and the NaOH_(aq.)(10%, 40 mL) and CH₂Cl₂(2 × 40 mL). The organic

residue partitioned between NaOH_(aq.)(10%, 30 mL) and phase was dried (MgSO₄) and concentrated. The residue was

CH₂Cl₂(2 × 30 mL). The combined organic phases were dried purified chromatographically (NH-silica gel; EtOAc/hexanes,

(MgSO₄) and concentrated. The residue was purified chromato- 3 : 7) to aﬀord 18 (68.7 mg, 16%), 15 (53.5 mg, 26%), and 16

graphically (NH-silica gel; EtOAc/hexanes, 4 : 6) to aﬀord a (36.7 mg, 16%), each as a colorless oil; data for 18: ¹H NMR

colorless oil (80.9 mg, 30%); ¹H NMR (400 MHz, CDCl₃): δ = (400 MHz, CDCl₃): δ = 2.08 (s, 6H), 2.12 (s, 6H), 3.14–3.41 (m,

2.08 (s, 12H), 3.21–3.40 (m, 48H), 4.23 (s, 8H), 7.01 (d, J = 44H), 4.18 (s, 4H), 4.20 (s, 4H), 6.96–7.04 (m, 9H), 7.07 (d, J =

8.0 Hz, 8H), 7.06–7.11 (m, 10H), 7.19–7.22 (m, 6H); ¹³C NMR 8.0 Hz, 4H), 7.11 (d, J = 8.0 Hz, 4H), 7.15 (s, 1H), 7.17–7.20 (m,

(100 MHz, CDCl₃): δ = 42.5, 61.3, 61.7, 69.1, 70.4, 70.5, 72.9, 3H), 7.22–7.26 (m, 3H); ¹³C NMR (100 MHz, CDCl₃): δ = 42.5,

127.3, 127.8, 128.1, 128.6, 129.1, 136.7, 138.2, 139.3 (one 42.5, 60.8, 61.4, 61.7, 61.8, 68.9, 69.0, 70.2, 70.2, 70.3, 70.5,

signal was missing, possibly due to a signal overlap); HR-MS 72.8, 73.0, 126.9, 127.3, 127.8, 128.0, 128.1, 128.6, 128.7, 128.9,

(ESI): calcd for [M + H]⁺C₆₈H₉₃N₄O₁₀⁺: m/z 1125.6892; found 129.1, 136.5, 136.8, 138.0, 138.1, 139.4, 139.5 (two signals were

1125.6847.

[2]Catenane 17. A solution of 1 (148 mg, 0.430 mmol), 2 [M + Na]⁺C₆₆H₈₈N₄O₉Na⁺: m/z 1103.6449; found 1103.6437.

(167 mg, 0.430 mmol), isophthalaldehyde (116 mg, [2]Catenane 19. A solution of 1 (156 mg, 0.453 mmol), 3

missing, possibly due to signal overlap); HR-MS (ESI): calcd for

0.865 mmol), and NaTFPB (382 mg, 0.431 mmol) in CHCl₃(195 mg, 0.451 mmol), isophthalaldehyde (121 mg,

(43.0 mL) was stirred at 50 °C for 24 h. After cooling to room 0.902 mmol), and NaTFPB (400 mg, 0.451 mmol) in CHCl₃

temperature, the mixture was slowly added to a solution of (75.1 mL) was stirred at 50 °C for 24 h. After cooling to room

NaBH₄(1.30 g, 34.4 mmol) in MeOH (172 mL) and then the temperature, the mixture was slowly added to a solution of

organic solvents were evaporated under reduced pressure. The NaBH₄(1.06 g, 28.0 mmol) in MeOH (140 mL) and then the

residue was partitioned between H₂O (50 mL) and CH₂Cl₂(2 × organic solvents were evaporated under reduced pressure. The

50 mL); the combined organic phases were dried (MgSO₄) and residue was partitioned between H₂O (50 mL) and CH₂Cl₂(2 ×

concentrated. The residue was dissolved in DMF (43.0 mL), 50 mL); the combined organic phases were dried (MgSO₄) and

paraformaldehyde (2.68 g, 86.4 mmol) and formic acid concentrated. The residue was dissolved in DMF (45.1 mL),

(3.26 mL, 86.4 mmol) were added, and then the solution was paraformaldehyde (2.80 g, 90.2 mmol) and formic acid

stirred at 70 °C for 16 h. The organic solvent was evaporated (3.41 mL, 90.4 mmol) were added, and then the solution was

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Organic & Biomolecular Chemistry

stirred at 70 °C for 16 h. The organic solvent was evaporated

under reduced pressure and the residue partitioned between

NaOH_(aq.)(10%, 50 mL) and CH₂Cl₂(2 × 50 mL). The organic

phase was dried (MgSO₄) and concentrated. The residue was

purified chromatographically (NH-silica gel; EtOAc/hexanes,

3 : 7) to aﬀord 19 (27.3 mg, 6%), 14 (41.1 mg, 19%), and 16

(3.6 mg, 1%), each as a colorless oil; data for 19: ¹H NMR

(400 MHz, CDCl₃): δ = 2.05 (s, 6H), 2.16 (s, 6H), 2.92–3.02 (m,

8H), 3.07–3.15 (m, 8H), 3.19 (s, 4H), 3.26–3.34 (m, 8H), 3.36 (s,

4H), 3.39 (s, 4H), 3.44 (s, 4H), 4.17 (s, 4H), 4.23 (s, 4H), 6.92 (s,

1H), 6.98 (d, J = 8.0 Hz, 4H), 7.02 (d, J = 8.0 Hz, 4H), 7.07–7.15

(m, 7H), 7.17 (s, 1H), 7.20 (d, J = 8.0 Hz, 4H), 7.23–7.28 (m,

3H); ¹³C NMR (100 MHz, CDCl₃): δ = 42.3, 42.6, 60.0, 61.4,

61.7, 62.0, 68.5, 68.8, 69.8, 69.8, 70.3, 72.7, 73.1, 126.6, 127.3,

127.7, 127.9, 128.1, 128.4, 128.6, 129.0, 129.1, 129.4, 136.3,

137.2, 137.6, 138.3, 139.3 (two signals were missing, possibly

due to signal overlap); HR-MS (ESI): calcd for [M + H]⁺

304, 1308; (b) S.-L. Huang, Y.-J. Lin, Z.-H. Li and G.-X. Jin,

Angew. Chem., Int. Ed., 2014, 53, 11218; (c) F. L. Thorp-

Greenwood, A. N. Kulak and M. J. Hardie, Nat. Chem.,

2015, 7, 526.

6 D. A. Leigh, R. G. Pritchard and A. J. Stephens, Nat. Chem.,

2014, 6, 978.

7 (a) G. W. Gokel, Crown Ethers and Cryptands, The Royal

Society of Chemistry, Cambridge, 1991; (b) Crown Ethers

and Analogous Compounds, ed. M. Hiraoka, Elsevier,

Amsterdam, 1992; (c) M. C. T. Fyfe and J. F. Stoddart, in

Advances in Supramolecular Chemistry, ed. G. W. Gokel, JAI,

London, 1999, vol. 5, pp. 1–53.

8 (a) G. Kaiser, T. Jarrosson, S. Otto, Y.-F. Ng, A. D. Bond and

J. K. M. Sanders, Angew. Chem., Int. Ed., 2004, 43, 1959;

(b) S. A. Vignon, T. Jarrosson, T. Iijima, H.-R. Tseng,

J. K. M. Sanders and J. F. Stoddart, J. Am. Chem. Soc., 2004,

126, 9884; (c) Y.-H. Lin, C.-C. Lai, Y.-H. Liu, S.-M. Peng and

S.-H. Chiu, Angew. Chem., Int. Ed., 2013, 52, 10231;

(d) K.-D. Wu, Y.-H. Lin, C.-C. Lai and S.-H. Chiu, Org. Lett.,

2014, 16, 1068; (e) T.-H. Ho, C.-C. Lai, Y.-H. Liu, S.-M. Peng

C₆₄H₈₅N₄O₈: m/z 1037.6367; found 1037.6322.

Acknowledgements

and S.-H. Chiu, Chem.

– Eur. J., 2014, 20, 4563;

(f) Y.-H. Lin, C.-C. Lai and S.-H. Chiu, Org. Biomol.

Chem., 2014, 12, 2907; (g) Y.-W. Wu, P.-N. Chen,

C.-F. Chang, C.-C. Lai and S.-H. Chiu, Org. Lett., 2015, 17,

2158; (h) Y.-W. Wu, S.-T. Tung, C.-C. Lai, Y.-H. Liu,

S.-M. Peng and S.-H. Chiu, Angew. Chem., Int. Ed., 2015, 54,

11745.

We thank the National Science Council (Taiwan) (MOST-104-

2826-M-002-012) and National Taiwan University (NTU-104-

R890913) for financial support.

Notes and references

9 S.-T. Tung, C.-C. Lai, Y.-H. Liu, S.-M. Peng and S.-H. Chiu,

Angew. Chem., Int. Ed., 2013, 52, 13269.

1 For recent reviews, see: (a) M. E. Belowich and

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(d) V. Marti-Centelles, M. D. Pandey, M. I. Burguete and

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thesis of Ligands, World Scientific Publishing, Singapore, 2004.

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J.-P. Sauvage, Chem. Soc. Rev., 2007, 36, 358; (b) J. E. Beves,

B. A. Blight, C. J. Campbell, D. A. Leigh and R. T. McBurney,

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K⁺ions, see: (a) A. P. de Silva, H. Q. N. Gunaratne,

T. Gunnlaugsson and M. Nieuwenhuizen, Chem. Commun.,

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decomposition in CDCl₃; similar tertiary amino derivatives

have been found to be much more robust (ref. 8h). For

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2008, 49, 2397; (b) S. Suzuki, K. Nakazono and T. Takata,

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Org. Biomol. Chem.

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