Synthesis of cyclic bis- and trismelamine derivatives and their complexation properties with barbiturates

Article abstract of DOI:10.1039/b615537e

Cyclic bis- and trismelamine derivatives were prepared from cyanuric chloride by stepwise substitutions with appropriate amines. The complexation abilities of these melamine derivatives with barbituric acid derivatives were evaluated by UV-vis spectroscopy and ¹H NMR. The structure was also confirmed by X-ray crystallography. Both the acyclic and the cyclic bismelamine derivatives formed a 1: 1 complex via six hydrogen bonds with barbituric acid derivatives. van't Hoff analyses on the complexation of the bismelamines with the barbituric acid derivative revealed that the complexation of the cyclic bismelamine was entropically favored and enthalpically less favored process than those of the acyclic bismelamine. X-Ray crystallographic analysis and ¹H NMR studies revealed that the cyclic trismelamine bound one barbituric acid derivative into the cavity via six hydrogen bonds by two melamine moieties and another barbituric acid via three hydrogen bonds by the residual melamine moiety. The Royal Society of Chemistry.

Full text of DOI:10.1039/b615537e

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis of cyclic bis- and trismelamine derivatives and their complexation
properties with barbiturates
Shin-ichi Kondo,* Tomohiro Hayashi, Yuichi Sakuno, Yoko Takezawa, Takashi Yokoyama, Masafumi Unno and
Yumihiko Yano
Received 26th October 2006, Accepted 3rd January 2007
First published as an Advance Article on the web 25th January 2007
DOI: 10.1039/b615537e
Cyclic bis- and trismelamine derivatives were prepared from cyanuric chloride by stepwise substitutions
with appropriate amines. The complexation abilities of these melamine derivatives with barbituric acid
derivatives were evaluated by UV-vis spectroscopy and 1H NMR. The structure was also confirmed by
X-ray crystallography. Both the acyclic and the cyclic bismelamine derivatives formed a 1 : 1 complex
via six hydrogen bonds with barbituric acid derivatives. van’t Hoff analyses on the complexation of the
bismelamines with the barbituric acid derivative revealed that the complexation of the cyclic
bismelamine was entropically favored and enthalpically less favored process than those of the acyclic
bismelamine. X-Ray crystallographic analysis and 1H NMR studies revealed that the cyclic
trismelamine bound one barbituric acid derivative into the cavity via six hydrogen bonds by two
melamine moieties and another barbituric acid via three hydrogen bonds by the residual melamine
moiety.
(bismelamine)3·(barbiturate)6.11 We have also reported that re-
Introduction
ceptors bearing a melamine moiety showed strong binding abil-
The molecular recognition of neutral target substances via hydro-
gen bonds has been attracting considerable attention in the last two
ity for imides such as flavin derivatives, barbituric acids, and
thymine derivatives via multiple hydrogen bonds.12 Melamine–
decades.1 Barbituric acids were attractive guest molecules because
baribituric acid complexation is also applied to supramolecular
of medicinal use as sedatives and anticonvulsants.2 Barbituric
acid derivatives have two sets of hydrogen bonding acceptor-
donor–acceptor arrays in the molecule. To associate barbituric
acid derivatives, two types of functionality were usually employed
as a recognition site of host molecules, i.e. diamidopyridine
and melamine groups. These two functionalities consist of a
complementary hydrogen bond donor–acceptor–donor array for
barbiturate.
Hamilton et al. reported that complexation of cyclic and acyclic
receptors bearing two diamidopyridine units linked through an
isophthaloyl spacer with barbituric acids via six hydrogen bonds in
apolar organic solvents such as chloroform and dichloromethane.3
Similar binding motifs bearing redox active,4 chiral5 metal ligand,6
and chromophore7 moieties have also been reported as barbiturate
and cyanurate receptors. The diamidopyridine group was applied
to construct more sophisticated materials such as supramolecular
polymers.8
materials such as organogel,13 supramolecular membranes,14 and
liquid crystals.15 Meanwhile, cyclic melamine derivatives have
been scarcely reported16 although cyclic bis diamidopyridine
derivatives have been prepared and evaluated at an early stage
of the study.3,17 Cyclic melamine derivatives form isolated binding
pockets to complex with guest barbiturates and are applicable to
analytical usages. Lo¨wik and Lowe reported the synthesis of cyclic
trismelamine derivatives by stepwise substitution and preliminary
complexation properties of these derivatives with cyanuric acid
and carbohydrates.16b,c Herein, we report the synthesis and com-
plexation properties of less explored cyclic bis- and trismelamine
derivatives 1–4. A barbiturate derivative bearing an anthryl group
(5b) was also prepared and was used as a probe for a complexation
study. The complexation properties of cyclic bis- and trismelamine
1
derivatives and barbiturates were studied by UV-vis, H NMR
spectroscopy, and X-ray crystallography.
Melamine (2,4,6-triamino-1,3,5-s-triazine) derivatives are easily
prepared from 2,4,6-trichloro-1,3,5-s-triazine (cyanuric chloride)
by stepwise substitutions with appropriate amines and widely
applied to supramolecular chemistry.9 Complex structures of
melamine derivatives and barbituric acids or isocyanurates were
systematically investigated by Whitesides and co-workers. They
prepared supramolecular structures such as linear and crin-
kled tapes and a rosette.10 Reinhoudt and Timmerman ex-
tended the rosette complexes by use of bismelamines based
on a calix[4]arene scaffold to give double rosette assemblies,
Results and discussion
Design and synthesis of cyclic bis- and trismelamine derivatives
The prepared cyclic melamine derivatives are listed in Scheme 1.
A m-xylylene spacer was employed to connect two melamine units
because the corresponding acyclic bismelamine 1 showed strong
complexation with barbituric acid derivatives via six hydrogen
bonds in chloroform.10f ,18 Cyclic bismelamine derivatives 2 and 3
were cyclized with different types of spacer, i.e. an alkyl spacer
and a bisphenol-A based spacer, respectively. Hamilton and co-
worker reported a cyclic bisamidopyridine derivative in which
m-phenylene and bisphenol-A were used as spacers.3d Cyclic
Department of Chemistry, Faculty of Engineering, Gunma University, Kiryu,
Gunma, 376-8515, Japan. E-mail: kondo@chem.gunma-u.ac.jp
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with appropriate amines in the presence of a base as shown in
below.
Preparation of the cyclic bismelamine derivatives (2 and 3)
is illustrated in Fig. 1. m-Xylylenediamine was reacted with 2-
diethylamino-4,6-dichloro-1,3,5-s-triazine (6) in the presence of
sodium carbonate in dichloromethane to gave 7 in 84% yield.
Cyclization of 7 and 1,12-diaminododecane in dilute conditions
in 1,4-dioxane yielded cyclic bismelamine receptor 2 in 50% yield.
The lower spacer of 3 was prepared from 1,3-dibromopropane and
bisphenol-A in three steps,19 and cyclization with 7 yielded cyclic
bismelamine receptor 3 in 43%.
Lo¨wik and Lowe reported the synthesis of trismelamine
derivatives bearing piperidine or m-xylylene as spacers with
stepwise substitution and finally intramolecular cyclization after
deprotection of terminal residues. As shown in Fig. 2, we selected
the preparation of 4 by intermolecular cyclization method. Two
mono Boc-protected m-xylylenediamine units were introduced
to 2-diethylamino-4,6-dichloro-1,3,5-s-triazine, followed by the
deprotection of the Boc groups by TFA to give 9. Two 2-
diethylamino-4,6-dichloro-1,3,5-s-triazines were introduced to the
diamine 9 to give 10. The slow and simultaneous addition of 10
and m-xylylenediamine gave a facile and efficient cyclization to
give 4 in a moderate yield.
Products were analyzed by 1H NMR, elemental analysis,
and electrospray ionization mass spectroscopy (ESI-MS). Proton
NMR spectraofcyclic melamine derivatives 2–4 gave broadsignals
at 25 ◦C in CDCl3, and the signals were slightly sharpened at
◦
1
45 C. However, H NMR spectra of acyclic bismelamine 1 gave
sharp signals at 25 ◦C indicating slow conformational change
such as ring flipping of the macrocycles. A similar result was also
reported by Lo¨wik and Lowe.16b
Complexation of cyclic bis- and trismelamine derivatives with
barbiturates
In general, it is difficult to determine the association constants
for complexation of melamine derivatives and barbiturates with-
out chromophore by UV-vis and fluorescent spectroscopies. A
barbiturate bearing chromophore is quite useful for the study
of complexation with receptors, however, only a limited num-
ber of examples have been reported previously. Prins et al.
reported a barbiturate bearing a chromogenic donor–p-acceptor
system with the bismelamine based on calix[4]arene skeleton.20
De Cola and Vo¨gtle reported a barbiturate bearing rhenium–
bipyridine complex.21 The anthryl group is a useful chromophore
since UV-vis and fluorescence change during complexation is
expected due to electronic perturbation of the large p-surface.
We prepared a barbituric acid derivative (5b) bearing an anthryl
Scheme 1
trismelamine derivative 4 has D3h symmetry and three melamine
units were connected via m-xylylene spacers. The acyclic and cyclic
bismelamine derivatives and the cyclic trismelamine derivative
were prepared from cyanuric chloride by stepwise substitutions
Fig. 1 Synthesis of 2 and 3. (i) m-Xylylenediamine, K2CO3, 1,4-dioxane, rt, 84%; (ii) 1,12-diaminododecane, K2CO3, 1,4-dioxane, reflux, 50%;
(iii), K2CO3, 1,4-dioxane, reflux, 43%.
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Fig. 2 Synthesis of 4. (i) 3-tert-Butoxycarbonylaminomethylbenzylamine, K2CO3, 1,4-dioxane, reflux, 98%; (ii) TFA–H2O, rt, 85%; (iii) 2,6-dichloro-
4-diethylamino-1,3,5-s-triazine, K2CO3, 1,4-dioxane, rt, 75%; (iv) m-xylylenediamine, K2CO3, 1,4-dioxane, reflux, 15%.
group as a chromophore from diethyl butylmalonate and 9-
chloromethylanthracene in two steps. The barbiturate 5b shows
well-resolved vibronic transitions of the anthryl group at 337,
353.5, 372.5, and 392.5 nm in CHCl3. Strong emission is also
observed at 399, 421.4, and 446 nm excited at 340 nm in CHCl3.
UV-vis spectroscopic titrations were carried out to determine the
association constants for 5b with 1–4. Cyclic bis- and trismelamine
derivatives showed remarkable spectral changes corresponding
to the anthryl group through isosbestic points indicating 1 : 1
complexation as shown in Fig. 3.
of 3 with 5b is enthalpy driven. The average enthalpy change of
six hydrogen bonds for complexation of 3 with 5b is 5.27 kJ mol−1.
This value is compatible with the values for complexation of
melamine–cyanuric acid derivatives (5.4 kJ mol−1) and others.22
The thermodynamic parameters for the association of acyclic host
1 with 5b were also determined to be DH = −40.3 kJ mol−1 and
DS = −44.8 J mol−1 K−1 (TDS at 298 K was −13.4 kJ mol−1).
These data showed acyclic host 1 formed a complex in a more
enthalpically favored process than 3 due to the flexible host
structure, however, the process is entropically disfavored. The
result is consistent with the so-called macrocyclic effect.23
All of the stoichiometries of the complex formation were
confirmed by Job’s plots (Fig. 4) in CHCl3. Receptors 3 and
4 showed maximum at mole fraction of 0.5 indicating that the
receptors and the barbiturate 5b form a 1 : 1 complex. The
association constants were calculated from the changes of the
absorbance at 400 nm by non-linear regressions. The results are
summarized in Table 1. To determine the association constants
of the receptors with barbiturate 5a, competitive titration in the
presence of 5b was employed. As shown in Fig. 5, addition of
5a in a solution of 5b and 3 formed free 5b through isosbestic
points. The association constants were calculated by computer-
aided regression using the association constants for 5b described
above, and the results were also summarized in Table 1. Cyclic
bismelamine derivative 2 showed a gradual decrease of the
association constants for 5 compared to that of 1 because of steric
repulsion of the dodecyl group suggested by molecular mechanics
calculations. Cyclic bismelamine 3, in which bisphenol-A was used
as a spacer, showed slightly higher but less pronounced association
constants for 5 relative to that of the acyclic bismelamine 1.
Thermodynamic parameters for the complexation are informative.
The thermodynamic parameters for the association of 3 with 5b
were determined by the van’t Hoff analysis (T = 288–313 K)
giving DH = −31.6 kJ mol−1 and DS = −12.3 J mol−1 K−1 (TDS
at 298 K was −3.7 kJ mol−1). The result indicates the association
The cyclic trismelamine derivative 4 was expected to form a com-
plex with barbiturate 5 with a potential of eight hydrogen bonds,
i.e., two sets of donor–acceptor–donor hydrogen bonds from two
melamine units and two hydrogen bond donor of NHs from
remaining melamine moiety. However the association constants
of 4 with 5 are similar to that of 1 suggesting the participation
of only six hydrogen bonds to form the complexes due to steric
hindrance of the disubstituted groups at the 5,5-positions of 5
pointed out by Hamilton and co-workers.1 Unfortunately, host–
guest complexes were not observed in ESI-MS studies because of
the difficulty of ionization of host–guest complexes in CHCl3.
X-Ray crystal structure of the 4 and 5a complex
To evaluate the complex of 4 with barbiturates, single crystals
suitable for X-ray analysis of the complex of 4 and 5a were
obtained by slow diffusion of cyclohexane into a CHCl3 solution
of 4 and 5a in a 1 : 1 molar ratio. The proton NMR spectrum
of the crystal dissolved in CDCl3 revealed that the ratio of 4
and 5a is 1 : 2 from the integrations of the corresponding peaks.
¯
X-Ray analysis of the complex (triclinic system, space group P1)
showed two 1 : 1 complexes of 4 and 5a were connected with
two other barbiturates 5a to form a 2 : 4 complex as shown in Fig. 6.
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Fig. 3 (a): Spectral changes of 5b upon addition of 3 in CHCl3 at 298 K.
[5b] = 1.0 × 10−4 mol dm−3, [3] = 0–3.0 × 10−4 mol dm−3. (b): Changes in
the intensity of absorbance at 400 nm of 5b upon addition of 3 in CHCl3
at 298 K.
Fig. 5 Competitive titration of 3 upon addition of 5a in the presence of 5b
in CHCl3. [3] = [5b] = 1.0 × 10−4 mol dm−3, [5a] = 0–4.0 × 10−4 mol dm−3
at 298 K. Inset: Changes in the intensity of absorbance at 400 nm upon
addition of 5b.
Table 1 Association constants for 5 with melamine derivatives in CHCl3
Ka/mol−1 dm3
Receptor
5aa
5bb
1
2
3
4
4.65 0.19 × 104
4.14 0.23 × 103
2.38 0.10 × 104
4.19 0.19 × 104
5.00 0.15 × 104
1.37 0.04 × 104
1.29 0.02 × 105
4.35 0.05 × 104
a Determined by the competitive titration method. [Receptor] = 1.0 ×
10−4 mol dm−3, [5b] = 1.0 × 10−4 mol dm−3, [5a] = 0–3.0 × 10−4 mol dm−3
in CHCl3, at 298 K. b Determined by UV-vis spectroscopy. [5b] = 1.0 ×
10−4 mol dm−3, [Receptor] = 0–3.0 × 10−4 mol dm−3 in CHCl3, at 298 K.
Two melamine moieties bind one barbiturate via six hydrogen
bonds and the other melamine moiety is oriented out of the
cavity forming an intermolecular hydrogen bond to another
barbiturate via three hydrogen bonds. The outer barbiturate
=
dimerized with the adjacent barbiturate via two C O · · · H–N
Fig. 4 Job’s plots for complexation of 5b with 3 (ꢀ) and 4 (ꢁ). Determined
by UV-vis spectroscopy. [5b] + [melamine] = 1.0 × 10−4 mol dm−3 in CHCl3
at 298 K.
˚
hydrogen bonds with the same N · · · O distance of 2.920 A.
The interatomic N · · · O and N · · · N distances corresponding to
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Fig. 6 An ORTEP drawing (30% probability ellipsoids) of the (4·5a2)2 complex grown from slow vapor diffusion of cyclohexane. Hydrogen atoms except
for NHs are omitted for clarity.
N–H · · · O and N–H · · · N bonds of 4 with internal 5a are in the
Dimerization of hosts was negligible since a dilution experiment in
CDCl3 by 1H NMR spectroscopy gave virtually identical spectra
in the experimental range (1.0 × 10−2–6.25 × 10−4 mol dm−3).
These results suggested that the 4·(5a)2 complex is also formed
in the solution state. The association constant (K12) for 4·(5a)2
from 4·5a and 5a was estimated to be 2.4 × 102 dm3 mol−1 by
non-linear curve fitting of changes of chemical shift (K11 = 4.19 ×
104 dm3 mol−1 was used for the calculation).
˚
ranges 2.855–3.132 and 2.847–2.862 A, respectively.
Hamilton et al. reported that the isophthaloyl spacer of
bis(diamidopyridine) was positioned in the same plane as the
pyridines with small deviations due to conjugation of the amide
groups.3d However, in the solid structure of the complex of 4 and
5a, the spacer xylylene group was bent relative to the plane of
the triazine rings. The spacer phenylene ring was positioned out
of the plane of the triazine ring to reduce steric hindrance by
bending aside by about 61◦ and 63◦ with respect to the appended
NH groups. This result is ascribed to more flexible structure of
triazine-m-xylylene units than that of isophthaloyl amide.
The conflict of the results from UV-vis titration and 1H NMR
titration can be explained by the difference of concentrations in
the experiments. In dilute conditions (around 10−4 mol dm−3 for
UV-vis titration), a 1 : 1 complex was predominantly formed and
the formation of the 1 : 2 complex was negligible due to the
relatively smaller K12. However, a more concentrated condition
NMR titration
1
(around 10−2 mol dm−3 for H NMR titration) is sufficient for
To evaluate the formation of the complex in solution in more
the formation of 1 : 2 or higher order complex. Lo¨wik and Lowe
reported that the similar trismelamine derivative forms a 1 : 1
complex with cyanuric acid (Ka = 2.5 × 104 dm3 mol−1) via nine
hydrogen bonds in CDCl3.16b
1
detail, H NMR titration of 5a with 4 was performed in CDCl3.
As shown in Fig. 7, all protons of the alkyl chain in 5a showed an
upfield shift upon the addition of 4. The rate of the equilibrium
for the complexation is faster than the NMR time scale. Binding
isotherms of the titration for 5a with 4 showed a good fit to higher
order complexation such as host : guest = 1 : 2 model rather
than the 1 : 1 model. Although all protons of the alkyl chain
in 5a also showed an upfield shift upon addition of 3, binding
isotherms agreed with a 1 : 1 stoichiometry in CDCl3 as shown in
Fig. 8. Association constants for 3 and 5a were calculated from
non-linear curve fitting to give 2.97 0.55 × 104 dm3 mol−1 and
the value is in good agreement with the value determined by UV-
vis spectroscopy. A Job’s plot determined by 1H NMR showed a
similar tendency, i.e. a maximum was observed at mole fractions of
0.5 and ca. 0.6 for 3 and 4 with 5a, respectively as shown in Fig. 9.
Conclusion
The results presented herein show syntheses of novel and less
explored cyclic bis- and trismelamine derivatives in which m-
xylylene is used as a spacer group and complexation properties of
the macrocycles with barbituric acid derivatives. The barbiturate
5b bearing an anthryl moiety is a useful probe for the determi-
nation of the association constants for complexation. Van’t Hoff
analyses on the complexation of the bismelamine 1 and 3 with
the barbituric acid derivative 5b revealed that the complexation
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Fig. 8 The 1H NMR titration of 5a upon addition of 3 in CDCl3 at 298 K.
[5a] = 1.0 × 10−2 mol dm−3, [3] = 0–2.4 × 10−2 mol dm−3 (from the bottom
to the top). Methyl and methylene (C1 and C2) protons are represented by
closed circles, open triangles, and closed squares, respectively.
Fig. 7 The 1H NMR titration of 5a upon addition of 4 in CDCl3 at
298 K. [5a] = 1.0 × 10−2 mol dm−3, [4] = 0–2.0 × 10−2 mol dm−3 (from the
bottom to the top). The solid and dashed lines indicate calculated binding
isotherms based on host : guest = 1 : 2 and 1 : 1 models, respectively.
Methyl and methylene protons of butyl groups of 5a are represented by
closed squares and circles, respectively.
with thermal regulator ( 0.5 ◦C). 1H NMR spectra were measured
on JEOL JNM a-500 (500 MHz), JEOL AL300 (300 MHz)
and Varian GEMINI 200 (200 MHz) spectrometers. Electron
spray ionization mass spectra (ESI-MS) were recorded on an
Applied Biosystems/MDS-Sciex API-100 spectrometer. Column
chromatography was performed by using Wakogel C-200 (silica
gel, 70–250 lm, Wako Chemical Co. Ltd). Elemental analyses
were performed at the Center of Instrumental Analysis of Gunma
University.
of the cyclic bismelamine 3 with 5b was entropically favored
and enthalpically less favored process than those of the acyclic
bismelamine 1. In addition, we found that cyclic trismelamine, in
which m-xylylene was used as a spacer, formed 2 : 4 complex with
barbituric acids in both solution and the solid state. These cyclic
bis- and trismelamine derivatives can be used as a new class of
receptors for barbiturates and related compounds.
Synthesis of receptors
Experimental
The receptors were prepared according to the routes outlined
in Figs. 1 and 2. Preparation of 2,4-dichloro-6-diethylamino-s-
triazine (6) was carried out according to the literature procedures.9a
5,5-Dibutylbaributuric acid was prepared according to the
literature.24
All reagents used were of analytical grade. Acetonitrile was dried
and distilled over calcium hydride. Tetrahydrofuran was dried over
Na–benzophenone. UV-vis spectra were recorded on Shimadzu
UV-2200A, UV-2500PC and JASCO Ubest-560 spectrometers
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1,12-diaminododecane (2.00 g, 10.0 mmol) in chloroform were
separately added over 2 d. The mixture was stirred for an
additional 6 d, and then cooled and evaporated under reduced
pressure. The residue was extracted with CHCl3 (100 ml ×
3)–H2O. The combined organic layer was washed with brine,
dried over anhydrous sodium sulfate, and evaporated under
reduced pressure. The crude material was purified by column
chromatography on silica gel (5% MeOH–CHCl3 as eluent) to
give the product (3.16 g, 50%) as colorless foam; mp 82–84 ◦C
(Found: C, 64.20; H, 8.85; N, 26.48. C34H56N12 requires C, 64.52;
H, 8.92; N, 26.56%); dH (200 MHz; CDCl3; Me4Si) 1.13 (12H, t,
J 7.0, CH3), 1.20–1.34 (16H, m, CH2), 1.47–1.64 (4H, m, CH2),
3.34 (4H, q, J 5.7, CH2), 3.53 (8H, q, J 7.0, CH2), 4.54 (4H, d, J
5.6, CH2), 4.74 (2H, s, NH), 5.02 (2H, s, NH), 7.21–7.38 (4H, m,
C6H4). m/z (ESI; positive ion mode) 633.5 (M + H+. C34H57N12
requires 633.48).
N-1-(3-Bromopropyl)phthalimide
Fig. 9 Job’s plots for complexation of 5a with 3 (ꢀ) and 4 (ꢁ)
determined by 300 MHz 1H NMR spectroscopy. [5a] + [melamine] =
1.0 × 10−2 mol dm−3 in CDCl3 at 298 K.
A mixture of 1,3-dibromopropane (32.0 g, 158 mmol) and
potassium phthalimide (14.7 g, 79.4 mmol)◦in DMF (100 ml)
was stirred under nitrogen atmosphere at 80 C overnight. After
200 ml of water was added, the mixture was extracted with CHCl3
(100 ml × 3) and the combined organic layer was washed with
water (100 ml × 3), dried over anhydrous sodium sulfate, and
evaporated under reduced pressure. The residue was purified by
column chromatography on silica gel (CHCl3 : hexane = 1 : 1
as eluent) to give the product as a white powder (5.25 g, 25%);
mp 72–73 ◦C; dH (300 MHz; CDCl3; Me4Si) 2.24 (2H, quintet, J
6.8, CH2), 3.39 (2H, t, J 6.8, BrCH2), 3.81 (2H, t, J 6.8, NCH2),
7.69–7.71 (2H, m, Ar), 7.81–7.84 (2H, m, Ar).
1,3-Bis((2-chloro-4-diethylamino-1,3,5-s-triazin-6-
yl)aminomethyl)benzene (7)
A mixture of 6 (5.00 g, 22.6 mmol), m-xylylenediamine (1.55 g,
11.3 mmol), and sodium carbonate (2.40 g, 22.6 mmol) in CH2Cl2
(50 ml) and water (50 ml) was stirred at 40 ◦C for 10 h. The
resulting mixture was extracted with CH2Cl2 (30 ml × 3). The
combined organic layer was dried over anhydrous sodium sulfate
and evaporated under reduced pressure. The residue was purified
by recrystallization from acetone to give the product (4.82 g, 84%)
as a colorless powder; mp 153–154 ◦C (Found: C, 52.66; H, 6.05;
N, 28.08. C22H30Cl2N10 requires C, 52.28; H, 5.98; N, 27.71%); dH
(200 MHz; CDCl3; Me4Si) 1.02–1.03 (12H, m, CH3), 3.61–3.44
(8H, m, CH2), 4.59 (4H, d, J 6.0, CH2), 6.16 (2H, br s, NH),
7.18–7.27 (4H, m, C6H4).
2,2-Di(4-(3-phthalimido-1-propyloxy)phenyl)-propane
A
mixture of N-1-(3-bromopropyl)phthalimide (3.13 g,
11.7 mmol), bisphenol-A (1.33 g, 5.83 mmol) and potassium
carbonate (3.23 g, 23.4 mmol) in DMF (40 ml) was stirred
under nitrogen atmosphere at 80 ◦C for 1 d. The mixture was
extracted with CHCl3 (200 ml)–2 N HCl and the organic layer was
washed with water (100 ml × 3). The organic layer was dried over
anhydrous sodium sulfate and evaporated under reduced pressure.
The crude material was purified by column chromatography
(CHCl3 as an eluent) to give 1.89 g (54%) of the product as viscous
oil; dH (300 MHz; CDCl3; Me4Si) 1.60 (6H, s, CH3), 2.16 (4H,
quintet, J 6.6, CH2), 3.90 (4H, t, J 7.0, CH2), 4.00 (4H, t, J 7.0,
CH2), 6.70 (4H, d, J 8.6, Ar), 7.07 (4H, d, J 8.6, Ar), 7.69–7.73
(4H, m, Ar), 7.82–7.86 (4H, m, Ar).
1,3-Bis((2ꢀ-butylamino-4ꢀ-diethylamino-1ꢀ,3ꢀ,5ꢀ-s-triazin-6ꢀ-
yl)aminomethyl)benzene (receptor 1)
A mixture of 7 (2.0 g, 3.45 mmol), butylamine (0.56 g, 7.59 mmol)
and potassium carbonate (0.96 g, 6.95 mmol) in 1,4-dioxane
(100 ml) was refluxed overnight under nitrogen atmosphere. After
evaporation under reduced pressure, the residue was extracted
with CHCl3 (30 ml × 3) and water. The organic layer was dried
over anhydrous sodium sulfate and evaporated under reduced
pressure. The residue was purified by column chromatography
(5% MeOH–CHCl3 as eluent) to give the product as a colorless
powder (2.0 g, 88%); mp 91–93 ◦C (Found: C, 60.75; H, 8.56; N,
28.44. C30H50N12·H2O requires C, 60.37; H, 8.78; N, 28.16%); dH
(300 MHz; CDCl3; Me4Si) 0.91 (6H, t, J 7.2, CH3), 1.11 (12H, t,
J 6.9, CH3), 1.36 (4H, sextet, J 7.20, CH2), 1.52 (4H, quintet, J
7.2, CH2), 3.33 (4H, q, J 7.2, CH2), 3.52 (8H, t, J 6.9, CH2), 4.52
(4H, d, J 5.9, C6H4CH2), 4.76 (2H, br s, NH), 5.18 (2H, br s, NH),
7.20–7.26 (4H, m, C6H4); m/z (ESI; positive ion mode) 579.4 (M +
H+. C30H51N12 requires 579.44).
2,2-Di(4-(3-amino-1-propyloxy)phenyl)propane
Into a solution of 2,2-di(4-(3-phthalimino-1-propyloxy)phenyl)-
propane (1.89 g, 3.14 mmol) in EtOH (60 ml) was added
hydrazine monohydrate (2 ml) and the mixture was refluxed under
nitrogen atmosphere overnight. After evaporation, the residue
was extracted with CHCl3 (100 ml × 3)–diluted aqueous NaOH
(100 ml). The combined organic layer was dried over anhydrous
sodium sulfate and evaporated under reduced pressure to give
0.92 g (85%) of the product as pale yellow oil; dH (300 MHz;
CDCl3; Me4Si) 1.52 (4H, br s, NH2), 1.63 (6H, s, CH3), 1.89 (4H,
quintet, J 6.4, CH2), 2.90 (4H, t, J 6.4, CH2), 4.02 (4H, t, J 6.4,
CH2), 6.79 (4H, d, J 8.8, C6H4), 7.12 (4H, d, J 8.8, C6H4).
Receptor 2
Into a refluxed suspension of potassium carbonate (2.76 g,
20 mmol) in 1,4-dioxane (300 ml), 7 (5.05 g, 10.0 mmol) and
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Receptor 3
(100 ml × 3)–H2O (50 ml) and the combined organic layer was
dried over anhydrous sodium sulfate. The mixture was evaporated
under reduced pressure, the residue was chromatographed on silica
gel (CHCl3 : AcOEt = 20 : 3 followed by AcOEt) to give the
product as a viscous foam (2.56 g, 75%); dH (200 MHz; CDCl3;
Me4Si) 0.93–1.21 (18H, m, CH3), 3.38–3.61 (12H, m, CH2), 4.48–
4.62 (8H, m, CH2), 5.05–5.29 (2H, br s, NH), 6.60–6.77 (2H, br s,
NH), 7.11–7.29 (8H, m, C6H4).
Into a refluxing suspension of potassium carbonate (1.93 g,
14.0 mmol) in 1,4-dioxane (200 ml), 7 (3.54 g, 7.0 mmol) and
2,2-di(4-(3-amino-1-propyloxy)phenyl)propane (2.40 g, 7.0 mmol)
in 1,4-dioxane were separately added over 6 d. The mixture
was stirred for an additional 2 d, then cooled and evaporated
under reduced pressure. The residue was extracted with CHCl3
(100 ml × 3)–H2O. The combined organic layer was washed with
brine, dried over anhydrous sodium sulfate, and evaporated under
reduced pressure. The crude material was purified by column
chromatography on silica gel (5% MeOH–CHCl3 followed by 10%
MeOH–CHCl3 as eluent) to give the product (2.42 g, 43%) as a
white foam; mp 106–108 ◦C (Found: C, 64.40; H, 7.40; N, 20.57.
C43H58N12O2·1.5H2O requires C, 64.39; H, 7.67; N, 20.96%); dH
(200 MHz; CDCl3; Me4Si) 1.11 (12H, t, J 7.0, CH3), 1.66 (6H, s,
C(CH3)2), 2.01 (4H, q, J 5.7, CH2), 3.57–3.45 (12H, m, CH2), 4.01
(4H, d, J 5.8, CH2), 4.50 (4H, d, J 5.7, CH2), 5.1 (4H, br s, NH),
6.78 (4H, d, J 8.8, C6H4), 7.08 (4H, d, J, 8.7, C6H4), 7.20 (4H, s,
C6H4); m/z (ESI; positive ion mode) 775.5 (M + H+. C43H59N12O2
requires 775.49).
Receptor 4
Into a refluxed suspension of potassium carbonate (0.21 g,
1.52 mmol) in 1,4-dioxane, 10 (0.79 g, 1.00 mmol) and m-
xylylenediamine (0.13 ml, 0.98 mmol) in 1,4-dioxane (80 ml)
were added dropwise separately over 1 d and the mixture was
refluxed 2 d. After evaporation under reduced pressure, the residue
was extracted with CHCl3 (50 ml × 4)–H2O (50 ml) and the
combined organic layer was dried over potassium carbonate. After
the mixture was evaporated under reduced pressure, the residue
was chromatographed on silica gel (CHCl3 : AcOEt = 2 : 1 followed
by 1 : 1) and recrystallized from acetonitrile to give the product as
white solid (142 g, 17%); mp 130–133 ◦C (Found C, 62.26; H, 7.08;
N, 28.61. C45H60N18·H2O requires C, 62.05; H, 7.17; N, 28.94%);
dH (300 MHz; CDCl3; Me4Si) 1.09 (18H, t, J 7.2, CH3), 3.49 (12H,
q, J 7.2, CH2), 4.51 (12H, d, J 5.9, NHCH2), 5.11 (6H, br s, NH),
7.09–7.38 (12H, m, C6H4); m/z (ESI; positive ion mode) 853.5
(M + H+. C45H61N18 requires 853.53).
4,6-Bis(3-tert-butylcarbonylaminomethylphenylmethylamino)-2-
diethylamino-1,3,5-s-triazine (8)
A mixture of 6 (1.64 g, 7.4 mmol), 3-tert-butoxycarbonyl-
aminomethylbenzylamine (3.50 g, 14.8 mmol), and potassium
carbonate (2.05 g, 14.8 mmol) in 1,4-dioxane (100 ml) was refluxed
for 2 d. After addition of water (100 ml), the mixture was
evaporated under reduced pressure. The residue was extracted with
CHCl3 (100 ml × 3), and the combined organic layer was dried
over anhydrous sodium sulfate. After evaporation, the residue was
purified by column chromatography on silica gel (10% MeOH–
CHCl3 as eluent) to give the product as viscous foam (4.50 g,
98%); dH (200 MHz; CDCl3; Me4Si) 1.02–1.21 (6H, m, CH3), 1.46
(18H, s, CH3 of t-Bu), 3.48–3.61 (4H, m, CH2), 4.30 (4H, d, J 5.8,
CH2), 4.57 (4H, d, J 5.9, CH2), 4.83 (2H, br s, NH), 5.56 (2H, br s,
NH), 7.22–7.27 (8H, m, C6H4).
Diethyl 2-(9-anthrylmethyl)-2-butylmalonate
Into a suspension of sodium hydride (140 mg, 5.83 mmol)
in 20 ml of THF, diethyl butylmalonate (1.38 g, 6.38 mmol)
in THF was dropwise at rt under nitrogen atmosphere. After
stirring for 30 min, a THF solution of 9-chloromethylanthracene
(1.20 g, 5.30 mmol) was added dropwise and the resulting mixture
was refluxed under nitrogen atmosphere overnight. The reaction
mixture was quenched by addition of water, and the mixture
was evaporated under reduced pressure. After the residue was
extracted with CHCl3 (100 ml × 3)–3 N HCl, the combined organic
layer was washed with brine, and dried over anhydrous sodium
sulfate. Chloroform was evaporated under reduced pressure and
the residue was chromatographed on silica gel (hexane : CHCl3 =
2 : 1 as eluent) to give diethyl 2-(9-anthrylmethyl)-2-butylmalonate
as a pale yellow oil (1.99 g, 92%); dH (200 MHz; CDCl3; Me4Si)
0.86 (3H, t, J 7.0, CH3 of butyl), 0.95 (6H, t, J 7.0, CH3 of ethyl),
1.23–1.56 (4H, m, CH2), 1.86 (2H, t, J 9.0, CH2Pr), 3.90–3.73 (4H,
m, CH2 of ethyl), 4.39 (2H, s, CH2Anth), 7.50–7.20 (4H, m, 2-, 3-,
6-, and 7-H of anthryl), 7.95–7.99 (2H, m, 4- and 5-H of anthryl),
8.30–8.36 (3H, m, 1-, 8-, and 10-H of anthryl).
4,6-Bis(3-aminomethylphenylmethylamino)-2-diethylamino-1,3,5-
s-triazine (9)
A mixture of 8 (4.60 g, 7.5 mmol) in trifluoroacetic acid (50 ml)–
H2O (20 ml) was stirred at rt overnight. After evaporation under
reduced pressure, the residue was extracted with CHCl3 (100 ml ×
3)–H2O and the combined organic layer was dried over anhydrous
sodium sulfate. Evaporation under reduced pressure to give the
product (2.7 g, 85%) as a yellow oil; dH (200 MHz; CDCl3; Me4Si)
1.15 (6H, t, J 7.0, CH3), 1.6 (4H, br s, NH2), 3.57 (4H, q, J 7.0,
CH2), 3.88 (4H, s, CH2), 4.62 (4H, d, J 5.9, CH2), 5.21 (2H, br s,
NH), 7.28 (8H, m, C6H4).
5-(9-Anthrylmethyl)-5-butyl-barbituric acid (5a)
4,6-Bis((2ꢀ-chloro-4ꢀ-diethylamino-1ꢀ,3ꢀ,5ꢀ-s-triazin-6ꢀ-
yl)aminomethylphenylmethylamino)-2-diethylamino-1,3,5-s-
triazine (10)
Into a solution of urea (0.42 g, 7.01 mmol) in ethanol (10 ml),
sodium (0.25 g, 10.7 mmol) was added and the mixture was stirred
for 30 min under nitrogen atmosphere at rt, followed by diethyl 2-
(9-anthrylmethyl)-2-butylmalonate (0.45 g, 1.10 mmol) in ethanol
dropwise over 30 min. After the mixture was refluxed for 12 h, 3
N HCl was added and the mixture was evaporated under reduced
pressure. The residue was recrystallized from toluene to give 5a
A mixture of 6 (1.92 g, 8.7 mmol), 9 (1.83 g, 4.35 mmol),
and potassium carbonate (1.4 g, 10.1 mmol) in 1,4-dioxane
(100 ml)–H2O (50 ml) was refluxed overnight. After evaporation
under reduced pressure, the residue was extracted with CHCl3
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◦
as pale yellow needles (0.04 g, 10%); mp 267–268 C (Found: C,
1990, 1232; (d) S.-K. Chang, D. V. Engen, E. Fan and A. D. Hamilton,
J. Am. Chem. Soc., 1991, 113, 7640; (e) R. E. Mele´ndez, A. J. Carr,
B. R. Linton and A. D. Hamilton, in Controlling hydrogen bonding:
From molecular recognition to organogelation, ed. M. Fujita, Springer
Verlag, Berlin, 2000.
4 S. R. Collinson, T. Gelbrich, M. B. Hursthouse and J. H. R. Tucker,
Chem. Commun., 2001, 555.
73.96; H, 5.92; N, 7.24%. C23H22N2O3 requires C, 73.78; H, 5.92;
N, 7.48%); dH (200 MHz; CDCl3; Me4Si) 0.92 (3H, t, J 7.0, CH3 of
butyl), 1.10–1.48 (4H, m, CH2), 2.41–2.50 (2H, m, CH2Pr), 4.93
(2H, s, CH2Anth), 7.42–7.49 (4H, m, 2-, 3-, 6-, and 7-H of anthryl),
7.94–7.99 (2H, m, 4- and 5-H of anthryl), 8.19–8.24 (2H, m, 1- and
8-H of anthryl), 8.39 (1H, s, 10-H of anthryl).
5 B. S. Rasmussen, U. Elezcano and T. Skrydstrup, J. Chem. Soc., Perkin
Trans. 1, 2002, 1723.
6 (a) J. Larsen, B. S. Rasmussen, R. G. Hazell and T. Skrydstrup, Chem.
Commun., 2004, 202; (b) M. H. Al-Sayah, R. McDonald and N. R.
Branda, Eur. J. Org. Chem., 2004, 173.
Titration method
7 I. Aoki, Y. Kawahara, T. Sakai, T. Harada and S. Shinkai, Bull. Chem.
Soc. Jpn., 1993, 66, 927.
8 (a) V. Berl, M. Schmutz, M. J. Krische, R. G. Khoury and J.-M. Lehn,
Chem.–Eur. J., 2002, 8, 1227; (b) E. Kolomiets and J.-M. Lehn, Chem.
Commun., 2005, 1519.
9 (a) J. T. Thurston, J. R. Dudley, D. W. Kaiser, I. Hechenbleikner,
F. C. Schaefer and D. Holm-Hansen, J. Am. Chem. Soc., 1951, 73,
2981; (b) D. W. Kaiser, J. T. Thurston, J. R. Dudley, F. C. Schaefer, I.
Hechenbleikner and D. Holm-Hansen, J. Am. Chem. Soc., 1951, 73,
2984; (c) P. Gamez and J. Reedijk, Eur. J. Inorg. Chem., 2006, 29; (d) G.
Blotny, Tetrahedron, 2006, 62, 9507.
Into a solution of 5a (1.0 × 10−4 mol dm−3) in CHCl3, aliquots of
a stock solution (0.01 mol dm−3) of the receptor in CHCl3 were
added and UV-vis spectra were recorded. Association constants
were determined by the non-linear least-squares method following
absorbance at 400 nm. All measurements were carried out in at
least duplicate using independent samples.
Single-crystal X-ray crystallographic study
10 (a) J. A. Zerkowki and G. M. Whitesides, J. Am. Chem. Soc., 1994, 116,
4798; (b) J. A. Zerkowski, J. P. Mathias and G. M. Whitesides, J. Am.
Chem. Soc., 1994, 116, 4305; (c) J. P. Mathias, E. E. Simanek, J. A.
Zerkowski, C. T. Seto and G. M. Whitesides, J. Am. Chem. Soc., 1994,
116, 4316; (d) J. P. Mathias, E. E. Simanek and G. M. Whitesides, J. Am.
Chem. Soc., 1994, 116, 4326; (e) G. M. Whitesides, E. E. Simanek, J. P.
Mathias, C. T. Seto, D. N. Chin, M. Mammen and D. M. Gordon, Acc.
Chem. Res., 1995, 28, 37; (f) D. M. Bassani, X. Sallenave, V. Darcos
and J.-P. Desvergne, Chem. Commun., 2001, 1446; (g) M. J. Krische
and J.-M. Lehn, in The utilization of persistent H-bonding motifs in the
self-assembly of supramolecular architectures, ed. M. Fujita, Springer
Verlag, Berlin, 2000.
Single crystals of (4)2·(5a)4 were obtained by slow vapor diffusion
of cyclohexane into a chloroform solution of a 1 : 1 mixture
of 4 and 5a. A colorless prismatic crystal having approximate
dimensions of 0.20 × 0.20 × 0.25 mm was mounted in a glass
capillary. Intensity data were collected on a Rigaku RAXIS-IV
imaging plate diffractometer with graphite monochromated Mo-
˚
Ka (k = 0.71070 A) radiation at 113 K. Data were collected and
processed using the CrystalClear program (Rigaku). The structure
was solved by direct methods using the SIR97 program25 and
expanded using Fourier techniques using DIRDIF94 program.26
The structure was refined using the program SHELXL-97.27 All
hydrogen atoms were located in calculated positions. Crystal struc-
tural data for (4)2·(5a)4 [(4)·(5a)2]: C69H100N22O6, M = 1333.69,
11 A. G. Bielejewska, C. E. Marjo, L. J. Prins, P. Timmerman, F. de Jong
and D. N. Reinhoudt, J. Am. Chem. Soc., 2001, 123, 7518 and references
sited therein; for a review: P. Timmerman and L. J. Prins, Eur. J. Org.
Chem., 2001, 3191 and references cited therein.
12 (a) A. Takaki, K. Utsumi, T. Kajiki, T. Kuroi, T. Nabeshima and Y.
Yano, Chem. Lett., 1997, 75; (b) K. Utsumi, Y. Nishihara, K. Hoshino,
S. Kondo, T. Nabeshima and Y. Yano, Chem. Lett., 1997, 1081; (c) T.
Kajiki, H. Moriya, K. Hoshino, S. Kondo and Y. Yano, Chem. Lett.,
1999, 397; (d) T. Kajiki, H. Moriya, K. Hoshino, T. Kuroi, S. Kondo, T.
Nabeshima and Y. Yano, J. Org. Chem., 1999, 64, 9679; (e) H. Moriya,
T. Kajiki, S. Watanabe, S. Kondo and Y. Yano, Bull. Chem. Soc. Jpn.,
2000, 73, 2539; (f) S. Kondo, K. Utsumi and Y. Yano, Internet J. Sci.:
Biol. Chem., 1997, http://www.netsci-journal.com/97v1/97012/.
13 (a) S. Yagai, M. Higashi, T. Karatsu and A. Kitamura, Chem. Mater.,
2004, 16, 3582; (b) S. Yagai, T. Karatsu and A. Kitamura, Langmuir,
2005, 21, 11048.
¯
triclinic, space group P1, a = 14.995(2), b = 15.949(2), c =
◦
˚
17.6433(4) A, a = 69.348(10), b = 71.33(1), c = 88.86(1) , V =
3
−3
−1
˚
3692.2(8) A , Z = 2, Dc = 1.200 g cm , T = 233 K, l = 0.80 cm ,
R1 = 0.0836 for 5059 F0 > 4rF0 and 0.1391 for all 15745 reflections,
wR2 = 0.2366, GOF = 0.831.†
Acknowledgements
14 T. Kawasaki, M. Tokuhiro, N. Kimizuka and T. Kunitake, J. Am. Chem.
Soc., 2001, 123, 6792.
15 F. Wu¨rthner, S. Yao, B. Heise and C. Tschierske, Chem. Commun., 2001,
2260.
16 (a) P. L. Anelli, L. Lunazzi, F. Montanari and S. Quici, J. Org. Chem.,
1984, 49, 4197; (b) D. W. P. M. Lo¨wik and C. R. Lowe, Eur. J. Org.
Chem., 2001, 2825; (c) D. W. P. M. Lo¨wik and C. R. Lowe, Tetrahedron
Lett., 2001, 41, 1837.
The authors are grateful to Dr Ryoji Tanaka of Gunma University
for his helpful discussion for X-ray crystallographic analysis. This
work was supported in part by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Culture, Sports, Science
and Technology, Japan.
17 (a) C. Picard, L. Cazaux, T. Pigot and P. Tisne`s, J. Inclusion Phenom.
Mol. Recognit. Chem., 1994, 18, 45; (b) B. S. Rasmussen, U. Elezcano
and T. Skrydstrup, J. Chem. Soc., Perkin Trans. 1, 2002, 1723; (c) M. H.
Al-Sayah, R. McDonald and N. R. Branda, Eur. J. Org. Chem., 2004,
173; (d) Y. Molard, D. M. Bassani, J.-P. Desvergne, N. Moran and
J. H. R. Tucker, J. Org. Chem., 2006, 71, 8123.
18 (a) A. G. Bielejewska, C. E. Marjo, L. J. Prins, P. Timmerman, F. D.
Jong and D. N. Reinhoudt, J. Am. Chem. Soc., 2001, 123, 7518; (b) P. V.
Mason, N. R. Champness, S. R. Collinson, M. G. Fisher and G.
Goretzki, Eur. J. Org. Chem., 2006, 1444.
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