Tiara[ n]uril: A Glycoluril-Based Macrocyclic Host with Cationic Walls

Article abstract of DOI:10.1021/acs.joc.8b02913

The synthesis of new cationic macrocyclic host molecules is described. These macrocycles are comprised of glycoluril oligomers linked to two pyrazolium groups, which form part of a cationic wall facing into their cavities. A number of derivatives have been prepared with an objective to increasing the cavity size, and each new product has been fully characterized. Preliminary investigations of pK_as of Me₁₀Tu[3]²⁺ and an interaction of L-glutamine indicate a potential for binding anionic molecules that also carry H-bond donor groups.

Full text of DOI:10.1021/acs.joc.8b02913

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Article
Tiara[n]uril: a glycoluril-based macrocyclic host with cationic walls
Pradeep Kumar C, Rajni Dhiman, Clifford E. Woodward,
Hasti Iranmanesh, Jonathon E Beves, and Anthony I. Day
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b02913 • Publication Date (Web): 28 Feb 2019
Downloaded from http://pubs.acs.org on February 28, 2019
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Tiara[n]uril: a glycoluril-based macrocyclic host with cationic walls
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Pradeep Kumar C.,a Rajni Dhiman,a Clifford E. Woodward,a Hasti Iranmanesh,b Jonathon
E. Beves,b and Anthony I. Day*a
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a. Chemistry, School of PEMS, University of New South Wales Canberra, Australian
Defence Force Academy, Canberra, ACT 2600, Australia. Email: a.day@adfa.edu.au
b. School of Chemistry, UNSW Sydney, Sydney, NSW, Australia.
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Abstract
The synthesis of new cationic macrocyclic host molecules is described. These
macrocycles are comprised of glycoluril oligomers linked to two pyrazolium groups,
which form part of a cationic wall facing into their cavities. A number of derivatives
have been prepared with an objective to increasing the cavity size and each new
product has been fully characterized. Preliminary investigations of pKas of
Me10Tu[3]2+ and an interaction of L-glutamine, indicate a potential for binding
anionic molecules that also carry H-bond donor groups.
Introduction
The most common glycoluril based macrocyclic host is cucurbit[n]uril (Q[n]), which
has found utility in numerous chemical applications.1-18 Various derivatives of Q[n]
have also been reported such as inverted forms or a catalogue of methylene linked
mismatches leading to interesting new hosts but none of these examples carry a
positive charge within their cavities.1,2
Another macrocyclic host which is essentially an inverted cyclic oligomer of
glycolurils known as bambus[n]uril (Bu[n]) has the distinction of having an
electropositive cavity capable of effective anion binding in water.19 Anion binding in
Q[n] has mostly been confined to examples where a cation (H+ or metal ion) resides at
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their portals and an anion is bound within the cavity.20 Here in, we report the
synthesis of a new water-soluble cyclic oligomer with a cavity, which has cations
built into its walls and hence has the potential to bind anions and/or electronegative
groups within its cavity through screening from the solvent (water).
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Results and Discussion
While investigating the use of pyrazole as a formaldehyde scavenger under acidic
conditions as an approach to removing methylene groups from glycoluril diethers, we
discovered the facile condensation reaction between pyrazole and dimethylglycoluril
diether 1 that affords the pyrazolium adducts 2 and 3 (Scheme 1). This reaction was
very clean consuming all starting diether 1 to give products 2 and 3 in a ratio of
~1.8:1 respectively.
Scheme 1. The condensation reaction between diether 1 and pyrazole.
As we have a particular interest in macrocyclic hosts this result then led us to
investigate the potential to synthesize a macrocycle where the two pyrazole
rings were linked, eg dipyrazole methane 4.21 Under the same acidic conditions
as above, the diether 1 condenses to furnish the macrocycle, Me6Tu[3]2+,
containing a single dipyrazolium moiety (Scheme 2). Purification on cation
exchange resin gave the major product as the dipyrazolium macrocycle,
Me6Tu[3]Cl2 in 60% yield.
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R
R
O
R
H+
N
R
R
6
7
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N
HN
+
NH
N
1
N
N
N
N
N
N
R
Me
N
Me
R
R
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O
3
Me6Tu[3]2+
Me10Tu[3]2+
R = H
R = Me
4 R = H
5 R = Me
Scheme 2. The acid catalyzed condensation reaction between diether 1 and dipyrazole
methanes 4 or 5 forms the macrocycles Me6Tu[3]2+ and Me10Tu[3]2+ respectively.
This molecule contains a cavity, where one side of the molecular cavity is a
concave wall in an arc composed of three glycoluril moieties and the remaining
wall of pyrazolium ions provides two adjacent planar facets completing the
cavity. While this molecular structure appears to bear some resemblance to an
analogue of cucurbituril22 its chemical properties do not, and as a consequence
we have named this molecule tiara[n]uril (Tu[n]). The molecular shape loosely
resembles a tiara, with the carbonyl O of the wall of glycolurils jewelling the
front and the dipyrazolium wall forming the band at the back (Figure 1). As will
become clear in the remaining discussion the n refers to the number of repeating
glycolurils.
Top view
Side view
Figure 1. The hydrogen atoms and the counter ions have been omitted to clearly show the
skeleton of the molecular model of Me6Tu[3] emphasizing the resemblance to a tiara.
We soon found that while this molecule was stable to acidic and near neutral
conditions it was not stable to basic conditions including weakly basic (aqueous
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NaOAc). This was evident by the occurrence of multiple resonances in the 1H
NMR spectra of basic solutions aged by 24 h. Base sensitivity was overcome by
replacing dipyrazole methane 4 in the reaction process, with the methyl
substituted dipyrazole 5.21 The efficiency of macrocyclization was unchanged
affording Me10Tu[3]2+ (Scheme 2, R = Me). Optimal yields of 65% were achieved
by a reaction process with a two-portion addition of the diether 1, which
minimized the formation of decamethylcucurbit[5]uril,23 a by-product in this
reaction.
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Figure 2. The 1H NMR spectrum of Me10Tu[3]Cl2 in D2O with assignment of the
significant resonances.
The symmetry of Me10Tu[3]2+ was evident from the 1H NMR spectrum with 3 distinct
sets of proton resonances characteristic for the macrocycle. The magnetically
nonequivalent methylenes at the center of the glycoluril oligomer moiety (g-CH2) and
those between the pyrazolium groups and the ends of the glycoluril oligomer moiety
(g-CH2-pz) show clearly define doublets at  6.25, 5.78, 5.56, 4.44 ppm, with integral
ratios 4:4:4:4 (Figure 2). The two upfield doublets (g-CH2) show similar chemical
shifts to methylene proton resonances for cucurbit[n]uril24 consistent with a
macrocycle and two adjacent glycoluril moieties. The remaining protons of
Me10Tu[3]2+, all appear as singlets at  3.75, 2.69, 1.94, 1.85 and 1.77 ppm
(respectively CH2 at a; four chemically identical methyl groups on the pyrazolium
moieties; three singlet resonances for three pairs of methyl groups on the glycoluril
moieties). ESMS also gave a double charged ion at m/z 406.3 consistent with this
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dicationic structure, further substantiated through elemental analysis for
C33H40N16O6Cl2.11H2O. Additional support for this structure came from a single
crystal X-ray diffraction of the salt Me10Tu[3](PF6)2, crystalized from MeOH/H2O.25
These crystals showed the Me10Tu[3]2+ molecule in two different orientations at ~90°
to each other and one has a molecule of MeOH at its cavity center lying parallel to the
equatorial plane and aligned with the longest cavity dimension (~ 5.9 Å van der
Waals radii included, Supporting Information Figure S18-21). The other Me10Tu[3]2+
only has an H2O at each of its portals. The MeOH at the cavity center provides an
indication of the molecular occupation capacity for Me10Tu[3]2+. While an anion may
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-
be expected to occupy the cavity, the PF6 ion is too large (5.10 Å) to pass through the
portal opening (dia. ~ 2.1 Å). Interestingly the MeOH orientation in either occupancy
states within the cavity, finds the electronegative O (O0BA) in close proximity to the
pyrazolium ions (~ 3 Å) indicating a dipole-ion interaction. The portals of the MeOH
occupied cavities are each capped by H2O molecules, which are H-bonded to the
C=Os of the portals. The H atom of MeOH (H0BA) is H-bonded to the O atom of the
water cap (O0AA) and not to the portal C=O .
The absence of Tu[n] homologues larger than n = 3 was intriguing and as a cursory
study this aspect to Tu synthesis was explored further with two approaches. The first
was to modify the dipyrazole by inserting a spacer moiety between the pyrazoles such
as dipyrazoles 6, 7 and 8 (Scheme 3).26,27 The second was to use an alternatively
substituted glycoluril such as cyclopentanoglycoluril 9 (Scheme 4), which is known to
have the propensity to favour higher homologues in the synthesis of
cyclopentanocucurbit[n]uril.28
O
O
Me
N
Me
Me
R
Me
NH
N
N
N
N
Me
N
N
N
Me
Me
N
N
Me
Me
N
H
Me
H+
m,p
1
+
2
6 R = CH2 meta
or
7 R = CH2 para
p-XyMe8Tu[2]
m-XyMe8Tu[2]
8 R = Phenyl para
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Scheme 3. The acid catalyzed condensation reaction between diether 1 and dipyrazole xylyl
derivatives 6 or 7 to form the macrocycles p-XyMe8Tu[2]2+ and m-XyMe8Tu[2]2+
respectively. Extended dipyrazolylbiphenyl 8 gave no macrocyclic products.
7
8
9
It was found that the meta-xylylpyrazole 6 afforded a new cationic macrocycle
m-XyMe8Tu[2] and increasing the distance between pyrazolyl ends with the para
derivative 7 (~ 5.4 to 8.2 Å; Figure S13) gave p-XyMe8Tu[2] where both were
linked by only two glycoluril moieties (Scheme 3). Despite of the reduction in the
number of glycoluril moieties and based upon molecular models the cavity size
has not changed. However, the shape of the cavity was slightly modified
(Supporting Information Figure S17). It is not clear why both the m- and p-
xylyldipyrazole derivatives 6 and 7 form Tu[2]s. It was anticipated that the
significantly greater distance between the pyrazole ends of 7 would facilitate the
formation of Tu[n > 2]2+. In contrast, the dipyrazolylbiphenyl 827 with its
pyrazole ends further apart gave only intractable polymeric material, evident as
broad resonances by 1H NMR.
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O
O
Me
N
Me
Me
N
H+
N
N
N
N
N
N
N
N
N
N
O
5
+
O
Me
O
O
3
9
Me4CyP3Tu[3]
Scheme 4. The acid catalyzed condensation reaction between diether 9 and dipyrazole 5 to
form the macrocycle Me4CyP3TU[3]2+
The second approach toward higher homologues involved the use of
cyclopentanoglycoluril diether 928 and its condensation with dipyrazole 5. This
afforded Me4CyP3Tu[3] but again only three glycoluril moieties were introduced
(Scheme 4). While the cavity size remains the same, this provided another example of
a Tu[3] except with alternative substitution on the glycoluril moieties.
The solubility of Me10Tu[3]Cl2 in pure water is relatively high at 73 g/L and it was of
interest to determine if the positively charged pyrazolium walls of the cavity in
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combination with the arc of C=O’s had any binding potential. It was anticipated that
this space could facilitate a function as an anion or an electronegative group
receptor,29 supported by the H-bonding acceptor potential of the arc of C=O’s. Hence
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anions such as HSO4 and amino acids were considered. It was anticipated that
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buffering effects should occur if
a
binding association was present.
Me10Tu[3](HSO4)2 was readily prepared from Me10Tu[3]Cl2 dissolved in
concentrated H2SO4 followed by precipitation from dry Et2O and recrystallization. A
titration of aliquots of hydroxide revealed a buffer region consistent with a pKa ~ 3 for
-
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HSO4 with no distinction between the two mole equiv. of the anion (pKa of HSO4
alone = 1.99).30 Modeling31 indicates that at least one HSO4 can be accommodated
within the cavity of Me10Tu[3]2+, however, it can not be concluded that this pKa effect
is specifically due to cavity encapsulation. The recrystallized chloride salt
Me10Tu[3]Cl2 was determined to have a pKa of 3.4, indicating the first of two host
dependent pKas. In addition, Me10Tu[3]2+ irrespective of the anion has a second pKa2
of 11.1, which relates to the acidity of the methyl groups on the pyrazolium moieties
(pKa titration curves, Figure S9-10). The acidity of these methyl groups is further
supported by deuterium exchange, where the four methyl groups become methyl-d3
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within 7 h (DO- /D2O 0.54 M, Figure 3). A H NMR spectrum further substantiates
2
the exchange, with the CD3 resonances occurring slightly isotope shifted to 2.66 ppm
(Supporting Information Figure S8).
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Figure 3. H NMR time course of Me10Tu[3]Cl2 (20mM) in D2O after the addition of
NaOD/D2O 0.54 M. The mark (*) indicates the pyrazole methyl resonance, which decreases
as the protons are exchanged with deuterium.
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As a preliminary exploration of association of an organic molecule through ion-ion
and H-bond interaction, an aqueous buffered solution of Me10Tu[3]2+ (pH 6.6) was
added to L-glutamine in the same buffer. The sensitivity of circular dichroism (CD)
and a potential for induced chirality through association was expected.32 CD spectra
showed a significant maxima red shifted (4 nm) to 210 nm and a positive increase in
molar ellipticity ([] = 1.2 and 2.9) following the addition of 2 and 2.25 mole equiv.
of Me10Tu[3]2+ respectively. This was an interesting result though we remain
cognizant of the other competing ions of Cl- from Me10Tu[3]Cl2 and the phosphate in
the buffer. A binding constant was then determined for the association between L-
glutamine and Me10Tu[3]2+ through competitive displacement of the fluorescent
anionic dye sodium 6-(p-toluidino)-2-naphthalenesulfonate (TNS). The association
constant for L-glutamine@ Me10Tu[3]2+ was found to be ~ 2.2 x102 M-1 assuming a
binding ratio of 1:1 (Supporting Information).
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1H NMR spectra of Me10Tu[3]2+ in buffered D2O (pD 6.6) with the addition of L-
glutamine showed no significant change in proton resonances of either the host or the
guest. Given that the binding affinity was in the order of 102 M-1 and the anticipated
that association would be at the portal, a resonance shift was not expected. If cavity
-
encapsulation was to occur it would most likely be the –CO2 , and H-bonding from
+
the –NH3 to the carbonyls. Under this circumstance the resonance of protons exterior
and near the portals would result in very small or insignificant chemical shifts
consistent with our finding.
Conclusion
We have demonstrated a relatively facile synthesis of a new family of glycoluril-
based macrocycles that have incorporated into their walls pyrazolium moieties. Their
structures create cationic cavities furnished with potential H-bond acceptors as C=O
arcs, both at the top and bottom of their portals. A measurable interaction between
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Me10Tu[3]2+ and HSO4 or L-glutamine has been shown through an increase in the
pKa for the first, and changes in the CD spectra for the amino acid. A greater number
of examples of H-bond donor anion associations with novel tiarauril macrocycles is
required to establish their potential but the indicators mentioned above and the MeOH
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bound in the cavity in the solid state, suggest that further exploration would be
fruitful.
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We have demonstrated that substitution variations can be included either on the
glycoluril moiety or between the pyrazolium groups, which conceivably indicates
chemical opportunities yet to be realized. The attainment of larger cavities with
various substitutions, warrants further investigation and will be the subject of our
future work.
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Experimental Section
Instrumentation
NMR spectra were recorded at 400 and 100 MHz respectively for the nuclei 1H and
13C. Chemical shifts for each nuclei were respectively reported with the solvent at the
internal standard HDO 4.78 ppm and with external dioxane 67.19 ppm.
Synthesis of glycoluril dipyrazolium products 2 and 3
Dimethyl glycoluril diether 1 (1.0 g, 3.94 mmol) and pyrazole (0.55 g, 7.92 mmol),
were added together and mixed as a fine powders. To this mixture was added 32%
HCl (2.5 mL). The mixture was stirred at 50 °C for 30 min and then the temperature
was gradually increased to 80 °C and maintained overnight. The temperature was
increased to 95 °C and heating continued for an additional 5 hr. After cooling the acid
was removed via rotary evaporation and the residue examined by 1H NMR which
showed two main products in a ratio of ~1.8:1. Purification was achieved by cation
exchange chromatography (Dowex X50) eluting with 0.5 M HCl and 45% formic
acid. The separate fractions were precipitated from water with NH4PF6 and the PF6
salts were recrystallized from water/acetonitrile.
Dipyrazolium 2 obtained as colorless needles (998 mg, 63%) Mp dec. 206 °C
1H NMR (DMSO-d6): δ 1.97 (6H, s), 6.07 (4H, d, J = 15.6 Hz), 6.30 (4H, d, J = 15.6
Hz), 6.82 (2H, s), 8.70 (4H, s). 13C{1H} NMR (DMSO-d6): δ 17.3, 55.3, 78.0, 108.3,
140.1, 153.3. MS (ES): m/z 178 (M2+/2). Anal. Calcd for C16H20N8O2 (PF6)2.CH3CN
(687.3680): C, 31.45; H, 3.37; N, 18.34. Found: C, 31.68; H, 3.36; N, 18.03.
Dipyrazolium 3 obtained as a colorless crystalline solid (254 mg, 21%) Mp > 250 °C
1H NMR (CH3CN-d3/D2O 6:1) δ 1.75 (3H, s), 1.81 (3H, s), 4.30 (2H, d, J = 16.4 Hz),
5.42 (2H, d, J = 16.4 Hz), 5.76 (4H, d, J = 15.6 Hz), 6.29 (4H, d, J = 15.6 Hz), 6.72
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(2H, t, J = 2.8 Hz), 8.34 (4H, d, J = 2.8 Hz). 13C{1H} NMR (CH3CN-d3/D2O 6:1): δ
17.3, 17.5, 45.3, 56.3, 78.17, 78.19, 108.8, 140.0, 154.6. MS (ES) m/z 275.3 (M2+/2).
Anal. Calcd for C24H30N12O4 (PF6)2 (840.5085): C, 34.30; H, 3.60; N, 20.00. Found:
C, 34.49; H, 3.49; N, 20.26.
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Synthesis of dipyrazole derivatives
1,1’-Di(3,5-dimethylpyrazol-4-yl)methane
3,5-Dimethylpyrazole (7.4 g, 77.1 mmol), tetrabutylammonium chloride (950 mg),
50% NaOH (65 mL) and DCM (130 mL) were combined. The mixture was refluxed
for 8 hr with vigorous stirring. After cooling to RT the organic phase was collected,
dried over anhydrous K2CO3 and the solvent removed in vacuo to give a viscous
liquid (9.85 g) that was dissolved in 48% HBr solution (50 mL). The solvent was
reduced to near dryness using the rotary evaporator to obtain a crystalline residue
(sometimes the HBr salt remained as a viscous yellow liquid). Adding acetone (50
mL) to the oil and allowing the solution to stand overnight at RT afforded off white
crystals. The crystals were collected by decantation to give bis(3,5-dimethyl-1H-
pyrazol-1-yl)methane HBr salt.
The HBr salt was placed in a reaction flask and in an oven which was heated to 200
°C (the flask was open and vented into a fume cupboard). At the desired temperature,
the entire crystalline white solid melted then turned into an off white solid. The
temperature was maintained at 200 °C for 1hr before cooling to RT. The off-white
solid was dissolved in water and solid NaOH was added until pH 10 was obtained.
The solid suspension which formed was collected by filtration and dried under
vacuum, to give an off white solid (6.03 g, 77% overall yield). No further purification
was required for the next step. The physical properties were identical to those
reported.21,34
The synthesis of ’-bis(3,5-dimethylpyrazol-4-yl)-p-xylene (8), ’-bis(3,5-
dimethylpyrazol-4-yl)-m-xylene (9) and 4, 4’-bis((3,5-dimethylpyrazol-4-
yl)methyl)biphenyl (7) were prepared following the typical procedure outlined below
for 8:
4, 4’-Bis((3,5-dimethylpyrazol-4-yl)methyl)biphenyl (7)
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The physical data was consistent with that previously reported.35 Mp >300 °C
’-Bis(3,5-dimethylpyrazol-4-yl)-p-xylene (8)
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’-dibromo-p-xylene (264 mg,1.00 mmol) dissolved in anhydrous THF (20 mL)
was added to NaH (60% oil dispersion) (90 mg, 2.25 mmol) at 0 °C under an inert
atmosphere. Acetylacetone (225 mg, 2.25 mmol) in THF (20 mL) was then added
dropwise to the mixture and upon completion the temperature was allowed to increase
to RT over 30 min. The reaction mixture was then heated at reflux overnight. After
cooling to RT the solution was poured into water, neutralized and the organics were
extracted using DCM. The DCM extracts were dried over MgSO4 and the solvent
removed in vacuo leaving a viscous liquid. The crude tetraone (2.00 g, 7.57 mmol)
was dissolved in MeOH (40 mL) and 50% hydrazine solution (50%) (1.0 mL, 15.9
mmol) was added. The mixture was stirred at 50 °C for 24 h before the MeOH was
removed using a rotary evaporator. The residue was washed with water to yield the
desired dipyrazole 8 as a colorless solid. The physical data was consistent with that
previously reported.26,27,34 Mp >290 °C
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’-Di(3,5-dimethylpyrazol-4-yl)-m-xylene (9)
The physical data was consistent with that previously reported.27 Mp >300 °C
General procedure for the synthesis of Tu[n] derivatives
Typical example: A mixture of a dipyrazole (1.0 mmol) and a glycoluril diether (2.00
mmol) were ground together to form a fine powder before 32% HCl (2 mL) was
added at RT. After 30 min the temperature was increased to 50 °C and maintained at
that temperature for 90 min. The temperature of the reaction mixture was then
increased to 90 °C. After 2 hr an additional portion of glycoluril diether (1.00 mml)
was added and the mixture was left at 90 ° C overnight. After cooling the acid was
removed via rotary evaporation and the residue examined by 1H NMR for maximum
product formation. The crude mixture was purified using cation exchange
chromatography eluting with 0.5 M HCl and 45% formic acid. The products thus
obtained were crystallized as the chloride from water or water/acetonitrile.
Me6Tu[3]Cl2
This compound was prepared as described in the general procedure from 4,4’-
dipyrazolylmethane 421b (1.31 mmol,) and dimethylglycoluril diether 1 (2.62 mmol)
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to give after purification a colorless crystalline product (396 mg, 60% relative to 1).
1H NMR (D2O): δ  1.80 (6H, s), 1.74 (6H, s), 1.63 (6H, s), 3.74 (2H, s), 4.30 (4H, d,
J = 16.0 Hz), 5.39 (4H, d, J = 16.0 Hz), 5.81 (4H, d, J = 16.0 Hz), 6.29 (4H, d, J =
16.0 Hz), 8.25 (4H, s). 13C{1H} NMR (D2O): δ 16.3, 16.9, 17.3, 43.8, 55.0, 76.9,
77.2, 78.0, 119.8, 137.9, 155.0. MS (ES): m/z 378.2 (M2+/2). HRMS (ES-TOF)
calculated for C33H40N16O6Cl (M+) 791.3005, found 791.3004.
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Me10Tu[3]Cl2
This compound was prepared as described in the general procedure from dipyrazole 5
(1.31 mmol) and diether 1 (2.62 mmol) to give the product as a colorless crystalline
solid (461 mg, 65%)
1H NMR (D2O): δ 1.79 (6H, s), 1.88 (6H, s), 1.96 (6H, s), 2.72 (12H, s), 3.77 (2H,
s), 4.46 (4H, d, J = 16.0 Hz ), 5.59 (4H,d , J = 16.0 Hz ), 5.80 (4H,d, J = 16.0 Hz ),
6.30 (4H, d, J = 16.0 Hz). 13C{1H} NMR (D2O): δ 10.9, 16.4, 16.9, 17.7, 43.9, 51.5,
76.8, 77.03, 77.9, 146.5, 154.8. UV (H2O)  max 235 nm,  = 14701. MS (ES): m/z
406.3 (M2+/2). Anal. Calcd for C37H48N16O6Cl2.9H2O (1045.8683): C, 42.49; H, 6.36;
N, 21.43. Found: C, 42.58; H, 6.06; N, 21.60.
Me10TU[3](HSO4)2
This salt was prepared by dissolving Me10TU[3]Cl2 in a minimum volume of conc
H2SO4. After a few min allowing the expulsion of HCl the sulfate salt was then
precipitated by the addition of dry diethyl ether. Collecting by filtration and washing
with additional dry ether and then ethanol to give a dry colorless solid. Recrystallized
1
for water/acetonitrile. By H and 13C{1H} NMR the sulfate was identical to the
-
chloride form. Calcd for C37H48N16O6.2HSO4 .6H2O (1115.1265): C, 39.85; H, 5.42;
N, 20.10; S, 5.75. Found: C, 39.82; H, 5.47; N, 19.87; S, 5.72.
Me4CyP3Tu[3]
This compound was prepared as described in the general procedure from dipyrazole 5
(504 mg, 2.47 mmol) and cyclopentanoglycoluril diether 6 (1.97 g, 7.41 mmol) to
give after purification the product (454 mg, 20% relative to 5).
1H NMR (D2O): δ 1.75 – 1.78 (2H, t), 1.95 - 1.98 (4H, m), 2.27 – 2.30 (4H, t), 2.37 –
2.42 (8H, m), 2.72 (12H, s), 3.78 (4H, s), 4.42 (4H, d, J = 16 Hz), 5.56 (4H, d, J = 16
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Hz), 5.86 (4H, d, J = 16 Hz), 6.34 (4H, d, J = 16 Hz). 13C{1H} NMR (D2O): δ 10.8,
15.8, 22.5, 23.3, 33.8, 35.1, 37.2, 45.9, 52.2, 83.4, 83.8, 85.2, 146.5, 155.0, 155.6. MS
(ES): m/z 424.2 (100 [M2+/2]). HRMS (ES-TOF) calculated for C40H48N16O6 (M2+)
424.1971, found 424.1970.
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m-XyMe8Tu[2]
This compound was prepared as described in the general procedure from the m-xylyl
dipyrazole 9 (500 mg, 1.70 mmol) and diether 1 (864 mg, 3.40mmol) to give after
purification the product (125 mg, 16%).
1H NMR (D2O): δ 1.81 (6H, s), 1.93 (6H, s), 2.41 (12H, s), 3.77 (4H, s), 4.50 (2H, d,
J = 16 Hz), 5.46 (2H, d, J = 16 Hz), 5.65 (4H, d, J = 16 Hz), 6.20 (4H, d, J = 16 Hz),
6.74 (1H, s), 7.38 (3H, b s). MS (ES): m/z 354.4 (100, [M2+/2]. HRMS (ES-TOF)
calculated for C36H44N12O4 (M2+) 354.1804, found 354.1808.
p-XyMe8Tu[2]
This compound was prepared as described in the general procedure from the p-xylyl
dipyrazole 8 (500 mg, 1.70 mmol) and diether 1 (864 mg, 3.40 mmol) to give after
purification the product (331 mg, 25%).
1H NMR (D2O): δ 1.85 (6H, s), 2.01 (6H, s), 2.61 (12H, s), 3.82 (4H, s), 4.42 (2H, d,
J = 16 Hz), 5.50 (2H, d, J = 16 Hz), 5.68 (4H, d, J = 16 Hz), 6.22 (4H, d, J =16 Hz),
7.22 (4H, s). 13C{1H} NMR (D2O): δ 9.7, 16.3, 16.9, 27.3, 44.6, 51.3, 76.4, 77.4,
120.0, 128.3, 138.1, 145.2, 154.3. MS (ES): m/z 354.3 (100, [M2+/2]. HRMS (ES-
TOF) calculated for C36H44N12O4 (M2+) 354.1804, found 354.1802.
Acknowledgments
This work was supported by the UNSW Canberra postgraduate research student
scholarship scheme.
Supporting Information Statement
1H and 13C{1H} NMR spectra of purified compounds includes 2, 3, Me6Tu[3]Cl2,
2
Me10Tu[3]Cl2, m-XyMe8Tu[2]Cl2, p-XyMe8Tu[2]Cl2 and Me10Tu[3]Cl2. A H NMR
spectrum of the crude deuterium exchange product d12-Me10Tu[3]Cl2. CD spectra of
L-glutamine with Me10Tu[3]Cl2 are provided, and plots for pKa measurements of
Me10Tu[3]Cl2 and Me10Tu[3](HSO4)2. X-ray crystallographic data and the CIF file.
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The Supporting Information is available free of charge on the ACS Publications
website.
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References
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1. Assaf, K. I.; Nau, W. M. Cucurbiturils: From Synthesis to High-Affinity
Binding and Catalysis. Chem. Soc. Rev., 2015, 44, 394–418.
2. Isaacs, L. Stimuli Responsive Systems Constructed Using Cucurbit[n]uril-
Type Molecular Containers. Acc. Chem. Res., 2014, 47, 2052–2062.
3. Masson, E.; Ling, X.; Joseph, R.; Kyeremeh-Mensah, L.; Lu, X. Cucurbituril
Chemistry: A Tale of Supramolecular Success. RSC Adv., 2012, 2, 1213–
1247.
4. Liu, J.; Lan, Y.; Yu, Z.; Tan, C. S. Y.; Parker, R. M.; Abell, C.; Scherman, O.
A. Cucurbit[n]uril-Based Microcapsules Self-Assembled Within Microfluidic
Droplets: A Versatile Approach for Supramolecular Architectures And
Materials. Acc. Chem. Res., 2017, 50, 208–217.
5. Liu, J.; Tan, C. S. Y.; Lan, Y.; Scherman, O. A. Aqueous Polymer Self-
Assembly based on Cucurbit[n]uril-Mediated Host-Guest. Macromol. Chem.
Phys., 2016, 217, 319–332.
6. Barrow, S. J.; Setu Kasera, S.; Rowland, M. J.; del Barrio, J.; Scherman, O. A.
Cucurbituril-Based Molecular Recognition. Chem. Rev., 2015, 115, 12320–
12406.
7. X. Ma, X.; Zhao, Y. Biomedical Applications of Supramolecular Systems
Based On Host−Guest Interactions. Chem. Rev., 2015, 115, 7794–7839.
8. Gürbüz, S.; Idris, M.; Tuncel, D. Cucurbituril-Based Supramolecular
Engineered Nanostructured Materials. Org. Biomol. Chem., 2015, 13, 330–
347.
9. Saleh, N.; Ghosh, I.; Nau, W. M. Cucurbiturils in Drug Delivery and For
Biomedical Applications. Supramolecular Chemistry, 13 (Supramolecular
Systems in Biomedical Fields), 2013, 164–212.
10. Saluja, V.; Sekhon, B. S. Calixarenes And Cucurbiturils: Pharmaceutical and
Biomedical Applications. J. Pharm. Ed. Res., 2013, 4, 16–25.
11. Ghosh I.; Nau, W. M. The Strategic Use of Supramolecular pKa Shifts to
Enhance the Bioavailability of Drugs. Adv. Drug Deliv. Rev., 2012, 64, 764–
783.
12. A. I. Day, A. I.; Collins, J. G. Cucurbituril Receptors and Drug Delivery. in
Supramolecular Chemistry from molecules to nanomaterials, J.W. Steed and
P.A. Gale (eds). John Wiley & Sons Ltd, Chichester, UK, 2012, 3, 983–1000.
13. Walker, S.; Oun, R.; McInnes, F. J.; Wheate, N. J. The Potential of
Cucurbit[n]urils in Drug Delivery. Isr. J. Chem., 2011, 51, 616–624.
14. Macartney, D. H. Cucurbit[n]uril Type Hosts for the Reversal of Steroidal
Neuromuscular Blocking Agents. Future Med. Chem., 2013, 15, 2075–2089.
15. Elbashir, A. A.; Aboul-Enein, H. Y. Supramolecular Analytical Application of
Cucurbit[n]uril Using Fluorescence Spectroscopy. Crit. Rev. Anal.
Chem., 2015, 45, 52–61.
16. Kaifer, A. E. Toward Reversible Control of Cucurbit[n]uril Complexes. Acc.
Chem. Res., 2014, 47, 2160–2167.
17. Da Silva, J. P.; Choudhury, R.; Porel, M.; Pischel, U.; Jockusch, S.; Hubbard,
P. C.; Ramamurthy, V.; Canario, A. V. Synthetic Versus Natural Receptors:
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2
3
4
5
6
7
8
9
Supramolecular Control of Chemical Sensing in Fish. ACS Chem. Biol., 2014,
9, 1432–1436.
18. Lee, H. H.; Choi, T. S.; Lee, S. J.; Lee, J. W.; Park, J.; Ko, Y. H.; Kim, W. J.;
Kim, K.; Kim, H. I. Supramolecular Inhibition of Amyloid Fibrillation by
Cucurbit[7]uril. Angew. Chem., Int. Ed., 2014, 53, 7461–7465.
19. Lizal, T.; Sindelar, V. Bambusuril Anion Receptors. Isr. J. Chem., 2018, 58,
326–333.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
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32
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35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
20. a) Zhang, Y.-Q.; Zhu, Q.-J.; Xue, S.-F.; Tao, Z. Chlorine Anion Encapsulation
by Molecular Capsules Based on Cucurbit[5]uril and
Decamethylcucurbit[5]uril. Molecules 2007, 12, 1325–1333. b) Lui, J.-X.;
Long, L.-S.; Huang, R.-B.; Zheng, L.-S. Interesting Anion-Inclusion Behavior
of Cucurbit[5]uril and Its Lanthanide-Capped Molecular Capsule. Inorg.
Chem., 2007, 46, 10168–10173.
21. a) Cuadro, A. M.; Elguero, J.; Navarro, P. Binuclear pyrazoles. I. Synthesis
and Cytotoxic Activity of 1,1’-Dibenzyl and 1,1’-Dihydroxymethyl-4,4’-
Bispyrazoles. Chem. Pharm. Bull., 1985, 33(6), 2535–2540. b) Wheate, J. N.;
Broomhead, J. A.; Collins, J. G.; Day, A. I. Thermal Rearrangement of N-
Substituted Pyrazoles to 4,4′-Dipyrazolylmethane and 1,1,2-(4,4′,4′′-
Tripyrazolyl)ethane. Aust. J. Chem., 2001, 54, 141–144.
22. Lagona, J.; Fettinger, J. C.; Isaacs, L. Cucurbit[n]uril Analogues. Org. Lett.,
2003, 5, 3745–3747.
23. Flinn, A.; Hough, G. C.; Stoddart, J. F.; Williams, D. J.
Decamethylcucurbit[5]uril. Angew. Chem., Int. Ed., 1992, 31, 1475–1477.
24. Day, A.; Arnold, A.P.; Blanch, R. J.; Snushall, B. Controlling factors in the
Synthesis of Cucurbituril and Its Homologues. J. Org. Chem., 2001, 66, 8094–
8100.
25. Crystallographic data for Me10Tu[3](PF6)2 has also been deposited with the
Cambridge Crystallographic Data Centre as supplementary no. CCDC-
1869840. Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, CambridgeCB21EZ, UK (e-mail:
deposit@ccdc.cam.ac.uk).
26. Hayter, M.J.; Bray, D. J.; Clegg, J. K.; Lindoy, L.F. New Bis-pyrazole
Derivatives Synthesized from Aryl- and Xylyl-Linked Bis(-diketone)
Precursors. Synth. Commun., 2006, 36(6), 707–714.
27. Tăbăcaru, A.; Pettinari, C.; Marchetti, F.; Galli, S.; Masciocchi, N.
Bis(pyrazolato)-Based Metal-Organic Frameworks Fabricated with 4,4’-
Bis((3,5-dimethyl-1H-pyrazol-4-yl)methyl)biphenyl and Late Transition
Metals. Cryst. Growth Des., 2014, 14, 3142–3152.
28. Wu, F.; Wu, L.-H.; Xiao, X.; Zhang, Y.-Q.; Xue, S.-F.; Tao, Z.; Day, A. I.
‘Locating the Cyclopentano Cousins of the Cucurbit[n]uril Family’ J. Org.
Chem. 2012, 77, 606–611. b) Zhao, Y.; Mandadapu, V.; Iranhmanesh, H.;
Beves, J. E.; Day, A. I. The Inheritance Angle: A Determinant for the Number
of Members in the Substituted Cucurbit[n]uril Family. Org. Lett., 2017, 19,
4034–4037.
29. a) Chun, Y.; Singh, N. J.; Hwang, I.-C.; Lee, J.W.; Yu, S. U.; Kim, K. S.
Calix[n]imidazolium as a New Class of Positively Charged Homo-Calix
Compounds. Nat. Comm., 2013, 4, 1797. DOI: 10.1038/ncomms2758. b)
Chellappan, K.; Singh, N. J.; Hwang, I.-C.; Lee, J.W.; Kim, K. S. A
Calix[4]imidazolium[2]pyridine as an Anion Receptor. Angew. Chem. Int. Ed.
2005, 44, 2899–2903.
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30. ED Lide, D. R. Handbook of Chemistry and Physics CRC press LLC 2000,
Dissociation Constants of Inorganic Acids and Bases.
31. HyperChem professional 8.0.7 for Windows Molecular Modelling System,
HyperCube Inc., Ontario, Canada 2009.
7
32. a) Kikuchi, Y.; Kobayashi, K.; Aoyama, Y. Complexation of Chiral Glycols,
Steroidal Polyols, and Sugars with a Multibenzenoid, Achiral Host as Studied
by Induced Circular Dichroism Spectroscopy: Exciton Chirality Induction in
Resorcinol-Aldehyde Cyclotetramer and Its Use as a Supramolecular Probe
for the Assignments of Stereochemistry of Chiral Guests. J. Amer. Chem. Soc.
1992, 114, 1351–1358. b) Yuan, L.; Wang, R.; Macartney, D. H. Chiroptic
Behaviour of a Chiral Guest in an Achiral Cucurbit[7]uril Host. Tetrahedron:
Asymmetr. 2007, 18, 483–487. c) Wu, W.; Cronin, M. P.; Wallace, L.; Day, A.
I. An Exploration of Induced Supramolecular Chirality Through Association
of Chiral Ammonium Ions and Tartrates with the Achiral Host Cucurbit[7]uril.
Isr. J. Chem. 2018, 58, 479–486.
33. Julia, S.; Sala, P.; del Mazo, J.; Sancho, M.; Ochoa, C.; Elguero, J.; Fayet,
J.P.; Vertut, M.-C. N-Polyazolylmethanes. 1. Synthesis and NMR Study of N,
N’-Diazolylmethanes. J. Heterocycl. Chem. 1982, 19, 1141–1145.
34. Tăbăcaru, A.; Pettinari, C.; Masciocchi, N.; Galli, S.; Marchetti, F.; Angjellari,
M. Pro-Porous Coordination Polymers of the 1,4-Bis((3,5-Dimethyl-1H-
Pyrazol-4-Yl)-Methyl)Benzene Ligand with Late Transition Metals. Inorg.
Chem. 2011, 50(22), 11506–11513.
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