Synthesis, characterization, photophysical and electrochemical properties of triazinooxacalix[2]arenes with bisphenol A motif

Article abstract of DOI:10.1016/j.tet.2018.04.064

Oxygen atom bridged calixarene derivatives called oxacalixarenes were synthesized from bisphenol A and cyanuric chloride by aromatic nucleophilic substitution through addition elimination mechanism. All the synthesized oxacalixarenes exhibit strong absorb

Full text of DOI:10.1016/j.tet.2018.04.064

Tetrahedron xxx (2018) 1e7
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Synthesis, characterization, photophysical and electrochemical
properties of triazinooxacalix[2]arenes with bisphenol A motif
Kannan Rajavelu, Perumal Rajakumar*
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai, 600 025, Tamilnadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Oxygen atom bridged calixarene derivatives called oxacalixarenes were synthesized from bisphenol A
and cyanuric chloride by aromatic nucleophilic substitution through addition elimination mechanism. All
the synthesized oxacalixarenes exhibit strong absorbance band between 225 and 286 nm due to the
presence of triazine and phenoxy units. The oxacalixarenes 7 and 10 show strong fluorescence emission
and higher lem values than all other oxacalixarenes due to the presence of rigid aromatic spacer units
such as binol and biphenyl. All the oxacalixarenes exhibit quasi-reversible behaviour and potential shift
observed in cyclic voltammetry.
Received 14 March 2018
Received in revised form
18 April 2018
Accepted 20 April 2018
Available online xxx
Keywords:
Bisphenol A
© 2018 Published by Elsevier Ltd.
Triazinooxacalix[2]arenes
Photophysical
Electrochemical properties
1. Introduction
sulfur7 and nitrogen8 along with the bridging oxygen.9 Heter-
eocalixarenes can be synthesized either by fragment coupling
The design and synthesis of new and functional macrocyclic
host molecules has been one of the driving forces to promote the
major advances in supramolecular chemistry.1 Crown ether type of
calixarenes are the third generation of supramolecules,2 which
consists of the upper rim and a narrow lower rim and a central
annulus. Calix[n]arene are [1n] metacyclophane which are rela-
tively easy to prepare and functionalize due to their high level
preorganization and conformational preferences. Calixarenes are
useful host molecules in supramolecular systems and have a wide
range of industrial applications such as metal sequestration and
waste remediation.3 Incorporation of the bridging atoms other than
carbon within ‘classical’ carbon-bridged calix[n]arenes framework
provide means to produce new macrocyclic host molecules called
heterocalixarenes with unexplored chemical and physical proper-
ties.4 Recently, Katz and co-workers5 reported a new class of oxa-
calixarenes based on molecular tweezers which shows the
capability of binding aromatic guest molecule.
approach10 or by one pot macrocyclic condensation.11 The elec-
tronic properties and the cavity size can be tuned in calixarenes to
improve their self-assembly and recognition abilities. The hetero-
calixarene play an important role in host-guest chemistry12 with
various guest species like cations, anions and neutral molecules
including fullerenes. Oxacalixarene13 is an important class of the
heterocalixarenes that has shown a fast growth in the calixarene
chemistry due to increasing amount of effort devoted to the syn-
thesis and conformational investigation. The oxacalixarene de-
rivatives have been reported earlier for the detection of explosives
due to their ability to form host-guest complexes through specific
chemical interactions.14 The heterocalixarenes containing triazine
bridge with either oxygen or nitrogen bridging atom could have
different degree of conjugation with the neighbouring aromatic
rings. Such macrocycles have definite electronic characteristics,
unique binding properties and to complex with acidic guest mol-
ecules.15 Electron deficient triazine rings in the oxacalixarene forms
ternary complexes with halide ion and possess water molecule in
The chemistry of heterocalixarene6 has a growing interest in
calixarene field because of the easy availability, fine tunable cavities
and potential applications in supramolecular chemistry. The cal-
ixarene skeleton can be modified with heteroatoms including
the solid state.16 Such complexes could have anion-
between the halide ion and one triazine ring.
p interaction
Melamine is one of the triazine derivatives widely used as
building block in supramolecular chemistry, generating a wide
range of the structural motifs, including cyclic rosettes,17 linear or
crinkled tapes18 and molecular strands or ribbons.19 Oxacalixarenes
can exist in thermodynamically favourable 1,3 alternate (partial
* Corresponding author. Tel.: þ91 44 2220 2814.
E-mail address: Perumalrajakumar@gmail.com (P. Rajakumar).
https://doi.org/10.1016/j.tet.2018.04.064
0040-4020/© 2018 Published by Elsevier Ltd.
Please cite this article in press as: Rajavelu K, Rajakumar P, Synthesis, characterization, photophysical and electrochemical properties of
triazinooxacalix[2]arenes with bisphenol A motif, Tetrahedron (2018), https://doi.org/10.1016/j.tet.2018.04.064

2
K. Rajavelu, P. Rajakumar / Tetrahedron xxx (2018) 1e7
cone) arrangement and explore their broad applications such as ion
sensitive electrodes,20 sensors,21 self-assembly22 and for the mea-
surement of sodium levels in blood.23 The oxacalixarenes can be
synthesized by aromatic nucleophilic substitution reaction through
addition and elimination mechanism of the bisphenol A with cya-
nuric chloride by step wise fragment coupling approach. The pre-
sent investigation deals with synthesis, structural characterization
and optical as well as electrochemical properties of the oxacalix-
arenes 1e10 (Fig. 1) with bisphenol A at the intra annular position.
The mass spectrum (HRMS) of the precyclophane 13 showed mo-
lecular ion peak at m/z 525.1869 [M þ H]þ along with isotopic peaks
at 527.1678 and 529.1403. Further, the structure of the pre-
cyclophane 13 was also confirmed from the spectral and analytical
data.
With the precyclophane 13 in our hand, the synthesis of the
oxacalixarenes 1 to 10 was then focused under various reaction
conditions. To optimize the yield of the oxacalixarenes 1e10,
various solvents such as acetone, THF and acetonitrile were
employed for the reaction of the precyclophane 13 with the
bisphenol A 11. The use of acetonitrile or THF for the macrocyclic
coupling gave only 24% yield of the oxacalixarene 1. However the
yield of oxacalixarene 1 was better (36%) in acetone than in any
other solvents. To improve the yield of the oxacalixarene 1, the
reaction of the precyclophane 13 with the bisphenol A 11 was tried
using various inorganic and organic bases such as K2CO3, Na2CO3
and Et3N, but still the yield of 1 was poor (10%). However macro-
cyclic coupling of 1.0 equiv. of the bisphenol A 11 with 1.0 equiv. of
the precyclophane 13 in the presence of DIPEA in acetone under
high dilution conditions at room temperature for 48 h gave the
oxacalixarene 1 in 36% yield (Scheme 1).
The high dilution technique has been employed to avoid the
formation of linear trimeric and polymeric products and also the
higher order oligomers such as 3:3 and 4:4. However all such
higher order oligomers are insoluble and hence chromatographic
technique could not be employed for the purification of such
polymeric and higher order oligomeric products. In the 1H NMR
spectrum, the oxacalixarene 1 showed a twelve proton singlet at
2. Results and discussion
The oxacalixarenes 1e10 can be synthesized by aromatic
nucleophilic substitution24 through addition elimination mecha-
nism. The precycophane 13 was obtained in 87% by the reaction of
1.0 equiv. of the bisphenol A 11 with 2.1 equiv. of cyanuric chloride
12 in the presence of DIPEA in dry THF (Scheme 1). To avoid the
formation of bis and tris alkylated product, ice bath was used and
the yield of 13 can be slightly improved when a large excess amount
of cyanuric chloride 12 was used. Under optimized conditions the
yield of the precyclophane 13 obtained was only 40%. When THF
was used as the solvent with different bases such as Et3N and K2CO3
instead of DIPEA, the yield of the precyclophane 13 was reduced
drastically. In the 1H NMR spectrum, the precyclophane 13 dis-
played a six proton singlet at
to the bisphenol A unit and a two proton doublet at
proton doublet at 7.33 for the protons in the benzene ring of the
bisphenol A unit. In the 13C NMR spectrum the precyclophane 13
showed the methyl carbon of the bisphenol A unit at 30.9 in
addition to the signals for the other aliphatic and aromatic carbons.
d
1.74 for two methyl group attached
d
7.11 and a two
d
d
1.67 for the methyl protons of the bisphenol A unit in addition to
the signals for the aromatic protons. In the 13C NMR spectrum, the
d
Fig. 1. Molecular structure of the oxacalixarenes 1e10 with bisphenol A unit at intra annular position.
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triazinooxacalix[2]arenes with bisphenol A motif, Tetrahedron (2018), https://doi.org/10.1016/j.tet.2018.04.064

K. Rajavelu, P. Rajakumar / Tetrahedron xxx (2018) 1e7
3
Scheme 1. (i) DIPEA, dry THF, 0 ꢀC to rt, 4 h (ii) DIPEA, acetone, rt, 48 h.
oxacalixarene 1 displayed the methyl carbon attached to the
bisphenol A at 68.9, in addition to the signals for the other
methylene protons located in between the two naphthyl rings in
addition to the signals for the aromatic protons. In the 13C NMR
spectrum the oxacalixarene 8 showed the methylene carbon in
between the two naphthyl rings and the methyl carbon in
d
aliphatic and aromatic carbons. The mass spectrum (HRMS) of the
oxacalixarene 1 showed molecular ion peak at m/z 679.1611 [M þ
H]þ along with the isotopic peaks at 681.1519 and 682.1503 (SI,
Fig. S4.1). Further, the structure of the oxacalixarene 1 was also
confirmed from elemental analysis.
Similarly, the oxacalixarenes 2, 3, 4 and 5 were obtained in 28%,
22%, 20% and 21% yields, respectively by the reaction of the
resorcinol derivatives 14, 15, 16 and 17 with the precyclophane 13
for 48 h in acetone in the presence of DIPEA at room temperature
under high dilution condition. In the 1H NMR spectrum, the oxa-
bisphenol A at d 24.0, 28.8 respectively, in addition to the signals for
the other aliphatic and aromatic carbons. The mass spectrum
(HRMS) of the oxacalixarene 8 showed the molecular ion peak at m/
z 751.1656 [M þ H]þ in addition to the isotopic signals at 753.1761
and 755.1962 (SI, Fig. S4.4). Further, the structure of the oxacalix-
arene 8 was also confirmed from elemental analysis. Similarly, the
reaction of the 4,40-dimethoxy-2,20-dihydroxybenzophenone 21
with the precyclophane 13 in the presence of DIPEA in for 48 h
acetone under high dilution conditions at room temperature gave
the oxacalixarene 9 in 20% yield. In the 1H NMR spectrum, the
calixarene 4 showed six proton singlet at
d 1.73 for the methyl
attached to the bisphenol A unit and the three proton singlet at
d
4.05 for the ester methoxy protons in addition to the signals for
oxacalixarene 9 showed a singlet at
attached to bisphenol A unit and a six proton singlet at
d
1.59 for the two methyl
3.81 for
the aromatic protons. In the 13C NMR spectrum, the oxacalixarene 4
d
displayed the methyl carbons attached to the bisphenol A unit at
methoxy protons in addition to the signals for the aromatic protons.
In the 13C NMR spectrum, the oxacalixarene 9 displayed the
bisphenol A attached to methyl carbon and the ester methoxy
d
28.7 and the ester methoxy carbon at d 52.7, in addition to the
other aliphatic and aromatic carbon signals. The mass spectrum
(HRMS) of the oxacalixarene 4 showed the molecular ion peak at m/
z 619.0908 [M þ H]þ along with the isotopic peaks at 621.0880 and
623.0564 (SI, Fig. S4.3).
The oxacalixarene 8 was obtained in 28% yield by the macro-
cyclization of the precyclophane 13 under high dilution condition
with methylene binaphthol 20 for 48 h in acetone in the presence of
DIPEA at room temperature. The 1H NMR spectrum of the oxaca-
carbon at d 28.8, 55.8, respectively, in addition to the signals for the
other aliphatic and aromatic carbons. The mass spectrum (HRMS)
of the oxacalixarene 9 showed the molecular ion peak at m/z
725.1310 [M þ H]þ along with isotopic peak at 727.1447 and
728.1532 (SI, Fig. S4.5). Further, the structure of the oxacalixarene 9
was confirmed from elemental analysis. Finally, in order to create
structural rigidity the biphenyl-4,40-diol 22 was reacted with the
precyclophane 13 to give the oxacalixarene 10 in 22% yield. The
structure of the oxacalixarenes 2, 3, 5, 6, 7 and 10 was also
lixarene 8 displayed a six proton singlet at
attached to bisphenol A unit and two proton singlet at
d
1.73 for the two methyl
4.95 for
d
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K. Rajavelu, P. Rajakumar / Tetrahedron xxx (2018) 1e7
confirmed from spectral and analytical data.
The oxacalixarenes 1e10 show a strong emission band in the range
of 428e435 nm as shown in Fig. 3(a and b) and Table 1. The oxa-
calixarenes 7 and 10 show a strong fluorescence emission with
higher lem values when compared with other than oxacalixarenes
The oxacalixarenes 1e10 has two chlorine atoms on the upper
rim and hence further functionalization could be carried out using
2.1 equiv. of the various nucleophiles such as amines and pyridine
through addition elimination mechanism. Such transformation has
been reported in the literature,25 however the reaction of the
oxacalixarenes 1 to 10 with various amines gave only mixture of the
inseparable products and various techniques to purify the products
was futile and hence the structure of the products could not be
identified.
due to the presence of highly p-conjugated aromatic chromophores
such as binol and biphenyl units, respectively. Similarly, fluores-
cence intensity of the oxacalixarenes 2 and 9 shows weak emission
due to presence of the electron donating substituent in the spacer
units.
4. Electrochemical studies
3. Photophysical properties
The redox property of oxacalixarenes 1e10 was studied using
the cyclic voltammetry. The cyclic voltammogram of the oxacalix-
arenes 1e10 was obtained in acetonitrile containing 0.1 M TBAP as
the supporting electrolyte at scan rate is 100 mV sꢂ1 as shown in
Fig. 4 and Table 2. The oxacalixarenes 1, 2 and 3 exhibited two
oxidation peaks between ꢂ0.30e1.67 V and two reduction peaks
between 1.18 and ꢂ1.43 V and the oxacalixarenes 4, 5, 6, 9 and 10
showed two oxidation signal and one reduction signal due to
presence of the electron donating substituents in the molecular
systems. But the oxacalixarenes 7 and 8 exhibit three oxidation and
The UVevis absorption spectra of the oxacalixarenes 1e10 were
recorded in CH3CN (1 ꢁ 10ꢂ3 L molꢂ1 cmꢂ1) and the lmax values are
summarized in Table 1. The UVevis spectrum of the oxacalixarenes
1e10 exhibit strong absorption band between 225 and 286 nm
which shows
p-p* transition due to the presence of triazine and
phenoxy units in the cyclic systems as shown in Fig. 2(a and b).
The molar absorptivity for the oxacalixarenes 3 and 5 is found to
be high due to the presence of electron donating and electron
withdrawing group in the intra annular position, which indicate
that the oxacalixarenes 3 and 5 show self-complementary property.
The molar absorptivity of the oxacalixarenes 7 and 9 is found to be
low due to the presence of rigid binol system and electron with-
drawing benzophenone chromopore as the spacer units. However
the oxacalixarene 8 shows a small hypsochromic or blue shift when
compared with other than oxacalixarenes due to presence of the
methylene unit in between the two naphthyl ring system which
could prevent the conjugation.
three reduction peaks due to extended
p-conjugated binol and
methylene binaphthol spacer units in the molecular frame. All the
oxacalixarenes exhibit the oxidation reduction signals with quasi-
reversible behaviour in cyclic voltammetry.26
The reversible oxidation potential of oxacalixarene 1 with the
positive potential value of 1.64 V is due to presence of the electron
rich phenoxy group and electron deficient triazine rings. For the
oxacalixarenes 2 and 3, the oxidation potential value gradually
increases due to electron donating groups. However, for the oxa-
calixarenes 4 and 5, the potential value gradually decreases and the
potential shift was observed at 1.67 and 1.54 V respectively due to
the presence of electron withdrawing carbethoxy group. The oxa-
Fluorescence emission spectrum was obtained by exciting all the
oxacalixarenes 1e10 at the corresponding absorption maximum.
Table 1
calixarenes 6 and 7 with extensive p-conjugation with the triazine
Photophysical properties of the oxacalixarenes 1e10 in acetonitrile.
moiety exhibit less shift in the oxidation potential at 0.47 and
0.48 V respectively due to presence of the aromatic spacer units viz:
naphthalene and binol.
The oxacalixarene derivatives 8, 9 and 10 have higher positive
potential in the order is 1.17, 1.05 and 1.44 V respectively due to
Oxacalixarenes
lmax (nm)
ε (L,molꢂ1,cmꢂ1
)
lem (nm)
1
2
3
4
5
6
7
8
9
10
231
227
227, 279, 286
229
690
710
1000, 260, 220
660
431
428
431
432
433
432
435
432
430
434
highly conjugated delocalized
p-electrons and electron deficient
226, 279, 285
1190, 230, 230
triazine rings. The cathodic peak potential for the oxacalixarenes
1e10 shows a higher negative potential range at ꢂ0.02 to ꢂ1.22 V is
due to structural rigidity of the aromatic spacer units. However,
249
228
225
282
249
700
560
880
620
950
oxacalixarene derivatives 6, 7, 8, 9 and 10 with extensive
p-
conjugation with triazine rings require more energy for the
Fig. 2. UVevis absorption spectra of a) the oxacalixarenes 1e5 and b) the oxacalixarenes 6e10 in acetonitrile.
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K. Rajavelu, P. Rajakumar / Tetrahedron xxx (2018) 1e7
5
Fig. 3. Emission spectra of a) the oxacalixarenes 1e5 and the oxacalixarenes 6e10 in acetonitrile.
reduction process27 and the negative potential shift was observed
from the lower to higher potential value in the cyclic voltammetry.
apparatus by the open capillary tube method. The UVeVis spectra
were recorded on a Hitachi U-3210 spectrophotometer. The emis-
sion spectra were recorded on a HORIBA JOBIN YVON Fluoromax-4
spectrophotometer. The 1H and 13C NMR spectra were recorded on
a Bruker 300 MHz NMR spectrometer. The chemical shifts are re-
5. Experimental section
ported in ppm (d) with TMS as an internal standard and the
5.1. Material and methods
coupling constants (J) are expressed in Hz. High resolution mass
spectra (HRMS) were recorded on Q-Tof Micro mass spectrometer.
Elemental analyses were performed on a Perkin-Elmer 240B
elemental analyser. Electrochemical studies were carried out on a
CH Instrument electrochemical analyser.
All the reagents and solvents were obtained from Alfa Aesar,
Merck or Avra chemical companies. The known products were
identified by the comparison of their melting points and spectral
data is already reported in the literature. Melting points were un-
corrected and were determined using Toshniwal melting point
Fig. 4. Cyclic voltammogram of the oxacalixarenes 7e10 in acetonitrile scanned at 100 mV sꢂ1
.
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triazinooxacalix[2]arenes with bisphenol A motif, Tetrahedron (2018), https://doi.org/10.1016/j.tet.2018.04.064

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K. Rajavelu, P. Rajakumar / Tetrahedron xxx (2018) 1e7
Table 2
Electrochemical parameters of the oxacalixarenes 1e10 in acetonitrile.
compd
Epc1 (V)
Epc2 (V)
Epc3 (V)
Epa1 (V)
Epa2 (V)
Epa3 (V)
D
Ep1(V)
DEp2 (V)
DEp3 (V)
1
2
3
4
5
6
7
8
9
ꢂ0.52
ꢂ0.54
ꢂ0.44
1.41
1.64
1.61
1.68
1.67
1.54
0.47
0.48
1.17
1.05
1.44
-
-
1.17
1.16
1.18
ꢂ1.15
ꢂ1.14
ꢂ1.19
e
e
ꢂ1.69
ꢂ1.70
ꢂ1.62
0.19
1.56
0.45
2.79
2.75
2.87
1.67
1.54
0.47
0.50
2.43
1.05
1.44
-
-
e
e
e
e
e
ꢂ1.22
ꢂ0.49
ꢂ0.75
0.96
ꢂ0.07
ꢂ1.43
ꢂ1.21
e
e
1.07
e
e
e
e
ꢂ0.30
ꢂ0.64
0.32
-
e
e
-
1.78
1.63
-
-
ꢂ0.02
ꢂ1.13
e
ꢂ1.05
ꢂ1.40
e
ꢂ1.60
2.83
3.03
-
-
0.44
ꢂ1.01
0.42
0.24
10
ꢂ0.97
e
e
5.2. Synthesis of precyclophane 13
and resorcinol 14 (0.22 g, 2.00 mmol) and after eluting from the
column with EtOAc:Hexane (1:4). Yield: 28%; mp: 230e232 ꢀC; 1H
To a solution of DIPEA/(4.0 equiv.) in dry THF (200 mL) in ice
bath, Bisphenol A (2 g, 14 mmol) and cyanuric chloride (6.10 g,
33 mmol) each in dry THF (100 mL) was separately and simulta-
neously added in dropwise under high dilution condition during a
period of 4 h. The reaction mixture was stirred for another 4 h at
room temperature. After the reaction was complete, the solvent
was removed under reduced pressure and then extracted with
EtOAc (3 ꢁ 100 mL). The combined organic layer was washed with
water (100 mL) and brine (50 mL) and dried over anhydrous
Na2SO4. Ethyl acetate was removed under reduced pressure and the
final residue was purified by column chromatography on silica gel
using n-Hexane:EtOAc (9:1) as the eluent to afford the pure pre-
cyclophane 13 as colourless solid (3.0 g, 87%); mp: 242e244 ꢀC; 1H
NMR (300 MHz, CDCl3): dH 1.74 (s, 6H); 7.11 (d, J ¼ 8.1 Hz, 4H); 7.33
(t, J ¼ 8.4 Hz, 4H). 13C NMR (75 MHz, CDCl3): dC 30.9, 42.7, 120.4,
128.3, 148.8, 149.0, 171.0, 173.0. HRMS (EIS-MS) m/z 525.1869 [M þ
H]þ.
NMR (300 MHz, CDCl3):
d
1.74 (s, 6H); 6.88 (d, J ¼ 8.4 Hz, 3 H); 6.99
(d, J ¼ 8.4 Hz, 4H); 7.17 (d, J ¼ 8.4 Hz, 5H). 13C NMR (75 MHz, CDCl3):
dC 29.0, 41.6, 112.7, 118.1, 120.5, 126.9, 148.1, 148.6, 151.4, 171.0, 171.9,
174.5. HRMS (EIS-MS) m/z 561.0843 [M þ H]þ. Anal. Calcl. for
C27H18Cl2N6O4: C, 57.77; H, 3.23; N, 14.97. Found: C, 57.49; H, 3.49;
N, 14.66%.
5.3.3. Oxacalixarene 3
Following the general procedure A, oxacalixarene 3 was ob-
tained as colourless solid from precyclophane 13 (0.5 g, 0.95 mmol)
and 3,5-dihydroxytoluene 15 (0.15 g, 1.05 mmol) and after eluting
the from column with EtOAc:Hexane (1:4). Yield: 22%; mp:
248e250 ꢀC; 1H NMR (300 MHz, CDCl3): dH 1.76 (s, 6H); 2.28 (s, 3H);
6.66 (s, 1H); 6.70 (s, 2H); 7.01 (d, J ¼ 8.7 Hz, 4H); 7.22 (d, J ¼ 8.4 Hz,
4H). 13C NMR (75 MHz, CDCl3): dC 21.5, 28.9, 41.5, 109.6, 118.7, 120.6,
126.7,138.3,148.0,148.7,151.0,171.0,171.9,174.4. HRMS (EIS-MS) m/
z 575.4022 [M þ H]þ. Anal. Calcl. for C28H20Cl2N6O4: C, 58.45; H,
3.50; N, 14.61. Found: C, 58.18; H, 3.72; N, 14.26%.
5.3. General procedure for the synthesis of oxacalixarenes
(procedure A)
5.3.4. Oxacalixarene 4
Following the general procedure A, oxacalixarene 4 was ob-
tained as colourless solid from precyclophane 13 (1.0 g, 1.91 mmol)
and 3,5-dihydroxymethylbenzoate 16 (0.34 g, 2.01 mmol) and after
eluting from the column with EtOAc:Hexane (1:4). Yield: 20%; mp:
230e232 ꢀC; 1H NMR (300 MHz, CDCl3): dH 1.73 (s, 6H); 4.05 (s,
To a solution of DIPEA (4.78 mmol, 2.5 equiv.) in acetone
(200 mL), precyclophane (1.91 mmol, 1.0 equiv.) and dihydroxy
derivatives (1.91 mmol, 1.0 equiv.) each in acetone (100 mL) was
separately and simultaneously added in dropwise under high
dilution condition during a period of 4 h. The reaction mixture was
further stirred for another 48 h at room temperature. The solvent
was then removed under reduced pressure and washed with water
(50 mL) to give the residue which was then extracted with EtOAc
(3 ꢁ 100 mL). The combined organic phase was washed with water
(50 mL), brine (50 mL) and dried over anhydrous Na2SO4 and the
solvent was removed under reduced pressure to give a residue,
which was purified by column chromatography on silica gel using
the eluent as mentioned under each compound.
3H); 7.01 (d, J ¼ 8.1 Hz, 5H); 7.16 (d, J ¼ 7.5 Hz, 4H); 7.61 (s, 2H). 13
C
NMR (75 MHz, CDCl3): dC 28.7, 41.4, 52.7, 116.9, 119.6, 120.7, 126.6,
130.3, 147.9, 148.6, 151.1, 170.8, 172.0, 174.8. HRMS (EIS-MS) m/z
619.0908 [M þ H]þ. Anal. Calcl. for C29H20Cl2N6O6: C, 56.23; H, 3.25;
N, 13.57. Found: C, 55.95; H, 3.44; N, 13.27%.
5.3.5. Oxacalixarene 5
Following the general procedure A, oxacalixarene 5 was ob-
tained as colourless solid from precyclophane 13 (0.58 g,
0.95 mmol) and 3,5-dihydroxyethylbenzoate 17 (0.18 g, 1.01 mmol)
and after eluting from the column with EtOAc:Hexane (1:4). Yield:
21%; mp: 238e240 ꢀC; 1H NMR (300 MHz, CDCl3): dH 1.50 (t,
J ¼ 7.2 Hz, 3H); 1.73 (s, 6 H); 4.50 (q, 2H); 7.02 (d, J ¼ 8.7 Hz, 5H);
7.15 (d, J ¼ 8.7 Hz, 4H); 7.61 (s, 2H). 13C NMR (75 MHz, CDCl3): dC
14.5, 28.7, 41.4, 61.9, 116.6, 119.5, 120.7, 126.6, 130.7, 147.9, 148.6,
151.1, 164.3, 170.8, 171.9, 174.9. HRMS (EIS-MS) m/z 633.4383 [M þ
H]þ. Anal. Calcl. for C30H22Cl2N6O6: C, 56.88; H, 3.50; N, 13.27.
Found: C, 56.65, H, 3.68; N, 12.94%.
5.3.1. Oxacalixarene 1
Following the general procedure A, oxacalixarene 1 was ob-
tained as colourless solid from precyclophane 13 (0.5 g, 0.96 mmol)
and bisphenol A 11 (0.24 g, 1.05 mmol) and after eluting from the
column with EtOAc:Hexane (1:4). Yield: 36%; mp: 270e272 ꢀC; 1H
NMR (300 MHz, CDCl3): dH 1.67 (s,12H); 7.02 (d, J ¼ 8.1 Hz, 8 H); 7.11
(d, J ¼ 8.1 Hz, 8H). 13C NMR (75 MHz, CDCl3): dC 31.4, 42.9, 120.9,
127.5, 148.4, 149.3, 171.6, 173.9. HRMS (EIS-MS) m/z 679.1611 [M þ
H]þ. Anal. Calcl. for C36H28Cl2N6O4: C, 63.63; H, 4.15; N, 12.37.
Found: C, 63.85; H, 4.39; N, 12.06%.
5.3.6. Oxacalixarene 6
Following the general procedure A, oxacalixarene 6 was ob-
tained as colourless solid from precyclophane 13 (0.8 g, 1.53 mmol)
and naphthalene-2,7-diol 18 (0.25 g, 1.53 mmol) and after eluting
from the column with EtOAc:Hexane (1:4). Yield: 25%; mp:
5.3.2. Oxacalixarene 2
Following the general procedure A, oxacalixarene 2 was ob-
tained as colourless solid from precyclophane 13 (1.0 g, 1.91 mmol)
Please cite this article in press as: Rajavelu K, Rajakumar P, Synthesis, characterization, photophysical and electrochemical properties of
triazinooxacalix[2]arenes with bisphenol A motif, Tetrahedron (2018), https://doi.org/10.1016/j.tet.2018.04.064

K. Rajavelu, P. Rajakumar / Tetrahedron xxx (2018) 1e7
7
218e220 ꢀC; 1H NMR (300 MHz, CDCl3): dH 1.56 (s, 6H); 6.95 (d,
6. Conclusion
J ¼ 7.8 Hz, 3H); 7.09 (d, J ¼ 7.5 Hz, 4H); 7.16 (d, J ¼ 7.5 Hz, 4H); 7.53
(d, J ¼ 7.5 Hz, 3H). 13C NMR (75 MHz, CDCl3): dC 32.5, 43.3, 120.4,
122.2,127.4, 127.6, 138.0,147.6, 149.9, 151.3, 171.4, 172.7,174.2. HRMS
(EIS-MS) m/z 611.4343 [M þ H]þ. Anal. Calcl. for C31H20Cl2N6O4: C,
60.89; H, 3.30; N, 13.74. Found: C, 60.65; H, 3.62; N, 13.46%.
The oxacalixarenes 1e10 with bisphenol A unit at the intra
annular junction have been successfully synthesized by aromatic
nucleophilic substitution through addition elimination process and
characterized from spectral and analytical data. The photophysical
properties show that the presence of electron donating and elec-
tron withdrawing substituents exhibit better molar absorptivity.
The oxacalixarenes 7 and 10 show better fluorescence emission
with higher lem values than the other oxacalixarenes. All the oxa-
calixarenes exhibit quasi-reversible behaviour in cyclic voltam-
metry due to presence of the electron donating and electron
5.3.7. Oxacalixarene 7
Following the general procedure A, oxacalixarene 7 was ob-
tained as colourless solid from precyclophane 13 (0.8 g, 1.53 mmol)
and (S)-Binol 19 (0.46 g, 1.60 mmol) and after eluting from the
column with EtOAc:Hexane (1:4). Yield: 24%; mp: 286e288 ꢀC; 1H
NMR (300 MHz, CDCl3): dH 1.77 (s, 6H); 6.56 (d, J ¼ 7.5 Hz, 4 H); 7.05
(d, J ¼ 7.5 Hz, 4H); 7.24 (d, J ¼ 9.3 Hz, 4H); 7.46 (d, J ¼ 8.4 Hz, 4H);
7.94 (t, J ¼ 8.4 Hz, 4H). 13C NMR (75 MHz, CDCl3): dC 28.6, 41.8,120.3,
120.7, 122.2, 125.9, 126.2, 126.6, 127.1, 128.0, 129.0, 131.5, 132.9,
146.8, 148.5, 149.0, 171.0, 172.6, 173.5. HRMS (EIS-MS) m/z 737.5889
[M þ H]þ. Anal. Calcl. for C41H26Cl2N6O4: C, 66.76; H, 3.59; N, 16.61.
Found: C, 66.49; H, 3.79; N, 16.32%.
withdrawing substituents with extensive
triazine spacer units.
p-conjugation with
Acknowledgments
The authors thank UGC, New Delhi, India, for financial support
and DST-FIST for providing NMR and mass spectral facilities to the
Department of Organic Chemistry, University of Madras and
Chennai, India. KR thanks University of Madras for University
Research Fellowship (URF) and providing infrastructure facility.
5.3.8. Oxacalixarene 8
Following the general procedure A, oxacalixarene 8 was ob-
tained as violet solid from precyclophane 13 (0.35 g, 0.66 mmol)
and methylenebinaphthol 20 (0.20 g, 0.66 mmol) and after eluting
from the column with EtOAc:Hexane (1:4). Yield: 28%; mp:
194e196 ꢀC; 1H NMR (300 MHz, CDCl3): dH 1.73 (s, 6H); 4.95 (s, 2H);
6.63 (d, J ¼ 7.8 Hz, 4H); 6.98 (d, J ¼ 6.9 Hz, 6H); 7.39 (d, J ¼ 7.5 Hz,
Appendix A. Supplementary data
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.tet.2018.04.064.
2H); 7.47 (m, 4H); 7.81 (d, J ¼ 7.5 Hz, 2H); 8.13 (d, J ¼ 8.1 Hz, 2H). 13
C
NMR (75 MHz, CDCl3): dC 24.0, 28.8, 42.0, 120.1, 120.5, 124.4, 125.4,
125.7, 126.3, 127.2, 127.7, 128.5, 131.8, 132.8, 147.1, 148.7, 149.0, 170.8,
172.4, 173.4. HRMS (EIS-MS) m/z 751.1656 [M þ H]þ. Anal. Calcl. for
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42H28Cl2N6O4: C, 67.12; H, 3.75; N, 11.80. Found: C, 66.89; H, 3.91;
N, 11.57%.
5.3.9. Oxacalixarene 9
Following the general procedure A, oxacalixarene 9 was ob-
tained as colourless solid from precyclophane 13 (1.0 g, 1.91 mmol)
and 4,40-Dimethoxy-2,20-dihydroxybenzophenone 21 (0.55 g,
2.01 mmol) and after eluting from the column with EtOAc:Hexane
(1:4). Yield: 20%; mp: 290e292 ꢀC; 1H NMR (300 MHz, CDCl3): dH
1.59 (s, 6H); 3.81 (s, 6H); 6.60 (m, 4H); 6.90 (d, J ¼ 8.4 Hz, 4H); 7.13
(t, J ¼ 8.4 Hz, 2H); 7.16 (s, 4H).13C NMR (75 MHz, CDCl3): dC 28.8,
41.9, 55.8, 107.1, 117.7, 120.6, 124.4, 127.4, 132.4, 148.5, 149.4, 151.1,
163.0, 171.5, 172.6, 173.9, 189.5. HRMS (EIS-MS) m/z 725.1310 [M þ
H]þ. Anal. Calcl. for C36H26Cl2N6O7: C, 59.60; H, 3.61; N, 11.58.
Found: C, 59.39; H, 3.79; N, 11.30%.
5.3.10. Oxacalixarene 10
Following the general procedure A, oxacalixarene 10 was ob-
tained as colourless solid from precyclophane 13 (0.8 g, 1.53 mmol)
and biphenyl-4,40-diol 22 (0.29 g, 1.59 mmol) and after eluting from
the column with EtOAc:Hexane (1:4). Yield: 22%; mp: 258e260 ꢀC;
1H NMR (300 MHz, CDCl3): dH 1.56 (s, 6H); 6.95 (d, J ¼ 8.4 Hz, 4 H);
7.09 (d, J ¼ 8.4 Hz, 4H); 7.16 (d, J ¼ 8.1 Hz, 4H); 7.53 (d, J ¼ 8.4 Hz,
4H).13C NMR (75 MHz, CDCl3): dC 32.5, 43.3, 120.4, 122.2, 127.4,
127.7, 138.0, 147.6, 149.9, 151.3, 171.4, 172.7, 174.2. HRMS (EIS-MS) m/
z 637.4716 [M þ H]þ. Anal. Calcl. for C33H22Cl2N6O4: C, 62.18; H,
3.48; N, 13.18. Found: C, 61.97; H, 3.71; N, 12.89%.
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Please cite this article in press as: Rajavelu K, Rajakumar P, Synthesis, characterization, photophysical and electrochemical properties of
triazinooxacalix[2]arenes with bisphenol A motif, Tetrahedron (2018), https://doi.org/10.1016/j.tet.2018.04.064