Synthesis of thia-calix[4]arene hydroxamic acids by microwave irradiation

Article abstract of DOI:10.1080/00397910802139429

Thia-calix[4]arene hydroxamic acids have been synthesized by partial reduction of nitro-thia-calix[4]arenes with hydrazine hydrate, Rn/Ni, and their coupling with benzoyl chloride under the influence of microwave irradiation with 90-95% yield and 3-6 min

Full text of DOI:10.1080/00397910802139429

This article was downloaded by: [University of Illinois Chicago]
On: 16 April 2013, At: 13:38
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic
Organic Chemistry
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Synthesis of Thia-calix[4]arene
Hydroxamic Acids by
Microwave Irradiation
Y. K. Agrawal a & J. P. Pancholi a
a Analytical Laboratory, Institute of Pharmacy and
Faculty of Science, Nirma University of Science and
Technology, Ahmedabad, India
Version of record first published: 11 Jul 2008.
To cite this article: Y. K. Agrawal & J. P. Pancholi (2008): Synthesis of Thia-
calix[4]arene Hydroxamic Acids by Microwave Irradiation, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry,
38:14, 2446-2458
To link to this article: http://dx.doi.org/10.1080/00397910802139429
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-
and-conditions
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden.
The publisher does not give any warranty express or implied or make any
representation that the contents will be complete or accurate or up to

date. The accuracy of any instructions, formulae, and drug doses should be
independently verified with primary sources. The publisher shall not be liable
for any loss, actions, claims, proceedings, demand, or costs or damages
whatsoever or howsoever caused arising directly or indirectly in connection
with or arising out of the use of this material.

Synthetic Communications1, 38: 2446–2458, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802139429
Synthesis of Thia-calix[4]arene Hydroxamic
Acids by Microwave Irradiation
Y. K. Agrawal and J. P. Pancholi
Analytical Laboratory, Institute of Pharmacy and Faculty of Science,
Nirma University of Science and Technology, Ahmedabad, India
Abstract: Thia-calix[4]arene hydroxamic acids have been synthesized by partial
reduction of nitro-thia-calix[4]arenes with hydrazine hydrate, Rn=Ni, and their
coupling with benzoyl chloride under the influence of microwave irradiation with
90–95% yield and 3–6 min reaction time.
Keywords: Microwave irradiation; thia-calix[4]arene
INTRODUCTION
Thiacalixarenes are a new class of calixarene with sulfur atoms[1] in place
of the usual methylene. Their chemical modification leads to a great
variety of derivatives with modified solubility, conformational mobility,
and complexing abilities. These compounds have emerging applications
as sensors,[2] catalysts,[3] stationary phases for gas chromatography,[4]
chelating adsorbents for heavy metal ions,[5] highly selective means for
the luminescence determination of terbium,[6] and components in the
construction of ionsensors.[7] In recent decades, microwave technology
has taken an important place in chemical laboratory practice as a very
effective, nonpolluting method for activating reactions. The use of micro-
waves provide fast heating of the chemicals, thus enhancing reaction rates
and significantly shortening preparation time.[8]
Received January 16, 2008
Address correspondence to Y. K. Agrawal, Institute of Pharmacy, Nirma Uni-
versity of Science and Technology, Sarkhej-Gandhinagar Highway, Ahmdabad
382 481, India. E-mail: drykagrawal@yahoo.com
2446

Thia-calix[4]arene Hydroxamic Acids
2447
Herein, we report microwave-irradiated synthesis of thia-calix[4]-
arene, biphenylthia-calix[4]arene, and their nitro and hydroxamic acid
derivatives for the first time.
p-tert-Butylthiacalix[4]arene (3) is conveniently synthesized using
p-tert-butylphenol (1), elemental sulfur S8 (2), and NaOH in tetraethylene
glycol dimethyl ether (TEGDME).[9] As nitration of p-tert-butylthiaca-
lix[4]arene cannot be carried out by reaction conditions normally used
in classical calixarene chemistry, which lead to only the oxidation of
the bridging sulphur atoms.[10] we have synthesized it using KNO3=AlCl3
in the presence of TEGDME[11] followed by de-t-butylation[12] to get
compound (5), which is partially reduced to obtain the corresponding
hydroxylamine (6), whose condensation with benzoyl chloride yields
thiacalix[4]arene hydroxamic acid (TC4HA)[13] (7) (Fig. 1).
Thia-biphenylcalix[4]arene (9) has been synthesized by 9 h of reflux
of biphenyl-4-ol, S8. diphenylether (DPE), and NaOH,[14] which is
nitrated with KNO3=AlCl3 in the presence of TEGDME to obtain
compound 10. Compound 10 is partially reduced with hydrazin hydrate
in the presence of Raney Ni (W-4) to give the corresponding hydroxyl-
amine (11). Compound 11 is reacted with benzoyl chloride, which gives
thiabiphenyl-calix[4]arene hydroxamic acid (TBPC4HA) (12) (Fig. 2).
Compound 16 has been synthesized to investigate how its ion extrac-
tion properties changed compared to methylene-bridged calixcrowns.
Compound 9 was refluxed in the presence of ditosylate of tetraethylenegly-
col, K2CO3, and CH3CN for 3 days to obtain thiacalix[4]monocrown[15]
(13), whose nitration with KNO3=AlCl3 in the presence of TEGDME
gives compound 14, which is partially reduced with Raney Ni and
hydyrazin hydrate to the corresponding hydroxylamine (15). Further,
compound 15 is condensed with benzoyl chloride to form thiabiphenyl-
calix[4]monocrown hydroxamic acid (TBPC4MCHA) (16) (Fig. 3).
These conventional syntheses have three major disadvantages: longer
reaction time, large amount of solvents (which is not eco friendly), and very
poor yield. To overcome these, we have developed a synthesis under micro-
wave irradiation in the absence of solvent. The reaction time is 3–6 min
with 90% to 95% yield depending on the compounds to be synthesized.
The structural identification and composition of newly synthesized
thia-calix[4]arene hydroxamic acids (TCHAs) have been confirmed by
Fourier transform infrared spectrometer (FT-IR), 1H NMR, 13C
NMR, and C, H, N analysis.
The FT-IR (KBr) spectrum of compounds 7, 12, and 16 displayed three
sharp bands at 920, 1600, and 3300cmꢀ1. The band at 3300cmꢀ1 is due to O-
H stretching vibration. It is known that O-H stretching vibration bands
occur at around 3600 cmꢀ1, but this band shifts to lower frequencies because
hydrogen bonding. Particularly in hydroxamic acids, the ꢀOH group is

2448
Y. K. Agrawal and J. P. Pancholi
Figure 1. Synthetic scheme for compound 7.

Thia-calix[4]arene Hydroxamic Acids
2449
Figure 2. Synthetic scheme for compound 12.
placed very close to the polar carbonyl C O group. The band at 1600 cmꢀ1 is
=
=
=
assigned to the C O of the hydroxamic acid group. The position of the C O
stretching band is highly influenced by the surrounding groups and mostly
shifted to lower frequencies. Thus hydrogen bonding again lowers the

2450
Y. K. Agrawal and J. P. Pancholi
Figure 3. Synthetic scheme for compound 16.
frequencies. N-O stretching gives a sharp band at 920cmꢀ1. In addition,
compounds 7, 12, and 16 give sharp bands at 680 cmꢀ1 for C-S stretching
vibrations and a band at 1370 cmꢀ1 for NO2 stretching vibrations.
1
The H NMR dimethyl sulfoxide (DMSO) spectrum of compounds
7, 12, and 16 shows five singlets at 7.0–7.5 ppm for aromatic protons,
8.05 and 8.3 ppm for hydroxyl groups, and 8.5 ppm for hydroxamic acid
groups. In addition, compound 7 shows a singlet at 10.0 ppm for the
hydroxyl group. Compound 12 displayed multiples at 8.0 ppm for

Thia-calix[4]arene Hydroxamic Acids
2451
aromatic hydrogens, and compound 16 shows a singlet at 3.01 ppm for
methylene of crown ether.
The 13C NMR (DMSO) spectrum of compounds 7, 12, and 16 dis-
played singlets at 120–130 and 140–160 ppm for aromatic carbons and
a singlet at 165–175 ppm for ketone groups. Compound 7 shows a singlet
at 167.69 for the CO-N(OH) group. Compound 12 shows a singlet at
146.6 ppm for the CH-N group, and compound 16 shows a triplet at
73.8 ppm for methylene of crown moieties.
The presence of a hydroxamic acid group is proved by the results
obtained and also from elemental analysis carried out in our laboratory.
EXPERIMENTAL
Melting points were uncorrected. FT-IR spectra were recorded on Jasco
FT-IR 6100 spectrometer. 1H NMR and 13C NMR spectra were recorded
on a Bruker Avance II spectrometer operating at 400 MHz in dimethyl
sulfoxide (DMSO) with trimethyl selane (TMS) as an internal standard.
An elemental analysis has been carried out in the analytical laboratory
of the institute. The de-tert-butylation and nitration of P-tert-butyl
thiacalix[4]arene have been carried out according to reported proce-
dures. Moreover, biphenyl thiacalix[4]arene monocrown and biphenyl
thia-calix[4]arene were also prepared from reported procedures.
Synthesis of Compound 3
Conventional Method
A mixture of t-butyl phenol (20.0 g, 0.1333 M), elemental sulfur S8
(8.848 g, 0.2765 M), and TEGDME (6 ml) was stirred under inert nitro-
gen to remove the evolving H2S gas. Solid NaOH (2.64 g, 0.0660 M)
was added to this yellow solution, and the mixture was maintained for
2 h at a temperature of 145–145 ꢁC. During this time, the reaction mixture
changed from yellowish to red and finally to almost a black color. The
temperature was elevated to 170 ꢁC over the next 30 min and maintained
at 170 ꢁC–180 ꢁC for another 2 h. The reaction mixture was warmed up
to 230 ꢁC over 1 h and maintained at this temperature for a further 3 h.
During this time, the reaction mixture is converted to a black slurry. It
was cooled to room temperature, diluted with CHCl3, and acidified by
2 M HCl. The organic fraction was collected and washed with water,
and chloroform was removed in a rotary evaporator. We got a liquid
light-brown color residue. The final off-white compound 7 is obtained
by stirring this residue overnight in ethyl acetate (100 ml). Mp: 318 ꢁC.

2452
Y. K. Agrawal and J. P. Pancholi
Microwave-Assisted Method
We took a mixture of t-butylphenol (2.0 g, 0.01333 M), elemental sulfur
S8 (0.8848 g, 0.02765 M), and TEGDME (1 ml) in a 50-ml beaker and
placed it in a microwave oven for 1 min at 60% output. Then we added
NaOH (0.264 g, 0.0066 M) and again put it in the oven for 2 min at 60%
output to get a blackish slurry. We added 20 ml of chloroform and 2 M
HCl, separated the organic layer, and allowed it to concentrate. Stirring
it in ethyl acetate gave an off-white compound 7. Mp: 318 ꢁC.
Synthesis of Compound 5
Conventional Method
TEGDME (6.0 ml, 0.0269 M) and KNO3 (2.5 g, 0.0247 M) were added to
a suspension of tetrahydroxythiacalix[4]arene (2.0 g, 0.0040 M) in CH2Cl2
(50 ml). This reaction mixture was stirred for 15 to 20 min at room
temperature then cooled to 0 ꢁC. AlCl3 (3.0 g, 22.5 M) was added to this
suspension. Slowly, a colorless mixture became orange; we refluxed it
for another 22 h. We cooled the mixture at room temperature and added
distilled water (50–70 ml) to hydrolyze it. The organic layer was
further washed with water until it attained neutral pH; we separated it
from aqueous media, dried it over Na2SO4, and evaporated the orga-
nic layer in a rotary evaporator to get slurry, from which compound 5
was precipitated out with diethyl ether in 60% yield. Mp: 260–262 ꢁC.
Microwave-Assisted Method
Tetrahydroxythiacalix[4]arene (2.0 g, 0.0040 M) was added to a suspension
of TEGDME (6.0 ml, 0.0269 M) and KNO3 (2.5 g, 0.0247 M) in a 50-ml
beaker. It was heated at 60% output for 1.5 min and cooled to 0 ꢁC, then
AlCl3 (3.0 g, 0.0225 M) was added. The mixture was heated 2 min at
60% output to obtain a brown solution. Upon isolation of it from diethy-
lether, we got a yellowish compound 5 at 90% of yield. Mp: 260–262 ꢁC.
Synthesis of Compound 7
Conventional Method
In a 250-ml flat- bottomed flask equipped with magnetic stirrer, we added
nitro-thiacalix[4]arene (1.2 g, 0.00177 M) in 15 ml of dioxane and Rn-Ni
(0.6–0.8 g), then cooled the mixture to 0 ꢁC. NHNH2(1.0 ml, 0.0196 M)
was added dropwise at 0 ꢁC over 30 min. It was stirred for more 1 h then

Thia-calix[4]arene Hydroxamic Acids
2453
filtered to give a hydroxyl amine. This solution in situ was used for
hydroxamic acid preparation. It was kept below 0 ꢁC and benzoyl chlor-
ide (0.5 ml, 0.00427 M) was added. The temperature of 0 ꢁC was main-
tained. An aqueous suspension of sodium carbonate was added and
stired for more 30 min while it warmed to room temperature. After filter-
ing the solids, we obtained 0.80 g of cream-colored compound, thiacalil-
x[4]arene hydroxamic acid. Mp: 110–115 ꢁC.
Microwave-Assisted Method
Nitro-thiacalix[4]arene (1.2 g, 0.00177 M), Rn-Ni (0.6–0.8 g), and
NHNH2 (1.0 ml, 0.0196 M) were placed in a domestic Kenstar microwave
oven at 0% output for 3.5 min to obtain hydroxyl amine, which was in
situ condensed with benzoyl chloride (0.5 ml, 0.00427 M) in the presence
of an aqueous suspension of Na2CO3 in the oven at 0% output for 2 min
to obtain compound 7 with 89% yield. Mp: 110–115 ꢁC.
Data
TC4HA (3): Yield 89%, mp 110–115 ꢁC, IR (KBr): n ¼ 3300 cmꢀ1 (OH),
ꢀ1
1600 cmꢀ1 (C O), 1370 cm
(-NO2-), 680 cmꢀ1 (C-S). 1H NMR
=
(DMSO, d): 10 (s, 4H, OH), 7.57 (m, Ar-H, 8H, J ¼ 6.84), 8.05 (t,
N-OH, 2H). 13C NMR (DMSO, d): 127.3 (s, 4C, Ar-S-Ar), 130 (t,
=
Ar-H), 132.2 (m, 2C, ArC-NO2), 167 (s, 2C, C O). Anal. calcd. for
C38H24N4O12S4: C, 53.26; H, 2.82; N, 6.54; S, 14.97. Found: C, 53.25;
H, 2.83; N, 6.57; S, 14.94.
Synthesis of Compound 9
Conventional Method
A mixture of biphenyl-4-ol (10 g, 0.0588 M), elemental sulfur S8 (3.64 g,
0.1139 M), and diphenyl ether (8 ml) was stirred under N2 to remove
evolving H2S gas. Solid NaOH (1.143 g, 0.0285 M) was added to this yel-
lowish solution, and the mixture was maintained for 2 h at 145–145 ꢁC.
During this time, the reaction mixture changed from yellowish to red
and finally to almost a black color. Temperature was elevated to
170 ꢁC over the next 30 min and maintained at 170–180 ꢁC for another
2 h. The reaction mixture was then warmed up to 230 ꢁC over 1 h and
maintained at this temperature for a further 3 h. During this time, the
reaction mixture became thick, and a precipitate appeared, accompanied
by color change from black to red to yellow.

2454
Y. K. Agrawal and J. P. Pancholi
The reaction mixture was cooled to room temperature, diluted with
chloroform, and acidified by HCl. The organic fraction was collected and
washed with water, and chloroform was removed in a rotary evaporator.
We got a liquid light-brown residue. To this, ethyl acetate (100ml) was
added, and the mixture was stirred overnight. The precipitate was filtered
to give compound 9 as a final product (almost 2.20g). Mp: >350 ꢁC.
Microwave-Assisted Method
A mixture of biphenyl-4-ol (1.0 g, 0.0588 M), elemental sulfur S8 (3.64 g,
0.1139 M), and DPE (1 ml) in a 50-ml beaker was placed in a microwave
oven for 1 min at 60% output. NaOH (1.143 g, 0.0285 M) was added, and
the mixture was put in the oven for a further 2 min at 60% output. We
got blackish slurry. Chloroform (20 ml) and 2 M HCl were added. The
organic layer was separated and allowed it to concentrate. After stirring
in ethylacetate, we obtained compound 9. Mp: >350 ꢁC.
Synthesis of Compound 10
Conventional Method
TEGDME (3.7 ml, 0.0165 M) and KNO3 (1.54 g, 0.0152 M) were added
to a suspension of biphenylthia-calix[4]arene (BPTC) (2.0 g, 0.0024 M)
in CH2Cl2 (50 ml). This reaction mixture was stirred for 15 to 20 min at
room temperature, then cooled to 0 ꢁC. AlCl3 (1.85 g, 0.0138 M) was
added to the suspension. Slowly the colorless mixture became orange;
it was refluxed for 22 h. This mixture cooled to room temperature, and
distilled water (50–70 ml) was added to hydrolyze it. The organic layer
was further washed with water until it attained neutral pH then separated
from the aqueous media and dried over Na2SO4. The organic layer was
evaporated in a rotary evaporator to get slurry, from which product 10
was precipitated out with diethyl ether in 65% yield.
Microwave-Assisted Method
BPTC (2.0 g, 0.0024 M) was added to a suspension of TEGDME (3.7 ml,
0.0165 M) and KNO3 (1.54 g, 0.0152 M) in a 50-ml beaker. This mixture
was heated at 60% output for 1.5 min, then cooled to 0 ꢁC. AlCl3 (1.85 g,
0.0138 M) was added heated up to 2 min at 60% output. We got a brown
solution. Upon isolation of it from diethyl ether, we got a yellowish
compound 10 at 90–95% yield.

Thia-calix[4]arene Hydroxamic Acids
2455
Synthesis of Compound 12
Conventional Method
In a 250-ml flat-bottomed flask equipped with magnetic stirrer, nitro-
BPTC (1.0 g, 0.0010 M) in 15 ml of dioxane and Rn-Ni (0.8–1.0 g) were
added and cooled to 0 ꢁC. Then NHNH2 (0.7 ml, 0.0137 M) was added
dropwise at 0 ꢁC order 30 min. It was stirred for more than 1 h, then fil-
tered to get a hydroxyl amine. This solution in situ is used for hydroxamic
acid preparation. Again we brought the temperature of this solution
below 0 ꢁC and added benzoyl chloride (0.3 ml, 0.0025 M). It was stirred
for 30 min and allowed it to warm to room temperature. After filtering
the solids, we got 0.60 g of yellow-colored compound 12.
Microwave-Assisted Method
Nitro-BPTC (1.0 g, 0.0010 M), Rn-Ni (0.8–1 g), and NHNH2 (0.7 ml,
0.0137 M) were placed in a domestic Kenstar microwave oven at 0%
output for 3.5 min. The hydroxyl amine was condensed with benzoyl
chloride (0.3 ml, 0.0025 M) in the presence of an aqueous suspension of
sodium carbonate in the oven at 0% output for 3 min to obtain com-
pound 12 in 91% yield.
Data
BPTC4HA (12): Yield 91%, mp 220–225 ꢁC, IR (KBr): n ¼ 3300 cmꢀ1
ꢀ1
1
(OH), 1600 cmꢀ1 (C O), 1370 cm (-NO2-), 680 cmꢀ1 (C-S). H NMR
(DMSO, d): 9.66 (s, 4H, OH), 7.99 (m, Ar-H, 8H, J ¼ 4), 7.65 (m,
Ar-H, 20H), 8.0 (t, N-OH, 2H). 13C NMR (DMSO, d): 127.3
(s, 4 C, Ar-S-Ar), 130 (t, Ar-H), 132.2 (m, 2 C, ArC-NO2), 167 (s, 2C,
=
=
C O). Anal. calcd. for C62H40N4O12S4: C, 64.13; H, 3.47; N, 4.82; S,
11.05. Found: C, 64.13; H, 3.45; N, 4.83; S, 11.06.
Synthesis of Compound 14
Conventional Method
TEGDME (3.097 ml, 0.0138 M) and KNO3 (1.28 g, 0.01273 M) were
added to the suspension of TBPCMC (2.0 g, 0.0020 M) in CH2Cl2
(50 ml). This reaction mixture was stirred for 15 to 20 min at room tem-
perature then cooled to 0 ꢁC. AlCl3 (1.54 g, 0.0116 M) was added to the

2456
Y. K. Agrawal and J. P. Pancholi
suspension. Slowly, a colorless mixture became orange. It was refluxed
for 22 h and allowed to cool to room temperature. Distilled water (50–
70 ml) was added to hydrolyze it. The organic layer was further washed
with water until it attained neutral pH, separated from the aqueous
media, and dried over Na2SO4. The organic layer was evaporated in a
rotary evaporator to get a slurry, from which product 14 was precipitated
out with diethyl ether in 60% yield.
Microwave-Assisted Method
BPTCMC (2.0 g, 0.0020 M) was added to a suspension of TEGDME
(3.097 ml, 0.0138 M) and KNO3 (1.28 g, 0.0127 M) in a 50-ml beaker
and heated at 60% output for 1.5 min then cooled to 0ꢁC. AlCl3
(1.54 g, 0.0116 M) was added, and the mixture was heated up to 2 min
at 60% output to get a brown solution. Upon isolation of it from diethyl
ether, we got compound 14 in 92% yield.
Synthesis of Compound 16
Conventional Method
In a 250-ml flat-bottomed flask equipped with magnetic stirrer, nitro-
BPTCMC (1.0 g, 0.0008 M) in 15 ml of dioxane and Rn-Ni (0.8–1.0 g)
were added and cooled to 0 ꢁC. Then NHNH2 (0.60 ml, 0.012 M) was
added dropwise at 0 ꢁC over 30 min and stirred for more 1 h. The solu-
tion was filtered to get a hydroxyl amine. This solution in situ was
used for hydroxamic acid preparation: again the solution was cooled
below 0 ꢁC, and benzoyl chloride (0.2 ml, 0.0017 M) was added. It was
stirred for more than 30 min, then allowed to attain room tem-
perature. After filtering the solids, we got 0.62 g of yellow-colored
compound 16.
Microwave-Assisted Method
Nitro-BPTCMC (1.0 g, 0.0008 M), Rn-Ni (0.8–1 g), and NHNH2
(0.60 ml, 0.012 M) were placed in a domestic Kenstar microwave oven
at 0% output for 3.5 min. The hydroxyl amine was condensed with ben-
zoyl chloride (0.2 ml, 0.00170 M) in the presence of an aqueous suspen-
sion of sodium carbonate in an oven at 0% output for 3 min to obtain
compound 16 in 90% yield.

Thia-calix[4]arene Hydroxamic Acids
2457
Data
BPTCMC4HA (16): Yield 90%, mp > 300 ꢁC, IR (KBr): n ¼ 3300 cmꢀ1
ꢀ1
1
(OH), 1600 cmꢀ1 (C O), 1370 cm (-NO2-), 680 cmꢀ1 (C-S). H NMR
(DMSO, d): 7.34 (s, Ar-H, 8H, J ¼ 8.9), 8.3 (t, N-OH, 2H), 3.010 (t,
-OCH2-, 8H). 13C NMR (DMSO, d): 73.8 (t, 8C, -OCH2-), 125.5
=
=
(s, 4C, Ar-S-Ar), 133 (m, 2C, ArC-NO2), 170 (s, 2C, C O). Anal. calcd.
for C70H54N4O15S4: C, 63.72; H, 4.13; N, 4.25; S, 9.72. Found: C, 63.75;
H. 4.12; N, 4.22; S, 9.71.
REFERENCES
1. Lhotak, P. Chemistry of thiacalixarenes, Eur. J. Org. Chem. 2004, 1675.
2. Higuchi, Y.; Narita, M.; Nimi, T.; Ogawa, N.; Hamada, F.; Kumagai, H.;
Iki, N.; Miyano, S.; Kabuto, C. Fluorescent chemo-sensor for metal cations
based on thiacalix[4]arenes modified with dansyl moieties at the lower rim,
Tetrahedron 2000, 56, 4659.
3. Morohashi, N.; Hattori, T.; Yokomakura, K.; Kabuto, C.; Miyano, S.
Dinuclear titanium(IV) complex of p-tert-butylthiacalix[4]arene as a novel
bidentate lewis acid catalyst, Tetrahedron Lett. 2002, 43, 7769.
4. (a) Iki, N.; Narumi, F.; Suzuki, T.; Sugawara, A.; Miyano, S. A new chiral
stationary phase for gas chromatography by use of a chiral thiacalix[4]arene
derivative, Chem. Lett. 1998, 1065; (b) Narumi, F.; Iki, N.; Suzuki, T.;
Onodera, T.; Miyano, S. Enantiomer 2000, 5, 83.
5. Matsumiya, H.; Masai, H.; Terazono, Y.; Iki, N.; Myano, S. Chelating
adsorbent for heavy metal ions prepared by loading anion-exchange resin
with thia-calix[4]arene tetrasulfonate, Bull. Chem. Soc. Jpn. 2003, 76, 133.
6. Horiuchi, T.; Iki, N.; Oka, H.; Miyano, S. Highly selective luminescence
determination of terbium at the sub-ppb level with sulfonylcalix[4]arene-p-
tetrasulfonate, Bull. Chem. Soc. Jpn. 2002, 75, 2615.
7. Zairi, S.; Martelet, C.; Renault, N. J.; Vocanson, E.; Lamartine, R.; Mgaieth,
R.; Maaref, H.; Gamoudi, M. p-type porous-silicon transducer for cation
detection: Effect of the porosity, pore morphology, temperature and ion
valency on the sensor response and generalisation of the nernst equation,
Appl. Phys. A 2001, 73, 585.
8. Hedidi, M.; Hamdi, S. M.; Mazari, T.; Boutemeur, B.; Rabia, C.; Chemat,
F.; Hamdi, M. Microwave-assisted synthesis of calix[4]resorcinarenes, Tetra-
hedron 2006, 62, 5652.
9. Kumagai, H.; Hasegawa, M.; Miyanari, S.; Sugawa, Y.; Sato, Y.; Hori, T.;
Ueda, S.; Kamiyama, H.; Miyano, S. Facile synthesis of p-tert-butylthiaca-
lix[4]arene by the reaction of p-tert-butylphenol with elemental sulfur in the
presence of a base, Tetrahedron Lett. 1997, 38, 3971.
10. Higuchi, Y.; Narita, M.; Niimi, T.; Ogawa, N.; Hamada, F.; Kumagai, H.;
Iki, N.; Miyanoc, S.; Kabutod, C. Fluorescent chemo-Sensor for metal

2458
Y. K. Agrawal and J. P. Pancholi
cations based on thiacalix[4]arenes modified with dansyl moieties at the lower
rim, Tetrahedron 2000, 56, 4659.
11. Lhotak, P.; Moravek, J.; Stibor, I. Diazo Coupling: an alternative method for
the upper rim amination of thiacalix[4]arches, Tetrahedron Lett. 2002, 43,
3665.
12. Desroches, C.; Parola, S.; Vocanson, F.; Perrin, M.; Lamartine, R.; Toffee,
J. L.; Bouixa, J. Nitration of thiacalix[4]arene using nitrosium nitrate com-
plexes: Synthesis and characterization of tetranitro, tetraamino and tetra-(4
pyridylimino) tetrahydroxythiacalix[4]arene, New J. Chem. 2002, 26, 651.
13. Agrwal, Y. K.; Bhatt, S. K. Catalytic approach for the synthesis of bis-calix-
arenes, Synth. Commun. 2007, 37, 551.
14. Lhotak, P.; Mejkal, S.; Stibor, I.; Havlicek, J.; Tkadlecova, M.; Petrickova,
H. Synthesis of a deep-cavity thiacalix[4]arene, Tetrahedron Lett. 2003, 44,
8093.
15. Kim, J. S.; Lee, W. K.; Sim, W.; Ko, J. W.; Cho, M. H.; Ra, D. Y.; Kim, J.
W. Calix[4]arenes bridged with two different crown ether loops: Influence of
crown size on metal ion recognition, J. Inclusion Phenom. Macrocyc. Chem.
2000, 37, 359.