Selective oxidation of thiacalix[4]arenes to the sulfinyl and sulfonyl counterparts and their complexation abilities toward metal ions as studied by solvent extraction

Article abstract of DOI:10.1016/S0040-4020(01)00482-3

Practical methods for the synthesis of sulfinyl-(5,6) and sulfonylcalix[4]arenes (7,8) were provided by the selective oxidation of thiacalix[4]arenes (3,4) with controlled amounts of an oxidant such as NaBO₃ or hydrogen peroxide under mild conditions. The coordination ability of thiacalix[4]arene 4 and the sulfinyl and sulfonyl analogs (6,8) toward a wide variety of metal ions was investigated by solvent extraction and compared to that of the conventional methylene-bridged calix[4]arene 2. It was shown that the metal-ion selectivities of the sulfur-containing ligands 4, 6, and 8 were controlled by the oxidation state of the bridging sulfur moiety, which was best understood based on the hard and soft acid-base (HSAB) principle by assuming the critical role of the bridging groups in coordination to the metal center. Thus, 4 preferred soft metal ions by binding with S, while 8 did hard ones by ligating with sulfonyl O in addition to the adjacent two phenoxide oxygens, respectively. In good accordance with this hypothesis, 6 could bind to both hard and soft metal ions by using sulfinyl O and S, respectively. These made sharp contrast to the parent methylene-bridged 2, which could not essentially extract any metal ions at all, lacking lone pair electrons on the methylene bridge for coordination.

Full text of DOI:10.1016/S0040-4020(01)00482-3

TETRAHEDRON
Pergamon
Tetrahedron 57 '2001) 5557±5563
Selective oxidation of thiacalix[4]arenes to the sul®nyl
and sulfonyl counterparts and their complexation abilities
toward metal ions as studied by solvent extraction
q
p
Naoya Morohashi, Nobuhiko Iki, Atsushi Sugawara and Sotaro Miyano
p
Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 07,
Aoba-ku, Sendai 980-8579, Japan
Received 30 March 2001; accepted 1 May 2001
AbstractÐPractical methods for the synthesis of sul®nyl-'5,6) and sulfonylcalix[4]arenes '7,8) were provided by the selective oxidation of
thiacalix[4]arenes '3,4) with controlled amounts of an oxidant such as NaBO or hydrogen peroxide under mild conditions. The coordination
3
ability of thiacalix[4]arene 4 and the sul®nyl and sulfonyl analogs '6,8) toward a wide variety of metal ions was investigated by solvent
extraction and compared to that of the conventional methylene-bridged calix[4]arene 2. It was shown that the metal-ion selectivities of the
sulfur-containing ligands 4, 6, and 8 were controlled by the oxidation state of the bridging sulfur moiety, which was best understood based on
the hard and soft acid±base 'HSAB) principle by assuming the critical role of the bridging groups in coordination to the metal center. Thus, 4
preferred soft metal ions by binding with S, while 8 did hard ones by ligating with sulfonyl O in addition to the adjacent two phenoxide
oxygens, respectively. In good accordance with this hypothesis, 6 could bind to both hard and soft metal ions by using sul®nyl O and S,
respectively. These made sharp contrast to the parent methylene-bridged 2, which could not essentially extract any metal ions at all, lacking
lone pair electrons on the methylene bridge for coordination. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
Si'CH ) , by stepwise reaction of p-tert-butylmethoxy-
3 2
benzene and dichlorodimethylsilane followed by cycliza-
1
4
In molecular recognition and supramolecular chemistry,
calixarenes 'e.g. 1, 2, Scheme 1) play unique roles as
tion '13% yield). However, these works were seemingly
only limited to the synthesis and study on the physico-
chemical properties of the hetero-calixarenes themselves,
as the synthetic dif®culty may have had prevented their
application to molecular receptors.
2
3
synthetic receptors. For example, metal binding abilities
of calixarene-based receptors have been successfully
applied to extractants, chromogenic sensors, ¯uorometric
4
5
6
sensors, ionophores for ion-selective electrodes and ®eld
7
8
effect transistors, and luminescence labeling reagents.
9
Recently, we reported a facile synthesis of 3 by base-
catalyzed condensation of p-tert-butylphenol and elemental
sulfur '54% yield). The ready availability of 3 in sub-
stantial quantities has allowed us to investigate and develop
its functions. As a remarkable result of the replacement of
Undoubtedly, these applications rely on the feasibility of
the calixarene platform to be variously designed by intro-
ducing proper ligating functional groups via etheri®cation
1
5
1
0
16
of the phenolic oxygens 'lower rim) and/or substitution of
1
1
the p-position 'upper rim). Replacement of the methylene
bridges of the conventional calixarenes by hetero atoms
should be an alternative resort to construct a calixarene-
type receptor, which, however, has very rarely been prac-
ticed due to the synthetic dif®culty. As one of such trials,
Sone et al. ®rst synthesized p-tert-butylthiacalix[4]arene '3)
by acid catalyzed cyclization of an acyclic tetramer '4%
XˆCH
by S, 3 can extract transition metal ions such as
2
Co , Cu and Zn quantitatively from aqueous phase
2
1
21
21
1
2,13
yield).
K oÈ nig et al. synthesized p-tert-butylsilacalix[4]-
arene-tetramethyl ether, in which the linking units 'X) are
q
See Ref. 1.
Keywords: calixarenes; complexation; sul®des; oxidation.
Corresponding authors. Tel./fax: 181-22-217-7264;
e-mail: iki@orgsynth.che.tohoku.ac.jp;
miyano@orgsynth.che.tohoku.ac.jp
p
t
Scheme 1. Structures of calix[4]arenes. Oct denotes 1,1,3,3-tetramethyl-
butyl group.
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020'01)00482-3

5558
N. Morohashi et al. / Tetrahedron 57 ꢀ2001) 5557±5563
Scheme 4. Four possible stereoisomers of sul®nylcalix[4]arene by combi-
nation of con®guration of four SvO groups. Abbreviations ccc, cct, ctc,
and ttt stand for cis±cis±cis, cis±cis±trans, cis±trans±cis, and trans±
trans±trans, respectively. Conformational isomers by orientation of phenyl
groups are omitted for clarity.
Scheme 2. Oxidation of bridging sulfur in thiacalix[4]arenes.
commonly available to elucidate the role of the bridging
groups X 'ˆCH , S, SO, and SO ).
2
2
into organic phase. On the other hand, 1 could not extract
them at all under the same conditions, clearly indicating the
important role of the bridging entity X in the metal extrac-
2. Results and discussion
1
7
tion.
2.1. Syntheses of sul®nyl- and sulfonylcalix[4]arenes
Soon after the synthesis of thiacalix[4]arenes 3 and 4, we
realized that the bridging epithio function would provide the
base for various transformations which could not be attained
by the conventional methylene-bridged calixarenes. In this
1
As was reported brie¯y in the previous communication, all
four epithio groups of thiacalix[4]arene 3 were readily
oxidized to give the sul®nyl or sulfonyl counterparts
'Scheme 2). Thus, heating a mixture of thiacalix[4]arene 3
1
context, we reported in a previous communication that
controlled oxidation of thiacalix[4]arene '3,4) affords prac-
tical routes to the synthesis of sul®nyl-'5,6) and sulfonyl-
calix[4]arenes '7,8). Also reported were the intrinsic metal
ion selectivities of these sulfur containing calix[4]arene
analogs, recon®rming the importance of the bridging
entities as evidenced by solvent extraction studies; 3
preferred transition metal ions, while 8 liked alkaline
earth metal ions, and quite interestingly, 5 could bind to
both transition and alkaline earth metals. These make
sharp contrast to the common understanding that methyl-
ene-bridged 1 could not bind to any of them in solvent
extraction systems.
and a 2.2-fold excess of NaBO as oxidizing agent in
3
CH COOH±CHCl gave the corresponding sulfonyl analog
3
3
7 in an excellent yield. Hydrogen peroxide could also be
used as the oxidant 'see Section 4). On the other hand,
1
8
reduction of the amount of NaBO to a 1.1 M equivalent
3
enabled the isolation of sul®nylcalix[4]arene 5 in moderate
but acceptable yield, the reaction mixture of which
seemingly contained calixarenes with variously oxidized
sulfur bridges that were eventually end in the sulfonyl
derivative 7.
It has been shown by X-ray crystallography that 1 and 3
while 5 and
It should
1
9,15b
adopt cone conformation in the solid state,
7 have 1,3-altenate conformation 'Scheme 3).
1
8,20
Needless to say, the binding property of host molecules to
various kinds of metal ions is an indispensable information
to design molecular receptors and functional devices. The
aims of this paper are ®rstly to describe the details of the
syntheses of sul®nyl-'5,6) and sulfonyl-'7,8) analogs of
thiacalix[4]arenes '3,4), and secondly to report the results
of a comprehensive study on the binding ability of calix[4]-
arenes 2, 4, 6, and 8 to a quite wide range of metal ions
be noted that sul®nylcalix[4]arene 'e.g. 5) has theoretically
four possible stereoisomers depending on the disposition of
the four SO groups, even if the ¯ip-¯op motion of the phenol
units is taken into account 'Scheme 4). The oxidation of
thiacalix[4]arene 3, however, allowed the isolation of 5, in
which the four SO groups are arranged in a trans±trans±
trans 'all-trans) con®guration in regard to any of the two
adjacent SO pairs. The preferential formation of this par-
ticular stereoisomer among the four may, at least partly, be
ascribed to the least electronic repulsion brought about by
2
1
the highly dipolar SO groups.
From the view point of solubility in organic solvent 'vide
2
2
infra), it seemed that tert-octyl group is preferable to tert-
butyl as the p-substituent. Therefore, p-tert-octylthiacalix-
15b
4]arene 4 was subjected to the same oxidation protocol
[
to afford the corresponding sul®nyl and sulfonyl counter-
parts 6 and 8 in similar yields 'Scheme 2). These p-tert-
octylcalixarenes '4, 6, and 8) gave similar NMR data to
those of the tert-butyl counterparts '3, 5, and 7) except
Scheme 3. Cone and 1,3-alternate conformations of calix[4]arenes. Xˆ
t
t
CH
2
, S, SO, or SO
2
. RˆBu or Oct .

N. Morohashi et al. / Tetrahedron 57 ꢀ2001) 5557±5563
Table 1. The E% values of metal ions by 2, 4, 6, and 8
5559
'a) Soft to intermediate metal ions
2
1
21
21
21
21
21
21
1
21
31
21
21
31
M
pH
Mn
Fe
Co
8.0
Ni
Cu
8.0
Zn
Pd
±
Ag
Cd
Au
±
Hg
Pb
Bi
a
b
8.0
6.8
8.0
8.0
5.9
8.4
7.9
6.3
2.8
c
c
2
4
6
8
6
80
12
2
98
99
9
0
99
64
2
6
91
10
4
6
100
79
10
14
6
99
±
±
±
21
0
100
0
0
3
89
±
37
100
90
73
92
15
98
14
4
31
38
12
42
78
26
d
c
c
d
e
e
e
56
72
89
0
f
f
e
'b) Hard metal ions
2
1
21
21
21
31
31
31
41
41
41
M
pH
Mg
Ca
Sr
9.8
Ba
Y
Pr
Eu
Ti
Zr
Hf
9.8
9.8
9.8
6.0
6.3
6.3
2.2
1.4
1.4
2
4
6
8
0
0
55
56
6
2
69
100
0
0
10
95
0
0
9
80
9
5
98
44
0
3
100
100
0
0
100
100
3
4
99
75
21
0
0
100
99
22
100
99
d
d
'c) Those extracted only by 6
2
1
31
51
51
51
31
Ru
3.3
31
31
31
M
pH
Be
Sc
V
Nb
Ta
Al
Ga
In
5.3
2.8
2.8
4.8
4.8
3.5
3.0
4.9
c
2
4
6
8
0
0
100
0
8
2
100
10
0
2
41
5
8
13
85
12
5
5
1
2
3
5
68
0
3
8
100
7
9
0
97
0
±
0
42
5
'd) Those not extracted by 2, 4, 6, and 8
1
1
1
1
1
31
61
Mo
5.0
31
21
1
31
M
pH
Li
Na
K
Rb
Cs
Cr
Rh
Pt
Tl
Sb
9.7
9.7
9.7
9.7
9.7
5.1
5.9
9.9
5.7
9.7
2
4
6
8
0
0
17
18
2
1
23
4
0
0
0
0
0
1
1
0
7
7
12
14
9
3
8
8
0
0
0
0
6
2
9
5
9
1
3
4
0
3
2
2
0
3
0
0
E% ˆ 0 means less than 0.4%.
a
3
In 0.05 M HNO solution.
b
c
d
e
f
3
In 1.0 M HNO solution.
The [Metal]aq was not measured due to the formation of precipitate of the unknown species.
23
21
21
21
21
These metal ions were extracted by use of 2£10 M 6; Cu 81% at pH 4.8, Cd 44% at pH 8.3, Sr 90% at pH 10.6, Ba 85% at pH 10.6.
4 3 4
Me NNO instead of Me NCl was added in aqueous phase.
21 31
The metal ion M may be oxidized to M by complexation with 8 to give high E%.
1
that 6 gave splitted H NMR patterns for methyl protons at 1
and methylene protons at 2 position of tert-octyl group 'see
Section 4), providing another evidence of the all-trans
con®guration of the four SvO groups. Thus, we have
where [metal]aq,init and [metal]aq are the concentrations of
metal ions in aqueous phase before and after extraction,
respectively.
now suf®cient amounts of S-, SO-, and SO -bridged p-
2
tert-octylcalixarenes in hand to carry out solvent-extraction
study to elucidate the role of the bridging moiety X.
Table 1 lists the E% values of metal ions at representative
pH, which was mainly categorized by hardness and softness
2
3
1
21
of the ions. Soft metal ions such as Ag and Hg were
extracted only by 4, whereas many of the ®rst transition
metal ions were extracted by 4 and 6 'Table 1a). On the
other hand, hard metal ions were extracted by 6 and 8 'Table
2
.2. Coordination abilities toward metal ions
2
1
31
31
31
31
31
1
b). It is interesting that Be , Ru , Al , Ga , In , Sc ,
51
51
and Nb were extracted only by 6 'Table 1c). Note that
The metal-binding ability of calix[4]arene 'XˆCH ) and the
V
metal ions such as alkali metal ions, Cr , Mo , Rh ,
2
3
1
61
31
analogs with XˆS, SO, and SO was assessed by solvent
2
31
51
21
1
extraction toward almost all available metal ions except
radioactive ones. It was found that calix[4]arenes 2, 4, 6,
and 8 provided a higher solubility to the formed metal
Sb , Ta , Pt and Tl could not be extracted under the
conditions examined 'Table 1d).
1
complexes in chloroform than tert-butyl counterparts did.
The above-mentioned results were summarized as follows
in periodic tables 'Fig. 1) by de®ning the metals of E%
greater than 30% as extracted. The methylene bridged 2
could not extract any of the metal ions examined 'Fig.
1a). Roughly speaking, 4 extracted soft to intermediate
The pH of the aqueous phase was varied in the range where
metal hydroxides did not form. The percent extraction, E%,
for various metal ions by 2, 4, 6, and 8 were calculated by
Eq. '1)
1
21
metal ions 'Ag , Hg , and ®rst transition metal ions)
very well, but showed little af®nity to hard metal ions
E% ˆ ꢀ‰metalŠaq;init 2 ‰metalŠ †=‰metalŠ
aq
£ 100% ꢀ1†
aq;init

5560
N. Morohashi et al. / Tetrahedron 57 ꢀ2001) 5557±5563
Figure 2. Proposed coordination manners of p-tert-octylthiacalix[4]arene
t
'
4) and the sul®nyl '6) and sulfonyl '8) analogs. RˆOct . For clarity, only
0
half part of calix[4]arene ring is depicted. M and M denote soft and hard
metal ions, respectively.
oxygens to form two sets of ®ve-membered chelated rings as
1
17
evidenced by H NMR study. Although the 1:1 complex
was converted to a 3:4 'ˆ3/Zn) complex by losing some
ligand on recrystallization from benzene±methanol, the
2
2
above coordination mode by O , S, O was unambiguously
2
4
substantiated by X-ray crystallography of the 3:4 complex.
21
Considering the tridentate ability of 3 to Zn ion, herein we
would like to propose the coordination modes depicted in
Fig. 2 to explain the results of metal extraction by 4, 6, and
1
8. First, 4 may bind to soft metal ions by the coordination of
a lone pair electrons of sulfur atom besides two phenolic
21
24
oxygens 'Fig. 2a) as proven for the Zn complex with 3.
Second, lacking the lone pair electrons on S, 8 could not
coordinate to soft metal ions but did to hard metal ions by
2
5
ligation of sulfonyl oxygen 'Fig. 2b). Third, 6 could switch
the coordinating atom between S and O of sul®nyl group
depending on the hardness and softness of the metal ions
2
6
'Fig. 2c and d). In other words, the extraction selectivity of
these sulfur bridged calix[4]arenes '4, 6, and 8) may be
explained by the `hard and soft acids and bases 'HSAB)
2
3
ruleꢀ. Here, it is assumed that the adjacent phenol moieties
of 6 and 8 orient to the same direction 'i.e. syn manner) to
facilitate the coordination of two phenolate oxygens to
2
7
metal ions 'Fig. 2b±d), although the corresponding tert-
butyl counterparts 5 and 7 adopt 1,3-alternate conformation
in the solid state as stated above 'i.e. anti manner for
adjacent phenyl groups). The fact that several hard metal
21
ions 'such as Be ) could be extracted only by 6 but not by 8
may suggest that the electron density on oxygen atom of
sul®nyl group is higher than the one of sulfonyl group to
coordinate to the cationic center.
Figure 1. Periodic tables of the extracted metal ions ꢀE% . 30%† by p-tert-
octylcalix[4]arene 2, and the analogs with S '4), SO '6), and SO '8) bridges
in place of CH
2
2
.
'Fig. 1b). On the other hand, the sulfone 8 far preferred
harder metal ions 'alkaline earth metal ions, lanthanoid
ions, Ti , Zr and Hf , see Fig. 1d). Interestingly, the
sulfoxide counterpart 6 could extract many of not only soft
but also hard metal ions 'Fig. 1c).
Consideration of the results of the solvent extraction study
may provide some cues to possible applications. For
example, hard and soft metal ions could be separated each
other by extraction by using 4 or 8. Furthermore, although
41
41
41
5
1
51
Nb and Ta ions are much alike in chemical properties,
the sharp difference in the extractability between them by 6
'Table 1c) may be reliable for separating them. Another
®nding of interest is the strong coloration of organic phase
Previously, we reported a detailed study of extraction of
21
Zn ion with 3, showing that the extracted 1:1 complex
contained the metal center ligated by one of the four
bridging sulfurs in addition to the adjacent two phenoxide
21
upon extraction of some metal ions by 6; Fe gave light red
whereas V and Ru gave purple color, meaning that 6 is
5
1
31

N. Morohashi et al. / Tetrahedron 57 ꢀ2001) 5557±5563
5561
a potential candidate for chromogenic receptor for those
metal ions.
unambiguously assigned by DEPT. Found: C, 60.88; H,
6.12; S, 16.06%. Calcd for C H O S : C, 61.19; H, 6.16;
S, 16.34%.
4
0
48
8 4
3
. Conclusion
4.2.2. p-tert-Octylsul®nylcalix[4]arene /6). To a solution
of 4 '3.0 g, 3.18 mmol) in chloroform '60 cm ) were added
3
3
acetic acid '75 cm ) and NaBO ´4H O '2.1 g, 14 mmol).
After the mixture had been stirred at 508C for 2 h, 6 was
It has been demonstrated that the oxidation of sul®de
linkages of thiacalix[4]arenes to sulfoxides and sulfons
were readily accomplished by controlling the stoichiometry
of oxidizing agent. The solvent extraction study of thia-
calix[4]arene and the sul®nyl and sulfonyl analogs toward
quite a wide variety of metal ions showed that selectivity
toward metal ions greatly depended upon the oxidation state
of the sulfur moiety, which is best understood by HSAB rule
assuming a crucial role of the coordination of the bridging
groups to metal ions. This hypothesis of the metal selectivity
of thia-, sul®nyl- and sulfonylcalix[4]arenes may be highly
useful for investigating the structures, physicochemical
properties, and functions of the metal complexes.
3
2
3
extracted with chloroform '30 cm £3). After phase sepa-
ration, methanol was added to the chloroform phase to
precipitate the product, which was recrystallized from
dichloromethane±methanol and dried in vacuo '808C,
12 h) to give a pure sample of 6 '1.11 g, 34.6%). Mp
1
280±2828C 'decomp.). FAB MS m/z 1009 'M 11).
2
1
1
IR 'KBr) 3294 'OH), 2951'CH), 1015 'SO) cm . H
NMR '400 MHz, CDCl3, TMS) dˆ0.74 '36H, s,
±C'CH ) CH C'CH ) ), 1.27 and 1.36 '12H, s,
3
2
2
3 3
±C'CH ) CH C'CH ) ), 1.63 and 1.69 '4H, d, J
gem
ˆ
3
2
2
3 3
214.8 Hz, ±C'CH ) CH C'CH ) ), 7.60 '8H, s, Ar±H),
3
2
2
3 3
1
3
.25 '4H, s, ±OH). C NMR '400 MHz, CDCl CDCl ,
9
2 2
TMS) dˆ29.5, 31.8, 32.4, 38.6, 40.6, 57.3
t
'±C'CH ) CH C'CH ) ), 142.2 'C ±Oct ), and 152.6
4
. Experimental
3
2
2
3 3
Ar
1
3
'
C ±OH). The C resonances for ipso carbons with respect
Ar
4
.1. General methods
to H and SvO group were not observed possibly due to the
long spin-lattice relaxation time caused by the introduction
of bulky tert-octyl group. Found: C, 66.57; H, 7.91; S,
12.75%. Calcd for C H O S : C, 66.62; H, 7.99; S,
Mps were taken using a Yamato MP-21 apparatus and are
uncorrected. Microanalyses were carried out in the Institute
of Chemical Reaction Science, Tohoku University. Merck
silica gel 60GF254 was used for TLC. H NMR was
measured on a Bruker DPX-400 spectrometer operated at
5
6
80
8 4
12.71%.
1
4.2.3. p-tert-Butylsulfonylcalix[4]arene /7). In a typical
run, to a solution of 3 '1.0 g, 1.38 mmol) in chloroform
4
00 MHz. IR spectra were obtained with a Shimadzu
3
3
IR-460. Mass spectra were recorded with a JEOL JMS-
GC mate GC±MS system.
'30 cm ) were added acetic acid '50 cm ) and NaBO ´4H O
3 2
'2.0 g, 13 mmol). After the mixture had been stirred at 508C
3
for 18 h, 7 was extracted with chloroform '30 cm £3) and
4
.2. Materials
worked up as usual. The product was recrystallized from
benzene±methanol and dried in vacuo '808C, 12 h) to give
a pure sample of 7 '1.06 g, 90.0%). Mp.3608C; FAB MS
Unless stated otherwise, reagent-grade reagents and
solvents were used as received from chemical suppliers.
1
m/z 849 'M 11); IR 'KBr) 3354 'OH), 2964 'CH), 1319,
2
8
4a
15
15
21
1
The calixarenes 1, 2, 3, and 4 are synthesized as
described in the literatures. Standard solutions for metal
ions were purchased from Kanto Kagaku, Tokyo. The
pH buffers tris'hydroxymethyl)aminomethane 'Tris), 2-
morphorinoethanesulfonic acid 'MES), piperazine-1,4-
bis'2-ethanesulfonic acid) 'PIPES), and N-cyclohexyl-2-
aminoethanesulfonic acid 'CHES) were purchased from
Wako Pure Chemical Industries, Osaka.
1159 'SO
C'CH ), 8.13 '8H, s, Ar±H), OH protons '4H) were not
detected. C NMR 'CDCl
'C'CH ) and 125.9 and 133.2 'CAr). Two of the
resonances were not observed possibly due to their long
relaxation time. Calcd for C40 : C, 56.58; H, 5.70;
S, 15.11. Found: C, 56.63; H, 5.68; S, 15.01.
2
) cm ; H NMR 'CDCl
3
) dˆ1.29 '36H, s,
)
3 3
1
3
CDCl
) d 30.8 'C'CH ), 34.6
2
)
3 3
2
1
3
)
3
C
Ar
3
H O S
48 12 4
4.2.4. p-tert-Octylsulfonylcalix[4]arene /8). For instance,
4 '100 mg, 0.07 mmol) was dissolved in chloroform '2 cm )
and then acetic acid '3 cm ) and NaBO ´4H O '0.14 g
3 2
3
4.2.1. p-tert-Butylsul®nylcalix[4]arene /5). In a typical
run, to a solution of 3 '2.0 g, 2.76 mmol) in chloroform
3
3
40 cm ) were added acetic acid '50 cm ) and NaBO ´4H O
3
'
0.93 mmol) were added. The mixture was stirred at 508C
for 18 h. After being cooled, the reaction mixture was added
3
2
'
1.9 g, 12 mmol). After the mixture had been stirred at 508C
3
3
2 M HCl '2 cm ) product was extracted with chloroform
for 4.5 h, 5 was extracted with chloroform '30 cm £3).
After phase separation, methanol was added to the chloro-
form phase to precipitate the product, which was recrystal-
lized from dichloromethane±methanol and dried in vacuo
3
3
'3 cm £3) and washed with 6 M HCl aq. soln. '2 cm £3).
The chloroform solution was evaporated to dryness to give
crude product, which was then recrystallized from benzene±
methanol mixture to give a pure sample of 8 '102 mg,
90.1%). Procedure using hydrogen peroxide as an oxidizing
agent; 4 '2.0 g, 1.38 mmol) was dissolved in chloroform
'
2
3
808C, 12 h) to give a pure sample of 5 '0.67 g, 30.7%). Mp
1
958C 'decomp.). FAB MS m/z 785 'M 11). IR 'KBr)
2
1
1
188 'OH), 2953'CH), 1001 'SO) cm ; H NMR
3
3
'
'
400 MHz, CDCl , TMS) dˆ1.29 '36H, s, C'CH ) ), 7.65
'40 cm ) and then tri¯uoroacetic acid '10 cm ) and an aq.
soln. of hydrogen peroxide '30%, 20 cm ) were added. The
mixture was stirred at 808C for 24 h. After being cooled, the
3
3 3
1
8H, s, Ar±H), 9.30 '4H, s, OH). C NMR '400 MHz,
3
3
CDCl CDCl , TMS) dˆ31.1 'C'CH ) ), 34.5 'C'CH ) ),
2
2
3 3
3 3
3
1
1
22.5 and 127.7 'C ±SO), 123.9 and 130.0 'C ±H),
Ar
reaction product was extracted with chloroform '30 cm £3)
Ar
t
42.1 'C ±Bu ), and 152.4 'C ±OH), which were
and worked up as the same above to give essentially pure
Ar
Ar

5562
N. Morohashi et al. / Tetrahedron 57 ꢀ2001) 5557±5563
sample of 8 '1.80 g, 79.5%). Compound 8: mp 3368C
'
5. 'a) Grady, T.; Butler, T.; MacCraith, B. D.; Diamond, D.;
McKervey, M. A. Analyst 1997, 122, 803±806.
'b) McCarrick, M.; Harris, S. J.; Diamond, D. Analyst 1993,
118, 1127±1130. 'c) Kubo, Y.; Tokita, S.; Kojima, Y.; Osano,
Y.; Matsuzaki, T. J. Org. Chem. 1996, 61, 3758±3765.
6. 'a) Aoki, I.; Sakaki, T.; Shinkai, S. J. Chem. Soc., Chem.
Commun. 1992, 730±732. 'b) Jin, T.; Ichikawa, K.; Koyama,
T. J. Chem. Soc., Chem. Commun. 1992, 499±501.
1
decomp.); FAB MS m/z 1074 'M 11); IR 'KBr) 3389
2
1
1
OH), 2957 'CH), 1306, 1140 'SO ) cm ; H NMR
'
2
'
'
CDCl ) dˆ0.68 '36H, s, ±C'CH ) CH C'CH ) ), 1.32
3
3 2
2
3 3
24H, s, ±C'CH ) CH C'CH ) ), 1.73 '8H, s,
3 2 2 3 3
±
C'CH ) CH C'CH ) ), 8.10 '8H, s, Ar±H); OH protons
3 2 2 3 3
1
3
'
4H) were not detected. C NMR 'CDCl ) d 31.1, 31.8,
3
3
1
6
2.3, 38.7, 56.5, '±C'CH ) CH C'CH ) ) and 126.9,
3 2 2 3 3
33.7, 143.9, and 151.2 'C ). Calcd for C H O S : C,
56 80 12 4
7. For reviews, see: 'a) Diamond, D. J. Incl. Phenom. 1994, 19,
149±166. 'b) Diamond, D.; MacKervey, M. A. Chem. Soc.
Rev. 1996, 15±24. 'c) Diamond, D.; Nolan, K. Anal. Chem.
Ar
2.65; H, 7.51; S, 11.95. Found: C, 62.53; H, 7.34; S, 11.76.
2
001, 73, 23A±29A. For example, see: 'd) Tanaka, M.;
4
.3. Solvent extraction
Kobayashi, T.; Yamashoji, Y.; Shibutani, Y.; Yakabe, K.;
Shono, T. Anal. Sci. 1991, 7, 817±818.
The procedure for solvent extraction is as follows. To a vial
tube were pipetted an aqueous solution '10 cm ) containing
3
8
. 'a) Cobben, P. L. H. M.; Egberink, R. J. M.; Bomer, J. G.;
Bergveld, P.; Verboom, W.; Reinhoudt, D. N. J. Am. Chem.
Soc. 1992, 114, 10,573±10,582. 'b) Lugtenberg, R. J. W.;
Egberink, R. J. M.; Engbersen, J. F. J.; Reinhoudt, D. N.
J. Chem. Soc., Perkin Trans. 2 1997, 1353±1357.
24
metal ion ꢀ‰MetalŠ
ˆ 1:0 £ 10 M†; Me NCl '0.1 M)
aq;int
4
3
for 6 and 8 as well as a pH buffer '0.05 M) and a 10 cm
2
4
of chloroform solution '[2, 4, 6 or 8ˆ5.0£10 M). The
mixture was shaken for 24 h at 300 strokes per min at
23^28C. After the aqueous phase was separated by centri-
fugation, the total concentration of the metal species
9
. Steemers, F. J.; Meuris, H. G.; Verboom, W.; Reinhoudt,
D. N.; van der Tol, E. B.; Verhoeven, J. W. J. Org. Chem.
1
997, 62, 4229±4235.
remaining in the aqueous phase, [Metal] , was measured
aq
1
0. For comprehensive review, see: 'a) Roundhill, D. M. Prog.
Inorg. Chem. 1995, 43, 533±592. See e.g. 'b) Arnaud-Neu, F.;
Collins, E. M.; Deasy, M.; Ferguson, G.; Harris, S. J.; Kaitner,
B.; Lough, A. J.; McKervey, M. A.; Marques, E.; Ruhl, B. L.;
Schwing-Weill, M. J.; Seward, E. M. J. Am. Chem. Soc. 1989,
by atomic absorption spectrometer or inductively coupled
plasma atomic emission spectrophotometer. The pH of the
aqueous phase was adjusted with HNO ±NH '1.0±2.2),
3
3
glycine±HNO3 '2.5±3.5), succinic acid±NH3 '4.0±5.0),
MES±NH '5.5±6.0), PIPES±NH '6.3±7.0), Tris-HNO
3
3
3
1
11, 8681±8698. 'c) Arduini, A.; Casnati, A.; Dodi, L.;
Pochini, A.; Ungaro, R. J. Chem. Soc., Chem. Commun.
990, 1597±1598. 'd) Nagasaki, T.; Shinkai, S. Bull. Chem.
or Tris-HCl '7.5±8.5), CHES±NH or NH ±HCl '9.0±
3
3
1
1
prevented them from precipitating at the interface between
0.0). The formation of ion pairs of 6 and 8 with Me N
4
1
5
two phases. In this study, the metal species V , Mo ,
1
61
Soc. Jpn. 1992, 65, 471±475. 'e) Ogata, M.; Fujimoto, K.;
Shinkai, S. J. Am. Chem. Soc. 1994, 116, 4505±4506.
4
Zr , and Hf denote VO , MoO , ZrO , and HfO ,
1
41
1
2
51
21
21
21
2
51
'f) Arnaud-Neu, F.; Barrett, G.; Corry, D.; Cremin, S.;
Ferguson, G.; Gallagher, J. F.; Harris, S. J.; KcKervey,
M. A.; Schwing-Weill, M.-J. J. Chem. Soc., Perkin Trans. 2
respectively. Nb and Ta were used as the solutions in
.0 M HF.
1
1997, 575±579.
'g) Talanova, G. G.; Hwang, H.-S.; Talanov, V. S.; Bartsch,
Acknowledgements
R. A. J. Chem. Soc., Chem. Commun. 1998, 1329±1330.
This work was supported by the Proposal-Based New
Industry Creative Type Technology R and D Promotion
Program from the New Energy and Industrial Technology
Development Organization 'NEDO) of Japan.
11. See e.g. 'a) Gutsche, C. D.; Nam, K. C. J. Am. Chem. Soc.
1988, 110, 6153. 'b) Agrawal, Y. K.; Sanyal, M. Analyst 1995,
120, 2759±2762. 'c) Arnaud-Neu, F.; B oÈ hmer, V.; Dozol,
J.-F.; Gr uÈ ttner, C.; Jakobi, R. A.; Kraft, D.; Mauprivez, O.;
Rouquette, H.; Schwing-Weill, M.-J.; Simon, N.; Vogt, W.
J. Chem. Soc., Perkin Trans. 2 1996, 1175±1182.
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. Preliminary account: Iki, N.; Kumagai, H.; Morohashi, N.;
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. 'a) Gutsche, C. D. In Calixarenes; Stoddart, J. F., Ed.; Mono-
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. Mandolini, L.; Ungaro, R. Calixarenes in Action; Imperial
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. 'a) Ohto, K.; Yano, M.; Inoue, K.; Yamamoto, T.; Goto, M.;
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1
18. After our communication had appeared, Hosseini et al.
8
93±902. 'b) Harrow®eld, J. M.; Mocerino, M.; Peachey, B. J.;
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Cian, A. D.; Fisher, J. Tetrahedron Lett. 1999, 40, 1129±1132.
1

N. Morohashi et al. / Tetrahedron 57 ꢀ2001) 5557±5563
5563
'
b) Mislin, G.; Graf, E.; Hosseini, M. W.; Cian, A. D.; Fisher,
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1
2
21
21
0. The X-ray crystal structure of 5 was ®rst presented at the 13th
Symposium on Biofunctional Chemistry, Ehime, Japan,
September 14, 1998, 0P1B002; and 1998 International
Symposium on Organic Reactions, Hsinchiu, Taiwan,
November 12, 1998, A13. See also: Iki, N.; Kumagai, H.
Shokubai ꢀCatalyst) 1999, 41, 612±615. Iki, N.; Kumagai,
H. Chem. Abstr., 132:194303. The same structure was
25. Recently, complexes of 7 with Co and Ni ions were
prepared and X-ray crystallographic analyses of them proved
the coordination manner of Fig. 2b. Kajiwara, T.; Yokozawa,
S.; Ito, T.; Iki, N.; Morohashi, N.; Miyano, S. Chem. Lett.
2
001, 6±7.
2
6. Very recently, X-ray crystallographic evidences were
obtained to show that the sul®nyl function of 5 can bind to
metal ions by both sul®nyl sulfur and oxygen. For example, a
1
8a
reported by Hosseini et al. independently.
2
1
3
:2 'ˆ5/Pd) Pd complex of 5 contained both SvO±Pd and
2
1. cf. Recently, we could obtain 5 with four SvO groups
oriented in cis±cis±cis manner by oxidation of tetrabenzyl
ether of 3 having cone conformation, followed by de-benzyl-
ation. In this case, steric bulk of the benzyl moiety determined
the orientation of the SvO groups during oxidation process.
See: Morohashi, N.; Iki, N.; Kabuto, C.; Miyano, S.
Tetrahedron Lett. 2000, 41, 2933±2937.
OvS±Pd bonds. Morohashi, N.; Iki, N.; Kajiwara, T.; Ito, T.;
Miyano, S. Chem. Lett. 2001, 66±67.
2
7. The conformational change upon complexation is con®rmed
by X-ray analysis of metal complexes of 5 and 7 as mentioned
2
5,26
above.
8. Gutsche, C. D.; Iqbal, M. Org. Synth. 1990, 68, 234±237.
2
2
2. Hereinafter, 1,1,3,3-tetramethylbutyl group is denoted as tert-
t
octyl or Oct group.