Preferential precipitation of C70 over C60 with p-halohomooxacalix[3]arenes

Article abstract of DOI:10.1039/b208107e

Preferential precipitation of C₇₀ from a toluene solution of C₆₀ and C₇₀ was accomplished with p-trihalohomooxacalix[3]arenes (I₃·X·X·X) prepared by the reductive coupling of diformylphenols. Heavy halogens, Br and/or I, are essential at the para position of I₃·X·X·X for obtaining good yields and selectivities. C₇₀ with up to 92% purity was obtained after the preferential precipitation.

Full text of DOI:10.1039/b208107e

View Article Online / Journal Homepage / Table of Contents for this issue
Preferential precipitation of C70 over C60 with p-halohomooxa-
calix[3]arenes
Naoki Komatsu*
Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa,
Sakyo-ku, Kyoto 606-8502, Japan
Received 19th August 2002, Accepted 21st October 2002
First published as an Advance Article on the web 27th November 2002
Preferential precipitation of C70 from a toluene solution of C60 and C70 was accomplished with p-trihalohomooxa-
calix[3]arenes (13ؒXؒXؒX) prepared by the reductive coupling of diformylphenols. Heavy halogens, Br and/or I,
are essential at the para position of 13ؒXؒXؒX for obtaining good yields and selectivities. C70 with up to 92% purity
was obtained after the preferential precipitation.
Introduction
Encapsulation of fullerenes is a subject of current interest in the
fields of supramolecular and fullerene chemistry.1–8 A practical
goal in this area of chemistry is to develop an efficient method
for the separation of specific size and/or isomers of fullerenes
from mixtures.9 Actually, selective complexation of fullerenes
Scheme 2
hassofarbeenreportedwithcalixarenes,10–22 cyclodextrins,15,23–25
cyclotriveratrylenes26–28 andmetalloporphyrins.29 In1992,select-
[3]arenes with different substituents, 13ؒIؒIؒBz (Bz = CH2Ph),
13ؒIؒBzؒBz, 13ؒIؒIؒOctt (Octt = 1,1,3,3-tetramethylbutyl) and
14ؒIؒIؒIؒOctt, were prepared by reductive heterocoupling
between 4-substituted-2,6-diformylphenol (2ؒR) and the tris-
(trimethylsilyl) ether of 4-substituted-2,6-bis(hydroxymethyl)-
;phenol (4ؒR)30 which was prepared via 3ؒR as shown in
Scheme 3. The 2,6-bis(hydroxymethyl)phenols with benzyl and
tert-octyl substituents (3ؒBz and 3ؒOctt) were prepared accord-
ing to the reported method.35 Since the direct hydroxymethyl-
ation of p-iodophenol was reported to fail, 3ؒI was prepared in a
similar indirect route starting from the commercial compound
to that described in ref. 36. The trimethylsilylation of 3 was
carried out with N,O-bis(trimethylsilyl)trifluoroacetamide
(BTSTA) in acetonitrile to give 4 in high yields after rapid
column chromatography with hexane and careful evaporation
of the solvents.37,38
ive extraction of C60 into a water layer was accomplished using γ-
cyclodextrin25 and water soluble calix[8]arene22 by Wennerström
and Verhoeven and their co-workers, respectively. Selective pre-
cipitation from an organic solution of a fullerene mixture, which
is a more practical method by which to separate fullerenes, was
reported in 1994 using p-tert-butylcalix[8]arene19,20 and cyclo-
triveratrylene28 by Shinkai and Atwood and their co-workers.
More recently, a few bridged or cyclic dimers were found to
encapsulateC70 preferentiallytoC60 insolution.14,17,26,29 However,
no host molecules preferentially precipitating C70 have been
reported except for one example using p-tert-butylcalix-
[6]arene.16,20 Herein is described a selective precipitation of C70
over C60 with p-halohomooxacalix[3]arenes.
Results
Synthesis of homooxacalix[n]arenes (1nؒR)
The homooxacalix[n]arenes (1nؒR) were prepared according to
the recent report based on the reductive coupling of 4-substi-
tuted-2,6-diformylphenols (2ؒR).30 p-Triiodohomooxacalix[3]-
arene (13ؒIؒIؒI) was prepared stepwise from 2,6-diformylphenol
(2ؒH)31 through a combination of iodination32,33 and reductive
coupling30 (Scheme 1) because diformylation of p-iodophenol34
gave 2ؒI in very low yield. p-Trihalohomooxacalix[3]arenes with
different halogens, 13ؒIؒIؒBr and 13ؒIؒBrؒBr, were prepared
through the iodination33 of the corresponding 13ؒHؒHؒBr and
13ؒHؒBrؒBr as shown in Scheme 2. Other p-halohomooxacalix-
Precipitation of C70 with homooxacalix[n]arenes
Thus prepared homooxacalix[n]arenes with a variety of para-
substituents were first examined for precipitation of C70 (Table
1). About 70% of C70 was precipitated by 13ؒIؒIؒI from a toluene
solution of C70 (ca. 1 mg cmϪ3) as a complex (runs 1 and 2).
Under similar conditions, however, no precipitate was observed
for C60 with 13ؒIؒIؒI (run 3). These contrasting results clearly
show a potential of 13ؒIؒIؒI for separation of C70 from a mixture
of C60 and C70.
The number of alkyl groups and the nature of the halogens at
the para position of p-halohomooxacalix[n]arenes (n = 3 or 4)
remarkably affected the yield of C70 (runs 4–9). p-Iodoho-
mooxacalix[n]arenes (n = 3 or 4) with one alkyl group afforded
Scheme 1
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 4 – 2 0 9
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
204

View Article Online
Table 1 Precipitation of C70 with p-halohomooxacalix[n]arenes with various substituentsa
Host (1nؒR)
Precipitate
Weight/mg
Toluene/cm3
Yield (%) of C70
b
Run
n
R
Weight/mg (µmol)
C70/mg (µmol)
1
2
3
4
5
6
7
8f
9
3
3
3
3
3
4
3
3
3
IؒIؒI
IؒIؒI
IؒIؒI
24.1 (31)
52.8 (67)
4.3 (5.5)
12.7 (17)
24.0 (31)
15.8 (15)
5.1 (7.1)
5.6 (7.8)
45.9 (71)
51.3 (61)
111.6 (130)
3.8 (5.3)c
30.2 (36)
54.8 (65)
31.5 (37)
4.7 (5.6)
48
96
52.5
109.2
0
9.6
16.1
9.2
trace
trace
52.5
71
67
4.5
21.5
43
21.5
3.5
5.5
96
0c
IؒIؒBzd
IؒIؒOctt e
IؒIؒIؒOctt e
IؒBzؒBz
IؒBzؒBzd
BrؒBrؒBr
22
20
20
∼0
∼0
33
4.7 (5.6)
111.1 (130)
c
a Mixtures were stirred at room temperature overnight unless otherwise noted. b Calculated from recovery (%) of C70 from the filtrate. C60. d Bz =
CH2Ph. e Octt = 1,1,3,3-tetramethylbutyl. f At Ϫ30 ЊC.
Scheme 3
C70 precipitates in low yields (runs 4–6), while only a trace
amount of precipitate was obtained using p-iodohomooxa-
calix[3]arene with two alkyl groups (runs 7–8). p-Tribromo-
homooxacalix[3]arene gave C70 complex in 33% yield (run 9),
which is less than half of the yield with p-triiodohomooxa-
calix[3]arene (runs 1 and 2). A similar precipitation experiment
were obtained (runs 10 and 11). The precipitate from a toluene
solution of the fullerene mixture (C60 : C70 : C>70 = 2 : 6 : 2) with
13ؒIؒIؒI included a considerable amount of higher fullerenes
(C>70) along with C70; that is, 13ؒIؒIؒI cannot discriminate C70
and C>70, which is another limitation of this method for the
purification of fullerenes. When a toluene solution of 13ؒIؒIؒI
was added to a toluene solution of raw fullerene mixture
(fullerene extract, C60 : C70 = 8 : 2), precipitation was not
observed to give a dark brown homogeneous solution.
with a more concentrated toluene solution of C70 (2.5 mg cmϪ3
)
has been carried out with p-tert-butylcalix[6]arene which gives
C70 complex in 31% yield.20
In order to recover the fullerene and reuse the host molecules,
liberation of the complexes was carried out. Since the binding
of the C70 complexes with 13ؒIؒIؒI, 13ؒIؒIؒBr and 13ؒIؒBrؒBr was
very tight, it was very difficult to liberate the fullerene by a
simple way like that used for the tert-butylcalix[8]arene-C60 com-
plex.19,20 Eventually, C70-13ؒIؒIؒI was dissolved in o-dichloro-
benzene (ODCB), and the host molecules were extracted with
basic aqueous solution.
Preferential precipitation of C70 over C60 with
homooxacalix[3]arenes
Selective precipitation of C70 from fullerene mixtures was
carried out under more concentrated conditions than those in
Table 1.39 The results are summarized in Table 2. The selectivity
and the yield of C70 strongly depend on the nature of the
halogens at the para position of the host molecules. The order
of efficiency in the purification of C70 followed the size of the
halogens, I > Br > Cl > F (runs 2, 7, 13 and 14). As compared to
13ؒIؒIؒI and 13ؒBrؒBrؒBr, 13ؒClؒClؒCl gave low selectivity (run
12) or low yield of C70 (run 13), and 13ؒFؒFؒF afforded low yield
of C70 with the highest purity (run 14). When 13ؒIؒIؒI or
13ؒBrؒBrؒBr was added to the toluene solution of a fullerene
mixture (C60 : C70 = 1 : 1, w/w), the ratios of C60 : C70 and
the yields of C70 of the precipitates were 21 : 79–38 : 62 and
75–91%, respectively (runs 2, 7 and 9–11). The purity of C70 in
the precipitates increased to 92% and 88% from 83% and 80%,
respectively, after the selective precipitation (runs 1 and 8). The
attempt to obtain pure C70 by this method was not successful;
92% purity is the upper limit of this purification. p-Iodoho-
mooxacalix[3]arenes with one or two Br groups, 13ؒIؒIؒBr and
13ؒIؒBrؒBr (runs 3 and 6), afforded almost the same results as
that of 13ؒIؒIؒI (run 2), while the ones with one alkyl group,
13ؒIؒIؒBz and 13ؒIؒIؒOctt (Octt = 1,1,3,3-tetramethylbutyl), gave
much lower yields of C70 (runs 4 and 5). These results show that
three heavy halogens are essential for obtaining both good yield
and selectivity. The selectivity seems to be similar to the
reported ones with tert-butylcalix[6]arene.16,20 When other
solvent systems were used instead of toluene, similar results
Discussion
The host : guest ratio of the 13ؒIؒIؒI–C70 and 13ؒBrؒBrؒBr–C70
complexes is calculated to be about 2 : 5 and 1 : 3 from the
results of the elemental analyses.† The ratio was reported to
be 1 : 2 in p-tert-butylcalix[6]arene–C70,20p-tert-butylcalix[6]-
arene–C60 and calix[6]arene–C70 complexes,16 1 : 1 in 13ؒBrؒBrؒ
41
Br–C60,40 13ؒButؒButؒBut–C60,41 p-tert-butylcalix[5]arene–C60
and p-methylcalix[5]arene–C60 complexes,42 and 2 : 1 in
13ؒBzؒBzؒBz–C60 (Bz = CH2Ph),43 p-phenylcalix[5]arene–C60,11
hexahomotrioxacalix[3]naphthalene–C60,13 and p-diiodotri-
methylcalix[5]arene–C60 complexes.42,44 Such an unprecedented
large capacity of p-trihalohomooxacalix[3]arenes for C70 may be
attributed to its shallow cavity, intermolecular π–π interactions
among the guest molecules,45 the large van der Waals radii of
the heavy halogens, and strong van der Waals interactions
between the heavy halogens and the guests.44,46 Unfortunately, a
crystal structure of the complexes has not been determined yet.
† Anal. Calcd for C398H42I6O12 (2 : 5 complex): C 82.76, H 0.73, I 13.18;
found: C 83.14, H 0.84, I 12.61%. Anal. Calcd for C234H21Br3O6 (3 : 1
complex): C 88.71, H 0.67, Br 7.57; found: C 88.66, H 0.65, Br 7.67%.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 4 – 2 0 9
205

View Article Online
Table 2 Selective precipitation of C70 with p-halohomooxacalix[3]arenes with various substituentsa
Host (13ؒR)
Fullerene mixture
Precipitate
Filtrate
C60 : C70
b
b
Run
R
Weight/mg (µmol)
C60(mg)/C70(mg) (ratio)
Toluene/cm3
C60 : C70
Yield (%)c
1
2
IؒIؒI
IؒIؒI
IؒIؒBr
6.9 (8.8)
12.8 (16)
17.0 (23)
11.6 (15)
41.3 (53)
15.3 (22)
15.3 (24)
11.5 (18)
8.0 (12)
7.4 (11)
7.3 (11)
11.6 (23)
12.1 (24)
10.9 (24)
2.6/13.0 (17 : 83)
20.3/20.4 (50 : 50)
20.2/20.2 (50 : 50)
10.2/9.9 (51 : 49)
20.9/21.7 (49 : 51)
19.6/20.1 (49 : 51)
20.1/19.8 (50 : 50)
4.0/16.2 (20 : 80)
10.0/9.8 (50 : 50)
9.8/10.0 (50 : 50)
10.2/9.8 (51 : 49)
9.7/9.7 (50 : 50)
20.2/20.1 (50 : 50)
9.8/9.8 (50 : 50)
7
11
11
11
17
11
11
7
8 : 92
24 : 76
24 : 76
14 : 86
11 : 89
24 : 76
38 : 62
12 : 88
23 : 77
22 : 78
21 : 79
48 : 52
37 : 63
6 : 94
93
88
93
18
20
90
91
84
75
79
76
93
63
19
63 : 37
86 : 14
91 : 9
3
4d
5d
6
IؒIؒBze
IؒIؒOctt f
IؒBrؒBr
BrؒBrؒBr
BrؒBrؒBr
BrؒBrؒBr
BrؒBrؒBr
BrؒBrؒBr
ClؒClؒCl
ClؒClؒCl
FؒFؒF
55 : 45
55 : 45
87 : 13
84 : 16
45 : 55
76 : 24
78 : 22
78 : 22
67 : 33
63 : 37
55 : 45
7
8
9
10
11
12
13
14
6
10 ϩ 5g
5 ϩ 5h
5
11
5
a Mixtures were stirred at room temperature overnight unless otherwise noted. b Weight ratio based on area ratio in HPLC. c Yield of C70 in the
precipitates was calculated from the weights of C60 and C70, and the C60 : C70 ratios of the precipitates and filtrates. d At Ϫ30 ЊC for 2 days.
e Bz = CH2Ph. f Octt = 1,1,3,3-tetramethylbutyl. g Toluene (10 cm3) ϩ hexane (5 cm3). h 1,1,2,2-Tetrachloroethane (5 cm3) ϩ hexane (5 cm3).
Fig. 1 Time-course of the absorption spectra of C70 (2.0 × 10Ϫ4 M)–p-
triiodohomooxacalix[3]arene (13ؒIؒIؒI, 8.4 × 10Ϫ3M) in toluene at 20 ЊC.
The time-course of the change in absorption spectra of C70
was measured in the presence of 13ؒIؒIؒI in toluene at 20 ЊC as
shown in Fig. 1. The brown color of C70 discharged gradually as
the precipitation of C70-13ؒIؒIؒI proceeded with time. Although
a monotonous decrease in the absorption spectra was observed,
there was no significant change in the shape of the spectra,
indicating that no stable complex existed in solution. On the
other hand, no spectroscopic change occurred in the solution of
C60 and 13ؒIؒIؒI, indicating that no complex or precipitate
formed under the conditions.
Scheme 4
The results mentioned above imply that most of the starting
α-cyano-4-hydroxycinnamic acid as a matrix. High resolution
compounds, 13ؒIؒIؒI and the fullerenes, exist separately in
mass spectra were recorded on an Applied Biosystems, Marier
solution, and that the complexes with two or three C70, which
(ESI-MS). Absorption spectra were measured in toluene on a
should exist in a small amount in solution, form precipitates
Hitachi UV2001. HPLC analyses were performed at 35 ЊC on a
(Scheme 4b), while the C60 complexes do not precipitate at all
Shimadzu LC-10 equipped with an Imtakt Cadenza CD-C18
(Scheme 4a). On the preferential precipitation of the fullerene
column (100 × 4.6 mm) with hexane–propan-2-ol = 4 : 6 (v/v) as
mixture, at least one of the complexes, 13ؒIؒIؒI–C60C70, 13ؒIؒIؒI–
an eluent at 0.8 cm3 minϪ1 using UV detection at 285 nm. Melt-
(C70)2C60, and 13ؒIؒIؒI–(C60)2C70, is considered to precipitate
ing points were determined with a Yanaco MP-J3 apparatus
along with the C70 complexes, because there is always some C60
and are uncorrected. Flash chromatography was performed
in the precipitate (Scheme 4c).
with a Wakogel C-300. CH2Cl2 was freshly distilled from CaH2
under argon.
Experimental
Synthesis of 4-substituted-2,6-diformylphenols (2ؒR)
1H (400 MHz) and 13C (100 MHz) NMR spectra were obtained
Compounds 2ؒR were prepared according to the literature
on a JEOL JNM-FX400 in CDCl3 with Me4Si as internal
standard. Chemical shifts are reported in δ and the coupling
constants (J) are in Hz. MALDI-TOF-MS analyses were per-
formed by a Shimadzu/Kratos KOMPACT MALDI II using
an ethanol–water solution of 2,5-dihydroxybenzoic acid or
method34 except for 4-iodo-2,6-diformylphenol.
2,6-Diformyl-4-fluorophenol (2ؒF). Yield 20 %; mp 108–109 ЊC
(Found: C, 57.05; H, 2.97. Calc. for C8H5FO3: C, 57.15; H,
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 4 – 2 0 9
206

View Article Online
3.00%); δH 7.69 (2H, d, J 7.2, Ar–H), 10.22 (2H, s, CHO), 11.39
(1H, s, OH); δC 123.3, 123.8, 153.1, 157.9, 159.8, 191.0.
4-Iodo-2,6-bis(trimethylsilyloxymethyl)phenol trimethylsilyl
ether (4ؒI). δH 0.16 (18H, s, TMS), 0.24 (9H, s, TMS), 4.57
(4H, s, CH2O), 7.60 (2H, s, Ar–H).
4-Benzyl-2,6-diformylphenol (2ؒBz). Yield 47%; mp 105–107
ЊC (Found: C, 75.04; H, 4.94. Calc. for C15H12O3: C, 74.99; H,
5.03%); δH 4.00 (2H, s, CH2), 7.16–7.34 (5H, m, Ph–H), 7.78
(2H, s, Ar–H), 10.19 (2H, s, CHO), 11.50 (1H, s, OH); δC 40.4,
123.0, 126.7, 128.7, 128.8, 133.1, 137.7, 139.5, 162.1, 192.1.
Synthesis of homooxacalix[n]arenes via reductive coupling
7,15,23-Triiodo-2,3,10,11,18,19-hexahomo-3,11,19-trioxa-
calix[3]arene-25,26,27-triol
(p-triiodohomooxacalix[3]arene,
13ؒIؒIؒI). As shown in Scheme 1, two synthetic routes were
followed from 2ؒH. The reductive homocoupling of 2ؒH and
2ؒI afforded 13ؒHؒHؒH and 13ؒIؒIؒI in 14% and 11% yields,
respectively, following the reported procedure.30 The 13ؒHؒHؒH
obtained was iodinated according to the following procedure:
a yellow solution of 13ؒHؒHؒH (0.13 g, 0.32 mmol) and
BTMAؒICl2 in dichloromethane (30 cm3)–methanol (12 cm3)
was stirred at room temperature for 0.5 hour. Then, CaCO3
(0.20 g, 2.0 mmol) was added to the mixture. After being stirred
for 19 hours, the suspension was filtered through Celite, and the
filtrate was concentrated to about a half in volume and washed
with 5% NaHSO3 (30 cm3) twice. The combined water layer
was extracted with dichloromethane (30 cm3) once, and the
dichloromethane layers were combined, concentrated and
chromatographed on silica gel to give 13ؒIؒIؒI (0.19 g, 76%) as a
white solid. Mp >300 ЊC (Found: C, 36.72; H, 2.64. Calc. for
C24H21I3O6: C, 36.67; H 2.69%); δH 4.62 (12H, s, CH2), 7.42
(6H, s, Ar–H), 8.67 (3H, s, OH); δC 70.3, 81.1, 126.4, 138.3, 155.6;
MALDI-TOF-MS (pos): calcd. for C24H21I3NaO6 809.12,
found 809.06 (M ϩ Naϩ).
2,6-Diformyl-4-iodophenol (2ؒI). Since the diformylation of
4-iodophenol gave the desired product only in 3% yield, 2,6-
diformylphenol (2ؒH)31 was iodinated with benzyltrimethyl-
ammonium dichloroiodate (BTMAؒICl2) in the presence of
NaHCO3.33
To a CH2Cl2–methanol (40 cm3 : 16 cm3) solution of 2ؒH
(0.60 g, 4.0 mmol) was added BTMAؒICl2 (1.6 g, 4.6 mmol) and
NaHCO3 (2.3 g, 27 mmol), and the resulting yellow suspension
was stirred at room temperature for 9 hours. After filtration
through a Celite-SiO2 bed, the filtrate was concentrated and
submitted to flash column chromatography on silica gel to give
2ؒI (0.77 g, 68%). Mp 145–148 ЊC (Found: C, 35.09; H, 1.73.
Calc. for C8H5IO3: C, 34.81; H, 1.83%); δH 8.22 (2H, s, Ar–H),
10.16 (2H, s, CHO), 11.55 (1H, s, OH); δC 80.8, 125.0, 154.6,
162.9, 190.8.
Synthesis of 4-substituted-2,6-bis(hydroxymethyl)phenols (3ؒR)
Compounds 3ؒR were prepared according to the literature
method35 except for 4-iodo-2,6-bis(hydroxymethyl)phenol.
7,15,23-Trifluoro-2,3,10,11,18,19-hexahomo-3,11,19-trioxa-
calix[3]arene-25,26,27-triol (p-trifluorohomooxacalix[3]arene,
13ؒFؒFؒF). 13ؒFؒFؒF was prepared according to the reported
procedure.30 Yield 29%; mp 218–220 ЊC (Found: C, 62.06; H,
4.63. Calc. for C24H21F3O6: C, 62.34; H, 4.58%); δH 4.66 (12H, s,
CH2), 6.86 (6H, d, Ar–H), 8.55 (3H, s, OH); δC 70.8, 115.9,
116.2 (d, J 23), 125.1 (d, J 7.1), 151.7 (d, J 2.3), 155.6 (d, J 240);
MALDI-TOF-MS (pos): calcd. for C24H21F3NaO6 485.41,
found 485.40 (M ϩ Naϩ).
4-Benzyl-2,6-bis(hydroxymethyl)phenol (3ؒBz). Mp 92–93 ЊC
(ethyl acetate) (Found: C, 73.76; H, 6.57. Calc. for C15H16O3:
C, 73.74; H, 6.61%); δH 2.47 (2H, s, OH), 3.87 (2H, s, CH2Ph),
4.75 (4H, d, J 2.4, CH2O), 6.89 (2H, s, Ar–H), 7.14–7.29 (5H,
m, CH2Ph), 7.92 (1H, s, ArOH).
4-tert-Octyl-2,6-bis(hydroxymethyl)phenol (3ؒOctt). Mp
63–66 ЊC (ethyl acetate) (Found: C, 69.76; H, 9.74. Calc. for
C16H30O4(C16H26O3 ϩ ½ethyl acetate): C, 69.64; H, 9.74%); δH
0.72 (9H, s, C(CH3)3), 1.32 (6H, s, C(CH3)2), 1.68 (2H, s, CH2),
4.81 (4H, s, CH2O), 7.05 (2H, s, Ar–H).
7,15-Diiodo-23-benzyl-2,3,10,11,18,19-hexahomo-3,11,19-
trioxacalix[3]arene-25,26,27-triol (13ؒIؒIؒBz). 13ؒIؒIؒBz was
prepared according to the reported procedure30 using 2,6-
diformyl-4-iodophenol (0.19 g, 0.72 mmol), 2,6-bis(trimethyl-
silyloxymethyl)-4-benzylphenol trimethylsilyl ether (0.17 g, 0.31
mmol), trimethylsilyl trifluoromethanesulfonate (0.26 cm3, 1.4
mmol), triethylsilane (0.24 cm3, 1.5 mmol) and dichloro-
methane (20 cm3). Yield 6%; δH 3.86 (2H, s, CH2Ph), 4.61 (4H,
s, CH2), 4.62 (4H, s, CH2), 4.65 (4H, s, CH2), 6.94 (2H, s,
Bz–Ar–H), 7.11–7.26 (5H, m, Bz), 7.41 (2H, s, I–Ar–H), 8.45
(1H, s, Bz–Ar–OH), 8.76 (2H, s, I–Ar–OH); δC 40.82, 70.23,
70.30, 71.27, 80.97, 123.84, 126.04, 126.42, 126.65, 128.41,
128.77, 130.40, 132.39, 138.18, 138.26, 141.09, 153.85, 155.69;
MALDI-TOF-MS (pos): calcd. for C31H28I2NaO6 772.81,
found 773.14 (M ϩ Naϩ).
4-Iodo-2,6-bis(hydroxymethyl)phenol (3ؒI)36. A commercial
2-methoxyisophthalic acid was demethylated in aqueous HI
solution at reflux temperature,47 reduced to dimethanol with
lithium aluminum hydride,48 and iodinated with BTMAؒICl2 in
the presence of NaHCO3.36
Typical procedure for the synthesis of 4-substituted-2,6-
bis(trimethylsilyloxymethyl)phenol trimethylsilyl ethers (4ؒR)
To an acetonitrile solution (30 cm3) of 3ؒOctt was added
BTSTA (4.5 cm3, 17 mmol) dropwise over 5 minutes at room
temperature under Ar. The resulting pale yellow solution was
stirred for 22 hours, the mixture was concentrated on a rotary
evaporator and rapidly passed through a short column using
hexane as eluent. After careful concentration on a rotary
evaporator, the desired compound, 4ؒOctt, was obtained as a
colourless oil containing a small amount of hexane in almost
quantitative yield, and used immediately in the next coupling
reaction.
15,23-Dibenzyl-7-iodo-2,3,10,11,18,19-hexahomo-3,11,19-tri-
oxacalix[3]arene-25,26,27-triol (13ؒIؒBzؒBz). 13ؒIؒBzؒBz was
prepared according to the reported procedure30 using 4-benzyl-
2,6-diformylphenol (0.10 g, 0.42 mmol), 2,6-bis(trimethyl-
silyloxymethyl)-4-iodophenol trimethylsilyl ether (0.11 g, 0.22
mmol), trimethylsilyl trifluoromethanesulfonate (0.14 cm3, 0.80
mmol), triethylsilane (0.14 cm3, 0.88 mmol) and dichloro-
methane (12 cm3). Yield 26%; δH 3.84 (4H, s, CH2Ph), 4.59
(2H, s, CH2), 4.63 (2H, s, CH2), 4.63 (2H, s, CH2), 6.92 (4H, s,
Bn–Ar–H), 7.07–7.26 (10H, m, Ph), 7.38 (2H, s, I–Ar–H), 8.54
(2H, s, Bn–Ar–OH), 8.85 (1H, s, I–Ar–OH); δC 40.82, 70.24,
71.23, 80.86, 123.90, 124.13, 126.01, 126.72, 128.39, 128.77,
130.30, 130.37, 132.26, 138.14, 141.16, 153.95, 155.80.
4-tert-Octyl-2,6-bis(trimethylsilyloxymethyl)phenol trimethyl-
silyl ether (4ؒOctt). δH 0.14 (18H, s, TMS), 0.23 (9H, s, TMS),
0.69 (9H, s, C(CH3)3), 1.36 (6H, s, C(CH3)2), 1.71 (2H, s, CH2),
4.65 (4H, s, CH2O), 7.27 (2H, s, Ar–H).
4-Benzyl-2,6-bis(trimethylsilyloxymethyl)phenol trimethylsilyl
ether (4ؒBz). δH 0.11 (18H, s, TMS), 0.22 (9H, s, TMS), 3.94
(2H, s, CH2Ph), 4.61 (4H, s, CH2O), 7.09 (2H, s, Ar–H),
7.17–7.29 (5H, m, Ph).
7,15-Diiodo-23-tert-octyl-2,3,10,11,18,19-hexahomo-3,11,19-
trioxacalix[3]arene-25,26,27-triol (13ؒIؒIؒOctt). 13ؒIؒIؒOctt was
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 4 – 2 0 9
207

View Article Online
prepared according to the reported procedure30 using 2,6-
diformyl-4-iodophenol (0.20 g, 0.73 mmol), 2,6-bis(trimethyl-
silyloxymethyl)-4-tert-octylphenol trimethylsilyl ether (0.15 g,
0.31 mmol), trimethylsilyl trifluoromethanesulfonate (0.26 cm3,
1.4 mmol), triethylsilane (0.24 cm3, 1.5 mmol) and dichloro-
methane (20 cm3). Yield 17%; δH 0.71 (9H, s, C(CH3)3), 1.30
(6H, s, C(CH3)2), 1.67 (2H, s, –CH2–But), 4.62 (4H, s, CH2),
4.63 (4H, s, CH2), 4.70 (4H, s, CH2), 7.09 (2H, s, Octt–Ar–H),
7.43 (4H, s, I–Ar–H), 8.40 (1H, s, Octt–Ar–OH), 8.79 (2H, s,
I–Ar–OH); δC 31.54, 31.84, 32.32, 37.83, 56.80, 70.16, 70.31,
71.77, 80.95, 122.99, 126.44, 126.75, 127.56, 138.12, 138.26,
141.67, 152.99, 155.70; MALDI-TOF-MS (pos): calcd. for
C32H38I2NaO6 795.49, found 795.48 (M ϩ Naϩ).
geneous solution was vigorously stirred at room temperature
for an hour. After separation of the two layers, the organic layer
was washed with 1 M NaOH (15 cm3) twice. The combined
water extracts were made acidic with conc. HCl and extracted
with dichloromethane (20 cm3) three times and toluene (30 cm3)
once. Concentration of the combined dichloromethane extracts
gave pure 13ؒIؒIؒI (3.7 mg). On the other hand, the o-dichloro-
benzene layer was combined with toluene extract, dried over
MgSO4 and concentrated in vacuo to give liberated fullerenes
(9.0 mg).
Acknowledgements
The author is grateful to Professors Keiji Maruoka, Atsuhiro
Osuka and Kazumi Matsushige (Kyoto University) for their
encouragement, Dr Tomonari Wakabayashi (Kyoto University)
for his helpful suggestions, Mr Itaru Yazawa (Imtakt Co.)
for his kind offering of a HPLC column (Cadenza CD-C18),
Mr Koji Sasaki for his assistance of measuring HRMS, and
Messrs Takashi Onozawa and Susumu Kosugiyama (Tokyo
Chemical Industry Co., Ltd.) for their assistance with
experiments and their kind donation of some reagents. A part
of this work was supported by a Grant-in-Aid for Research for
Young Researchers from Kyoto University-Venture Business
Laboratory (KU-VBL).
31-tert-Octyl-7,15,23-triiodo-2,3,10,11,18,19,26,27-octa-
homo-3,11,19,27-tetraoxacalix[4]arene-33,34,35,36-tetraol
(14ؒIؒIؒIؒOctt). This compound was obtained in a small amount
(3.8 mg) as a byproduct in the preparation of 13ؒIؒIؒOctt; δH
0.71 (9H, s, C(CH3)3), 1.29 (6H, s, C(CH3)2), 1.67 (2H, s, –CH2–
But), 4.63 (8H, s, CH2), 4.64 (4H, s, CH2), 4.69 (4H, s, CH2),
7.09 (2H, s, Octt–Ar–H), 7.41–7.44 (6H, m, I–Ar–H), 8.01 (1H,
s, Octt–Ar–OH), 8.30 (1H, s, I–Ar–OH), 8.37 (2H, s, I–Ar–OH);
δC 31.56, 31.85, 32.33, 37.80, 56.73, 70.27, 70.38, 70.38, 71.87,
80.90, 80.90, 123.02, 126.41, 126.46, 126.82, 127.72, 138.33,
138.43, 138.54, 141.60, 153.17, 155.76, 155.88; MALDI-TOF-
MS (pos): calcd. for C40H45I3NaO8 1057.55, found 1057.79
(M ϩ Naϩ).
References
Synthesis of p-trihalohomooxacalix[3]arenes (13ؒIؒIؒBr and
13ؒIؒBrؒBr, Scheme 2)
1 S. Shinkai and A. Ikeda, Pure Appl. Chem., 1999, 71, 275.
2 A. L. Balch and M. M. Olmstead, Coord. Chem. Rev., 1999,
185–186, 601.
p-Bromohomooxacalix[3]arenes (13ؒHؒHؒBr and 13ؒHؒBrؒBr)
were obtained in 3% yield after the purification of the mixture
from the reductive coupling of 2,6-diformylphenol (2ؒH) and
4-bromo-2,6-diformylphenol (2ؒBr).30 The 13ؒIؒIؒBr and
13ؒIؒBrؒBr were obtained by iodination of 13ؒHؒHؒBr and
13ؒHؒBrؒBr with BTMAؒICl2 (2.2 and 1.1 equiv.) in the pres-
ence of NaHCO3 (4.6 and 2.3 equiv.), respectively, in dichloro-
methane–methanol (5 : 2 v/v) followed by a similar work-up to
that in the synthesis of 13ؒIؒIؒI.
3 S. Shinkai and A. Ikeda, Gazz. Chim. Ital., 1997, 127, 657.
4 T. Braun, Fullerene Sci. Technol., 1997, 5, 615.
5 A. Ikeda and S. Shinkai, Chem. Rev., 1997, 97, 1713.
6 C. L. Raston, in Comprehensive Supramolecular Chemistry, ed.
G. W. Gokel, Pergamon, Oxford, 1996, vol. 1, pp. 777–787.
7 P. Lhotak and S. Shinkai, J. Synth. Org. Chem., Jpn., 1995, 53, 963.
8 E. C. Constable, Angew. Chem., Int. Ed. Engl., 1994, 33, 2269.
9 J. Theobald, Sep. Sci. Technol., 1995, 30, 2783.
10 T. Haino, Y. Yamanaka, H. Araki and Y. Fukazawa, Chem.
Commun., 2002, 402.
11 M. Makha, M. J. Hardie and C. L. Raston, Chem. Commun., 2002,
1446.
12 T. Haino, H. Araki, Y. Yamanaka and Y. Fukazawa, Tetrahedron
Lett., 2001, 42, 3203.
13 S. Mizyed, M. Ashram, D. O. Miller and P. E. Georghiou, J. Chem.
Soc., Perkin Trans. 2, 2001, 1916.
14 J. Wang, S. G. Bodige, W. H. Watson and C. D. Gutsche, J. Org.
Chem., 2000, 65, 8260.
23-Bromo-7,15-diiodo-2,3,10,11,18,19-hexahomo-3,11,19-tri-
oxacalix[3]arene-25,26,27-triol (13ؒIؒIؒBr). δH 4.62 (2H, s, CH2),
4.63 (2H, s, CH2), 4.64 (2H, s, CH2), 7.25 (2H, s, Ar–H), 7.42
(4H, s, Ar–H), 8.65 (1H, s, OH), 8.67 (2H, s, OH); δC 70.33,
70.34, 70.51, 81.07, 111.26, 125.77, 126.27, 132.27, 138.18,
154.62, 155.45; HRMS (EI): calcd. for C24H20BrI2O6 736.8527,
found 736.8541.
15 K. Komatsu, K. Fujiwara, Y. Murata and T. Braun, J. Chem. Soc.,
Perkin Trans. 1, 1999, 2963.
16 J. L. Atwood, L. J. Barbour, C. L. Raston and I. B. N. Sudria,
Angew. Chem., Int. Ed., 1998, 37, 981.
17 T. Haino, M. Yanase and Y. Fukazawa, Angew. Chem., Int. Ed.,
1998, 37, 997.
18 T. Suzuki, K. Nakashima and S. Shinkai, Tetrahedron Lett., 1995,
36, 249.
19 T. Suzuki, K. Nakashima and S. Shinkai, Chem. Lett., 1994, 699.
20 J. L. Atwood, G. A. Koutsantonis and C. L. Raston, Nature, 1994,
368, 229.
15,23-Dibromo-7-iodo-2,3,10,11,18,19-hexahomo-3,11,19-tri-
oxacalix[3]arene-25,26,27-triol (13ؒIؒBrؒBr). δH 4.63 (2H, s,
CH2), 4.64 (2H, s, CH2), 4.64 (2H, s, CH2), 7.25 (4H, s, Ar–H),
7.43 (2H, s, Ar–H), 8.66 (2H, s, OH), 8.68 (1H, s, OH); δC 70.34,
70.53, 81.06, 111.27, 125.79, 126.29, 132.22, 132.28, 132.33,
138.14, 138.19, 138.25, 154.64, 155.46; HRMS (EI): calcd. for
C24H20Br2IO6 688.8677, found 688.8683.
21 R. M. Williams, J. M. Zwier and J. W. Verhoeven, J. Am. Chem. Soc.,
1994, 116, 6965.
22 R. M. Williams and J. W. Verhoeven, Recl. Trav. Chim. Pays-Bas,
1992, 111, 531.
General procedure for the precipitation of the complex of fuller-
ene with homooxacalix[n]arene (Tables 1 and 2)
To a toluene solution of fullerene was added a toluene solution
of homooxacalix[n]arene, and the mixture was stirred at room
temperature. After filtration of the formed precipitate, the
filtrate was concentrated and washed with acetone thoroughly
to give the recovered fullerene. The ratios of C60 : C70 in both
precipitate and filtrate were determined by HPLC.
23 T. Andersson, M. Sundahl, G. Westman and O. Wennerström,
Tetrahedron Lett., 1994, 35, 7103.
24 T. Andersson, G. Westman, O. Wennerström and M. Sundahl,
J. Chem. Soc., Perkin Trans. 2, 1994, 1097.
25 T. Andersson, K. Nilsson, M. Sundahl, G. Westman and
O. Wennerström, J. Chem. Soc., Chem. Commun., 1992, 604.
26 H. Matsubara, S. Oguri, K. Asano and K. Yamamoto, Chem. Lett.,
1999, 431.
Recovery of fullerene from the C60/C70–13ؒIؒIؒI complex
27 H. Matsubara, A. Hasegawa, K. Shiwaku, K. Asano, M. Uno,
S. Takahashi and K. Yamamoto, Chem. Lett., 1998, 923.
28 J. W. Steed, P. C. Junk, J. L. Atwood, M. J. Barnes, C. L. Raston and
R. S. Burkhalter, J. Am. Chem. Soc., 1994, 116, 10346.
To an o-dichlorobenzene solution (12 cm3) of the complex (12.4
mg) was added 1 M NaOH (10 cm3), and the resulting hetero-
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 4 – 2 0 9
208

View Article Online
29 J.-Y. Zheng, K. Tashiro, Y. Hirabayashi, K. Kinbara, K. Saigo,
T. Aida, S. Sakamoto and K. Yamaguchi, Angew. Chem., Int. Ed.,
2001, 40, 1858.
30 N. Komatsu, Tetrahedron Lett., 2001, 42, 1733.
31 C. Zondervan, E. K. van den Beuken, H. Kooijman, A. L. Spek and
B. L. Feringa, Tetrahedron Lett., 1997, 38, 3111.
32 B. Krenke and W. Friedrichsen, J. Chem. Soc., Perkin Trans. 1, 1998,
3377.
33 S. Kajigaeshi, T. Kakinami, H. Yamasaki, S. Fujisaki, M. Kondo
and T. Okamoto, Chem. Lett., 1987, 2109.
34 L. F. Lindoy, G. V. Meehan and N. Svenstrup, Synthesis, 1998,
1029.
35 P. D. Hampton, Z. Bencze, W. Tong and C. E. Daitch, J. Org. Chem.,
1994, 59, 4838.
36 G. T. Crisp and P. D. Turner, Tetrahedron, 2000, 56, 407.
37 P. Chirakul, P. D. Hampton and E. N. Duesler, Tetrahedron Lett.,
1998, 39, 5473.
38 P. D. Hampton, C. E. Daitch and E. N. Duesler, New. J. Chem.,
1996, 20, 427.
39 A. N. Ponomarev, B. M. Aksel’rod, V. T. Barchenko, V. P. Belousov,
Z. S. Egorova, I. V. Igonchenkov, A. Y. Isakov, O. Y. Kut’eva,
V. A. Nikitin, D. V. Nikitin, S. V. Ruzaev, A. V. Rumyantsev,
O. S. Tulyakov, N. A. Charykov, M. E. Yudovich and A. L. Yurin,
Russ. J. Phys. Chem., 2000, 74, 1942.
40 K. Tsubaki, K. Tanaka, T. Kinoshita and K. Fuji, Chem. Commun.,
1998, 895.
41 A. Ikeda, Y. Suzuki, M. Yoshimura and S. Shinkai, Tetrahedron,
1998, 54, 2497.
42 T. Haino, M. Yanase and Y. Fukazawa, Tetrahedron Lett., 1997, 38,
3739.
43 J. L. Atwood, L. J. Barbour, P. J. Nichols, C. L. Raston and
C. A. Sandoval, Chem. Eur. J., 1999, 5, 990.
44 T. Haino, M. Yanase and Y. Fukazawa, Angew. Chem., Int. Ed.
Engl., 1997, 36, 259.
45 L. A. Bulavin, I. I. Adamenko, V. M. Yashchuk, T. Y. Ogul’chansky,
Y. I. Prylutskyy, S. S. Durov and P. Scharff, J. Mol. Liq., 2001, 93,
187.
46 S. Talukdar, P. Pradhan and A. Banerji, Fullerene Sci. Technol.,
1997, 5, 547.
47 G. R. Sprengling and J. H. Freeman, J. Am. Chem. Soc., 1950, 72,
1982.
48 J. H. Freeman, J. Am. Chem. Soc., 1952, 74, 6257.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 4 – 2 0 9
209