A convenient preparation of C-silylated calixarenes

Article abstract of DOI:10.1055/s-2008-1067250

Calix[4]arenes having multiple silyl groups on the upper (wide) rim were prepared from the corresponding bromocalixarenes by halogen-metal exchange with t-BuLi followed by silylation. The best results were obtained using the clear supernatant from a mixtu

Full text of DOI:10.1055/s-2008-1067250

2968
PAPER
A Convenient Preparation of C-Silylated Calixarenes
C-Silylated
C
a
a
lixarenes ul F. Hudrlik,* Anne M. Hudrlik, Wondwossen D. Arasho, Raymond J. Butcher
Department of Chemistry, Howard University, Washington, DC 20059, USA
Fax +1(202)8065442; E-mail: phudrlik@howard.edu
Received 20 March 2008; revised 11 June 2008
action for the preparation of p-C-silylated calixarenes.5a,b
Two examples of p-C-silylated calix[4]arenes have been
reported using halogen–metal exchange on bromocalix-
arenes with t-BuLi in THF, followed by treatment with
Abstract: Calix[4]arenes having multiple silyl groups on the upper
(wide) rim were prepared from the corresponding bromocalixarenes
by halogen–metal exchange with t-BuLi followed by silylation. The
best results were obtained using the clear supernatant from a mix-
ture of chlorosilane and triethylamine. With the higher molecular Me3SiCl.6,9 In each case, products were purified by chro-
weight chlorosilanes, an aqueous workup was replaced by a filtra-
tion through a column of silica gel. p-(Trimethylsilyl)calixarene 17,
matography. In one case, fractional crystallization was
also employed to separate the tetrakis-Me3Si compound
the silicon analogue of the well-studied p-tert-butylcalixarene 1,
from the tris.6 We report here a convenient method to in-
formed a crystalline complex with toluene having a toluene mole-
troduce multiple silyl groups onto calix[4]arenes (using
cule in the cone cavity with the toluene methyl protruding out at an
readily available halogenated calixarenes) via halogen–
metal exchange, which generally does not require chro-
matography. In principle, this methodology should be ap-
plicable to the preparation of other multiply silylated
molecules as well.
angle.
Key words: calixarenes, silicon, halogen–metal exchange
Calixarenes1 are of considerable current interest in molec-
ular recognition and supramolecular chemistry, and as
building blocks for more complicated structures. They are
easily prepared from inexpensive starting materials, are
easily modified at the upper (wide) and lower (narrow)
rims, and have been shown to exist in several well-defined
conformations (for calix[4]arenes: cone, partial cone, 1,2-
alternate, and 1,3-alternate). Many functional groups have
been introduced onto the upper rim of calixarenes, prima-
rily by electrophilic aromatic substitution reactions.
Preparation of Substrates
Halogenated calix[4]arenes were prepared using standard
procedures as outlined below. All the reactions gave good
yields, and products were easily purified by crystallization
without chromatography.
The preparation of the tetrabromocalix[4]arene substrates
is shown in Scheme 1. Thus, p-tert-butylcalix[4]arene
(1)10 was dealkylated using AlCl3 and phenol in toluene11
to give p-H-calixarene 212 (50–74% yield). Calixarene 2
was treated with NaH/PrI in DMF11 to give the tetrapropyl
ether 3 (80–88% yield), and with NaH/BnBr in DMF to
give tetrabenzyl ether 413 (76–81% yield). This
procedure11,14 is known to give calix[4]arenes fixed in the
cone conformation15 when propyl or larger groups are in-
troduced. The tetrabromo substrates 516 (86–93% yield)
Silylated calixarenes are of potential interest in molecular
recognition because some tetracoordinate silicon com-
pounds can form relatively stable hypercoordinate com-
pounds with nucleophiles,2 suggesting the possibility that
silylated calixarenes may be useful for recognition of an-
ionic guests.3–6 Silyl ethers of calixarenes (lower rim) are
well known.7 We became interested in the preparation of
calixarenes having multiple silicon groups, especially at
the upper (wide) rim. Upper rim substituents are frequent-
ly introduced onto calixarenes by electrophilic substitu-
tion reactions. However, the introduction of silyl groups
onto aromatic rings by electrophilic aromatic substitution,
although known, is not a general method.8 More common-
ly, carbon–silicon bonds are made by reactions of organo-
metallic reagents with chlorosilanes. These reactions have
not generally been used for the introduction of multiple si-
lyl groups. If such reactions did not proceed in high yield,
attempted introduction of multiple silyl groups onto large
molecules would produce mixtures of completely and par-
tially silylated compounds, which might be difficult to
separate. We have reported the use of the Wurtz–Fittig re-
H
H
t-Bu
t-Bu
t-Bu
H
t-Bu
H
AlCl3
phenol
toluene
r.t.
OH
OH
OH
OH
OH
OH
H
HO
HO
NaH
R-X
1
2
H
DMF
r.t.
H
H
Br
Br
Br
Br
NBS
MEK
OR
OR
OR
RO
OR
OR
OR
RO
3 R = Pr
4 R = Bn
5 R = Pr
6 R = Bn
SYNTHESIS 2008, No. 18, pp 2968–2976
Advanced online publication: 04.09.2008
x
x.
x
x
.
2
0
0
8
DOI: 10.1055/s-2008-1067250; Art ID: M01508SS
© Georg Thieme Verlag Stuttgart · New York
Scheme 1

PAPER
C-Silylated Calixarenes
2969
spectrum of 11 indicates a flattened cone conforma-
tion.5c,22) The product was purified by column chromatog-
raphy, and 10 was obtained pure as white crystals in 62%
yield.
Br
Br
2
OMe
OH
OMe
OR
OR
OH
MeO
We believe that the initially-generated tetralithio interme-
diate was reacting in part with traces of HCl in the chlo-
rosilane. We therefore tried repeating the reaction, and
adding Et3N to the reaction mixture before adding the
chlorosilane. There was little change in the spectra of the
crude product. We therefore decided to try mixtures of the
amine and the chlorosilane.23
MeO
7
8 (R = H)
9 (R = Bn)
Scheme 2
and 617 (78–88% yield) were prepared by treatment of 3
and 4 , respectively, with NBS in methyl ethyl ketone
(MEK). 18
When Me3SiCl is mixed with Et3N, a fine white precipi-
tate (Et3N·HCl) immediately appears (even when each re-
agent is freshly distilled from CaH2). The precipitate
settles after a few days, and the mixture can be stored for
several days, especially if kept cold. However, we centri-
fuged the mixture, and used the clear supernatant shortly
afterwards.
A substrate for the preparation of disilylated calix[4]ar-
enes, the dibromide 9, was prepared as shown in
Scheme 2. Dimethoxycalixarene 7 was prepared in 70–
95% yields by selective alkylation of tetrahydroxycalix-
arene 2 with MeOTs and K2CO3 in MeCN.19 Taking ad-
vantage of the fact that the phenolic rings are more
reactive toward electrophilic substitution than are the cor-
responding ethers, 7 can be converted to the dibromide 8.
Although attempts to effect this conversion with
bromine19 did not lead cleanly to 8 in our hands, when 7
was treated with NBS in MEK,18,20 the dibromide 819 was
produced cleanly in 73–96% yields. Treatment of 8 with
NaH/BnBr in DMF yielded benzyl ether 95c in 80–92%
yields.
Typically, the Me3SiCl and Et3N were premixed in a ni-
trogen- or argon-flushed, septum-capped centrifuge tube,
the resulting white precipitate was compacted by centri-
fuge, and the supernatant was withdrawn by a syringe, and
added to the cold mixture of 5 and t-BuLi. This procedure
gave a crystalline crude product after workup. MALDI-
TOF MS of the crude product showed a peak at m/z 903.8
corresponding to the tetrasilyl compound 10 (as the Na
adduct); partially silylated compounds were not observed.
1
In addition, the H NMR spectrum indicated the product
was rather pure 10 with no evidence for the tris(trimethyl-
silyl)calixarene 11. Calixarene 10 could be purified by a
simple recrystallization, and was obtained in 79% yield.
Halogen–Metal Exchange Reactions
Our initial attempts to prepare C-silylated calixarenes by
halogen–metal exchange21 followed by silylation led to
the desired product as the major component of a mixture.
For example, treatment of tetrabromide 5 with t-BuLi in
THF at –78 °C followed by Me3SiCl (distilled from
CaH2), gave an oily crude product. MALDI-TOF mass
spectral analysis indicated that the tetrakis(trimethyl-
silyl)calixarene 10 was the major product, but that the
corresponding tris(trimethylsilyl)calixarene 11 was also
This procedure was carried out using several chlorosi-
lanes, and using both the propyl and benzyl ether sub-
strates 5 and 6. The results are summarized in Table 1.
Using Me3SiCl or PhMe2SiCl with 6 gave the tetrasilyl-
ated calixarenes 12 (86–92% yields), and 13 (92% yield),
respectively. In both cases, the products were purified
only by simple recrystallization; chromatography was not
necessary.
1
When Ph2MeSiCl and (allyl)Me2SiCl were used as silylat-
ing agents in the above procedure, chromatography was
necessary to purify the products 14, 15, and 16. [In all of
these reactions, the reaction mixtures were worked up by
concentration on the rotary evaporator, partitioning be-
tween aqueous NaHCO3 and Et2O,24 drying, and again
concentrating. The products were routinely placed under
oil-pump vacuum (ca. 0.05 mm) for about two hours. The
aqueous workup would be expected to convert any re-
maining chlorosilane into silanol and disiloxane, and the
higher molecular weight disiloxanes are not volatile.]
present (Figure 1). The H NMR spectrum showed the
peaks expected for 10 and additional small peaks, includ-
ing those expected for 11. (Samples of calixarenes 10 and
11 were available from a Wurtz–Fittig silylation reac-
tion,5b and they can be easily distinguished in the 1H NMR
spectra. The propyl OCH2 groups of 11 give rise to mul-
tiplets of equal size at about d = 4.0 and 3.7; the propyl
OCH2 groups of 10 give a triplet at about d = 3.85. The
SiMe3
Me3Si
SiMe3
SiMe3
H
SiMe3
Me3Si
Me3Si
For benzyl ether substrate 6 with Ph2MeSiCl, a solid crude
product was obtained, but recrystallization did not provide
a pure product. Chromatography resulted in silylated
calixarene 14 in 61% yield, which appeared to be almost
pure by 1H NMR spectroscopy. For propyl ether substrate
5 and (allyl)Me2SiCl, a crude product consisting of an oil
and solid was obtained, and chromatography resulted in
RO
OR
OR
OR
OR
OR OR
RO
10
11
R = Pr
Figure 1 Calixarenes 10 and 11
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

2970
P. F. Hudrlik et al.
PAPER
very bulky groups have been incorporated on the upper
rim.
Table 1 Silylations of Tetraabromocalixarenes and Removal of
Benzyl Ethers
5, 6
Dibromide 9 was used as a substrate for reactions to intro-
duce two silicon groups. As in the above silylations, com-
pound 9 was treated with t-BuLi in THF followed by the
chlorosilane/Et3N mixture (clear supernatant after centri-
fugation). Disilylated calixarenes 21–24 were obtained in
good yields in most cases. The results are summarized in
Table 2.
a
R3Si
R3Si
R3Si
OH
R3Si
R3Si
SiR3
R3Si
SiR3
b
OH
OH
OR
OR
OR
HO
17–20
RO
10, 12–16
Table 2 Silylations of Dibromocalixarene 9 and Removal of Benzyl
Ethers
(a) (1) t-BuLi, THF, –78 °C; (2) R3SiCl, Et3N. (b) H2, Pd/C, EtOAc.
R3Si
OR
Product R3Si
Yield (%) Product Yield (%)
R3Si
OPr
OBn
OBn
OBn
OPr
OBn
10
12
13
14
15
16
Me3Si
79
92
92
79a
86a
65
–
–
R3Si
OBn
a
Me3Si
17
18
19
–
88
92
68
–
b
9
OMe MeO
OBn
PhMe2Si
Ph2MeSi
(allyl)Me2Si
(allyl)Me2Si
OMe
OH
OH
MeO
R3Si
20b
86
25–27
21–24
a Non-aqueous workup.
b PrMe2Si.
(a) (1) t-BuLi, THF, –78 °C; (2) R3SiCl, Et3N.
(b) H2, Pd/C, EtOAc.
R3Si
Product
21
Yield (%) Product
Yield (%)
pure silylated calixarene 15 in 52% yield. For 6 and
(allyl)Me2SiCl, an oily crude product was obtained, and
chromatography resulted in pure silylated calixarene 16 as
a colorless oil in 48–65% yields. In this reaction, MALDI-
TOF MS was run on the crude product, and a large peak
for the tetrasilylated compound 16 (as Na adduct) was ob-
served; no trisilylated material was detected.
Me3Si
84
57
79a
60
25
26
–
78
84
–
PhMe2Si
Ph2MeSi
(allyl)Me2Si
22
23
24
27b
95
a Non-aqueous workup.
b PrMe2Si.
To avoid the problem of separating the product from the
higher molecular weight disiloxanes, we developed a non-
aqueous workup procedure in which the crude product
was concentrated by rotary evaporator as before, and then
immediately passed through a silica gel column without
taking fractions. The chlorosilanes presumably react with
the silica gel and do not elute. The reactions which were
rerun using this procedure gave products that could be pu-
rified by crystallization, and yields were better. Thus,
treatment of benzyl ether substrate 6 with t-BuLi followed
by the supernatant from Ph2MeSiCl/Et3N, and using the
nonaqueous workup procedure, resulted in pure silylated
calixarene 14 in 79% yield. A similar reaction using the
propyl ether substrate 5 and (allyl)Me2SiCl resulted in si-
lylated calixarene 15 in 86% yield.
Initially the aqueous workup procedure was used for these
reactions. When Me3SiCl was used as the silylating agent,
the product 21 was purified by only recrystallization (81–
84% yields). Chromatography was initially used for puri-
fication of the other products, giving 22 from PhMe2SiCl
in 57–66% yields as a crystalline product and 24 from (al-
lyl)Me2SiCl in 60% yield as an oil. Attempts were made
to purify calixarene 23 (from 9 and Ph2MeSiCl) by recrys-
tallization, but the product was not pure by 1H NMR spec-
troscopic analysis. A reaction in which the product was
purified by careful chromatography resulted in pure 23 in
65% yield.
The benzyl groups in calixarenes 12–14 and 16 were re-
moved by hydrogenolysis (treatment with H2 in the pres-
ence of Pd/C) to give the hydroxycalixarenes 17–20 (see
Table 1). Hydrogenolysis of the Ph2MeSi calixarene 14 to
give 19 was slow (complete in 6 h), while with the other
substrates, the reactions were complete in two hours. (The
product from the hydrogenolysis of allyldimethylsilyl-
calixarene 16 was propyldimethylsilylcalixarene 20.) The
Ph2MeSi calixarenes 14 and 19 are notable in that four
When the nonaqueous workup procedure became avail-
able, this was applied to the reaction of 9 and Ph2MeSiCl,
giving pure 23 as a white powder in 79% yield. The other
silylations were not repeated using the nonaqueous work-
up procedure, but that is expected to be the better proce-
dure for reactions with the higher molecular weight
chlorosilanes.
The benzyl groups were removed from calixarenes 21, 22,
and 24 uneventfully by treating with H2 in the presence of
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

PAPER
C-Silylated Calixarenes
2971
Pd/C in ethyl acetate, giving the hydroxycalixarenes 25– Calixarene 17 is the silicon analogue of the well-studied
27 (27 as the PrMe2Si compound, Table 2). However, p-tert-butylcalix[4]arene 1. The complex of 1 and toluene
attempted debenzylation of the Ph2MeSi calixarene 23 un- is well known,30 and was the first30a solid state complex
der the same conditions (2 h) led to recovered 23. Use of involving a calixarene to be reported.31 The X-ray crystal
reaction times up to seven hours led to small amounts of structure showed a cone conformation of the calixarene,
product, but the reaction did not go to completion.
with the methyl group of the toluene inserted well into the
cone cavity. (Further refinement aided by solid-state
NMR indicated that the toluene symmetry axis is slightly
tilted off the axis of symmetry of the calixarene,30d,e and
that about 5–10% of the toluene has the methyl protruding
The conformations and NMR spectra of these calixarenes
deserve comment. All of the previously reported calix-
arenes prepared in this work, and most of the new calix-
arenes (except as noted below) were in the cone
conformation as shown by NMR spectroscopy.25,26 The
out of rather than into the calix cavity.30d
)
cone conformation of the tetrahydroxy and dihydroxy- A diametrically dimethylated (25,27-dimethoxy-26,28-
calixarenes is presumably due to the stability provided by dihydroxy)-tert-butylcalixarene formed a complex with
hydrogen bonding, while that of the tetrapropyloxy and toluene analogous to that of 1.32 A number of X-ray struc-
tetrabenzyloxy calixarenes arises from the method of tures of tert-butylcalixarenes complexed with metals at
preparation14 of 3 and 4, and the fact that conformational the oxygens have been reported, many including a toluene
interconversion of calix[4]arenes is blocked when the in the calix cavity. Different orientations of toluene in the
phenolic oxygens are alkylated with propyl (or larger) cavities have been observed,33 possibly due to differences
groups.15 However, while dihydroxy(dimethoxy) calix- in pitch of the cavity due to hydrogen bonding or metal
arene 8 is a cone, the benzylated compound 9 (drawn as a complexation at the oxygen atoms.32
cone) appeared to be a mixture, and the silylation products
The tert-butyl groups extend the calix cavity, and are be-
21–24 showed broad resonances in the 1H NMR spectra,
lieved to be instrumental in the complexation of neutral
1
suggesting conformational equilibrium on the H NMR
guests by simple calixarenes.30d Removal of the tert-butyl
time scale. Removal of the benzyl groups gave calixare-
group from 1 (to give 2) dramatically reduces the ability
1
nes 25–27, which again showed sharp H NMR spectra
of the calixarene to complex simple aromatic guest mole-
characteristic of the cone conformation, presumably be-
cules.34 X-ray crystal structures of toluene complexes of
cause the H-bonding ability was restored.
simple calix[4]arenes having some other para substitu-
1
The H NMR spectrum of tetrahydroxy(tetrakis)TMS ents have been reported. An analogue of 1 having 1,1,3,3-
calixarene 17 showed the presence of CH2Cl2 (ca. 1:1 ra- tetramethylbutyl groups showed a cone structure with tol-
tio) when it was recrystallized from CH2Cl2–MeOH, even uene in the lattice,34 while the isopropyl analog of 1
after placing under oil-pump vacuum (0.1 mm) for two showed a structure with toluene in the cavity, but with the
hours. (The elemental analysis showed the presence of opposite orientation, with the methyl group pointing
CHCl3, which was used in the preparation of the analytical straight out.35
sample.) Some samples of the other calixarenes showed
We obtained crystals by allowing a solution of 17 in tolu-
1
smaller amounts of CH2Cl2 by H NMR spectroscopy,
ene immersed in a hot water bath to cool to room temper-
suggesting an affinity for complexing with these solvents.
ature overnight. Diffraction data were collected at 93 K.
The structure is shown in Figure 2. There is no crystallo-
graphically imposed symmetry on the molecule – every
atom is unique. The structure has two molecules of tolu-
Complexation Studies
ene per calixarene. One toluene is in the lattice. The other
Although complexation of the silylated calixarenes with
is in the cone cavity with the methyl group pointing out,
nucleophilic or anionic groups is expected to be more fa-
with the symmetry axis of the toluene tilted by about 60°
vorable if there are electron-withdrawing groups on the
from that of the calixarene.
silicon, we briefly studied some of the calixarenes synthe-
sized here. We did not observe complex-induced shifts by
1H NMR titration (using MeNO2 and calixarenes 12, 17,
or 25 in CDCl3, or calixarene 10 in xylene-d10; an attempt
with calixarene 18 suffered from low solubility in xylene).
A brief extraction study27 showed some extraction of tet-
rabutylammonium benzoate28 from water into CDCl3 us-
ing the tetrahydroxycalixarene 20 (with p-xylene as
standard). Suspecting this might be due to an acid-base in-
teraction with the calixarene hydroxyls, we also tried us-
ing the dihydroxycalixarene 25, which should have a
considerably higher pKa value,29 and did not observe any
extraction of the benzoate. We have prepared a complex
of tetrakis(trimethylsilyl)calixarene 17 with toluene, and
obtained a crystal structure by X-ray diffraction (below).
Figure 2 Structure of the toluene complex with calixarene 17; the
toluene in the lattice is omitted36
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

2972
P. F. Hudrlik et al.
PAPER
If the four rings in the calixarene system are consecutively cyclophanes.39 A complex of toluene with calixarene 17,
labeled as A, B, C, and D, then the plane of the encapsu- the silicon analogue of p-tert-butylcalixarene 1, was pre-
lated toluene is parallel to the B–D vector and perpendic- pared and a toluene was shown by X-ray to be in the cone
ular to the A–C vector. With the CH3 group of the toluene cavity with the toluene methyl protruding out of the cavi-
tilted by 60° from the vertical plane it is expected that the ty.
H’s attached to this group and those attached to ring car-
bons C13S, C14S, and C15S would make the closest con-
Unless otherwise stated, all reactions were carried out under argon
tacts with the calixarene skeleton. There are no close
contacts involving the hydrogen attached to C14S as it
projects into the cavity between the four oxygen atoms.
or N2, and transfers of liquids were carried out with N2- or argon-
flushed syringes. For experiments requiring anhydrous conditions,
glassware was dried overnight at 120 °C, and cooled in a desiccator.
The verb ‘concentrated’ refers to removal of solvent using a rotary
evaporator. THF was distilled from sodium and benzophenone.
DMF, Et3N, and Me3SiCl were distilled from CaH2. Petroleum ether
(PE) used refers to the fraction boiling in the range 30–60 °C. The
However, there are close contacts involving the H’s at-
tached to C13S and C15S (H13A and H15A) and the phe-
nyl carbon atoms of ring B and D (Table 3). There are also
close contacts between the toluene methyl H’s (H17A) chlorosilane/Et3N mixtures were prepared by mixing equal volumes
of the chlorosilane and Et3N in a centrifuge tube (which had been
flushed with argon, capped with a septum, and connected to the ar-
and the methyl H’s (H10L) of the calixarene tert-butyl
groups. As is usual in calixarenes, the protons attached to
gon line via a syringe needle), centrifuging for 3 min, and taking the
the four oxygen atoms are involved in hydrogen bonding
supernatant solution by a syringe. Column chromatography was
interactions in a head to tail fashion.
done as flash chromatography using 200–425 mesh silica gel. All
products were placed under oil pump vacuum (0.1–0.05 mm) at r.t.
Table 3 Closest Contacts between the Toluene and Calixarene
Skeletons
1
for at least 2 h. H (400 MHz) and 13C (100 MHz) NMR spectra
were obtained in CDCl3. Chemical shifts were reported in d using
CHCl3 (7.26) or CH2Cl2 (5.32) for 1H NMR (indicated as standard),
Atom 1
H13A
H13A
H13A
Atom 2
C3B
H···X distance (Å) C–H···X angle (°)
and CDCl3 (77.00) for 13C NMR as internal references. 13C NMR
assignments were made using DEPT. MALDI-TOF mass spectra
were performed using 2,5-dihydroxybenzoic acid as the matrix.
2.924
2.802
2.955
158.4
173.4
147.8
C4B
Silylation of Calixarenes 5, 6, and 9; Typical Procedures
1. Procedure Using Aqueous Workup; Preparation of
Compound 13
C5B
A solution of tetrabromocalixarene 6 (0.30 g, 0.27 mmol) in THF
(15 mL) was cooled to –78 °C. A solution of t-BuLi (2.0 mL, 1.5 M
in pentane, 3.0 mmol) was slowly added to the stirred mixture and
the stirring was continued for 2 h. A mixture of PhMe2SiCl and
Et3N (1:1 v/v; 1.0 mL, ca. 3 mmol of chlorosilane) was slowly add-
ed at –78 °C. The resulting mixture was slowly warmed to r.t. in 45
min and stirred for 2 h at r.t. The mixture was then transferred to a
one-necked flask and concentrated giving a solid, which was parti-
tioned between Et2O (20 mL) and H2O (15 mL). The organic layer
was washed with brine (15 mL), dried (MgSO4), and concentrated
giving a solid product. Recrystallization from MeOH–CH2Cl2 (9:1)
yielded 0.33 g (92%) of 13 as white crystals.
H15A
H15A
H15A
C2D
C3D
C4D
2.934
2.975
2.948
141.8
160.2
168.9
H17A
H17Ba
H10L (C10D) 2.363
H8BA (C8B) 2.513
158.5
132.0
a Intermolecular contact.
2. Procedure Using Non-aqueous Workup; Preparation of
Compound 15
A solution of tetrabromotetrapropoxycalixarene 5 (0.348 g, 0.38
mmol) in THF (15 mL) was cooled to –78 °C, and a solution of t-
BuLi (3.0 mL, 1.5 M in pentane, 4.5 mmol) was added slowly. The
mixture was stirred for 1.5 h at –78 °C. A mixture of allyldimethyl-
chlorosilane and Et3N (1:1 v/v; 1.0 mL, ca. 3.3 mmol of chlorosi-
Conclusion
Calixarenes with multiple silyl groups on the upper rim
can be easily prepared in high yields from the correspond-
ing halogenated calixarenes by halogen–metal exchange lane) was slowly added at –78 °C. The mixture was then allowed to
warm up to r.t. gradually in about 45 min and was stirred at r.t. for
followed by silylation. Yields and purities are improved
2 h. The mixture was then transferred to a one-necked flask and con-
when the silylation is carried out using the clear superna-
centrated. The crude mixture was immediately passed through a sil-
tant from a mixture of chlorosilane and triethylamine. Pre-
ica gel chromatography column (9.0 g, 1.2 × 22 cm) using PE–
sumably this removes the proton source as Et3N·HCl.
CH2Cl2 (1:1) as eluent. The eluent (ca. 150 mL) was concentrated
Silylation reactions using higher molecular weight chlo-
rosilanes were further improved by omitting an aqueous
workup, and instead passing the concentrated reaction
mixture through a silica gel column. In principle, this
methodology should be applicable to the preparation of
other multiply silylated molecules,37 such as organosili-
con dendrimers and hyper-branched polymers,38 and sili-
con-bridged macrocycles, such as siloxane-bridged
and the residue recrystallized from MeOH–CH2Cl2 (9:1) to give
0.324 g (86%) of 15 as white crystals.
Hydrogenation of Benzyl Ethers; Typical Procedure
Preparation of Compound 18
A three-necked 50 mL flask, fitted with a stopcock adapter attached
to a H2-filled balloon, was placed under argon on an argon line. The
tetrakis(dimethylphenylsilyl)calix[4]arene 13 (0.12 g, 0.091
mmol), 10% Pd/C (0.10 g), and EtOAc (20 mL) were added to the
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

PAPER
C-Silylated Calixarenes
Tetrakis(phenyldimethylsilyl)calixarenes
25,26,27,28-Tetrabenzyloxy-5,11,17,23-tetrakis(phenyl-
dimethylsilyl)calix[4]arene (13)
2973
flask. The connection to the argon bubbler was closed, the stopcock
to the H2-filled balloon was opened, and a small amount of H2 was
allowed to sweep through the flask for a few seconds by slightly
opening a septum on one of the necks. The mixture was stirred for
2 h. The mixture was then filtered using Celite and concentrated.
The crude solid was recrystallized from MeOH–CH2Cl2 (9:1) to
give 0.080 g (92%) of 18 as white crystals.
The crude product was recrystallized from 9:1 MeOH–CH2Cl2;
white crystals: mp 170–172 °C.
IR (KBr): 3062, 3021, 2955, 1465, 1424, 1255, 1245, 1209, 1116,
1107, 983, 830, 805, 774, 697 cm–1.
1H NMR (CH2Cl2 standard): d = 7.37–7.27 (m, 40 H, C6H5), 6.86 (s,
8 H, ArH), 4.98 (s, 8 H, OCH2Ph), 4.18 (d, J = 12.8 Hz, 4 H,
ArCH2Ar), 2.86 (d, J = 12.9 Hz, 4 H, ArCH2Ar), 0.33 [s, 24 H,
Si(CH3)2].
13C NMR: d = 156.2 (C), 139.5 (C), 137.8 (C), 134.3 (CH), 134.2
(C), 134.0 (CH), 130.4 (C), 130.0 (CH), 128.7 (CH), 128.0 (CH),
127.9 (CH), 127.7 (CH), 76.5 (CH2), 31.3 (CH2), –2.2 (CH3).
Tetrakis(trimethylsilyl)calixarenes
5,11,17,23-Tetrakis(trimethylsilyl)-25,26,27,28-tetrapropoxy-
calix[4]arene (10)
The crude product was recrystallized from 4:1 MeOH–acetone;
white powder; mp 196–197 °C; 198–199 °C (analytical sample).
IR (CHCl3): 2953, 2871, 1464, 1382, 1267, 1247, 1122, 1006, 881,
833 cm–1.
1H NMR (CHCl3 standard): d = 6.89 (s, 8 H, ArH), 4.44 (d, J = 12.5
Hz, 4 H, ArCH2Ar), 3.85 (t, J = 7.6 Hz, 8 H, OCH2CH2), 3.17 (d,
J = 12.5 Hz, 4 H, ArCH2Ar), 2.03 (m, 8 H, OCH2CH2), 1.00 (t,
J = 7.4 Hz, 12 H, OCH2CH2CH3), 0.05 [s, 36 H, Si(CH3)3].
13C NMR: d = 156.8 (C), 133.9 (C), 133.3 (CH), 132.8 (C), 77.0
(CH2), 30.6 (CH2), 23.3 (CH2), 10.3 (CH3), –0.9 (CH3).
MALDI-TOF MS (crude product): m/z calcd for [M + Na]+: 903.5;
found: 903.8; with no visible peak at m/z = 832 [11 + Na]+ (less than
1% would have been visible).
MALDI-TOF MS: m/z calcd for [M + Na]+: 1343.6; found: 1344.4.
25,26,27,28-Tetrahydroxy-5,11,17,23-tetrakis(phenyldimethyl-
silyl)calix[4]arene (18)
The crude product was recrystallized from 9:1 MeOH–CH2Cl2;
white crystals: mp 194–196 °C; 192.9–193.4 °C (analytical sam-
ple).
IR (KBr): 3206, 3170, 3017, 2950, 1588, 1475, 1245, 1127, 906,
835, 753 cm–1.
1H NMR (CHCl3 standard): d = 10.35 (s, 4 H, ArOH), 7.50 (d,
J = 1.7 Hz, 8 H, C6H5), 7.35 (m, 12 H, C6H5), 7.15 (s, 8 H, C6H5),
4.25 (d, J = 13.9 Hz, 4 H, ArCH2Ar), 3.53 (d, J = 13.9 Hz, 4 H,
ArCH2Ar), 0.45 [s, 24 H, Si(CH3)2].
13C NMR: d = 150.0, 138.2, 135.1, 134.1, 131.4, 129.1, 127.8,
127.7, 31.8, –2.2.
MALDI-TOF MS: m/z calcd for [M + Na]+: 983.4; found: 983.4.
Anal. Calcd for C52H80O4Si4: C, 70.85; H, 9.15. Found: C, 70.99; H,
9.57.
25,26,27,28-Tetrabenzyloxy-5,11,17,23-tetrakis(trimethyl-
silyl)calix[4]arene (12)
The crude product crystallized out from the Et2O solution in white
crystals; mp 176–177 °C.
IR (KBr): 3032, 2955, 1465, 1245, 1209, 1117, 984, 891, 830, 748,
692 cm–1.
Anal. Calcd for C60H64O4Si4: C, 74.95; H, 6.71. Found: C, 74.61; H,
6.85.
1H NMR (CH2Cl2 standard): d = 7.31–7.24 (m, 20 H, C6H5), 6.84 (s,
8 H, ArH), 4.92 (s, 8 H, OCH2Ph), 4.20 (d, J = 12.7 Hz, 4 H,
ArCH2Ar), 2.93 (d, J = 12.8 Hz, 4 H, ArCH2Ar), 0.07 [s, 36 H,
Si(CH3)3].
13C NMR: d = 155.9 (C), 138.1 (C), 133.9 (C), 133.4 (CH), 133.1
(C), 129.8 (CH), 128.0 (CH), 127.7 (CH), 76.6 (CH2), 31.1 (CH2),
–0.9 (CH3).
Tetrakis(diphenylmethylsilyl)calixarenes
25,26,27,28-Tetrabenzyloxy-5,11,17,23-tetrakis(diphenyl-
methylsilyl)calix[4]arene (14)
The reaction mixture was concentrated on the rotary evaporator,
and immediately passed through a silica gel column (2.5 × 10 cm)
using ca. 150 mL of 1:1 hexane–CH2Cl2. The solution was concen-
trated and recrystallized from 9:1 MeOH–CHCl3; white powder;
mp 94–97 °C.
MALDI-TOF MS: m/z calcd for [M + Na]+: 1095.5; found: 1096.0.
IR (KBr): 3062, 3022, 2950, 2919, 1460, 1424, 1250, 1209, 1122,
1107, 974, 784, 723, 697 cm–1.
1H NMR (CH2Cl2 standard): d = 7.31–7.16 (m, 60 H, C6H5), 6.83 (s,
8 H, ArH), 5.03 (s, 8 H, OCH2Ph), 4.16 (d, J = 12.7 Hz, 4 H,
ArCH2Ar), 2.82 (d, J = 12.9 Hz, 4 H, ArCH2Ar), 0.46 (s, 12 H,
SiCH3).
13C NMR: d = 156.4 (C), 137.6 (C), 137.0 (C), 135.5 (CH), 135.2
(CH), 134.4 (C), 130.1 (CH), 129.0 (CH), 128.4 (C), 127.9 (CH),
127.6 CH), 76.3 (CH2), 31.7 (CH2), –3.1 (CH3).
25,26,27,28-Tetrahydroxy-5,11,17,23-tetrakis(trimethyl-
silyl)calix[4]arene (17)
The crude product was recrystallized from 9:1:1 MeOH–acetone–
CH2Cl2; white crystals; mp 265–267 °C; 263.6–264.6 °C (analytical
sample recrystallized from MeOH–acetone–CHCl3).
IR (KBr): 3155, 3012, 2950, 1588, 1470, 1245, 1127, 906, 835, 753
cm–1.
1H NMR (CHCl3 standard): d = 10.2 (s, 4 H, ArOH), 7.18 (s, 8 H,
ArH), 4.26 (d, J = 14.0 Hz, 4 H, ArCH2Ar), 3.55 (d, J = 13.8 Hz, 4
H, ArCH2Ar), 0.17 [s, 36 H, Si(CH3)3].
MALDI-TOF MS: m/z calcd for [M + Na]+: 1591.6; found: 1594.0.
In the 1H NMR spectrum of the original sample, an additional peak
was present at d = 5.3, assigned to CH2Cl2. The integration suggest-
ed a 1:1 complex (area ratio of the peaks at d = 5.3 to 4.26 is
1.7:4.0).
13C NMR: d = 149.6 (C), 134.2 (CH), 133.6 (C), 127.8 (C), 31.7
(CH2), –1.1 (CH3).
25,26,27,28-Tetrahydroxy-5,11,17,23-tetrakis(diphenylmethyl-
silyl)calix[4]arene (19)
The crude product was recrystallized from 9:1 MeOH–acetone;
white powder; mp 241–243 °C; 249–250 °C (analytical sample).
IR (KBr): 3219, 3167, 3068, 3045, 3016, 2955, 1476, 1451, 1424,
1249, 1127, 1108, 787, 739, 725, 701 cm–1.
1H NMR (CH2Cl2 standard): d = 10.63 (s, 4 H, ArOH, exch. D2O),
7.46–7.21 (m, 40 H, C6H5), 7.14 (s, 8 H, ArH), 4.28 (d, J = 13.6 Hz,
4 H, ArCH2Ar), 3.52 (d, J = 13.7 Hz, 4 H, ArCH2Ar), 0.71 (s, 12 H,
SiCH3).
MALDI-TOF MS: m/z calcd for [M + Na]+: 735.3; found: 737.0.
Anal. Calcd for C40H56O4Si4·0.5 CHCl3: C, 62.94; H, 7.37. Found:
C, 62.65; H, 7.37.
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

2974
P. F. Hudrlik et al.
PAPER
13C NMR: d = 150.3 (C), 136.3 (CH), 136.2 (C), 135.2 (CH), 129.3
Bis(trimethylsilyl)calixarenes
26,28-Dibenzyloxy-25,27-dimethoxy-5,17-bis(trimethyl-
silyl)calix[4]arene (21)
The crude product was crystallized from CH2Cl2–MeOH; white
crystals; mp 148–150 °C.
(CH), 129.2 (C), 127.8 (CH), 127.7 (C), 31.9 (CH2), –3.0 (CH3).
MALDI-TOF MS: m/z calcd for [M + Na]+: 1231.4; found: 1232.1.
Anal. Calcd for C80H72O4Si4: C, 79.42; H, 6.00. Found: C, 79.29; H,
5.74.
IR (CHCl3): 3007, 2950, 2920, 2848, 1583, 1496, 1460, 1419, 1373,
1260, 1246, 1112, 1025, 917, 835, 690 cm–1.
1H NMR (CH2Cl2 standard): d = 7.55–6.61 (m, 20 H), 5.00–3.11 (m,
18 H), two singlets at 0.11 and –0.10 in 4:1 ratio (total integration
18 H).
Tetrakis(allyldimethylsilyl) and (Propyldimethylsilyl)calix-
arenes
5,11,17,23-Tetrakis(allyldimethylsilyl)-25,26,27,28-tetra-
propoxycalix[4]arene (15)
The reaction mixture was concentrated on the rotary evaporator,
and immediately passed through a silica gel column (1.2 × 22 cm)
using ca. 150 mL of 1:1 PE–CH2Cl2. The solution was concentrated
and recrystallized from 9:1 MeOH–CH2Cl2; white crystals; mp
142–143 °C; 145.9–146.5 °C (analytical sample).
1H NMR (CHCl3 standard): d = 6.89 (s, 8 H, ArH), 5.76–5.65 (m, 4
H, CH=CH2), 4.78 (d, J = 12.9 Hz, 8 H, CH=CH2), 4.45 (d, J = 12.6
Hz, 4 H, ArCH2Ar), 3.86 (t, J = 7.7 Hz, 8 H, OCH2CH2), 3.18 (d,
J = 12.7 Hz, 4 H, ArCH2Ar), 2.05–2.00 (m, 8 H, OCH2CH2), 1.56
(d, J = 8.1 Hz, 8 H, CH2CH=CH2), 1.01 (t, J = 7.5 Hz, 12 H,
OCH2CH2CH3), 0.07 [s, 24 H, Si(CH3)2].
13C NMR: d (major peaks) = 157.0, 138.1, 133.0, 128.1, 127.7,
127.4, 30.9, –0.9.
MALDI-TOF MS: m/z calcd for [M + Na]+: 799.4; found: 800.0.
26,28-Dihydroxy-25,27-dimethoxy-5,17-bis(trimethyl-
silyl)calix[4]arene (25)
The crude product (in EtOAc) was concentrated to give a white
powder; mp 301–302 °C; 301–302 °C (analytical sample).
IR (KBr): 3390, 3012, 2950, 2925, 2899, 2822, 1583, 1460, 1428,
1290, 1245, 1204, 1163, 1113, 912, 835, 774, 754 cm–1.
1H NMR (CHCl3 standard): d = 8.01 (s, 2 H, ArOH), 7.18 (s, 4 H,
ArH), 6.90 (d, J = 7.3 Hz, 4 H, ArH), 6.77 (t, J = 7.3 Hz, 2 H, ArH),
4.30 (d, J = 13.0 Hz, 4 H, ArCH2Ar), 4.00 (s, 6 H, OCH3), 3.43 (d,
J = 13.0 Hz, ArCH2Ar), 0.24 [s, 18 H, Si(CH3)3].
13C NMR: d = 153.9 (C), 153.1 (C), 133.7 (CH), 133.1 (C), 129.7
(C), 129.0 (CH), 127.6 (C), 125.4 (CH), 63.7 (CH3), 31.2 (CH2),
–0.76 (CH3).
13C NMR: d = 157.1 (C), 135.0 (CH), 133.9 (C), 133.6 (CH), 131.2
(C), 113.0 (CH2), 77.2 (CH2), 30.7 (CH2), 24.0 (CH2), 23.3 (CH2),
10.3 (CH3), –3.4 (CH3).
MALDI-TOF MS: m/z calcd for [M + Na]+: 1007.6; found: 1008.8.
Anal. Calcd for C60H88O4Si4: C, 73.11; H, 9.00. Found: C, 72.78; H,
9.05.
MALDI-TOF MS: m/z calcd for [M + Na]+: 619.3; found: 620.96.
5,11,17,23-Tetrakis(allyldimethylsilyl)-25,26,27,28-tetra-
benzyloxycalix[4]arene (16)
The crude product was chromatographed (silica gel, 2.5 × 12 cm,
PE, 10 mL fractions, fractions 20–24); colorless oil.
Anal. Calcd for C36H44O4Si2: C, 72.44; H, 7.43. Found: C, 72.66; H,
7.28.
Bis(phenyldimethylsilyl)calixarenes
26,28-Dibenzyloxy-25,27-dimethoxy-5,17-bis(phenyldimethyl-
silyl)calix[4]arene (22)
The crude product was chromatographed (silica gel, 1.2 × 21 cm,
4:1 PE–CH2Cl2, 7 mL fractions, fractions 5–8); colorless oil;
Rf = 0.4 (3:2 PE–CH2Cl2).
IR (CHCl3): 3028, 3009, 2960, 2925, 1631, 1583, 1470, 1455, 1256,
1245, 1124, 989, 897, 830, 698 cm–1.
1H NMR (CH2Cl2 standard): d = 7.36–7.27 (m, 20 H, C6H5), 6.86 (s,
8 H, ArH), 5.75–5.66 (m, 4 H, CH=CH2), 4.97 (s, 8 H, OCH2Ph),
4.83–4.78 (m, 8 H, CH=CH2), 4.21 (d, J = 12.8 Hz, 4 H, ArCH2Ar),
2.93 (d, J = 12.9 Hz, 4 H, ArCH2Ar), 1.60 (d, J = 8.1 Hz, 8 H,
CH2CH=CH2), 0.12 [s, 24 H, Si(CH3)2].
13C NMR: d = 156.0 (C), 137.9 (C), 135.1 (CH), 134.1 (C), 133.7
(CH), 131.5 (C), 129.9 (CH), 128.0 (CH), 127.8 (CH), 113.0 (CH2),
76.6 (CH2), 31.3 (CH2), 24.2 (CH2), –3.4 (CH3).
IR (CHCl3): 3012, 2950, 2919, 1583, 1460, 1424, 1260, 1112, 1015,
835, 810, 702, 671 cm–1.
1H NMR (CH2Cl2 standard): d = 7.52–6.72 (m, 30 H), 4.93–3.12 (m,
18 H), 0.36 (s, major), 0.11 (s, minor), overlapping with 0.0–0.5 (m,
small) (total integration 12 H).
13C NMR: d (major peaks) = 157.4, 139.1, 138.0, 136.3, 135.2,
134.2, 132.7, 131.3, 130.3, 128.7, 128.1, 127.9, 127.6, 122.8, 60.6,
30.9, –2.0.
MALDI-TOF MS: m/z calcd for [M + Na]+: 1199.6; found: 1200.2.
25,26,27,28-Tetrahydroxy-5,11,17,23-tetrakis(propyldimethyl-
silyl)calix[4]arene (20)
The crude product was recrystallized from 10:1 MeOH–acetone;
white crystals; mp 153–155 °C; 156–157 °C (analytical sample).
MALDI-TOF MS: m/z calcd for [M + Na]+: 923.4; found: 923.8.
26,28-Dihydroxy-25,27-dimethoxy-5,17-bis(phenyldimethyl-
silyl)calix[4]arene (26)
The crude product was recrystallized from 9:1 MeOH–acetone;
white crystals; mp 249–251 °C; 255–256 °C (analytical sample).
IR (KBr): 3165, 3012, 2955, 2863, 1588, 1475, 1455, 1245, 1158,
1127, 1102, 1061, 902, 830, 799 cm–1.
1H NMR (CHCl3 standard): d = 10.32 (s, 4 H, ArOH, exch. D2O),
7.19 (s, 8 H, ArH), 4.28 (d, J = 14.0 Hz, 4 H, ArCH2Ar), 3.58 (d,
J = 13.9 Hz, 4 H, ArCH2Ar), 1.57–1.32 (m, 8 H, SiCH2CH2CH3),
0.96 (t, J = 7.2 Hz, 12 H, SiCH2CH2CH3), 0.67 (crude t, J = 8.4 Hz,
8 H, SiCH2CH2CH3), 0.17 [s, 24 H, Si(CH3)2].
IR (KBr): 3380, 3063, 3017, 2945, 2925, 2822, 1583, 1470, 1424,
1286, 1250, 1209, 1158, 1117, 1020, 994, 912, 815, 769, 733, 702
cm–1.
1H NMR (CH2Cl2 standard): d = 8.14 (s, 2 H, ArOH), 7.52 (br, 4 H,
C6H5), 7.38 (br, 6 H, C6H5), 7.23 (s, 4 H, ArH), 6.88 (d, J = 7.4 Hz,
4 H, ArH), 6.78 (t, J = 7.3 Hz, 2 H, ArH), 4.32 (d, J = 13.1 Hz, 4 H,
ArCH2Ar), 4.01 (s, 6 H, OCH3), 3.42 (d, J = 13.1 Hz, 4 H,
ArCH2Ar), 0.54 [s, 12 H, Si(CH3)2].
13C NMR: d = 149.6 (C), 134.5 (CH), 132.9 (C), 127.7 (C), 31.8
(CH2), 18.6 (CH2), 18.4 (CH3), 17.4 (CH2), –2.9 (CH3).
MALDI-TOF MS m/z calcd for [M + Na]+: 847.4; found: 847.8.
Anal. Calcd for C48H72O4Si4: C, 69.84; H, 8.79. Found: C, 69.52; H,
8.78.
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

PAPER
C-Silylated Calixarenes
2975
13C NMR: d = 154.3 (C), 153.1 (C), 139.3 (C), 134.8 (CH), 134.3
(CH), 133.0 (C), 129.1 (CH), 128.9 (CH), 127.7 (CH), 127.1 (C),
125.5 (CH), 63.7 (CH3), 31.2 (CH2), –1.9 (CH3).
purchased in part with funds from NSF (CHE-0091603). We thank
Dr. Harold Banks for helpful discussions.
MALDI-TOF MS: m/z calcd for [M + Na]+: 743.3; found: 743.6.
References
Anal. Calcd for C46H48O4Si2: C, 76.62; H, 6.71. Found: C, 76.13; H,
6.97.
(1) (a) Gutsche, C. D. Calixarenes, In Monographs in
Supramolecular Chemistry; Stoddart, J. F., Ed.; The Royal
Society of Chemistry: London, 1989. (b) Böhmer, V.
Angew. Chem., Int. Ed. Engl. 1995, 34, 713. (c) Gutsche, C.
D. Calixarenes Revisited, In Monographs in
Bis(diphenylmethylsilyl)calixarenes
26,28-Dibenzyloxy-25,27-dimethoxy-5,17-bis(diphenylmethyl-
silyl)calix[4]arene (23)
The reaction mixture was concentrated on the rotary evaporator,
and immediately passed through a silica gel column (1.2 × 20 cm)
using ca. 150 mL of 4:1 PE–CH2Cl2. The solution was concentrated
and recrystallized from 9:1 MeOH–CHCl3; white powder; mp 84–
86 °C.
1H NMR (CH2Cl2 standard): d = 7.6–6.8 (40 H), 5.1–2.8 (18 H),
0.8–0.3 (6 H).
Supramolecular Chemistry; Stoddart, J. F., Ed.; The Royal
Society of Chemistry: London, 1998. (d) Calixarenes in
Action; Mandolini, L.; Ungaro, R., Eds.; Imperial College
Press: London, 2000. (e) Calixarenes 2001; Asfari, Z.;
Böhmer, V.; Harrowfield, J.; Vicens, J., Eds.; Kluwer
Academic Publishers: Dordrecht, 2001.
(2) (a) Chuit, C.; Corriu, R. J. P.; Reye, C.; Young, J. C. Chem.
Rev. 1993, 93, 1371. (b) Chuit, C.; Corriu, R. J. P.; Reye, C.
In Chemistry of Hypervalent Compounds; Akiba, K., Ed.;
Wiley-VCH: New York, 1999, 81–146. (c) Kira, M.;
Zhang, L. C. In Chemistry of Hypervalent Compounds;
Akiba, K., Ed.; Wiley-VCH: New York, 1999, 147–169.
(3) Recognition of anions: (a) Beer, P. D.; Gale, P. A. Angew.
Chem. Int. Ed. 2001, 40, 486. (b) Matthews, S. E.; Beer, P.
D. In Calixarenes 2001; Asfari, Z.; Böhmer, V.;
Harrowfield, J.; Vicens, J., Eds.; Kluwer Academic
Publishers: Dordrecht, 2001, 421–439.
13C NMR: d (major peaks) = 137.8, 136.8, 135.5, 135.3, 135.2,
134.9, 134.5, 134.3, 128.9, 128.8, 128.3, 128.1, 127.6, 127.5, 127.4,
127.3, –2.9.
MALDI-TOF MS: m/z calcd for [M + Na]+: 1047.4; found: 1047.8.
Bis(allyldimethylsilyl) and (Propyldimethylsilyl)calixarenes
5,17-Bis(allyldimethylsilyl)-26,28-dibenzyloxy-25,27-dimeth-
oxycalix[4]arene (24)
The product was chromatographed (silica gel, 4:1 PE–CH2Cl2) to
give a cloudy oil.
(4) Blanda, M. T.; Frels, J.; Lewicki, J. Supramol. Chem. 1998,
9, 255.
IR (CHCl3): 3063, 2955, 2925, 1630, 1460, 1419, 1260, 1113, 1025,
989, 917, 902, 825, 671 cm–1.
1H NMR (CH2Cl2 standard): d = 7.54–6.65 (m, 20 H), 5.60 (m, 2 H),
4.95–3.09 (m, 22 H), 1.55 (unresolved doublet, 4 H), two singlets at
0.14 and –0.05 in 4:1 ratio (total integration 12 H) (s, 12 H).
13C NMR: d (major peaks) = 157.3, 138.1, 136.3, 135.0, 134.5,
133.2, 132.4, 131.4, 128.6, 128.2, 127.9, 127.5, 122.8, 113.0, 30.9,
24.1, –3.5.
(5) (a) Hudrlik, P. F.; Hudrlik, A. M.; Arasho, W. D.; Zhang, L.;
Cho, J. Abstracts of Papers, 60th Southwest Regional
Meeting of the American Chemical Society, Fort Worth TX,
Sept 29–Oct 5, 2004; American Chemical Society:
Washington DC, 2004, Abstract 301. (b) Hudrlik, P. F.;
Arasho, W. D.; Hudrlik, A. M. J. Org. Chem. 2007, 72,
8107. (c) Hudrlik, P. F.; Hudrlik, A. M.; Zhang, L.; Arasho,
W. D.; Cho, J. J. Org. Chem. 2007, 72, 7858.
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MALDI-TOF MS: m/z calcd for [M + Na]+: 851.4; found: 851.7.
199.
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26,28-Dihydroxy-25,27-dimethoxy-5,17-bis(propyldimethyl-
silyl)calix[4]arene (27)
The crude product was recrystallized from 9:1 MeOH–CH2Cl2;
white powder; mp 239–241 °C.
IR (KBr): 3391, 3012, 2950, 2919, 2863, 1588, 1573, 1465, 1429,
1286, 1250, 1199, 1158, 1117, 994, 912, 820, 769 cm–1.
1H NMR (CHCl3 standard): d = 8.01 (s, 2 H, ArOH), 7.17 (s, 4 H,
ArH), 6.90 (d, J = 7.5 Hz, 4 H, ArH), 6.76 (m, 2 H, ArH), 4.30 (d,
J = 13.0 Hz, 4 H, ArCH2Ar), 4.00 (s, 6 H, OCH3), 3.42 (d, J = 13.1
Hz, ArCH2Ar), 1.36 (m, 4 H, SiCH2CH2CH3), 0.96 (t, J = 7.2 Hz, 6
H, SiCH2CH2CH3), 0.71 (crude t, J = 8.5 Hz, 4 H, SiCH2CH2CH3),
0.23 [s, 12 H, Si(CH3)2].
13C NMR: d = 153.9 (C), 153.1 (C), 134.0 (CH), 133.0 (C), 129.0
(CH), 128.9 (C), 127.5 (C), 125.4 (CH), 63.7 (CH3), 31.2 (CH2),
18.8 (CH2), 18.4 (CH3), 17.5 (CH2), –2.7 (CH3).
MALDI-TOF MS: m/z calcd for major component [M + Na]+:
675.3; found: 675.7; m/z calcd for the monsilylated minor compo-
nent [M + Na]+: 575.3; found: 575.5.
Acknowledgment
This material is based upon work supported in part by the U.S.
Army Research Office under contract/grant number DAAD13-98-
C-0042. We are very grateful to the W. M. Keck Foundation for fi-
nancial support. NMR spectra were obtained on a spectrometer
Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York

2976
P. F. Hudrlik et al.
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Synthesis 2008, No. 18, 2968–2976 © Thieme Stuttgart · New York