Multinuclear calixarene synthons with covalently linked aryl-palladium(II) complexes

Article abstract of DOI:10.1021/jo0494782

New synthetic procedures have been developed for potentially useful metallacalixarene building blocks. The metal sites were covalently connected to calix[n]arenes (n = 4, 6) by oxidative addition of 4-iodobenzyl precursors to either Pd(PPh₃)

Full text of DOI:10.1021/jo0494782

Mu ltin u clea r Ca lixa r en e Syn th on s w ith Cova len tly Lin k ed
Ar yl-P a lla d iu m (II) Com p lexes
Arjan W. Kleij,*,†,‡ Beatriz Souto,† Ce´sar J . Pastor,† Pilar Prados,† and J avier de Mendoza*,†,§
Departamento de Qu´ımica Orga´nica and Servicio Interdepartamental de Investigacio´n,
Universidad Auto´noma de Madrid, Cantoblanco, E-28049 Madrid, Spain, and Institute of
Chemical Research of Catalonia (ICIQ), E-43007 Tarragona, Spain
jmendoza@iciq.es; kleij@science.uva.nl
Received March 31, 2004
New synthetic procedures have been developed for potentially useful metallacalixarene building
blocks. The metal sites were covalently connected to calix[n]arenes (n ) 4, 6) by oxidative addition
of 4-iodobenzyl precursors to either Pd(PPh3)4 or Pd2(dba)3/tmeda (dba ) dibenzylideneacetone) to
furnish calixarene-modified aryl-Pd(II)I(Ln) complexes [Ln ) bis-PPh3 or N,N,N′,N′-tetramethyl-
ethylenediamine (tmeda)]. Methods were explored for the selective preparation of mono-Pd(II)-
calix[4]arene and di-Pd(II)-calix[n]arenes (n ) 4 or 6) complexes and also for bifunctional
calix[4]arene synthons with two Pd(II) complexes accompanied by 4-pyridylmethyl or 4-cyanobenzyl
groups. The properties of the Pd(II)-calix[n]arenes were studied in detail by one- and two-
dimensional NMR and mass spectrometric techniques. The X-ray molecular structures of two
4-iodobenzylcalix[4]arene precursors were also determined.
In tr od u ction
(catalytic) applications. More importantly, a detailed
control over the relative positions of multiple organo-
metallic groups enables a precise manipulation of the
metallacalixarene structure. From this point of view,
calixarenes are highly useful, rigid carrier molecules and
their topology should allow the introduction of functional
groups at preselected positions.This could give access to
catalyst systems displaying cooperative effects (e.g.,
enzymes), such as bimetallic activation of substrates.
Here, we present a general strategy toward lower rim
functionalized metallacalix[n]arenes (n ) 4, 6) that
possess organometallic groups covalently attached to the
calixarene support. Methods for the selective introduction
of a single or multiple Pd(II) center(s) will be described
as well as for novel metallacalixarene synthons with
potentially useful auxiliary groups.
Calix[4]- and calix[6]arenes1 have been widely used as
building blocks in supramolecular synthesis.2 On one
hand, calixarenes can possess a basket-shaped conforma-
tion useful for molecular recognition.3 On the other hand,
calixarenes have provided platforms for the immobiliza-
tion of (transition) metal centers that are useful in
catalysis,4 among other applications.5 Most of the previ-
ously reported approaches toward the synthesis of met-
allacalixarenes are based on coordination of calixarene
scaffolds endowed with N- or P-donor motifs for metal
coordination.6 The formation of less dynamic metal-to-
carbon (M-C) bonds7 can be a highly attractive feature
from a stability point of view (for example, metal leach-
ing), an aspect that may be preferred in long-term
* To whom correspondence should be addressed: tel +34-977-
920220; fax +34-977-920226 (J .M.); tel +31-20-5256960, fax +31-20-
5256422 (A.W.K.).
(5) For some leading examples of molecular capsules based on
calixarenes/cavitands, see (a) Mogck, O.; Paulus, E. F.; Bo¨hmer, V.;
Thondorf, I.; Vogt, W. J . Chem. Soc., Chem. Commun. 1996, 2533-
2534. (b) MacGillivray, L. R.; Atwood, J . L. Nature 1997, 389, 469-
472. (c) J olliffe, K. A.; Timmerman, P.; Reinhoudt, D. N. Angew. Chem.,
Int. Ed. 1999, 38, 933-937. (d) Rinco´n, A. M.; Prados, P.; de Mendoza,
J . J . Am. Chem. Soc. 2001, 123, 3493-3498. (e) Corbellini, F.;
Fiammengo, R.; Timmerman, P.; Crego-Calama, M.; Versluis, K.; Heck,
A. J . R.; Luyten, I.; Reinhoudt, D. N. J . Am. Chem. Soc. 2002, 124,
6569-6575. (f) Shivanyuk, A.; Rebek, J ., J r. J . Am. Chem. Soc. 2002,
124, 12074-12075.
† Universidad Auto´noma de Madrid.
‡ Present address: van ’t Hoff Institute for Molecular Sciences,
University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Am-
sterdam, The Netherlands.
§ Institute of Chemical Research of Catalonia (ICIQ).
(1) (a) Gutsche, C. D. Calixarenes; The Royal Society of Chemistry:
Cambridge, U.K., 1989. (b) Gutsche, C. D., Calixarenes Revisited; The
Royal Society of Chemistry: Cambridge, U.K., 1998. (c) Bo¨hmer, V.
Angew. Chem., Int. Ed. Engl. 1995, 34, 713-745.
(6) For recent reviews: (a) Harvey, P. D. Coord. Chem. Rev. 2002,
233-234, 289-309. (b) Redshaw, C. Coord. Chem. Rev. 2003, 244, 45-
70.
(2) (a) Lehn, J .-M., Supramolecular Chemistry. Concepts and Per-
spectives; VCH: Weinheim, Germany, 1995. (b) Cram, D. J . Nature
1992, 356, 29-36.
(3) (a) Calixarenes in Action; Mandolini, L.; Ungaro, R., Eds.;
Imperial College Press: London, 2000. (b) Beer, P. D.; Gale, P. A.
Angew. Chem., Int. Ed. 2001, 40, 487-516.
(4) (a) Molenveld, P.; Engbersen, J . F. J .; Kooijman, H.; Spek, A.
L.; Reinhoudt, D. N. J . Am. Chem. Soc. 1998, 120, 6726-6737. (b)
Parlevliet, F. J .; Zuideveld, M. A.; Kiener, C.; Kooijman, H.; Spek, A.
L.; Kamer, P. C. J .; Van Leeuwen, P. W. N. M. Organometallics 1999,
18, 3394-3405. (c) Plourde, F.; Gilbert, K.; Gagnon, J .; Harvey, P. D.
Organometallics 2003, 22, 2862-2875.
(7) (a) Stang, P. J .; Cao, D. H.; Chen, K.; Gray, G. M.; Muddiman,
D. C.; Smith, R. D. J . Am. Chem. Soc. 1997, 119, 5163-5168. Recent
examples of metal-to-oxygen bonds: (b) Floriani, C.; Floriani-Moro, R.
In Calixarenes 2001; Asfari, Z., Bo¨hmer, V., Harrowfield, J ., Vicens,
J ., Eds.; Kluwer Academic Press: Dordrecht, The Netherlands, 2001.
(c) Se´ne`que, O.; Rager, M.-N.; Giorgi, M.; Reinaud, O. J . Am. Chem.
Soc. 2001, 123, 8442-8443. (d) Cotton, F. A.; Daniels, L. M.; Lin, C.;
Murillo, C. A. Inorg. Chim. Acta 2003, 347, 1-8 and references therein.
(e) Iwasa, K.; Kochi, T.; Ishii, Y. Angew. Chem., Int. Ed. 2003, 115,
3786-3788.
10.1021/jo0494782 CCC: $27.50 © 2004 American Chemical Society
Published on Web 08/19/2004
6394
J . Org. Chem. 2004, 69, 6394-6403

Calixarene Synthons with Aryl-Pd(II) Complexes
SCHEME 1. Syn th esis of Mon o-P d (II)
Ca lix[4]a r en e 5
F IGURE 1. X-ray molecular structure of 2 with adopted
numbering scheme. For clarity, hydrogen atoms and cocrys-
tallized solvent molecules have been omitted and thermal
ellipsoids are shown at 30% probability.
Resu lts a n d Discu ssion
tion ionization time-of-flight (MALDI-TOF) mass spec-
trometry. The conformation and structural details were
revealed by single-crystal X-ray crystallography (Figure
1; for selected bond angles and distances see Table S1 in
Supporting Information).
The structure shows a monofunctionalized calix[4]-
arene in an almost ideal, rather open cone conformation.
All aromatic rings of the calixarene framework are
pointing outward as referred to the reference plane
defined by the calixarene methylene carbons. As ex-
pected, the iodobenzyl moiety in 2 is situated below the
lower rim cavity of the calixarene.
Attempts to prepare the corresponding Pd(II) deriva-
tive from 2 by standard procedures involving activation
of the carbon-iodine bond by a suitable Pd(0) precursor
[i.e., Pd(PPh3)4] were unsuccessful. Although 1H NMR
monitoring of the reaction indicated the initial formation
of a new species, as suggested by the appearance of new
sets of signals for the OH and OCH2 groups, extensive
decomposition of the intermediate product and/or the
Pd(0) reagent takes place subsequently, probably because
of the high acidity of the three free hydrogen-bonded
phenol OH groups present in 2 (δOH ) 9.97 and 9.33 ppm,
respectively).15
The free phenol positions in 2 were therefore protected.
Benzylation with an excess of benzyl bromide in dimethyl-
formamide (DMF), in the presence of NaH, afforded the
corresponding compound 3 in high yield (Scheme 1). The
symmetry of 3 was easily recognized in the NMR spectra.
The two proximal benzyl groups with respect to the aryl
iodide substituent gave rise to a neat AB pattern for the
Syn th esis of Mon osu bstitu ted Ca lix[4]a r en es. Se-
lective introduction of a single organometallic group at
the lower rim of the calix[4]arene backbone was achieved
by use of a recently disclosed methodology reported by
Ungaro and co-workers.8 One of the intermediate com-
ponents in their studies was a de-tert-butylated, tribenzoyl-
calix[4]arene, first described by Gutsche and Lin.9 At a
later stage, Chawla and Pathak10 reported the synthesis
of tribenzoyl derivative 1 (Scheme 1), and this species
was selected as starting point for the monofunctionalized
calixarene compounds in this work.
4-Iodobenzyltetra-tert-butylcalix[4]arene 211 could be
directly obtained (79% isolated yield) via a one-pot
alkylation-deprotection sequence,12 starting from a mix-
ture of conformers of 1,13 4-iodobenzyl bromide, and
excess sodium hydride, the principal quenching reagent
here being H2O.14 Monosubstitution in 2 was confirmed
by NMR spectroscopy and matrix-assisted laser desorp-
(8) Segura, M.; Sansone, F.; Casnati, A.; Ungaro, R. Synthesis 2001,
2105-2112.
(9) Gutsche, C. D.; Lin, L.-G. Tetrahedron 1986, 42, 1633-1640.
(10) Chawla, H. M.; Pathak, M. Bull. Soc. Chim. Fr. 1991, 128, 232-
243.
(11) (a) Santoyo-Gonza´lez, F.; Torres-Pinedo, A.; Sa´nchez-Ortega,
A. J . Org. Chem. 2000, 65, 4409-4414. (b) Perez-Balderas, F.; Santoyo-
Gonza´lez, F. Synlett 2001, 1699-1702.
(12) Although this compound was previously reported (see ref 11a),
we developed a slightly modified, simpler synthetic procedure that
obviates the use of heavy metal reagents and tedious workup proce-
dures.
(13) The tribenzoyl derivative
1 was prepared by a modified
literature procedure (see ref 9). The conformational properties differed
markedly from those reported earlier. For full details see Kleij, A. W.;
Souto, B.; Pastor, C. J .; Prados, P.; de Mendoza, J . J . Org. Chem. 2003,
68, 8711-8714.
(14) Presumably, the excess NaH reacts with the quenching reagent
(H2O) to form NaOH in situ that gives rise to fast deprotection of the
tribenzoyl intermediate (79% yield) under the employed conditions.
This procedure was reproduced with an isolated yield of 80%.
(15) A further demonstration of the acid instability of the Pd(II)-
calixarenes was given by attempting column chromatography with
silica stationary phases. This gave a fast decomposition of the products
as indicated by darkening of the material.
J . Org. Chem, Vol. 69, No. 19, 2004 6395

Kleij et al.
Therefore, solution mixtures of 8 or 9 and a suitable
Pd(0) precursor [e.g., Pd(PPh3)4] were stirred at ambient
temperature until complete conversion (1H NMR moni-
toring). The OCH2 signals were particularly diagnostic,
as they underwent large upfield shifts (∆δ ≈ 0.5 ppm)
upon introduction of the metal center, as well as the aryl
protons of the pendant arylmethyl groups (from ca. δ )
7.7 and 7.4 ppm to 6.5 and 6.3 ppm, respectively). These
spectroscopic changes could be ascribed to the anisotropy
of the close P-aryl groups. The resulting Pd(II) derivatives
10 and 11 were isolated as yellow solids in 72% and
almost quantitative yield, respectively.17 Although these
Pd(II)-containing calix[4]arenes 10 and 11 are stable in
the solid state as well as in solution in a number of
solvents [tetrahydrofuran (THF), CH2Cl2, and acetone],
particular care should be taken with long-term exposure
to more acidic or protic solvents such as CHCl3 and
MeOH. Prolonged standing in either of these solvents
caused solutions to darken, accounting for some decom-
position, as was evidenced by NMR (CDCl3) measure-
ments.
Compounds 10 and 11 constitute useful examples of
multicentered metallacalixarenes with direct M-C bonds
and potentially tunable metal centers via electronic and/
or steric modifications. The NMR spectroscopic data of
the aryl-Pd(II) groups in 10 and 11 agree with the values
reported for other nonsupported aryl-Pd(II) complexes of
this type.18
The MALDI-TOF mass spectrum (ditranol matrix +
NaI) of 10 exhibited an intense cluster at m/z ) 1838.5
(calcd 1839.3) that was attributed to the fragment ion
[(M - 2PPh3 + Na)+]. Additional isotopic patterns could
be detected, which were assigned to dipalladated calix-
[4]arenes. These clusters are probably a result of in situ
fragmentation/decomposition processes under the applied
conditions, as observed previously for complex 5. Conse-
quently, no molecular ion could be detected. This type of
fragmentation behavior is thus a common feature in the
mass spectra of all PPh3-containing Pd(II)-calix[4]arenes
presented in this investigation.
Syn th esis a n d Ch a r a cter iza tion of Difu n ction a l
Ca lix[4]a r en es. Disubstituted calix[4]arene 8 was used
as starting point for the preparation of cone calix[4]-
arenes bearing two different functional groups at the
lower rim. Apart from the 4-iodobenzyl groups, which can
be converted into aryl-Pd(II)I complexes after treatment
with Pd(PPh3)4 (vide supra), the possibility to introduce
other functional groups was also explored. These could
eventually be useful for the construction of catalytic
species with proximal auxiliary groups aimed at the
molecular recognition of specific substrates.
F IGURE 2. Part of the MALDI-TOF-MS spectrum of com-
pound 5 showing the observed (upper spectrum) and calculated
(lower spectrum) isotopic distribution for the fragment ion [(M
- 2PPh3 + K + dppe)+].
OCH2 unit, while the remaining OCH2 groups were
observed as singlets. Additionally, the 13C{1H} NMR
spectrum showed three separate signals for the OCH2
carbons. Tripropyl derivative 4 was obtained analogously
in quantitative yield (Scheme 1). In agreement with the
previous structure, the NMR spectrum of 4 showed the
presence of two distinct propyl groups. Use of propyl
instead of benzyl protection allowed a straightforward
synthesis of the corresponding Pd(II) complex 5 as a
yellow solid in moderate yield (58%).16 Although a peak
at m/z ) 1397.3 (calcd 1397.5), assignable to the [(M -
2PPh3 + K)+] fragment ion, was visible in the MALDI-
TOF mass spectrum of 5, phosphine exchange with 1,2-
diphenylphosphinoethane (dppe) resulted in a more
stable complex, as was confirmed by the presence of a
sizable [(M - 2PPh3 + K + dppe)+] fragment at m/z )
1533.4 (calcd 1533.5) (Figure 2).
Syn th esis a n d Ch a r a cter iza tion of Disu bstitu ted
Ca lix[4]a r en es. Treatment of the parent starting ma-
terials p-R-calix[4]arenes 6 (R ) tBu) and 7 (R ) H) with
4-iodobenzyl bromide in acetonitrile, with K2CO3 as base,
afforded the syn-1,3-bis(4-iodobenzyl)calix[4]arenes 8
(76%) and 9 (92%), respectively (Scheme 2). These
compounds were subsequently used as starting materials
for the preparation of the corresponding dipalladated
derivatives 10 and 11 (Scheme 2).
Treatment of 8 with NaH in DMF at room tempera-
ture, followed by slow addition of solid 4-chloromethyl-
pyridine hydrochloride, yielded the difunctional deriva-
tive 12 in 62% yield, after crystallization from CH2Cl2/
MeOH. A similar approach was used for the synthesis of
13 (90% yield) from 4-cyanobenzyl bromide (Scheme 3).
The 1H NMR spectra of these compounds showed the
(17) In this case, the diametrically opposite OH groups do not seem
to interfere with metalation, probably due to their lower acidity as
compared with the strongly chelated vicinal OH groups in 1, causing
a faster decomposition of acid-labile Pd-containing reagent/products.
(18) Wallow, T. I.; Goodson, F. E.; Novak, B. M. Organometallics
1996, 15, 3708-3716.
(16) Palladation was unsuccessfully attempted with tribenzyl-
protected derivative 3 (1H NMR monitoring), probably due to steric
reasons. Prolonged reaction times are unlikely to be beneficial due to
Pd-reagent and/or Pd-calixarene decomposition in methanol.
6396 J . Org. Chem., Vol. 69, No. 19, 2004

Calixarene Synthons with Aryl-Pd(II) Complexes
SCHEME 2. Syn th esis of Di-P d (II) Ca lix[4]a r en es 10 a n d 11
SCHEME 3. Syn th esis of Difu n ction a l Ca lix[4]a r en es
presence of two separate singlet resonances for the OCH2
Precursors 12 and 13 were then subjected to metal-
as well as the tert-butyl groups and one AB system
corresponding to the methylene CH2 fragments, while the
13C{1H} spectra showed sets of two peaks for each of these
compounds. The combined NMR data agrees with the
presence of a single, C2v-symmetrical species in a cone
conformation.
ation as described for 8 and 9. Dipalladium-dipyridylcalix-
[4]arene 14 was isolated as a bright yellow solid in a
moderate yield (46%, Scheme 3). The most significant
changes in the H NMR spectrum of 14 (as compared to
12) were found in the aromatic, OCH2, and tert-butyl
1
regions. Upon introduction of the Pd(II) centers, the aryl
J . Org. Chem, Vol. 69, No. 19, 2004 6397

Kleij et al.
SCHEME 4. Syn th esis of Bis-P d (II)-ca lix[6]a r en es 21 a n d 22
protons of the initial aryl iodide moiety shifted from δ )
7.52 and 6.94 ppm to 6.53 and 6.30 ppm, respectively.
Simultaneously, one of the OCH2 resonances appeared
at lower field (δ ) 5.02 ppm), whereas the other peak
shifted to higher field (δ ) 4.40 ppm) as compared to the
initial values of 4.87 and 4.71 ppm, respectively. Similar
changes were noted for the tert-butyl groups and the aryl
protons of the calix[4]arene backbone. MALDI-TOF mass
spectra of 14 (ditranol matrix) gave rather similar results
as reported for 10 and 11, i.e., no molecular ions were
detected and primary fragmentation processes involved
loss of iodide and/or phosphine ligands. A reasonably
resolved isotope pattern that was assigned to a dipalla-
dium fragment ion was found at m/z ) 1561.4 (calcd
1561.4) corresponding to [(M - 4PPh3 - I + ditranol)+].
Surprisingly, a similar palladation procedure involving
13 as a substrate did not give rise to formation of the
bis-Pd(II) derivative 15 (Scheme 3), even after prolonged
reaction times (>72 h) or elevated temperatures (up to
70 °C), and only a mixture of components could be
isolated. This difference in reactivity toward Pd(PPh3)4
between 13 and the pyridine-containing precursor 12
could be explained by the more sterically demanding
4-cyanobenzyl groups present in 13, which may give rise
to a larger repulsion between the aryl iodide and the
Pd(0) reagent during the oxidative addition. This as-
sumption was clearly supported by CPK model inspection
of the bis-Pd(II) targets 14 and 15.
protocol prompted us to prepare the analogous derivative
17, starting from 13 (Scheme 3), which was isolated in a
rather low yield (28%). The latter results supported the
earlier view that the steric requirements of the Pd(0)
reagent seem to be of importance for the introduction of
Pd(II) sites in this type of lower rim functionalized calix-
[4]arenes.
Once again, the mass spectrometric data for Pd(II)-
containing calixarenes 16 and 17 proved to be quite
helpful for molecular identification, as intensive [(M -
tmeda)+] and [(M - tmeda + K)+] fragment ions were
observed, providing direct evidence for the formation of
bis-Pd(II) species. More importantly, it can be assumed
that fragment ions still comprising bidentate donor
ligands (i.e., tmeda in compounds 16 and 17) as compared
to monodentate ligands (i.e., PPh3 in 8, 9, and 14)
probably have higher stability properties and, conse-
quently, give simpler and easy to interpret mass spectra.
Syn th esis a n d Ch a r a cter iza tion of Ca lix[6]a r en e
Der iva tives. The parent p-tert-butylcalix[6]arene 18 was
treated with an excess of 4-iodobenzyl bromide in THF/
DMF (5:1) with Me3SiOK as external base (Scheme 4).20
This known protocol afforded the 1,4-bis(4-iodobenzyl)
derivative 19 in excellent yield as a single species,
contrary to an earlier report for a fairly similar com-
pound.21 Compound 19 probably exists as a cone con-
former at room temperature in CDCl3 solution, as sug-
As an alternative Pd(0) source, we therefore turned to
Pd2(dba)3 (dba ) dibenzylideneacetone). Upon treat-
(19) For the introduction of multiple Pd(II) centers in dendrimer
systems by use of Pd2(dba)3 as reagent, see (a) Hoare, J . L.; Lorenz,
K.; Hovestad, N. J .; Smeets, W. J . J .; Spek, A. L.; Canty, A. J .; Frey,
H.; van Koten, G. Organometallics 1997, 16, 4167-4173. (b) Hovestad,
N. J .; Hoare, J . L.; J astrzebski, J . T. B. H.; Canty, A. J .; Smeets, W. J .
J .; Spek, A. L.; van Koten, G. Organometallics 1999, 18, 2970-2980.
(20) Kanamathareddy, S.; Gutsche, C. D. J . Org. Chem. 1994, 59,
3871-3879.
(21) A rather similar compound has previously been studied
with 4-tolyl instead of 4-iodobenzyl groups connected to positions 1
and 4 of the lower rim of the calix[6]arene. This compound exhibited
closely related spectroscopic features as reported here for 19. See
Kanamathareddy, S.; Gutsche, C. D. J . Org. Chem. 1992, 57, 3160-3166.
19
ment of 8 with a stoichiometric amount of Pd2(dba)3 in
the presence of N,N,N′,N′-tetramethylethylenediamine
(tmeda), the bis-Pd(II)-calixarene 16 was formed in 52%
yield within 15 min (cf. the syntheses of 10, 11, and 14).
A diagnostic neat color change of the reaction mixture
from dark purple to orange/yellow was noted upon full
consumption of the Pd(0) reagent, allowing an easy way
to monitor the reaction. The success of this synthetic
6398 J . Org. Chem., Vol. 69, No. 19, 2004

Calixarene Synthons with Aryl-Pd(II) Complexes
gested by the presence of two AB systems (2:1 integral
ratio) for the methylene protons. Furthermore, only one
set of singlet lines was observed for the OH and OCH2
groups. The 13C{1H} NMR analysis was also in agreement
with the assignment of a cone conformation, since only
two separate signals were observed at δ ) 32.5 and 31.9
ppm (1:2 ratio), respectively.20,22
The OH groups in 19 were subsequently protected by
treatment with methyl iodide, in the presence of NaH
as a base, to furnish the dibenzyltetramethylcalixarene
20 in nearly quantitative yield. The 1H NMR and 13C{1H}
spectra collected for 20 unequivocally revealed the pres-
ence of two different conformational isomers through the
presence of two sets of resonances for all groups. For the
major isomer, three separate patterns were observed for
the methylene protons at δ ) 4.23 (d), 3.84 (s), and 3.59
(d) ppm, whereas the minor isomer gave rise to two AB
systems in a 2:1 ratio. Furthermore, two (broadened)
singlet lines were found for OCH2 as well as OCH3 groups
for the solution mixture (see Experimental Section).
Remarkably, the 13C{1H} NMR spectrum of 20 displayed
methylene signals only at δ ) 30.2, 30.1, and 30.0 ppm
(partly overlapping), accounting for an all-syn orientation
of the aromatic rings in both isomers.20
At higher temperatures (298-393 K, C2D2Cl4; Sup-
porting Information) the signals sharpened significantly
and small shifts were noted for a number of groups, but
the isomer ratio (1.8:1, as measured by signal integration)
remained virtually unchanged, in agreement with the
presence of two stable conformers under these conditions.
Addition of MeOH-d4 (up to 40% v/v) to a CDCl3 solution
of 20 caused preferential precipitation of the major
isomer and thus enrichment in the solid state. Crystal-
lization from CHCl3/MeOH afforded suitable crystals for
X-ray structure determination (Figure 3; for selected
bond angles and distances, see Table S2 in Supporting
Information).23
The molecular structure of 20 is defined by two anti-
positioned iodobenzyl groups and alternating methoxy
substituents at the lower and upper rims of the calix-
arene. The structure of 20 could best be described as a
1,2,3-alternate conformation with the aromatic groups of
the calixarene backbone being neither purely syn- nor
purely anti-oriented with respect to each other. In
solution, a rotational process, accounting for the NMR
observations, is likely.24 This should involve a rapid
interconversion between different conformations that
primarily involve the methyl-substituted phenol rings.
A nonrigid conformation with two anti-positioned iodo-
benzyl groups was further suggested by a nuclear Over-
hauser effect spectroscopy (NOESY) experiment (500
MHz, 323 K; Supporting Information), which, for in-
stance, showed only weak through-space interactions
F IGURE 3. X-ray molecular structure of 20 with the adopted
numbering scheme. For clarity, hydrogen atoms and cocrys-
tallized solvent molecules have been omitted and thermal
ellipsoids are shown at 30% probability.
between the OCH3/CH2 groups and the aromatic protons
of the adjacent aryl rings. The minor isomer could
likewise be correlated with a structure having a nonrigid
conformation with two syn-positioned iodobenzyl groups.
Compound 19 (cone conformation) was submitted to
a similar palladation procedure as for 8 and 9 with
Pd(PPh3)4 as reagent in toluene. This furnished, after
workup, the bis-palladated calixarene 21 in good yield
(77%) as an orange solid. Analysis of the NMR data
revealed that 21 was isolated as a mixture of components.
Likely, compound 21 exists in solution as a mixture of
two conformers in equilibrium. The “through-the-
annulus” rotation of the unsubstituted phenol rings in
21 is slower than for 19 on the NMR time scale, probably
due to the steric hindrance caused by the PPh3 ligands,
which partly occupy the lower rim cavity.
Similar spectroscopic findings (i.e., two sets of signals
as noted for 20 and 21) characterize compound 22 (55%
yield), which was derived from the tetramethyl-substi-
tuted derivative 20 by treatment with Pd(PPh3)4 in THF.
Bis-Pd(II) calixarene 22 was only moderately soluble in
THF and (partly) precipitated from the mixture during
synthesis. The NMR features of 22 were in close agree-
ment with those reported for 20 and 21; that is, the major
component of 22 was associated with a nonrigid isomer
with two anti-positioned Pd(II) metal centers as referred
to the calixarene basal plane. Strong evidence for the
structure of 22 was further provided by MALDI-TOF
mass spectrometry, which demonstrated a reasonably
intense peak at m/z ) 2236.6 (calcd 2237.5) ascribed to
the fragment ion [(M - 2PPh3 + K)+].
(22) J aime, C.; de Mendoza, J .; Prados, P.; Nieto, P. M.; Sa´nchez,
C. J . Org. Chem. 1991, 56, 3372-3376.
(23) A separate measurement of another crystal gave again the
1,2,3-alternate conformation as a result, thereby supporting prefer-
ential crystallization of this isomer in the applied solvent combination.
(24) A rapid, full “lower-rim-through-the-annulus” rotation of the
methyl-substituted phenol rings in the temperature range 298-393
K could provide an explanation for the noted spectroscopic patterns
for the CH2 groups of both isomers. An opposite position of both aryl
iodide groups (major component with a nonrigid conformation) would
then give rise to one AB pattern (8H) and a singlet resonance (4H),
while a nonrigid conformer with two syn-related aryl iodide groups
would afford two AB patterns in a 2:1 ratio.
Con clu sion s
In summary, we have presented methodologies for the
functionalization of calixarene frameworks with useful
4-iodobenzyl groups, which can easily be converted into
J . Org. Chem, Vol. 69, No. 19, 2004 6399

Kleij et al.
5,11,17,23-Tet r a k is(1,1-d im et h ylet h yl)-25-(4-iod ob en -
zyloxy)-26,27,28-tr ip r op yloxyca lix[4]a r en e (4). This com-
pound was prepared similarly as 3 starting from 2 (0.29 g,
0.335 mmol), NaH (60% on a dispersion oil, 0.70 g, 17.5 mmol),
and propyl iodide (0.8 mL, 8.2 mmol) in dry DMF (20 mL),
quantitative yield; mp 125-126 °C; 1H NMR (200 MHz, CDCl3)
δ 7.72 (d, 3J ) 7.8 Hz, 2H, ArH), 7.25 (d, 3J ) 7.8 Hz, 2H,
ArH), 6.91 (s, 4H, ArH), 6.66 (s, 2H, ArH), 6.62 (s, 2H, ArH),
4.77 (s, 2H, OCH2), 4.38 [d, 2J (A-B) ) 12.5 Hz, 2H, CH2], 4.35
[d, 2J (A-B) ) 12.5 Hz, 2H, CH2], 3.73 (m, 6H, OCH2CH2CH3),
3.10 [d, 2J (A-B) ) 11.7 Hz, 2H, CH2], 3.09 [d, 2J (A-B) ) 12.5
Hz, 2H, CH2], 1.93 (m, 6H, OCH2CH2CH3), 1.07 (m, 9H, OCH2-
CH2CH3), 1.19 [s, 18H, C(CH3)3], 0.99 [s, 9H, C(CH3)3], 0.96
[s, 9H, C(CH3)3]; 13C{1H} NMR (125 MHz, CDCl3) δ 154.1,
153.2, 152.5, 144.6, 144.4, 144.1, 137.9, 137.2, 134.7, 134.3,
133.13, 133.10, 131.7, 125.3, 125.0, 124.9, 124.7 (ArC, ArCH),
93.5 (ArC-I), 77.1 (OCH2CH2CH3), 76.8 (OCH2), 76.7 (OCH2-
CH2CH3), 33.9, 33.8, 33.7 [3C(CH3)3, ratio 2:1:1], 31.6, 31.38,
31.36 [3C(CH3)3], 31.2, 31.1 (2CH2), 23.5, 23.1 (2OCH2CH2-
CH3), 10.5, 10.0 (2OCH2CH2CH3) (assignments based on
DEPT, COSY, and HETCOR experiments); MALDI-TOF MS
(ditranol + KI) m/z 887.6 [(M - I + Na)+] (calcd 887.6), 903.5
[(M - I + K)+] (calcd 903.6), 1013.4 [(M + Na)+] (calcd 1013.5),
1029.4 [(M + K)+] (calcd 1029.5). Anal. Calcd for C60H79IO4‚
H2O: C, 71.41; H, 8.09. Found: C, 71.66; H, 7.89.
organometallic groups that possess a direct and stable
palladium-carbon bond. The electronic as well as steric
features of the organometallic units can be altered by
simple ligand exchange reactions after introduction of the
metal sites. This is undoubtedly advantageous in cases
where these changes could lead to modified or improved
catalytic properties of these materials. On the other hand,
calixarene derivatives reminiscent of 17 could be an ex-
cellent starting point for supramolecular, self-assembling
capsule formation via halide abstraction procedures or
for self-assembling dendrimer construction. Analogously,
1,3-alternate isomers of either 14 or 17 could also provide
access to channel-like structures. Studies are currently
underway to exploit the full potential of these metalla-
calixarene synthons.
Exp er im en ta l Section
5,11,17,23-Tet r a k is(1,1-d im et h ylet h yl)-25-(4-iod oben -
zyloxy)-26,27,28-tr ih yd r oxyca lix[4]a r en e (2). A suspension
of 1 (1.42 g, 1.48 mmol), NaH (60% on a dispersion oil, 1.04 g,
26.0 mmol), and 4-iodobenzyl bromide (0.50 g, 1.68 mmol) in
dry DMF (30 mL) was stirred at room temperature for 2.5 h,
after which the mixture was quenched with excess H2O (60
mL) and stirred additionally for 1 h. The white solid precipitate
was filtered off and dissolved in CH2Cl2 (100 mL), washed once
with H2O (100 mL), dried (MgSO4), and filtered. Concentration
in vacuo and treatment with MeOH yielded pure 2 (1.01 g,
79% overall). Crystals suitable for X-ray diffraction were
obtained by crystallization from CH2Cl2/MeOH: mp 141-142
°C; 1H NMR (200 MHz, CDCl3) δ 9.97 (s, 1H, OH), 9.33 (s, 2H,
5,11,17,23-Tetr akis(1,1-dim eth yleth yl)-25-{4-[P dI(P P h3)2]-
ben zyloxy}-26,27,28-tr ip r op yloxyca lix[4]a r en e (5). A so-
lution of 4 (111.1 mg, 0.112 mmol) and Pd(PPh3)4 (131.3 mg,
0.114 mmol) in THF (30 mL) was stirred for 2 h at 50 °C and
then concentrated in vacuo. Addition of MeOH furnished 5 as
a bright, yellow solid (105.2 mg, 58%), which was directly
1
isolated and dried: mp 118-120 °C (decomp); H NMR (300
MHz, CDCl3) δ 7.54-7.48 (m, 6H, P-ArHortho), 7.33-7.20 (m,
4
3
3
9H, P-ArHmeta+para), 6.93 (d, J ) 2.4 Hz, 2H, ArH), 6.91 (d,
OH), 7.85 (d, J ) 7.8 Hz, 2H, ArH), 7.49 (d, J ) 8.6 Hz, 2H,
4J ) 2.2 Hz, 2H, ArH), 6.62 (s, 1H, ArH), 6.55 (s, 1H, ArH),
6.52 (s, 2H, ArH), 4.58 (s, 2H, OCH2), 4.41 [d, 2J (A-B) ) 12.5
Hz, 2H, CH2], 4.36 [d, 2J (A-B) ) 12.5 Hz, 2H, CH2], 3.93-
3.76 (m, 4H, OCH2 propyl), 3.71 (t, 3J ) 7.6 Hz, 2H, OCH2
ArH), 7.12 (s, 2H, ArH), 7.04 (s, 4H, ArH), 6.99 (s, 2H, ArH),
5.09 (s, 2H, OCH2), 4.27 [apparent t, J app(A-B) ) 14.1 Hz,
2
4H, 2CH2], 3.42 [apparent d, 2J app(A-B) ) 13.3 Hz, 4H, CH2],
1.22 [s, 9H, C(CH3)3], 1.21 [s, 27H, C(CH3)3]; 13C{1H} NMR
(75 MHz, CDCl3) δ 149.1, 148.4, 147.6, 143.6, 143.1, 138.1,
135.3, 133.5, 130.8, 128.2, 127.8, 127.5, 126.6, 125.8, 125.7,
125.6 (ArC, ArCH), 94.9 (Ar-C-I), 78.3 (CH2O), 34.3, 34.0,
33.9 [3C(CH3)3, ratio 1:1:2], 32.9, 32.4 (2CH2, ratio 1:1), 31.5,
31.2 [2C(CH3)3, ratio 3:1]; MALDI-TOF MS (ditranol) m/z 865.2
[(M + H)+] (calcd 865.4). Anal. Calcd for C51H61IO4‚0.5H2O:
C, 70.09; H, 7.15. Found: C, 70.28; H 6.86.
2
2
propyl), 3.11 [d, J (A-B) ) 12.4 Hz, 2H, CH2], 3.01 [d, J (A-
B) ) 12.6 Hz, 2H, CH2], 2.02-1.95 (m, 6H, CH2CH3), 1.21 [s,
18H, C(CH3)3], 0.97 [s, 9H, C(CH3)3], 0.93 [s, 9H, C(CH3)3], 0.79
(t, 3J ) 7.4 Hz, 9H, CH2CH3); 13C{1H} (75 MHz, CDCl3) δ 154.1,
153.1, 144.3, 144.0, 143.9, 135.2, 134.9 (br), 132.8, 132.4, 132.1,
132.2, 130.0, 129.6, 128.5, 128.4, 127.7 (br), 126.7, 125.1 (br),
124.5 (ArC, ArCH), 77.1, 76.43 (2OCH2CH2CH3, ratio 1:2),
76.38 (OCH2), 33.9, 33.7 [2C(CH3)3], 31.6, 31.3 [2C(CH3)3], 31.3,
31.1 (2CH2), 23.4, 23.1 (2OCH2CH2CH3, ratio 1:2), 10.5, 10.0
(2OCH2CH2CH3, ratio 1:2); 31P{1H} (121.5 MHz, CDCl3) δ 22.8
(PPh3); MALDI-TOF MS (ditranol + KI) m/z 1381.3 [(M -
2PPh3 + Na)+] (calcd 1381.5), 1397.3 [(M - 2PPh3 + K)+] (calcd
1397.5); MALDI-TOF MS (ditranol + KI + dppe) m/z 1517.4
[(M - 2PPh3 + Na + dppe)+] (calcd 1517.5), 1533.4 [(M -
5,11,17,23-Tet r a k is(1,1-d im et h ylet h yl)-25-(4-iod oben -
zyloxy)-26,27,28-tr iben zyloxyca lix[4]a r en e (3). A mixture
of 2 (0.32 g, 0.37 mmol), NaH (60% on a dispersion oil, 0.58 g,
14.5 mmol), and benzyl bromide (0.30 mL, 2.5 mmol) in dry
DMF (20 mL) was stirred at room temperature for 64 h. The
mixture was quenched with H2O and the precipitate was
filtered off. Trituration with methanol and drying in vacuo
yielded 3 as a white solid (0.41 g, 98%). Crystallization from
CH2Cl2/MeOH afforded white needles: mp 203-204 °C; 1H
NMR (300 MHz, CDCl3) δ 7.42 (d, 3J ) 8.2 Hz, 2H, ArH), 7.30-
7.20 (m, 8H, ArH), 6.93 (d, 3J ) 8.2 Hz, 2H, ArH), 6.80 (s, 2H,
ArH), 6.77 (s, 2H, ArH), 6.65 (s, 2H, ArH), 6.62 (s, 2H, ArH),
4.90 (s, 2H, OCH2), 4.82 [d, 2J (A-B) ) 11.7 Hz, 2H, OCH2],
4.79 (s, 2H, OCH2), 4.74 [d, 2J (A-B) ) 11.8 Hz, 2H, OCH2],
4.23 [d, 2J (A-B) ) 12.9 Hz, 2H, CH2], 4.09 [d, 2J (A-B) ) 12.3
2PPh3 + K + dppe)+] (calcd 1533.5). Anal. Calcd for C96H109
-
IO4P2Pd‚0.5H2O: C, 70.69; H, 6.80. Found: C, 70.54; H, 6.68.
5,11,17,23-Tetr a k is(1,1-d im eth yleth yl)-25,27-bis(4-iod o-
ben zyloxy)-26,28-d ih yd r oxyca lix[4]a r en e (8). A suspen-
sion of p-tert-butylcalix[4]arene 6 (0.88 g, 1.36 mmol), 4-iodo-
benzyl bromide (0.96 g, 3.23 mmol), and K2CO3 (0.71 g, 5.14
mmol) in acetonitrile (100 mL) was refluxed for 17 h. Then
the mixture was filtered hot and concentrated in vacuo. To
the residue were added CH2Cl2 (100 mL) and H2O (100 mL).
After thorough mixing, the aqueous layer was discarded and
the organic layer was dried on anhydrous K2CO3, filtered, and
concentrated under reduced pressure. The remaining oil was
triturated with MeOH to give 8 as a white solid (1.12 g, 76%).
Crystallization from CH2Cl2/MeOH afforded white needles: mp
2
Hz, 2H, CH2], 2.91 [d, J (A-B) ) 12.9 Hz, 2H, CH2], 2.82 [d,
2J (A-B) ) 12.9 Hz, 2H, CH2], 1.13 [s, 9H, C(CH3)3], 1.12 [s,
9H, C(CH3)3], 1.06 [s, 18H, C(CH3)3]; 13C{1H} NMR (75 MHz,
CDCl3) δ 153.0, 152.5, 144.7, 144.6, 144.5, 138.4, 138.2, 138.0,
136.9, 134.2, 133.3, 131.6, 129.6, 129.5, 128.0, 127.9, 127.7,
127.5, 125.2, 125.0, 124.8 (ArC, ArCH), 93.2 (ArC-I), 76.9,
76.5, 75.4 (3OCH2), 33.9, 33.7 [2C(CH3)3], 31.9, 31.3 [2C(CH3)3],
31.4, 29.7 (2CH2) (assignments based on COSY, HETCOR, and
DEPT experiments); MALDI-TOF MS (ditranol + KI) m/z
1157.6 [(M + Na)+] (calcd 1157.5), 1173.5 [(M + Na)+] (calcd
1173.5). Anal. Calcd for C72H79IO4‚0.5H2O: C, 75.57; H, 7.05.
Found: C, 75.64; H, 6.91.
1
228-229 °C; H NMR (200 MHz, CDCl3) δ 7.73 (d, 3J ) 7.8
Hz, 4H, ArH), 7.42 (d, 3J ) 8.6 Hz, 4H, ArH), 7.18 (s, 2H, OH),
7.05 (s, 4H, ArH), 6.79 (s, 4H, ArH), 5.00 (s, 4H, CH2O), 4.24
2
2
[d, J (A-B) ) 12.5 Hz, 4H, CH2], 3.29 [d, J (A-B) ) 13.3 Hz,
4H, CH2], 1.29 [s, 18H, C(CH3)3], 0.95 [s, 18H, C(CH3)3];
13C{1H} NMR (75 MHz, CDCl3) δ 150.5, 149.4, 147.2, 141.5,
6400 J . Org. Chem., Vol. 69, No. 19, 2004

Calixarene Synthons with Aryl-Pd(II) Complexes
137.7, 136.7, 132.4, 129.1, 127.5, 125.5, 125.0 (ArC, ArCH),
93.6 (Ar-C-I), 77.1 (CH2O), 33.9, 33.8 [2C(CH3)3], 31.7, 30.9
[2C(CH3)3], 31.6 (CH2) (spectroscopic assignment was derived
from a DEPT analysis); MALDI-TOF MS (ditranol) m/z 1081.3
[(M + H)+] (calcd 1081.3), 1103.3 [(M + Na)+] (calcd 1103.3),
1119.3 [(M + K)+] (calcd 1119.3). Anal. Calcd for C58H66I2O4‚
0.5H2O: C, 63.91; H, 6.20. Found: C, 63.82; H, 6.14.
a dispersion oil, 23.5 mmol) in DMF (30 mL) was stirred at
room temperature for 25 min. Then, 4-chloromethylpyridine
hydrochloride (1.00 g, 6.10 mmol) was added as a solid over a
period of 30 min. The resultant brownish suspension was
stirred for another 1.5 h and quenched with MeOH. Subse-
quently, H2O was added and the precipitate was filtered off
and dissolved in CH2Cl2 (100 mL). The resulting solution was
washed once with H2O (100 mL) and dried (MgSO4). After
filtration and concentration, the residue was treated with
MeOH to yield 12 as a white solid (0.60 g, 62%). Analytically
pure 12 was obtained from crystallization in CH2Cl2/MeOH,
as white needles: mp 204-206 °C; 1H NMR (300 MHz, CDCl3)
δ 8.46 (d, 3J ) 4.7 Hz, 4H, PyH), 7.52 (d, 3J ) 8.6 Hz, 4H,
25,27-Bis(4-iod ob en zyloxy)-26,28-d ih yd r oxyca lix[4]-
a r en e (9). A suspension of calix[4]arene 7 (0.47 g, 1.11 mmol),
4-iodobenzyl bromide (0.73 g, 2.46 mmol) and K2CO3 (0.70 g,
5.06 mmol) in acetonitrile (30 mL) was refluxed for 15 h. After
a similar workup procedure as for 8, compound 9 was isolated
as a white solid (0.87 g, 92%): mp 247-248 °C; 1H NMR (200
MHz, CDCl3) δ 7.73 (d, 3J ) 8.6 Hz, 4H, ArH), 7.69 (s, 2H,
3
ArH), 7.22 (3J ) 4.7 Hz, 4H, PyH), 6.94 (d, J ) 7.8 Hz, 4H,
3
ArH), 6.84 (s, 4H, ArH), 6.67 (s, 4H, ArH), 4.87 (s, 4H, OCH2),
OH), 7.42 (d, J ) 8.6 Hz, 4H, ArH), 7.18 (s, 2H, OH), 7.07 (d,
4.71 (s, 4H, OCH2), 4.12 [d, 2J (A-B) ) 12.5 Hz, 4H, CH2], 2.93
3
3J ) 7.5 Hz, 4H, ArH from calixarene), 6.89 (d, J ) 7.0 Hz,
2
[d, J (A-B) ) 12.5 Hz, 4H, CH2], 1.14 [s, 18H, C(CH3)3], 1.00
4H, ArH from calixarene), 6.77-6.64 (m, 8H, ArH from
calixarene), 5.01 (s, 4H, CH2O), 4.27 [d, 2J (A-B) ) 12.9 Hz,
4H, CH2], 3.37 [d, 2J (A-B) ) 12.9 Hz, 4H, CH2]; 13C{1H} NMR
(75 MHz, CDCl3) δ 153.1, 151.6, 137.8, 136.3, 133.0, 129.1,
128.5, 127.8, 125.6, 119.1 (ArC, ArCH), 93.8 (Ar-C-I), 77.5
(CH2O), 31.3 (CH2); MALDI-TOF MS (ditranol) m/z 857.1 [(M
+ H)+] (calcd 857.1), 879.1 [(M + Na)+] (calcd 879.0), 895.0
[(M + K)+] (calcd 895.0). Anal. Calcd for C42H34I2O4‚0.5H2O:
C, 58.28; H, 4.08. Found: C, 58.19; H, 4.32.
[s, 18H, C(CH3)3]; 13C{1H} NMR (75 MHz, CDCl3) δ 152.4,
149.6, 146.7, 145.4, 145.1, 137.3, 137.3, 133.9, 133.0, 131.0,
125.5, 125.1, 123.6, 118.6 (ArC, ArCH, PyC, PyCH), 93.7
(ArC-I), 76.4, 75.0 (2OCH2), 33.9, 33.8 [2C(CH3)3], 31.5, 31.3
[2C(CH3)3], 31.2 (CH2); FAB-MS (m-NBA) m/z 1263.5 (100) [(M
+ H)+] (calcd 1263.4), 1171.4 (38) [(M - py)+] (calcd 1171.4),
1045.5 (21) [(M - arylI)+] (calcd 1045.4). Anal. Calcd for
C
70H76I2N2O4‚CH2Cl2: C, 63.26; H, 5.83; N, 2.08. Found: C,
63.32; H, 6.00; N, 1.98.
5,11,17,23-Tetr akis(1,1-dim eth yleth yl)-25,27-bis{4-[P dI-
(P P h 3)2]ben zyloxy}-26,28-d ih yd r oxyca lix[4]a r en e (10). A
solution of 8 (140.4 mg, 0.130 mmol) and Pd(PPh3)4 (297.7 mg,
0.258 mmol) in toluene (25 mL) was stirred for 66 h at room
temperature. The solvent was removed under reduced pressure
and the residue was triturated with hot MeOH to give 10, after
drying, as a yellow solid (220 mg, 72%): mp 126-128 °C
5,11,17,23-Tetr a k is(1,1-d im eth yleth yl)-25,27-bis(4-iod o-
ben zyloxy)-26,28-bis(4-cyan oben zyloxy)calix[4]ar en e (13).
A mixture of 8 (0.85 g, 0.786 mmol), 4-cyanobenzyl bromide
(0.48 g, 2.45 mmol), and NaH (60% on a dispersion oil, 0.59 g,
14.8 mmol) in DMF (20 mL) was stirred for 2 h at room
temperature. The initial gray/black suspension turned into
brownish. The reaction mixture was quenched with MeOH/
H2O and worked up similarly as for 12. Trituration with MeOH
yielded 13 as a white solid (0.93 g, 90%). Analytically pure 13
was obtained by crystallization from CH2Cl2/MeOH as white
1
(decomp); H NMR (200 MHz, CDCl3) δ 7.49 (br m, 14H, OH
+ P-ArHortho), 7.22 (br m, 36H, P-ArH), 7.02 (br s, 4H, ArH),
3
6.61 (br s, 4H, ArH), 6.52 (br d, J ) 7.0 Hz, 4H, ArH), 6.26
(br d, 3J ) 7.0 Hz, 4H, ArH), 4.47 (br s, 4H, CH2O), 4.20 [br d,
2J (A-B) ) 12.9 Hz, 4H, CH2], 3.12 [d, 2J (A-B) ) 12.9 Hz,
4H, CH2], 1.32 [s, 18H, C(CH3)3], 0.86 [s, 18H, C(CH3)3];
13C{1H} NMR (75 MHz, CDCl3) δ 159.8 (ArCipso), 150.8 [d,
1J (P-C) ) 18.8 Hz, P-ArCipso], 146.2, 141.1 (ArC), 135.7 (br,
ArC), 134.8 (apparent t, J app ) 6.3 Hz, ArC), 132.2, 132.1,
131.9, 131.8, 131.6 (P-ArC and ArC), 130.4 (ArC), 129.9 (br,
ArC), 128.3 (ArC), 127.8 (br, ArC), 125.1 [J (P-C) ) 27.2 Hz,
P-ArC], 79.0 (OCH2), 33.8 and 33.7 [2C(CH3)3], 31.7, 30.9
[2C(CH3)3], 31.6 (CH2); 31P{1H} NMR (121.5 MHz, CDCl3) δ
23.2 (PPh3); MALDI-TOF MS (ditranol, NaI) m/z 1838.5
1
needles: mp 225-226 °C; H NMR (200 MHz, CDCl3) δ 7.54
(d, 3J ) 7.8 Hz, 4H, ArH), 7.46 (d, 3J ) 8.6 Hz, 4H, ArH), 7.31
(d, 3J ) 8.6 Hz, 4H, ArH), 6.98 (d, 3J ) 7.6 Hz, 4H, ArH), 6.76
(s, 4H, ArH), 6.72 (s, 4H, ArH), 4.85 (s, 4H, OCH2), 4.73 (s,
4H, OCH2), 4.06 [d, 2J (A-B) ) 12.5 Hz, 4H, CH2], 2.89 [d,
2J (A-B) ) 12.5 Hz, 4H, CH2], 1.09 [s, 18H, C(CH3)3], 1.05 [s,
18H, C(CH3)3]; 13C{1H} NMR (75 MHz, CDCl3) δ 152.1, 152.0,
145.4, 145.2, 143.0, 137.4, 137.2, 133.3, 132.6, 131.8, 131.1,
129.6, 125.4, 125.3 (ArC, ArCH), 118.8 (ArC-CtN), 111.6
(ArC-CtN), 93.7 (ArC-I), 76.3, 75.6 (2OCH2), 33.9 [C(CH3)3],
31.3 [C(CH3)3], 31.2 (CH2) (missing signals probably due to
overlap); FAB-MS (m-NBA) m/z 1309.5 (44) [(M)+] (calcd
1310.4), 1195.5 (28) [(M - arylnitrile)+] (calcd 1195.4), 1093.5
(100) [(M - arylI)+] (calcd 1093.4). Anal. Calcd for C74H76N2O4‚
H2O: C, 66.87, H, 5.91; N, 2.11. Found: C, 66.83; H, 5.77; N,
2.05.
[(M - 2PPh3 + Na)+] (calcd 1839.3). Anal. Calcd for C130
126I2O4P4Pd2‚H2O: C, 66.07; H, 6.23. Found: C, 65.95, H,
5.86.
-
H
25,27-Bis{4-[P d I(P P h 3)2]b en zyloxy}-26,28-d ih yd r oxy-
ca lix[4]a r en e (11). This compound was prepared similarly
as for 10, starting from 9 (194.5 mg, 0.227 mmol), Pd(PPh3)4
(531.2 mg, 0.460 mmol), and toluene (25 mL) to finally furnish
11 as a yellow solid (0.48 g, >98%): mp 154-156 °C (decomp);
5,11,17,23-Tetr akis(1,1-dim eth yleth yl)-25,27-bis{4-[P dI-
(P P h 3)2]ben zyloxy)}-26,28-bis[(4-pyr idyl)m eth yloxy]calix-
[4]a r en e (14). A yellow/orange solution of 12 (140.8 mg, 0.111
mmol) and Pd(PPh3)4 (257.8 mg, 0.223 mmol) in toluene (40
mL) was stirred at room temperature for 20 h. The volatiles
were then removed in vacuo and the product 14 was isolated,
as reported for 10 and 11, as a yellow solid (129.8 mg, 46%):
1H NMR (200 MHz, CDCl3) δ 7.52 (br m, 14H, OH
+
3
P-ArHortho), 7.25-7.13 (br m, 36H, P-ArH), 7.01 (d, J ) 7.0
Hz, 8H, ArH from calixarene), 6.74-6.56 (m, 8H, ArH), 6.26
(br d, 3J ) 7.8 Hz, 4H, ArH), 4.49 (br s, 4H, CH2O), 4.18 [br d,
2J (A-B) ) 13.3 Hz, 4H, CH2], 3.17 [d, 2J (A-B) ) 13.3 Hz,
4H, CH2]; 13C{1H} NMR (75 MHz, CDCl3) δ 159.9 (ArCipso),
153.1 [d, 1J (P-C) ) 23.4 Hz, P-ArCipso], 136.0 (br, ArC), 134.8
(apparent t, J app ) 6.1 Hz, P-ArC), 132.6, 132.3, 132.0, 131.7,
129.9, 128.7, 128.4, 128.2 (ArC, ArCH), 127.8 (apparent t, J app
) 5.0 Hz, P-ArC), 124.6, 118.7 (ArC), 79.1 (OCH2), 31.6 (CH2)
[missing ArC signal probably caused by coalescence with
other(s)]; 31P{1H} NMR (121.5 MHz, CDCl3) δ 23.2 (PPh3);
1
mp 124-126 °C (decomp); H NMR (200 MHz, CDCl3) δ 8.40
(d, 3J ) 5.5 Hz, 4H, PyrHortho), 7.47-7.50 (br m, 24H,
P-ArHortho), 7.18-7.34 (m, 40H, P-ArH + PyrH), 6.95 (s, 4H,
3
ArH), 6.53 (d, J ) 7.0 Hz, 4H, ArH), 6.43 (s, 4H, ArH), 6.30
(d, 3J ) 7.0 Hz, 4H, ArH), 5.02 (s, 4H, OCH2-Pyr), 4.40 (s,
2
2
4H, OCH2-ArPd), 4.11 (d, J ) 12.5 Hz, 4H, CH2), 2.87 (d, J
) 13.3 Hz, 4H, CH2), 1.29 [s, 18H, C(CH3)3], 0.86 [s, 18H,
C(CH3)3]; 13C{1H} NMR (75 MHz, CDCl3) δ 156.5 (ArCipso),
152.6 [d, 1J (P-C) ) 8.4 Hz, P-ArCipso], 149.4, 146.8, 145.3,
144.2, 136.0, 135.2, 135.2, 135.1 (ArC, ArCH), 134.8 [apparent
t, J (P-C) ) 6.3 Hz, P-ArC], 134.6, 132.4, 132.1, 132.0, 131.8,
131.6, 130.2, 129.7, 128.5, 128.4, 127.8 127.7, 127.6, 127.1,
125.7, 124.7, 123.9 (ArC, ArCH, P-ArC), 76.8 (OCH2), 74.0
MALDI-TOF MS (ditranol, NaI) m/z 1614.6 [(M - 2PPh3
+
Na)+] (calcd 1615.0). Anal. Calcd for C114H94I2O4P4Pd2‚H2O: C,
64.09, H, 4.53. Found: C, 63.66; H, 4.55.
5,11,17,23-Tetr a kis(1,1-dim eth yleth yl)-25,27-bis(4-iodo-
ben zyloxy)-26,28-bis[(4-p yr id yl)m eth yloxy]ca lix[4]a r en e
(12). A mixture of 8 (0.831 g, 0.768 mmol) and NaH (60% on
J . Org. Chem, Vol. 69, No. 19, 2004 6401

Kleij et al.
(OCH2), 34.0, 33.6 [2C(CH3)3], 31.6, 31.1 [2C(CH3)3], 31.0 (CH2);
31P{1H} NMR (121.5 MHz, CDCl3) δ 22.7 (PPh3); MALDI-TOF
MS (ditranol + NaI) m/z 2023.1 [(M - 2PPh3 + Na)+] (calcd
2024.4), 1874.1 [(M - 2PPh3 - I)+] (calcd 1875.5), 1561.4 [(M
The residue was treated with excess aqueous 1 M HCl to give
a yellowish suspension. The solid was filtered off and triturated
with MeOH to yield 19 as a slightly yellow solid (1.93 g, 97%).
Analytically pure 19 was obtained by crystallization from
MeOH/CH2Cl2 giving white needles: mp 194-196 °C; 1H NMR
(300 MHz, CDCl3) δ 8.05 (s, 4H, OH), 7.59 (d, 3J ) 8.2 Hz,
- 4PPh3 - I + ditranol)+] (calcd 1561.4). Anal. Calcd for C142
-
H
136I2N2O4P4Pd2‚2H2O: C, 66.59; H, 5.51; N, 1.09. Found: C,
3
66.22, H, 5.10; N, 0.98.
4H, ArH), 7.21 (d, J ) 8.2 Hz, 4H, ArH), 7.10 (s, 8H, ArH),
6.96 (s, 4H, ArH), 5.05 (s, 4H, OCH2), 4.30 [d, 2J (A-B) ) 14.1
5,11,17,23-Tetr akis(1,1-dim eth yleth yl)-25,27-bis{4-[P dI-
(tm ed a )]ben zyloxy}-26,28-d ih yd r oxyca lix[4]a r en e (16). A
mixture of 8 (235.6 mg, 0.218 mmol), Pd2(dba)3 (203.8 mg,
0.223 mmol), and tmeda (108.6 mg, 0.935 mmol) in THF (25
mL) was stirred at room temperature for 15 min. Then the
mixture was filtered to remove traces of Pd(0) and the resulting
clear, bright orange solution was concentrated under reduced
pressure. The residue was treated with Et2O/hexane (20 mL,
v/v ) 1:1) and the precipitate was filtered off and dried in
vacuo, giving 16 as a yellow solid (172.6 mg, 52%). Off-white,
needle-shaped crystals were obtained by crystallization from
CH2Cl2/MeOH: mp 178-180 °C (decomp); 1H NMR (200 MHz,
CDCl3) δ 7.46 (d, 3J ) 7.8 Hz, 4H, ArH), 7.37 (s, 2H, OH),
2
Hz, 4H, CH2], 3.83 [d, J (A-B) ) 13.5 Hz, 2H, CH2], 3.61 [d,
2J (A-B) ) 14.1 Hz, 2H, CH2], 3.54 [d, 2J (A-B) ) 14.1 Hz,
4H, CH2], 1.27 [s, 36H, C(CH3)3], 1.09 [s, 18H, C(CH3)3];
13C{1H} NMR (75 MHz, CDCl3) δ 149.9, 149.6, 147.8, 142.5,
137.6, 135.9, 132.2, 129.0, 126.8, 126.6, 125.9, 125.8, 125.6
(ArC, ArCH), 76.7 (OCH2), 34.2, 33.9 [2C(CH3)3, ratio 1:2], 32.5,
31.9 (2CH2, ratio 1:2), 31.6, 31.1 [2C(CH3)3, ratio 2:1] (the
assignment of the carbon resonances corresponding to the tBu
and CH2 groups was based on a separate DEPT experiment);
MALDI-TOF MS (ditranol + KI) m/z 1443.2 [(M + K)+] (calcd
1443.5). Anal. Calcd for C80H96I2O6‚3H2O: C, 65.84, H, 6.91.
Found: C, 66.01; H, 6.78.
3
7.22 (d, J ) 7.8 Hz, 4H, ArH), 7.01 (s, 4H, ArH), 6.73 (s, 4H,
5,11,17,23,29,35-Hexa k is(1,1-d im eth yleth yl)-39,42-bis-
(4-iod ob e n zyloxy)-37,38,40,41-t e t r a m e t h oxyca lix[6]-
a r en e (20). A mixture of 19 (0.65 g, 0.462 mmol) and NaH
(60% on a dispersion oil, 0.61 g, 15.3 mmol) in DMF (20 mL)
was stirred for 10 min at room temperature. After this period,
excess MeI (2.0 mL, 32.1 mmol) was added and the resultant
white suspension was stirred for another 18 h. The reaction
mixture was carefully quenched with H2O and subsequently
mixed with 1 M HCl (100 mL). After 0.5 h, the product was
extracted with CH2Cl2 (2 × 50 mL) and the organic layers were
washed with H2O (100 mL), dried (MgSO4), filtered, and
concentrated to a minimal volume (∼5 mL). Addition of MeOH
caused precipitation of 20 as a white solid, which was collected
by filtration and dried (0.65 g, 96%). Analytically pure 20 was
obtained by crystallization from CH2Cl2/MeOH: mp 308-309
ArH), 4.91 (s, 4H, OCH2), 4.25 (d, 2J ) 12.5 Hz, 4H, CH2), 3.22
(d, 2J ) 13.3 Hz, 4H, CH2), 2.81 (br m, 4H, part of AA′BB′
system, NCH2CH2N), 2.74 (s, 6H, NCH3), 2.62 (br m, 4H, part
of AA′BB′ system, NCH2CH2N), 2.37 (s, 6H, NCH3), 1.27 [s,
18H, C(CH3)3], 0.92 [s, 18H, C(CH3)3]; 13C{1H} NMR (75 MHz,
CDCl3) δ 150.8, 150.2, 146.5, 145.0, 141.0, 136.4, 132.5, 131.5,
127.8, 125.7, 125.3, 124.8 (ArC, ArCH), 78.3 (OCH2), 62.2, 58.3
(2NCH2CH2N), 50.2, 49.9 (2NCH3) 33.8, 33.7 [2C(CH3)3], 31.74
(CH2), 31.68, 31.0 [2C(CH3)3] (assignment based on DEPT
experiments); MALDI-TOF MS (ditranol) m/z 1410.1 [(M -
tmeda)+] (calcd 1410.2), 1399.3 [(M - I)+] (calcd 1399.5), 1283.2
[(M - I - tmeda)+] (calcd 1283.3). Anal. Calcd for C70H89I2N4O4-
Pd2‚H2O: C, 53.87; H, 6.38; N, 3.70. Found: C, 54.14, H, 6.29,
N, 3.74.
1
°C; H NMR (300 MHz, CDCl3, mixture of isomers) δ 7.72 (d,
5,11,17,23-Tetr akis(1,1-dim eth yleth yl)-25,27-bis{4-[P dI-
(tm ed a )]ben zyloxy}-26,28-bis(4-cya n oben zyloxy)ca lix[4]-
a r en e (17). A mixture of 13 (168.3 mg, 0.128 mmol), Pd2(dba)3
(125.7 mg, 0.137 mmol), and tmeda (102.0 mg, 0.878 mmol)
in THF (40 mL) was stirred at room temperature for 45 min.
Then the product was isolated as reported for 16 and crystal-
lized from CH2Cl2/hexane to afford 17 as a yellow solid (63.0
mg, 28%): mp 158-160 °C (decomp); 1H NMR (200 MHz,
J not resolved, ArH, minor), 7.70 (d, 3J ) 8.2 Hz, 4H, ArH,
major), 7.29 (d, 3J ) 7.6 Hz, 4H, ArH, major + minor), 7.19 (s,
4H, ArH, major), 7.01 (s, 4H, ArH, major), 6.98 (s, 6H, ArH,
minor), 6.92 (s, 6H, ArH, minor), 6.88 (s, 4H, ArH, major), 4.80
(s, 4H, OCH2, major), 4.51 [d, 2J (A-B) ) 15.3 Hz, 4H, CH2,
minor], 4.45 (s, 4H, OCH2, minor), 4.39 [d, 2J (A-B) ) 15.2
Hz, 2H, CH2, minor], 4.23 [d, 2J (A-B) ) 14.1 Hz, 4H, CH2,
2
3
3
major], 3.84 (s, 4H, CH2, major), 3.59 [d, J (A-B) ) 14.1 Hz,
CDCl3) δ 7.48 (d, J ) 7.8 Hz, 4H, ArH), 7.30 (d, J ) 7.8 Hz,
4H, ArH), 7.18 (d, 3J ) 7.8 Hz, 4H, ArH), 6.93 (d, 3J ) 7.8 Hz,
4H, ArH), 6.89 (s, 4H, ArH), 6.52 (s, 4H, ArH), 4.99 (s, 4H,
OCH2), 4.56 (s, 4H, OCH2), 4.19 (d, 2J ) 12.5 Hz, 4H, CH2),
2.96 (d, 2J ) 12.5 Hz, 4H, CH2), 2.73 (br m, 4H, part of AA′BB′
system, NCH2CH2N), 2.67 (s, 6H, NCH3), 2.55 (br m, 4H, part
of AA′BB′ system, NCH2CH2N), 2.16 (s, 6H, NCH3), 1.19 [s,
18H, C(CH3)3], 0.92 [s, 18H, C(CH3)3]; 13C{1H} NMR (75 MHz,
CDCl3) δ 152.6, 152.3, 145.1, 145.0, 144.4, 143.8, 136.2, 134.6,
132.6, 131.9, 130.1, 129.8, 127.6, 125.5, 124.7 (ArC, ArCH),
119.3 (ArC-CtN), 110.8 (ArC-CtN), 77.6, 74.7 (2OCH2),
62.0, 58.3 (2NCH2CH2N), 49.7 (overlapping NCH3) 33.9, 33.7
[2C(CH3)3], 31.6 (CH2), 31.5, 31.2 [2C(CH3)3] (assignment based
on DEPT analysis); MALDI-TOF MS (ditranol + NaI) m/z
1679.4 [(M - tmeda + K)+] (calcd 1679.3), 1663.4 [(M - tmeda
+ Na)+] (calcd 1663.3), 1640.4 [(M - tmeda)+] (calcd 1640.3)
(the cluster peaks with highest intensity are given). Anal.
Calcd for C86H108I2N6O4Pd2‚CH2Cl2: C, 56.75, H, 6.02, N, 4.56.
Found: C, 57.08, H, 5.85; N, 4.58.
4H, CH2, major], 3.52 [d, 2J (A-B) ) 15.2 Hz, 2H, CH2, minor],
3.43 [d, 2J (A-B) ) 15.2 Hz, 4H, CH2, minor], 2.83 (s, 12H,
OCH3, minor), 2.66 (br s, 12H, OCH3, major), 1.15 [s, 36H,
C(CH3)3, major], 1.10 [s, 36H, C(CH3)3, minor], 1.09 [s, 18H,
C(CH3)3, minor], 1.07 [s, 18H, C(CH3)3, major]; 13C NMR{1H}
(125 MHz, CDCl3, mixture of isomers) δ 154.2, 153.8, 151.9,
146.1, 145.7, 145.6, 137.7, 137.5, 137.5, 137.4, 133.6, 133.5,
133.3, 133.2, 133.1, 130.1, 129.4, 126.8, 125.9, 125.6, 125.2
(ArC, ArCH), 93.1 (ArC-I), 73.7 (OCH2, major), 73.4 (OCH2,
minor), 60.1 (OCH3, minor), 59.6 (OCH3, major), 34.12, 34.07
[2C(CH3)3], 31.4, 31.3 [2C(CH3)3], 30.2, 30.1, 30.0 (3CH2)
[assignment was fully supported by DEPT, COSY (H,H), and
HETCOR (C,H) experiments]; MALDI-TOF MS (ditranol + KI)
m/z 1483.4 [(M + K)+] (calcd 1483.6). Anal. Calcd for
C
84H104I2O6‚0.5H2O: C, 68.61; H, 7.06. Found: C, 68.45; H,
7.26.
5,11,17,23,29,35-Hexa k is(1,1-d im eth yleth yl)-39,42-bis-
{4-[P dI(P P h 3)2]ben zyloxy}-37,38,40,41-tetr ah ydr oxycalix-
[6]a r en e (21). A solution of 19 (247.0 mg, 0.176 mmol) and
Pd(PPh3)4 (423.3 mg, 0.366 mmol) in toluene (40 mL) was
stirred for 22 h at room temperature and then worked up as
reported for 10 and 11 to give 21 as a light-orange solid (0.36
g, 77%): mp 164-166 °C (decomp); 1H NMR (300 MHz, CDCl3,
mixture of isomers) δ 7.67 (br s, OH), 7.48 (br m, P-ArHortho),
7.26 (br m, P-ArH), 7.08 (br s, ArH), 7.00 (br s, ArH), 6.59-
6.53 (m, ArH), 6.43-6.36 (m, ArH), 6.21 (m, ArH), 5.01 (br,
OCH2), 4.75 (br, J unresolved, CH2), 4.65 (br s, OCH2), 4.25
5,11,17,23,29,35-Hexa k is(1,1-d im eth yleth yl)-39,42-bis-
(4-iod ob e n zyloxy)-37,38,40,41-t e t r a h yd r oxyc a lix[6]-
a r en e (19). To a suspension of p-tert-butylcalix[6]arene 18
(1.38 g, 1.42 mmol) in a mixture of anhydrous THF/DMF (50:
7) was added Me3SiOK (90%, 1.19 g, 9.28 mmol). The resultant
reddish solution was stirred at room temperature for 50 min.
Then, a solution of 4-iodobenzyl bromide (1.13 g, 3.81 mmol)
in anhydrous THF (5 mL) was added in one portion, upon
which an orange suspension was obtained. The mixture was
stirred at room temperature for 2 h and concentrated in vacuo.
2
2
2
(d, J ) 15.2 Hz, CH2), 4.18 (d, J ) 15.2 Hz, CH2), 4.06 (d, J
6402 J . Org. Chem., Vol. 69, No. 19, 2004

Calixarene Synthons with Aryl-Pd(II) Complexes
) 14.7 Hz, CH2), 3.82 (br s + unresolved signal, two CH2
patterns), 3.51 (d, 2J ) 14.7 Hz, CH2), 3.35 [d, 2J (A-B) ) 14.9
Hz, CH2], 1.29 [s, C(CH3)3], 1.25 [s, C(CH3)3], 1.11 [s, C(CH3)3],
0.75 [s, C(CH3)3]; 13C{1H} NMR (75 MHz, CDCl3, mixture of
isomers) δ 160.7 (ArCipso), 150.0 (br, ArC), 148.1 (ArC), 142.2
(br, ArC), 136.0 (ArC), 135.2-134.6 (br, ArC), 132.2, 131.9,
131.6, 130.2, 129.8, 128.9 (ArC), 127.8 (br, ArC), 127.6, 126.5,
126.3, 125.8, 125.6, 125.3, 124.5 (ArC, ArCH), 78.5 (br, OCH2),
[s, 36H, C(CH3)3], 0.96 [s, 18H, C(CH3)3]; 13C{1H} NMR (75
MHz, CDCl3, data for the 1,2,3-alternate conformer) δ 154.2
(ArCipso), 145.6, 135.9, 135.4, 135.2, 134.9, 134.8, 134.8, 134.6,
134.5, 133.5, 132.3, 132.1, 132.0, 131.7, 130.2, 129.7, 129.0,
128.2, 128.1, 127.9, 127.8, 127.7, 127.1, 125.8, 125.3, 124.6
(ArC, ArCH), 74.7 (br, OCH2), 59.4 (OCH3), 34.1 [br, C(CH3)3],
31.4, 31.3 [2C(CH3)3], 30.7 (br, CH2, overlapping signals);
31P{1H} NMR (121.5 MHz, CDCl3, data for the 1,2,3-alternate
conformer) δ 23.0 (PPh3); MALDI-TOF MS (ditranol + KI) m/z
2236.6 [(M - 2PPh3 + K)+] (calcd 2237.5). Anal. Calcd for
34.2, 33.9 [br, 2C(CH3)3], 32.3, 32.0, 31.2, 30.8, 30.6 [CH2
+
C(CH3)3]; 31P{1H} NMR (121.5 MHz, major isomer) δ 22.8
(PPh3); MALDI-TOF MS (2-amino-4-methyl-5-nitropyridine)
m/z 2276.2 [(M - PPh3 - I)+] (calcd 2275.7), 2013.4 [(M -
2PPh3 - I)+] (calcd 2013.6), 1489.7 [(M - 4PPh3 - I)+] (calcd
1489.4). Anal. Calcd for C152H154I2O6P4Pd2‚2H2O: C, 67.53; H,
5.89. Found: C, 67.34; H, 6.01.
C
156H162I2O6P4Pd2‚H2O: C, 68.34; H, 6.03. Found: C, 68.09,
H, 6.29.
Ack n ow led gm en t. Financial support from CICYT
(Spain, Grants PB1998-0088 and BQU2002-03536) is
gratefully acknowledged. A.W.K. thanks The Nether-
lands Organization for Scientific Research (NWO) for
its help (TALENT program). We acknowledge Dr. M.
Segura for helpful discussions and suggestions.
5,11,17,23,29,35-Hexa k is(1,1-d im eth yleth yl)-39,42-bis-
{4-[P dI(P P h 3)2]ben zyloxy}-37,38,40,41-tetr am eth oxylcalix-
[6]a r en e (22). A solution of 20 (171.0 mg, 0.117 mmol) and
Pd(PPh3)4 (274.2 mg, 0.237 mmol) in THF (30 mL) was stirred
at room temperature for 22 h. Then the white precipitate
formed was isolated by filtration. The filtrate was concentrated
in vacuo and treated with Et2O to yield an off-white solid
product. The two fractions were combined and dried to give
compound 22 (174.6 mg, 55%); 1H NMR (200 MHz, CDCl3, data
for the 1,2,3-alternate conformer) δ 7.50 (br m, P-ArHortho),
7.26 (br m, P-ArH), 6.92 (br s, ArH), 6.88 (br s, ArH), 6.54 (d,
3J ) 7.8 Hz, 2H, ArH), 6.48 (d, 3J ) 7.8 Hz, 2H, ArH), 4.47 (br
s, 4H, OCH2), 4.27 (d, 2J ) 14.9 Hz, 4H, CH2), 3.81 (s, 4H,
CH2), 3.56 (d, 2J ) 13.3 Hz, CH2), 2.63 (br s, 12H, OCH3), 1.13
Su p p or tin g In for m a tion Ava ila ble: General experimen-
tal methods, crystallographic studies and CIF files for 2 and
1
20, variable-temperature H NMR spectra (500 MHz) for 20,
NOESY spectrum for 20, and tables with bond lengths/angles
and crystallographic data for 2 and 20. This material is
available free of charge via the Internet at http://pubs.acs.org.
J O0494782
J . Org. Chem, Vol. 69, No. 19, 2004 6403