Novel chiral (salen)MnIII complexes containing a calix[4]arene unit as catalysts for enantioselective epoxidation reactions of (Z)-aryl alkenes

Article abstract of DOI:10.1002/ejoc.200500138

New asymmetric (salen)Mn^III and UO₂ complexes containing a calix[4]arene unit in the ligand framework were synthesized. The UO₂ complexes were characterized by ¹H-, ¹³C-, 2D TOCSY and T-ROESY NMR spectroscopy. Furthermore, the structure of one UO ₂ complex was determined by single-crystal X-ray analysis. The data showed that UO₂ complexes, which can be considered in first approximation models of the Mn=O oxidant active species, possess a chiral pocket and adopt relevant conformations for the selectivity of the oxygen transfer process. Epoxidation data of model alkenes with the Mn^III complexes showed moderate ee values and were not conclusive in indicating that the calix[4]arene unit might be able to influence the selectivity by a molecular recognition mechanism. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejoc.200500138

FULL PAPER
Novel Chiral (Salen)MnIII Complexes Containing a Calix[4]arene Unit as
Catalysts for Enantioselective Epoxidation Reactions of (Z)-Aryl Alkenes
Maria E. Amato,[a] Francesco P. Ballistreri,[a] Andrea Pappalardo,[a]
Gaetano A. Tomaselli,*[a] Rosa M. Toscano,[a] and David J. Williams[b]
Dedicated to Professor Giorgio Modena on the occasion of his 80th birthday
Keywords: Salencalix[4]arene / Alkenes / Epoxidation / Enantioselectivity
New asymmetric (salen)MnIII and UO2 complexes containing
a calix[4]arene unit in the ligand framework were synthe-
sized. The UO2 complexes were characterized by 1H-, 13C-,
2D TOCSY and T-ROESY NMR spectroscopy. Furthermore,
the structure of one UO2 complex was determined by single-
crystal X-ray analysis. The data showed that UO2 complexes,
which can be considered in first approximation models of the
Mn=O oxidant active species, possess a chiral pocket and
adopt relevant conformations for the selectivity of the oxygen
transfer process. Epoxidation data of model alkenes with the
MnIII complexes showed moderate ee values and were not
conclusive in indicating that the calix[4]arene unit might be
able to influence the selectivity by a molecular recognition
mechanism.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
(oxene),[4,5] is considered to have a non planar structure.
Recent theoretical studies[6] suggest that enantioselectivity
depend on several factors such as the folding of the oxo
species which causes the formation of a chiral pocket, the
presence of bulky substituents at the 3,3Ј-positions of the
salen ligand which regulates the alkene approaching path
from the side of aromatic rings, the occurrence of π conju-
gation involving the olefinic double bond, which provides
regioselectivity and then enantioselectivity and the elec-
tronic effects exhibited by substituents in the 5,5Ј positions
of the salen ligand able to tune the Mn=O bond strength,
which affects the first C–O bond formation step. In this
paper we report a study aimed at designing new salen cata-
lysts containing a calix[4]arene unit, which potentially
might control the alkene approach trajectory by a molecu-
lar recognition mechanism. Calixarenes[7,8] are well known
macrocycles able to exert selective molecular recognition of
neutral molecules by their hydrophobic cavities. The archi-
tecture of these macrocycles allows the easy chemical modi-
fication of both their upper and lower rims to achieve dif-
ferent spatial arrangements of the binding functionalities by
the shaping of the calixarene cavity.
Introduction
Enantioselective epoxidation reactions are of interest be-
cause chiral epoxides, owing to the presence of two contigu-
ous stereogenic centers, are versatile intermediates to obtain
biologically active compounds. Sharpless suggested a cata-
lytic system[1] to obtain very high ee values for the epoxid-
ation of functionalized alkenes. However, for unfunction-
alized alkenes the achievement of high selectivity represents
a challenge for asymmetric synthesis. To reach such a goal
Katsuki[2] and Jacobsen[3] have followed a biomimetic strat-
egy employing salen [N,NЈ-bis(salicylidene)ethylenediamin-
ato] MnIII derivatives as catalysts. The main problem in ob-
taining good ee values with unfunctionalized alkenes is the
control of the alkene approach to the metal site bearing the
transferable oxygen and its orientation upon approach. This
control in the case of salen derivatives is performed by low
energy non bonding interactions. The preferred approach-
ing pathway of alkene is determined by the stereochemistry
of the diimine bridge and by the presence of large substitu-
ents in the ligand. The presence of two stereogenic sp3 car-
bon atoms in the bridge induces flexibility and the salen
ligand can adopt a non planar structure.[2,3] Also the real
oxidant species, supposed to be a (salen) oxo MnV species
Results and Discussion
[a] Dipartimento di Scienze Chimiche, Università di Catania,
Viale A. Doria 6, 95125 Catania, Italy
Fax: +39-095-580138
Synthesis of Salen Calix[4]arene Ligands
E-mail: gtomaselli@mbox.unict.it
[b] Department of Chemistry, Imperial College,
London, South Kensington, London SW7 2AZ, UK
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
We have synthesized four new salen ligands with a built-
in calixarene cavity. The calixarene unit employed is the 5-
hydroxy-25,26,27,28-tetrapropoxycalix[4]arene (1), with a
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DOI: 10.1002/ejoc.200500138
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Enantioselective Epoxidation Reactions of (Z)-Aryl Alkenes
FULL PAPER
non-interconvertible cone conformation obtained by the
The structural characterization of all new compounds
presence of propoxy groups at the lower rim (Scheme 1).[9] was carried on by FAB+ and/or ESI-MS measurements, and
1
Into the calixarene moiety is incorporated a salicylaldehyde by NMR spectroscopy. The H NMR spectra of salen ca-
functionality (OH and CHO groups ortho to each other) in lix[4]arenes 5 and 6 are characterized by the presence of
order to build up the “teeth” of the metal binding system, four pairs of doublets for the bridged methylene protons
through a Schiff base formation with an appropriate chiral and four resonances for the pertinent carbons in the range
imino-amino counterpart. Because of the inherent chirality 31.2–31.7 ppm.[10] The high field aromatic region of the two
of the resulting calix[4]arene containing the salicylaldehyde stereoisomers shows a set of six shielded aromatic protons,
functionality 2, upon reacting the calix[4]arene salicylalde- which likely belong to the pair of aromatic rings (B and D)
hyde with appropriate imino-amino precursors we would of the calixarene skeleton flanking the one (ring A) bearing
expect the formation of couples of diastereomeric ligands the large salen-like residue. These features are suggestive of
(Schiff bases). In order to evaluate the role of the diimine a C2v cone conformation for the calix[4]arene platform for
bridge on the selectivity we have employed two different both compounds, with rings A and C pointing outwards
chiral amines, i.e. (1R,2R)-1,2-diphenylethylenediamine and and rings B and D inwards. This particular arrangement of
(1R)-trans-1,2-cyclohexanediamine, which were condensed the calixarene moiety, supported by the NMR-ROE data,
with 3,5-di-tert-butylsalicylaldehyde to yield imino-amino avoids possible steric interactions of the large diimine sub-
1
intermediates 3 and 4, respectively. Therefore, starting from stituent of ring A with the adjacent ring D. The H NMR
intermediate 1, we have developed a two-step synthesis, spectra of salen calix[4]arenes 7 and 8 are comparable to
leading to the formation of diastereomeric salen calix[4]ar- those of 5 and 6, respectively. The protons of the 1,2-cyclo-
enes 5 and 6 with imino-amino intermediate 3, and of 7 hexylylene moiety resonate as sharp multiplets in the ex-
and 8 with imino-amino intermediate 4.
pected upfield region (1.50–1.93 ppm).
Scheme 1. Synthesis of salen ligands containing a calix[4]arene unit.
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Preparation of (Salen) MnIII and UO2 Calix[4]arenes
Complexes
that they adopt a gauche conformation with a dihedral an-
gle of about 90° because of the coordination of the ura-
nyl(vi) ion. In solution, complex 10 adopts a less hindered
structure with respect to 9 as clearly indicated by the lack
of dipolar correlations between the aromatic protons of Ph–
31 and Ph–32 and the calix ring protons. The two diimine
protons H–31 and H–32 were found arranged in an almost
anti-periplanar conformation (AX pattern at δ = 6.2 and
Ligands 5–8 were utilized to prepare uranyl(vi) (9–12)
and Mn(iii) (13–16) complexes (Scheme 2), see Exp. Sect.
The extension of 2D NMR studies to the uranyl(vi) com-
plexes 9 and 10 helped us to assign the structure of dia-
stereoisomers 5 and 6. Additionally, since 9 and 10 can be
considered good models of the pseudo-octahedral salen
Mn=O species (oxene), (thought to be the real oxidant spe-
cies[2a–c,3a,6a,11] responsible for the selective oxygen transfer
to the olefin), such an information is valuable in assessing
possible parameters controlling the selectivity. The com-
3
5.9 ppm, J = 11.5 Hz) (Figure 1).
The solid-state structure and absolute configuration of
the uranyl complex 9 was established from a single-crystal
X-ray analysis (Figure 2).[12]
In the case of complexes 11 and 12, even if the signals
1
plete assignment of the signals, as well as the stereochemis- observed in the H NMR spectra appear quite broadened,
try and conformations of 9 and 10, were deduced on the a significant downfield shift (with respect to the ligands 7
basis of 2D TOCSY and T-ROESY experiments. In ad- and 8) of the resonances of the protons located nearby the
dition to the almost unbroken pattern of ROE connectivit- donor nitrogen atoms supports the presence of the bonded
ies, which was already present in the spectra of the free li- UO2 group. Unfortunately, for these compounds the di-
gands 5 and 6, several new cross peaks were observed in imine protons H–31 and H–32 signals are buried under pro-
the T-ROESY spectra of the complexes. In particular for poxy chain resonances, preventing a detailed conforma-
compound 9, significant strong dipolar contacts were ob- tional analysis. At any rate, the analysis of the resolved por-
served between H–24 and the aromatic protons of the tions and comparison with the NMR spectra of 9 and 10
phenyl ring bonded to C–31 (Ph–31) and between H–29 allowed the stereoisomer assignments, suggesting that, in
and H–31. The diimine protons H–31 and H–32 resonate solution, complexes 11 and 12 adopt conformations very
as singlets at δ = 6.02 and 6.34 ppm, respectively, indicating similar to those of 9 and 10, respectively.
Scheme 2. MnIII and UO2 salen calix[4]arene complexes.
Figure 1. Newman projection of the diimine bridge.
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Enantioselective Epoxidation Reactions of (Z)-Aryl Alkenes
FULL PAPER
Table 1. Enantioselective epoxidation of alkenes with NaClO cata-
lyzed by (Salen)MnIII calix[4]arenes in CH2Cl2/H2O at 25 °C.[a]
Figure 2. The molecular structure of 9.
Epoxidation Reactions with (Salen)MnIII Calix[4]arenes 13–
16
(Salen)MnIII calix[4]arene complexes were tested as cata-
lysts in epoxidation reactions of styrene, dihydronaphtalene
and of some standard cis-β-alkylstyrenes in order to test
their oxidant abilities. The reactions were performed in
CH2Cl2/H2O at 25 °C using NaClO as oxygen donor and
4-phenylpyridine N-oxide (4-PPNO) as coligand. In the
case of cis-β-alkylstyrenes the reaction affords mainly cis
epoxides together with minor amounts of trans epoxides.
Enantiomeric excess values for the formation of epoxides
(cis epoxides in the case of β-alkylstyrenes), determined by
capillary GLC analysis using chiral columns (see experi-
mental), are reported in Table 1.
[a] In all experiments [Alkene] = 0.14 m, [Catalyst] = 0.007 m, [Co-
ligand] = [4–PPNO] = 0.07 m, [NaClO] = 0.14 m, [Na2HPO4] =
0.05 m at pH = 11.2 as buffer. [b] Determined by GC on chiral
columns. [c] In the case of cis-β-alkylstyrenes ee values are referred
to the major cis epoxide (eecis). [d] Determined by measuring the
optical rotation. [e] No coligand added.
The presence of the coligand 4-PPNO helps in obtaining
higher ee values (entry 2 in Table 1). Most reactions, under
the adopted conditions, are quite fast and are completed or (catalysts 15 and 16) does not substantially affect the ee
almost completed with reaction times going from 15 min to values (compare catalysts 13 vs. 15 and 14 vs. 16), according
4 h. However, reactions with cis-β-ethylstyrene (entry 3) and to the observations reported in previous section (NMR
1,4-diphenyl 1-butene (entry 4) are quite slow and their con- studies) that catalyst couples 13 and 15 or 14 and 16 should
version values are nearly 30% even after 24 h. The presence adopt similar conformations in solution.
of a substituent on the β carbon atom larger than the
In order to try to understand the observed behavior, we
methyl group might decrease the reaction rate probably for determined the eefacial value[14a] (the facial selectivity in the
steric reasons. Ee values are quite low for a terminal alkene first step which depends on kmajor vs. kminor) and the relative
such styrene, but are almost three times higher for all the diastereoselectivity of the ring closure step[14a] (cis/trans
studied β alkylstyrenes. The low ee values for styrene were partitioning of intermediates Imajor and Iminor[14a]) for cis-β-
ascribed to a special type of enantiomeric leakage pathway methylstyrene and cis-β-ethylstyrene.
by Jacobsen,[13] who suggested that epoxidation proceeds
The eefacial values, reported in Table 2, are not very dif-
via a stepwise nonstereospecific mechanism,[3d,14] leading to ferent for the different catalysts. However, only for specu-
the irreversible formation of a radical intermediate, which lation purposes, these values might be considered as indica-
can collapse or can undergo rotation followed by collapse tive of a slightly better selectivity of catalysts 14 and 16
(Scheme 3).
than the corresponding 13 and 15 with both cis-β-methyl-
kmajor and kminor are related to the attack of the alkene styrene and cis-β-ethylstyrene. This behaviour might be as-
to the favored or disfavored catalyst face respectively. In the cribed to the different conformations adopted by the oxene
case of terminal alkenes (R = H) the trans formation, due intermediates derived from complexes 14 and 16 vs. 13 and
to the rotation followed by collapse of the radical interme- 15, respectively. In fact, assuming that uranyl complexes 9
diate, decreases the enantioselectivity because cis and trans and 10 represent models for oxene intermediates 13 and 14,
epoxides are enantiomers.[13] The observed ee values for the respectively, it is reasonable to make inferences based on
remaining alkenes indicate that the degree of enantio- the structural differences between 13 and 14. In the gauche
selectivity displayed by the catalysts synthesized in this conformation of complex 14 the chiral pocket (generated
work is moderate. The change of diimine bridge identity by the distorted R,R diimine bridge) should favor the attack
upon replacing the two phenyl rings linked to the two car- of alkene through the si enantioface (Figure 3, a), because
bon atom stereocenters 31 and 32 with a cyclohexane ring along the attack direction of the re enantioface repulsive
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G. A. Tomaselli et al.
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Scheme 3. Jacobsen nonstereospecific mechanism of alkene asymmetric epoxidation.
interactions arise between the alkene and the phenyl ring
bonded to the C-32 carbon atom of the bridge (Figure 3,
b). The si enantioface of alkene should be also favored if
we assume that the calixarene cavity is able to recognize the
alkene through the alkyl group.[15] Therefore, in this case,
the calixarene should work in synergy with the stereochem-
istry of the bridge (matching) and the oxygen is transferred
preferentially to the si face of alkene (epoxide 1R,2S), as
observed.
Table 2. Enantioselectivity and diastereoselectivity factors.
Also in the gauche conformation of complex 13 the dis-
symmetry of the diimine bridge should favor the si enanti-
oface of the alkene (Figure 4, a), because the attack by the
re enantioface implies the involvement of unfavourable ste-
ric interactions between the alkene and the phenyl ring
bonded to the C–31 carbon atom of the bridge (Figure 4,
b).
[a] eefacial
[cis]major/[trans]major
=
(eecis
×
%cis)
(1+eecis)/(1–eecis
[cis]minor/[trans]minor (1+eetrans)/(1–eetrans
+ (eetrans ×
%trans).[14a] [b]
)
=
.
)
Figure 3. Approach directions for the epoxidation of cis-β-methylstyrene with catalyst 14.
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Enantioselective Epoxidation Reactions of (Z)-Aryl Alkenes
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Figure 4. Approach directions for the epoxidation of cis-β-methylstyrene with catalyst 13.
carried out at 27 °C on a 500 MHz Varian Unity Inova spectrome-
ter (1H at 499.88 MHz, 13C NMR at 125.7 MHz) equipped with
pulse field gradient module (Z axis) and a tunable 5 mm inverse
detection probe. The chemical shifts (ppm) were referenced to TMS
(1H, 0.0 ppm) or CDCl3 (13C, 77.0 ppm). Gas chromatographic
analyses of the reaction mixtures were carried out on a gas chroma-
tograph equipped with a flame ionization detector and program
capability. The ee values were determined employing the chiral col-
umn DMePeBETACDX (25 m × 0.25 mm ID × 0.25 μm film), for
styrene (column conditions: 100 °C (5 min) to 118 °C (1 min) at
By way of contrast the calixarene, through the molecular
recognition of the alkyl group, should favour the attack of
the re enantioface of the alkene working thus in the oppo-
site way to the stereochemistry of bridge (mismatching). In
such a case, if the control of the calixarene on the stereo-
chemistry of the final product were more relevant than that
of the diimine bridge, the oxygen should be transferred
preferentially to the re face of alkene (epoxide 1S,2R). At
variance with these expectations we observed that the major
cis epoxide has still the 1R,2S configuration, even though 3 °C/min), for 1,2-dihydronaphthalene (isotherm 150 °C), for cis-β-
ethylstyrene (column conditions: 50 °C (0 min) to 150 °C (1 min)
at 2.5 °C/min) and for 1,4-diphenyl-1-butene (column conditions:
80 °C (3 min) to 198 °C (20 min) at 3 °C/min). For cis-β-methylsty-
rene the chiral column DMeTButiSililBETA (25 m × 0.25 mm ID
x 0.25 μm film) was used (column conditions: 50 °C (0 min) to
120 °C (1 min) at 2 °C/min). The injector and detector tempera-
tures were maintained at 250 °C for both columns. n-decane was
used as an internal standard throughout. ESI mass spectra were
obtained by employing an ES-MS spectrometer equipped with an
ion trap analyzer. FAB(+) mass spectra were obtained on a MS
50 spectrometer using 3-nitrobenzyl alcohol as a matrix. GC-MS
analyses of reaction mixtures were performed on a 5890 gas chro-
matograph (using an HP-1 dimethyl-polysiloxane 25 m capillary
column) equipped with a MS computerized system. The absolute
configurations of (1R,2S)-1,2-epoxy-1,2,3,4-tetrahydronaphthalene
and of (1R,2S)-1,2-epoxy-1-phenylpropane were determined by
measuring the optical rotations with a polarimeter. Commercial
reagents were used as received without further purification unless
otherwise noted. Dichloromethane was freshly distilled from cal-
cium hydride before use.
the observed eecis values (Table 1) are smaller than those
observed previously with catalyst 14. Therefore, present
data do not allow to conclude that the presence of the ca-
lixarene cavity in our salen catalysts is able to induce a mol-
ecular recognition mechanism in the selective oxygen trans-
fer to alkenes.
Conclusions
We have synthesized the first example of (salen) MnIII
and UO2 complexes containing a calix[4]arene unit in the
ligand framework. NMR studies and X-ray measurements
of the (salen) UO2 complexes, assumed to be structural
models of oxidant active species Mn=O (oxene), indicated
a good correlation between the conformations in solution
and in the solid state and allowed to suggest a rationale
of epoxidation enantioselectivity, based on possible relevant
conformations of oxenes and on the identities of alkenes.
Unfortunately, present data do not allow to indicate that
the presence of the calix[4]arene unit induces a catalytic se-
lectivity based on molecular recognition mechanism of the
alkene to be oxidized. At any rate, the catalysts synthesized
in this work represent the first example of salen derivatives
containing a calixarene unit, and work is in progress to try
to focus the relevant parameters to be controlled in order
to pursue molecular recognition based catalysts to perform
enantioselective epoxidations of unfunctionalized alkenes.
General Procedure for Epoxidation Reactions: To a stirred solution
of alkene (0.35 mmol), catalyst (0.0175 mmol) and 4-phenylpyri-
dine N-oxide (4-PPNO, 0.175 mmol) in CH2Cl2 (2.5 mL), kept in
a round-bottomed flask and maintained at 25 °C in a thermostatic
bath, buffered bleach (0.35 mmol, buffered to pH = 11.2 with 0.05
m Na2HPO4 and 1 m NaOH) was added. The course of the reaction
was monitored by GC against an internal quantitative standard (n-
decane). Upon complete consumption of the starting olefin, the
phases were separated, and the aqueous layer was extracted with
CH2Cl2. The combined organic phases were dried over Na2SO4 and
concentrated. The crude product was purified by PLC (SiO2).
Experimental Section
General Remarks: Melting points were determined on a Kofler hot
stage apparatus and are uncorrected. The NMR experiments were
1,2-Epoxy-1,2,3,4-tetrahydronaphthalene, 1,2-epoxy-1-phenylpro-
pane, 1,2-epoxy-1-phenylbutane and 1,2-epoxy-1,4-diphenylbutane
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G. A. Tomaselli et al.
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were synthesized by epoxidation of the corresponding olefins with
ppm. 13C NMR (125 MHz, CDCl3): δ = 10.2 (× 2), 10.3, 10.4, 23.0,
23.06, 23.1, 23.3, 31.0 (× 2), 31.2, 31.6, 76.5, 76.6, 76.94, 76.97,
117.0, 117.1, 122.0, 122.22, 122.24, 127.7, 128.1, 128.48, 128.53,
132.6, 133.5, 135.0, 135.2, 135.5, 135.7, 137.7, 147.7, 149.9, 156.2,
156.4, 156.9, 158.5, 195.1 ppm. MS (positive FAB): m/z = 637 [M
+ H]+. C41H48O6 (636.82): C 77.36, H 7.55; found C 77.40, H 7.53.
Evidence for the racemic nature of 2 was provided by the dia-
stereomeric interaction observed upon addition of the chiral Pirk-
m-chloroperbenzoic acid in CH2Cl2 and characterized by compari-
1
son of their H NMR spectra with those reported in literature.[16]
In order to determine the absolute configuration of the major en-
antiomer cis epoxide, 1,2-epoxy-1,2,3,4-tetrahydronaphthalene and
1,2-epoxy-1-phenylpropane were isolated from the reaction mixture
by preparative PLC (SiO2) using cyclohexane/EtOAc (15:1, v/v)
and cyclohexane, respectively. Measurements of optical rotation
gave [α]2D0 = +17.5 (c = 0.20, CHCl3) for 1,2-epoxy-1,2,3,4-tetra-
hydronaphthalene and [α]2D0 = –6.0 (c = 0.125, CHCl3) for 1,2-ep-
oxy-1-phenylpropane. Absolute configurations were assigned by
comparison of the signs of measured [α]2D0 to the literature val-
ues.[17,18]
le’s reagent [(S)-(+)-2,2,2-trifluoro-1-(9-anthryl)ethanol] to
a
CDCl3 solution of 2, which caused the expected doubling of most
resonances.
(1R,2R)-Diphenylethylenediamine Hydrochloride (D); (1R)-trans-
1,2-Cyclohexanediamine Hydrochloride (E): (1R,2R)-Diphenylethy-
lenediamine (0.5 g, 2.36 mmol) or (1R)-trans-1,2-cyclohexanedi-
amine (0.27 g, 2.36 mmol) was dissolved in anhydrous Et2O
(20 mL). The solution was stirred vigorously, while anhydrous HCl
(1.18 mL, 2.36 mmol, 2 m Et2O solution) was added dropwise over
10 min. After complete addition of the acid, the mixture was al-
lowed to stir at room temperature for 16 h. The precipitate was
collected by suction filtration, washed with diethyl ether and dried
in vacuo (90% isolated yield).
(3-Phenylpropyl)triphenylphosphonium Bromide (C): To a three-
necked round-bottom flask equipped with a condenser and a mag-
netic stirrer were added triphenylphosphane (13.2 g, 50.5 mmol), 1-
bromo-3-phenylpropane (10.05 g, 50.5 mmol) and 50 mL of tolu-
ene.[19] After being refluxed for 5 h, the reaction mixture was fil-
tered to give 19.2 g (83%) of a crystalline white solid (m.p. 210–
1
211 °C). H NMR (500 MHz, CDCl3): δ = 2.07 (m, 2 H), 3.13 (t,
J = 2.5 Hz, 2 H), 3.92 (m, 2 H), 7.20–7.37 (m, 5 H), 7.77–7.91 (m,
+
15 H) ppm. MS (positive FAB): m/z = 381 [M]
.
1
D: H NMR (500 MHz, D2O): δ = 4.53 (s, 2 H), 7.21–7.38 (m, 10
H) ppm. MS (positive FAB): m/z 213 [M]+.
cis-1,4-Diphenyl-1-butene:
A
100-mL round-bottom flask was
equipped with a condenser, additional funnel, N2 inlet and mag-
netic stirrer. This flame-dried apparatus was charged with a solu-
tion of (3-phenylpropyl)triphenylphosphonium bromide (2.2 g,
4.8 mmol) in dry THF (30 mL).[20] The mixture was stirred at room
temperature and 3 mL of 1.6 m nBuLi in hexane (4.8 mmol) was
slowly added. After the solution turned dark red, benzaldehyde
(0.518 g, 4.8 mmol) was added, then the color turned light orange.
The resulting mixture was stirred for 20 min, poured onto ice, and
diluted with diethyl ether. The aqueous phase was separated and
extracted three times with diethyl ether. The combined organic ex-
tracts were dried (MgSO4) and evaporated in vacuo to give a resi-
due which was extracted with cold hexane. Evaporation of hexane
solution gave 1.5 g (68%) of crude product. Chromatography on
silica gel (pentane) gave 600 mg (40%) of cis-1,4-diphenyl-1-butene
and 370 mg (25%) of trans-1,4-diphenyl-1-butene. The 1H NMR
and MS spectra correspond to those reported in the literature.[21]
E: 1H NMR (500 MHz, D2O): δ = 1.16 (m, 4 H), 1.60 (d, J =
11 Hz, 2 Heq), 1,80 (d, J = 11 Hz, 2 Hax), 2.71 (m, 2 H) ppm. MS
+
(ESI): m/z = 115 [M]
.
Condensation of Hydrochloride D or E with 3,5-Di-tert-butylsalicyl-
aldehyde (3 and 4): (1R,2R)-Diphenylethylenediamine hydrochlo-
ride (0.52 g, 2.1 mmol) or (1R)-trans-1,2-cyclohexanediamine hy-
drochloride (0.24 g, 2.1 mmol) was dissolved in MeOH/EtOH (1:1,
25 mL). 3,5-Di-tert-butylsalicylaldehyde (0.49 g, 2.1 mmol) was
then added, and the mixture was stirred at room temperature. After
24 h the solvent was removed under reduced pressure. The resulting
solid (compound 3 or 4) was washed with water (5 mL), diethyl
ether (10 mL) and dried in vacuo. Yield 90%.
1
3: H NMR (500 MHz, [D6]DMSO): δ = 1.24 (s, 9 H), 1.38 (s, 9
H), 4.80–5.22 (m, 2 H), 7.02–7.42 (m, 12 H), 8.55 (br. s, 3 H), 8.78
(s, 1 H), 13.14 (s, 1 H) ppm. MS (positive FAB): m/z 429 [M]+.
5-Hydroxy-25,26,27,28-tetrapropoxycalix[4]arene (1): Compound 1
was prepared according to literature procedures by lithiation of
cone 5-bromo-25,26,27,28-tetrapropoxycalix[4]arene[22] (1.21 g,
1.8 mmol) with nBuLi (10 mL of 1.6 m solution, 16 mmol) in dry
THF at –78 °C followed by O2 oxidation.[23] The yellow oil ob-
tained was purified by column chromatography (SiO2, eluent: hex-
ane/CHCl3, 4:1) (0.65 g, 60%). The 1H NMR and MS spectra
correspond to those reported in the literature.
4: 1H NMR (500 MHz, CDCl3): δ = 1.28 (s, 9 H), 1.43 (s, 9 H),
1.20–1.72 (m, 7 H), 2.27 (m, 1 H), 3.20 (m, 1 H), 3.47 (m, 1 H),
7.10 (d, J = 2.5 Hz, 1 H), 7.38 (d, J = 2.5 Hz, 1 H), 8.29 (br. s, 3
+
H), 8.51 (s, 1 H), 12.82 (s, 1 H) ppm. MS (ESI): m/z = 331 [M]
.
Salen Calix[4]arenes 5,6 and 7,8: The above imino-amino derivative
3 (0.29 g, 0.63 mmol) or 4 (0.23 g, 0.63 mmol) was dissolved in abs.
EtOH (30 mL) and stirred over 4-Å molecular sieves. A solution
of 2 (0.4 g, 0.63 mmol) and triethylamine (0.127 g, 1.26 mmol) in
abs. EtOH (6 mL) was added, and the reaction was stirred at room
temperature. The reaction was monitored by TLC (CH2Cl2/petro-
leum ether, 2:1). After 48–60 h the mixture was filtered and the
solution was concentrated under reduced pressure. The resulting
solid was washed with Et2O and the two diastereomeric com-
pounds of each reaction mixture were conveniently separated by
preparative PLC, using CH2Cl2/cyclohexane (2:1, v/v) as eluent,
with 70–75% recovery of each pure stereoisomer.
5-Hydroxy-25,26,27,28-tetrapropoxycalix[4]arene-4-carbaldehyde
(2): To a chilled solution of cone 5-hydroxy-25,26,27,28-tetraprop-
oxycalix[4]arene[24] (1) (0.8 g, 1.32 mmol) in dry CH2Cl2 (100 mL)
was added Cl2CHOCH3 (2.34 mL, 26.4 mmol) under N2. A 1 m
solution of SnCl4 in CH2Cl2 (1.32 mL, 1.32 mmol) was then added
and after 3–4 minutes the reaction was stopped with 1 m HCl. The
mixture was washed with a saturated aqueous solution of NaHCO3
and then with water, and dried over anhydrous Na2SO4. The sol-
vent was removed under reduced pressure and the resulting yellow
oil was purified by column chromatography (SiO2, eluent: petro-
leum ether/CH2Cl2, 4:1) to give 2 as a yellow solid. (0.62 g, 75%;
1
5: H NMR (500 MHz, CDCl3): δ = 0.89, 0.90, 1.02, 1.03 (t, J =
7.5 Hz, 3 H each), 1.26, 1.27 (s, 9 H each), 1.79–1.95 (m, 8 H),
m.p. 118–120 °C). 1H NMR (500 MHz, CDCl3): δ = 0.93–1.04 (m, 3.09, 3.11, 3.13, 3.49 (d, J = 13.5 Hz, 1 Heq each), 3.60–3.94 (m, 8
12 H), 1.80–2.02 (m, 8 H), 3.15, 3.19 (d, J = 13.5 Hz, ratio 1:3, 4
Heq), 3.70–3.92 (m, 8 H), 4.46, 4.48, 4.57 (d, J = 13.5 Hz, ratio
H), 4.29, 4.37, 4.38, 4.41 (d, J = 13.5 Hz, 1 Hax each), 4.73, 4.78
(ABq, J = 9.0 Hz, 1 H each), 5.59 (d, J = 7.0 Hz, 1 H), 5.75 (t, J
2:1:1, 4 Hax), 6.38–6.80 (m, 10 H), 10.22 (s, 1 H), 11.70 (s, 1 H) = 7.0 Hz, 1 H), 6.02 (d, J = 7.0 Hz, 1 H), 6.15 (d, J = 7.5 Hz, 1
3568 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2005, 3562–3570

Enantioselective Epoxidation Reactions of (Z)-Aryl Alkenes
FULL PAPER
H), 6.24–6.28 (m, 2 H), 6.63 (s, 1 H), 6.85 (t, J = 7.5 Hz, 1 H), 6.97
(d, J = 7.5 Hz, 1 H), 7.01 (d, J = 7.5 Hz, 1 H), 7.05, 7.28 (d, J =
2.5 Hz, 1 H each), 7.12–7.22 (m, 10 H), 8.42, 8.85 (s, 1 H each),
13.63, 14.02 (s, 1 H each) ppm. 13C NMR (125 MHz, CDCl3): δ =
9.87, 9.89, 10.7 (× 2), 22.8, 22.9, 23.4, 24.4, 29.2 (× 3), 29.7, 30.4,
30.98 (× 2), 31.32, 31.47 (× 3), 34.1, 34.9, 38.7, 76.4, 76.63, 76.64,
76.8, 80.4, 80.7, 115.1, 116.4, 117.7, 121.6, 122.1, 122.2, 126.3,
126.7, 127.1, 127.30, 127.35 (× 2), 127.7, 127.97 (× 2), 128.0 (× 2),
128.18 (× 2), 128.22 (× 2), 128.6, 132.3, 132.5, 133.2, 133.6, 136.5,
136.74, 136.78, 136.9, 139.75, 139.88, 139.91, 142.6, 149.8, 155.29,
155.35, 157.1, 157.8, 158.1, 164.1, 167.2 ppm. MS (ESI): m/z =
1046.6 [M + H]+. C70H82N2O6 (1047.42): C 80.31, H 7.84, N 2.68;
found: C 80.27, H 7.80, N 2.65.
33.4, 33.7, 34.3, 34.9, 72.7, 72.9, 76.6, 76.9, 77.1, 115.3, 116.7,
117.8, 118.5, 121.8, 122.3, 122.4, 122.7, 124.2, 126.2, 126.8, 127.0
(× 2), 127.2, 127.6, 127.9, 128.4, 128.8, 128.9, 129.7, 132.46, 132.53,
133.7, 137.1, 139.9, 142.4, 150.0, 155.4 (× 2), 157.6, 158.0, 158.3,
163.0, 165.9 ppm. MS (positive FAB): m/z = 949 [M + H]+.
C62H80N2O6 (949.32): C 78.48, H 8.44, N 2.95; found: C 78.45, H
8.41, N 2.92.
Uranyl Complexes 9–12: To a stirred solution of the ligand 5 or 6
(10 mg, 0.0096 mmol) or 7 or 8 (10 mg, 0.011 mmol) in MeOH
(5 mL), solid (AcO)2UO2·2H2O (5.94 mg, 0.014 mmol) was added.
The mixture was allowed to stir at room temperature for 1 d. The
precipited complex was collected by filtration and dried (Ϸ 74%
yield). Crystals of complex 9, suitable for X-ray analysis, were
grown from MeOH/CH2Cl2 mixture.
1
6: H NMR (500 MHz, CDCl3): δ = 0.84, 0.87, 1.04, 1.05 (t, J =
7.5 Hz, 3 H each), 1.25, 1.48 (s, 9 H each), 1.78–1.96 (m, 8 H),
3.06, 3.09, 3.11, 3.59 (d, J = 13.5 Hz, 1 Heq each), 3.60–4.02 (m, 8
H), 4.39, 4.35, 4.37, 4.40 (d, J = 13.5 Hz, 1 Hax each), 4.68, 4.66
(ABq, J = 9.1 Hz, 1 H each), 6.13 (t, J = 7.0 Hz, 1 H), 6.22 (d, J
= 7.0 Hz, 2 H), 6.28 (d, J = 7.0 Hz, 1 H), 6.30 (d, J = 7.0 Hz, 1
H), 6.32 (d, J = 7.5 Hz, 1 H), 6.46 (s, 1 H), 6.68 (br. d, 1 H), 6.70
(t, J = 7.5 Hz, 1 H), 6.86 (d, J = 7.5 Hz, 1 H), 6.98, 7.34 (d, J =
2.5 Hz, 1 H each), 7.10–7.22 (m, 10 H), 8.34, 8.84 (s, 1 H each),
13.54, 14.00 (s, 1 H each) ppm. 13C NMR (125 MHz, CDCl3): δ =
9.97, 10.02, 10.46, 10.57, 22.93, 22.97, 23.2, 23.4, 24.7, 29.5 (× 3),
30.9, 31.1, 31.3, 31.4 (× 3), 34.1, 35.0, 76.3, 76.5, 76.8, 79.7, 81.1,
114.9, 116.3, 117.9, 121.8, 121.9, 122.0, 125.6, 126.4, 127.0, 127.2,
127.4 (× 2), 127.6, 127.76, 127.82, 127.93, 128.1 (× 3), 128.2 (× 2),
128.3, 128.6, 128.7, 128.9, 132.9, 133.2, 134.0, 134.2, 136.1, 136.2,
136.3, 136.4, 139.5, 139.8, 140.1, 142.1, 149.5, 155.7, 155.8, 157.2,
157.3, 157.9, 164.3, 167.4 ppm. MS (ESI): m/z = 1046.6 [M + H]+.
C70H82N2O6 (1047.42): C 80.31, H 7.84, N 2.68; found: C 80.33,
H 7.86, N 2.70.
1
9: H NMR (500 MHz, CDCl3): δ = 0.82, 0.93, 0,98, 1.12 (t, J =
7.5 Hz, 3 H each), 1.29 (br. s, 18 H), 1.79–1.91 (m, 8 H), 2.85, 2.90,
3.07, 3.22 (d, J = 14.1 Hz, 1 Heq each), 3.60–3.98 (m, 8 H), 4.23,
4.27, 4.36, 4.43 (d, J = 14.1 Hz, 1 Hax each), 5.02 (d, J = 7.2 Hz,
1 H), 5.47–5.51 (m, 2 H), 5.61 (d, J = 7.2 Hz, 1 H), 5.69 (m, 2 H),
6.02 (s, 1 H), 6.34 (s, 1 H), 6.56–6.62 (m, 3 H), 6.95 (d, J = 7.5 Hz,
1 H), 6.80–7.03 (m, 2 H), 7.19, 7.65 (d, J = 2.5 Hz, 1 H each),
6.85–7.10 (m, 3 H), 7.46 (d, J = 7.5 Hz, 2 H), 7.72 (d, J = 7.5 Hz, 2
H), 7.91 (s, 1 H), 9.28, 9.57 (s, 1 H each) ppm. C70H80N2O8U·H2O
(1333.45): C 63.06, H 6.01, N 2.10; found: C 63.12, H 6.05, N 2.13.
1
10: H NMR (500 MHz, CDCl3): δ = 0.88, 0.92, 0.95, 1.18 (t, J =
7.5 Hz, 3 H each), 1.25, 1.46 (s, 9 H each), 1.78–1.96 (m, 8 H),
2.56, 2.83, 3.11, 3.35 (d, J = 13.5 Hz, 1 Heq each), 3.64–3.90 (m, 8
H), 4.02, 4.16, 4.39, 4.52 (d, J = 13.5 Hz, 1 Hax each), 5.9, 6.2
(ABq, J = 11.5 Hz, 1 H each), 5.39 (d, J = 7.0 Hz, 1 H), 5.44 (d,
J = 7.0 Hz, 1 H), 5.49 (t, J = 7.0 Hz, 1 H), 5.85 (d, J = 7.6 Hz, 1
H), 5.88 (d, J = 7.6 Hz, 1 H), 5.96 (t, J = 7.6 Hz, 1 H), 6.82 (t, J
= 7.0 Hz, 1 H), 6.94 (d, J = 7.0 Hz, 1 H), 7.05 (d, J = 7.6 Hz, 1
H), 6.97, 7.67(d, J = 2.75 Hz, 1 H each), 7.10–7.22 (m, 10 H), 7.55
(s, 1 H) 9.07, 9.69 (s, 1 H each) ppm. 13C NMR (125 MHz, CDCl3):
δ = 9.77, 9.84, 10.7, 10.9, 22.8, 22.9, 23.0, 23.6, 29.5, 29.7 (× 3),
30.9, 31.2, 31.3, 31.6 (× 3), 33.8, 35.0, 35.2, 75.9, 76.0, 76.6, 79.4,
79.7, 121.2, 121.4, 122.0, 122.6, 123.1, 124.4, 126.1, 126.2, 126.6,
127.1, 127.5, 127.8, 128.6, 128.7 (× 3), 128.9, 129.6 (× 2), 129.9,
130.6, 131.5, 131.7, 132.7, 133.2, 135.9, 136.6, 137.2, 138.7, 140.0,
141.3, 143.5, 151.8, 154.26, 154.32, 155.2, 158.2, 161.4, 161.9,
165.4, 166.6, 173.1 ppm. C70H80N2O8U·H2O (1333.45): C 63.06, H
6.01, N 2.10; found: C 63.15, H 6.08, N 2.15.
7: 1H NMR (500 MHz, CDCl3): δ = 0.85 (t, J = 7.5 Hz, 3 H), 0.89
(t, J = 7.5 Hz, 3 H), 1.03 (t, J = 7.5 Hz, 6 H), 1.26 (s, 9 H), 1.44
(s, 9 H), 1.75–1.93 (m, 8 H), 1.53, 1.71, 1.92 (m, 8 H), 3.04, 3.12,
3.14, 3.51 (d, J = 14 Hz, 1 Heq each), 3.29 (m, 2 H), 3.50–4.01 (m,
8 H), 4.32, 4.34, 4.41, 4.43 (d, J = 14 Hz, 1 Hax each), 6.15 (d, J =
7.0 Hz, 1 H), 6.25–6.36 (m, 5 H), 6.46 (s, 1 H), 6.78 (t, J = 7.0 Hz,
1 H), 6.85 (d, J = 7.0 Hz, 1 H), 6.91 (d, J = 7.0 Hz, 1 H), 7.01 (d,
J = 2.5 Hz, 1 H), 7.33 (d, J = 2.5 Hz, 1 H), 8.33 (s, 1 H), 8.76 (s,
1 H), 13.70 (br. s, 1 H), 14.10 (br. s, 1 H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 10.2, 10.75,10.85, 23.1, 23.2, 23.5, 23.6,
24.6 (× 2), 29.7 (× 3), 31.2, 31.4, 31.5, 31.7 (× 3), 33.4, 33.7, 34.3,
35.2, 72.5, 73.4, 76.6, 76.8, 77.1, 115.2, 116.6, 118.2, 122.0, 122.1,
122.2, 122.7, 124.2, 126.3, 126.9, 127.1, 127.3, 127.8, 128.0 (× 2),
128.6, 128.9, 129.7, 133.1, 133.6, 134.2, 136.3, 136.55, 136.60,
136.8, 140.2, 142.0, 149.7, 155.9, 156.1, 157.6, 157.7, 158.3, 163.4,
166.0 ppm. MS (positive FAB): m/z = 949 [M + H]+. C62H80N2O6
(949.32): C 78.48, H 8.44, N 2.95; found: C 78.52, H 8.47, N 2.98.
11: 1H NMR (500 MHz, CDCl3): δ = 0.85–1.04 (m, 12 H), 1.28 (s,
9 H), 1.80 (s, 9 H), 1.75–1.93 (m, 8 H), 1.53–2.50 (m, 8 H), 2.80–
3.07 (m, 4 H), 4.20–4.40 (m, 2 H), 3.50–4.01 (m, 8 H), 4.18–4.45
(m, 4 H), 7.75 (br. s, 1 H), 6.30–7.73 (m, 11 H), 9.43 (s, 1 H), 9.64
(s, 1 H) ppm. C62H78N2O8U·H2O (1235.35): C 60.29, H 6.32, N
2.27; found: C 60.35, H 6.33, N 2.28.
12: 1H NMR (500 MHz, CDCl3): δ = 0.85–1.04 (m, 12 H), 1.28 (s,
9 H), 1.80 (s, 9 H), 1.77–1.96 (m, 8 H), 1.54–2.57 (m, 8 H), 2.83–
3.15 (m, 4 H), 4.25–4.47 (m, 2 H), 3.50–4.05 (m, 8 H), 4.22–4.49
(m, 4 H), 5.80–7.90 (m, 12 H), 10.02 (s, 1 H), 10.20 (s, 1 H) ppm.
C62H78N2O8U·H2O (1235.35): C 60.29, H 6.32, N 2.27; found: C
60.40, H 6.35, N 2.29.
8: 1H NMR (500 MHz, CDCl3): δ = 0.85 (t, J = 7.5 Hz, 3 H), 0.87
(t, J = 7.5 Hz, 3 H), 1.04 (t, J = 7.5 Hz, 3 H), 1.05 (t, J = 7.5 Hz,
3 H), 1.14 (s, 9 H), 1.26 (s, 9 H), 1.75–1.93 (m, 8 H), 1.50, 1.71,
1,90 (m, 8 H), 3.02, 3.05, 3.09, 3.48 (d, J = 13.5 Hz, 1 Heq each),
3.26–3.40 (m, 2 H), 3.52–3.68 (m, 8 H), 3.76–3.86 (m, 8 H), 4.28,
4.33, 4.34, 4.39 (d, 13.5 Hz, 1 Hax each), 5.45 (m, 2 H), 5.84 (dd, J
= 6.5 Hz, 2.5 Hz, 1 H), 6.10 (d, J = 6.5 Hz, 1 H), 6.16 (t, J =
MnIII Complexes 13–16: To a solution of the ligand 5 or 6 (0.065 g,
6.5 Hz, 1 H), 6.22 (d, J = 6.5 Hz, 1 H), 6.59 (s, 1 H), 6.81 (t, J = 0.05 mmol) or 7 or 8 (0.047 g, 0.05 mmol) in abs. EtOH (15 mL)
7.0 Hz, 1 H), 6.92 (d, J = 7.0 Hz, 1 H), 6.98 (d, J = 7.0 Hz, 1 H),
7.04 (d, J = 2.5 Hz, 1 H), 7.22 (d, J = 2.5 Hz, 1 H), 8.33 (s, 1 H),
8.76 (s, 1 H), 13.67 (br. s, 1 H), 14.10 (br. s, 1 H) ppm. 13C NMR
was added a solution of Mn(OAc)3·2H2O (0.020 g, 0.075 mmol) in
EtOH (5 mL). The dark solution was allowed to stir overnight at
room temperature and was monitored by TLC (eluent: CH2Cl2/
(125 MHz, CDCl3): δ = 10.09, 10.15, 11.0, 23.07, 23.15, 23.60, cyclohexane, 2:1, v/v). Evaporation of the solvent gave a residue,
23.69, 24.4, 24.5, 29.3 (× 3), 29.9, 31.16, 31.23, 31.5, 31.7 (× 3), which was dissolved in CH2Cl2, filtered and concentrated to pro-
Eur. J. Org. Chem. 2005, 3562–3570
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3569

G. A. Tomaselli et al.
FULL PAPER
duce the MnIII catalyst (13–16) in a nearly quantitative yield. 13:
MS (ESI): m/z 1099 [LMn]+. C72H83 MnN2O8 (1159.39): C 74.61,
H 7.17, N 2.42; found: C 74.65, H 7.20, N 2.44.
[8] a) Calixarenes in action (Eds.: L. Mandolini, R. Ungaro), Im-
perial College Press: London, 2000; b) A. Friedrich, U. Radius,
Eur. J. Inorg. Chem. 2004, 21, 4300–4316.
[9] K. Iwamoto, K. Araki, S. Shinkai, J. Org. Chem. 1991, 56,
4955–4962.
[10] C. Jaime, J. de Mendoza, P. Prados, P. M. Nieto, C. Sánchez,
J. Org. Chem. 1991, 56, 3372–3376.
14: MS (ESI): m/z = 1099 [LMn]+. C72H83 MnN2O8 (1159.39): C
74.61, H 7.17, N 2.42; found: C 74.69, H 7.15, N 2.40. 15: ESI-
MS: m/z = 1001 [LMn]+. C64H81 MnN2O8 (1061.29): C 72.45, H
7.64, N 2.64; found: C 72.51, H 7.66, N 2.65. 16: MS (ESI) m/z =
1001 [LMn]+. C64H81 MnN2O8 (1061.20): C 72.45, H 7.64, N 2.64;
found: C 72.54, H 7.68, N, 2.66.
[11] T. Strassner, K. N. Houk, Org. Lett. 1999, 1, 419– 421.
[12] The tetradentate salen–like calix[4]arene ligand 5 chelates equa-
torially to the metal centre, which adopts a pentagonal bipy-
ramidal coordination geometry with axial oxo groups and with
the remaining equatorial site occupied by an adventitious water
molecule. The equatorial atoms are coplanar to within 0.11 Å
and the oxo ligands co–linear with their O···O vector inclined
by ca. 87° to this plane. The pattern of bonding to the uranium
centre does not differ significantly from that observed in, for
example, aqua-[N,NЈ-ethylenebis(3-ethoxysalicyliden-iminato-
N,NЈ,O,OЈ)]-dioxouranium(vi) (O. Signorini, E. R. Dockal, G.
Castellano, G. Olyva, Polyhedron 1996, 15, 245–255). The two
six-membered N,O chelate rings have distinctly different geom-
etries. Ring F has an asymmetric boat conformation with C–4
and the uranium atom lying 0.34 and 1.34 Å respectively out
of the plane of the remaining four atoms (which are coplanar
to within 0.05 Å), whereas ring G has a much flatter envelope
conformation with the metal atom lying only 0.37 Å out of
plane (the remaining five atoms are coplanar to 0.03 Å). The
five-membered N,N chelate ring has a δ conformation resulting
in a trans-axial disposition of the two phenyl substituents and a
gauche relationship for H–31 and H–32 (the H–C–C–H torsion
angle is –79°), in agreement with the solution phase NMR
spectroscopic data. The calix[4]arene unit has molecular C2v
symmetry with all four n-propyl groups lying on the same side
of the molecule. The aromatic rings A and C are folded “out-
wards” and inclined by ca. 127°, whilst rings B and D are
folded “inwards” and inclined by only ca. 20°. This latter ar-
rangement effectively fills the central cavity of the calix[4]arene,
the centroids of rings B and D being separated by only 4.78 Å.
The folding of the N,O chelate ring F coupled with the adop-
tion of a δ configuration for the N,N chelate ring results in the
C–31 phenyl ring being angled away from the upper face of the
calix[4]arene component; the distance of the ortho hydrogen on
the C–31 phenyl ring to the hydrogen atom para to the oxygen
on ring D (H–23) is 5.16 Å.
X-ray Crystallographic Study: Suitable crystals of this compound
were grown at room temperature from a solution in dichlorometh-
ane and methanol by slow concentration. Crystal data:
C70H82N2O9U·0.65(CH2Cl2)·1.6(CH3OH), M = 1439.88, ortho-
rhombic, P212121 (no. 19), a = 9.899(2), b = 16.956(5), c =
42.349(10) Å, V = 7108(3) Å3, Z = 4, Dc = 1.346 g cm–3, μ(Cu-
Kα) = 7.329 mm–1, T = 203 K, orange needles; 5833 independent
measured reflections, F2 refinement, R1 = 0.062, wR2 = 0.131, 3424
independent observed absorption corrected reflections [|Fo| Ͼ
4σ(|Fo|), 2θmax = 120°], 704 parameters. The absolute structure of
9 was determined by an R-factor test [R1+ = 0.0621, R1– = 0.0797].
CCDC-274942 contains the supplementary crystallogrtaphic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
The Supporting information (see footnote on the first page of this
article) section contains 1H and 13C NMR of reagents and products
reported in this paper, APT and g-COSY NMR spectra of calix[4]-
1
arene as well as H,13C NMR, T-ROESY, TOCSY spectra of ura-
nyl complexes.
Acknowledgments
We thank Prof. S. Pappalardo for suggestions, University of Cat-
ania and MIUR for financial support (COFIN 2003).
[1] a) T. Katsuki, K. B. Sharpless, J. Am. Chem. Soc. 1980, 102,
5974–5976; b) R. M. Hanson, K. B. Sharpless, J. Org. Chem.
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Received: February 24, 2005
Published Online: July 4, 2005
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