A Unique Binaphthyl Strapped Iron-Porphyrin Catalyst for the Enantioselective Epoxidation of Terminal Olefins

Article abstract of DOI:10.1002/chem.200305222

A new chiral binaphthyl-strapped iron-porphyrin 4b that exhibits unprecedented catalytic activity toward the enantioselective epoxidation of terminal olefins was synthesized. Typical enantiomeric excesses (ee) of 90% were measured with a maximum of 97% fo

Full text of DOI:10.1002/chem.200305222

FULL PAPER
A Unique Binaphthyl Strapped Iron Porphyrin Catalyst for the
Enantioselective Epoxidation of Terminal Olefins
Eric Rose,*[a] Qi-Zhi Ren,[b] and Bruno Andrioletti[a]
Abstract: A new chiral binaphthyl-strapped iron porphyrin 4b that exhibits unpre-
cedented catalytic activity toward the enantioselective epoxidation of terminal ole-
fins was synthesized. Typical enantiomeric excesses (ee) of 90% were measured
with a maximum of 97% for the epoxidation of styrene, whereas the turnover
numbers (TON) averaged 16000.
Keywords: asymmetric synthesis ¥
chirality epoxidation iron
porphyrinoids
¥
¥
¥
Introduction
rene which are difficult to epoxidize.[2h] Second, the epoxida-
tions generally proceed with low turnover numbers (TON).
On the other hand, metalloporphyrins have proven to be
robust catalysts for oxidative processes but the enantioselec-
tivities observed for the asymmetric epoxidation of terminal
olefins have often remained below expectations.[7]
Asymmetric synthesis is a promising field in modern syn-
thetic organic chemistry. During the past decades, dramatic
improvements have been reported in catalytic asymmetric
hydrogenation,[1] epoxidation of alkenes[2] and allylic alco-
hols,[3] and dihydroxylation[4] and cyclopropanation of pro-
chiral olefins.[5] Nevertheless, the development of new tools
is still crucial, particularly in the case of the enantioselective
catalytic epoxidation of terminal olefins where significant
improvement is still necessary from both a practical and
mechanistic point of view.[6] Indeed, with regard to green
and sustainable chemistry, chiral epoxides are becoming in-
creasingly important as synthetic intermediates and in the
development of new drugs. Metallosalens represent an im-
portant class of catalysts that are capable of efficiently epox-
idizing terminal olefins.[2f,g] However, they suffer from two
major drawbacks: first, although metallosalens are highly ef-
ficient for the epoxidation of cis-di-, tri-, and some tetrasub-
stituted olefins, they require temperatures as low as À788C
for the epoxidation of monosubstituted olefins such as sty-
Results and Discussion
In 1998, we reported the synthesis of a new family of chiral
porphyrin-based catalysts
1
bearing Mosher pickets
(Scheme 1).[8] During the course of this study, we found that
fine-tuning of the steric bulk of the strap dramatically influ-
ences the ee values.
Thus, we demonstrated that the most crowded systems 1b
and 1c induced the lowest enantioselectivities, whereas the
less bulky analogue 1a afforded the best ee value. Thus, it
appeared that providing more access to the catalytic center
increased the selectivity of the epoxidation reaction. These
results and those obtained with the binap-strapped porphyr-
in 3b (n=0, Scheme 2)[9] prompted us to prepare the so-
called ™homologated∫ catalyst 4b (n=1) whose strap differs
[a] Dr. E. Rose, Dr. B. Andrioletti
Universitÿ Pierre et Marie Curie
Laboratoire de Synthõse Organique et Organomÿtallique
UMR CNRS 7611, Tour 44 45, 1er ÿtage, BP 181
4, Place Jussieu, 75252 Paris cedex 05, (France)
Fax : (+33)144-275-504
E-mail: rose@ccr.jussieu.fr
andriole@ccr.jussieu.fr
[b] Dr. Q.-Z. Ren
School of Chemistry and Chemical Technology
Shanghai Jiaotong University
Shanghai, 200240 (P. R. China)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
Scheme 1. Structures of the Mosher porphyrins™.
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DOI: 10.1002/chem.200305222
Chem. Eur. J. 2004, 10, 224 230

224 230
in 84% yield and conveniently
converted into the diacid 6e by
using aqueous sodium hydrox-
ide at 1008C in 90% yield. It is
worth noting that
a
more
straightforward homologation
sequence such as the Arndt
Eistert[10] method was not re-
producible in our hands. A high
dilution reaction involving
a
stoichiometric amount of fresh-
ly prepared diacid chloride 6f
and aabb-o-TAPP[11] in THF in
the presence of N,N-diethylani-
line afforded the free base
binap-strapped porphyrin 4a in
31% reproducible yield. Finally,
the desired catalyst 4b was
quantitatively prepared by re-
fluxing the free base porphyrin
4a with an excess of FeBr2 in
acetic acid before oxidation in
air and washing with dilute hy-
Scheme 2. Structures of porphyrins 2 4.
from that of 3b (n=0) by only two CH2 groups. Two guide-
lines directed our choice: First, we decided to retain the C2-
symmetrical ™binap-strapped∫ porphyrins that already
proved to be efficient for the epoxidation of terminal ole-
fins.[7n,9] Indeed, this approach allowed us to isolate styrene
oxides with good enantiomeric excesses even after high
TON. As has been suggested by others, it appears that the
presence of two rigid ™binap-walls∫ efficiently directs the
approach of the olefin toward the metal center, induces a
good transfer of asymmetry and inhibits the oxidative degra-
dation of the catalyst as well as the formation of an unreac-
tive m-oxo dimer.[7b,d] In addition, C2-symmetrical porphyrins
are easily prepared from the readily available a2b2-tetrakis-
(o-aminophenyl)porphyrin. Second, considering the results
of the Mosher series,[8] we decided to ™homologate∫ the
binap handle (n=1) which should move the proximal me-
thoxy groups away from the metal center. The displacement
of the methoxy groups, while offering an easier access of the
olefin to the metal center, should prevent the observed oxi-
dation of the methoxy naphthyl moiety to the correspond-
ing naphthoquinone 2b (Scheme 2).
Scheme 3. Synthesis of compounds 5, 6a 6f.
drochloric acid. It is worth noting that metalation of 4a was
complete under these conditions, whereas no complexation
of the free base porphyrin 3a could be effected under simi-
lar conditions, thus confirming the idea that 4a offered an
easier access to the active site than 3a.
Preparation of the catalyst 4b was achieved by condens-
ing the chiral diacid chloride 6f with aabb-tetrakis(o-amino-
phenyl)porphyrin (aabb-o-TAPP)[11] in the presence of a
stoichiometric amount of N,N-diethylaniline. The diacid
chloride 6f was readily prepared from R-(+)-1,1’-binaphthol
in an overall yield of 43% (Scheme 3). In the first step, the
commercially available R-(+)-1,1’-binaphthol was quantita-
tively methylated by using NaH/MeI. The resulting diether 5
was then formylated with nBuLi/DMF in 71% yield. Subse-
quently, dialdehyde 6a was quantitatively reduced to the
corresponding diol 6b, converted to the dibromide 6c with
PBr3 according to Naruta×s procedure,[7c] and then treated
with NaCN. The resulting dicyano derivative 6d was isolated
Preliminary catalytic measurements revealed that complex
4b displayed remarkable activity toward the enantioselec-
tive epoxidation of terminal olefins (Table 1).
In a typical reaction, one equivalent of catalyst 4b was al-
lowed to react with 100 equivalents of iodosylbenzene and
1000 equivalents of olefin in CH2Cl2 at À58C. Under these
conditions, styrene was readily converted to styrene oxide in
97% ee (entry 1). Similarly, electron-deficient olefins such as
pentafluoro- (entry 2), fluoro- (entry 3), chloro- (entries 4
and 6) and nitrostyrenes (entry 5) were efficiently epoxi-
dized in about 90% ee. We also tested the efficiency of the
epoxidation using smaller amounts of the catalyst (Table 1).
Thus, we showed that a ratio catalyst/oxidant/olefin: 1/1000/
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E. Rose et al.
FULL PAPER
Table 1. Asymmetric epoxidation of styrene derivatives catalyzed by 4b.
Entry[a] Substrate
ee
ee
Best ee
Yield Config.[f]
[%][b] [%][c] previously [%][e]
reported[d]
[g]
1
2
styrene 97
pentafluorostyrene 96
9383
94
96
80
R
R
R
R
R
R
88[g]
-fluorosty3re3n92e 93 nd
87
4
5
6
3-chlorostyrene 88
3-nitrostyrene 90
4-chlorostyrene 84
87
87
81
90[g]
74[h]
70[i]
90
84
75
[a] The reactions were carried out in CH2Cl2 at À58C. Enantiomeric ex-
cesses were determined by GC with use of a Lipodex-E chiral capillary
column (50 mî0.25 mm). [b] Reaction conditions: catalyst 4b/PhIO/
olefin=1:100:1000. [c] Reaction conditions: catalyst 4b/PhIO/olefin=
1:1000:10000. [d] These results do not take into account the absolute con-
figuration of the chiral carbon atom. [e] Yields are based on consumed
PhIO. Results have been confirmed by integration of the peak of the ep-
oxide versus the peak of an internal reference (1,2,4-trichlorobenzene).
[f] Assigned by comparing the GC retention time with standard samples.
[g] Best ee values were obtained by using 2b.[9] Noticeably, ee values ob-
tained with D2-, D4-, C4-symmetrical porphyrins varied in a 20 69%
range, depending on the number, the rigidity, and the nature of the sub-
stituents. [h] Interestingly, the best ee values were obtained by using the
nonrigid tetralin derivative.[7f] [i] In this case the best ee values were ob-
tained using the threitol porphyrins first prepared by Collman and co-
workers and developed by Gross and co-workers later on.[7g,j]
10000 afforded similar enantiomeric excesses for the olefins
in this study. It is also worth noting that the chemical yields
based on the consumed PhIO varied from about 85% in
most cases but reached 96% in the case of styrene (Table 1,
entry 1). In addition, very good enantioselectivities were
maintained when the reactions were carried out at room
temperature. Thus, epoxidation of styrene at room tempera-
ture afforded the desired epoxide in 94% ee! Furthermore,
catalyst 4b proved to be extremely robust. It could be re-
used for a second run without significant loss of enantiose-
lectivity and the oxidation could be carried out in neat sty-
rene with equally good enantiomeric excesses. Figure 1
shows the relationship between the enantiomeric excess and
the TON. The graphs reveal that the enantiomeric excesses
decrease very slowly: after 15 turnovers, the ee value is 90
%; from 15 to 4200 TON, the ee are still close to 90% and
remain close to 80% even after 16000 TON. Another inter-
esting feature concerns the turnover frequency (TOF) of the
catalyst that reaches 2000 turnovers per hour at room tem-
perature. Even after a high TON, no bleaching was ob-
served, which underlines the robustness of the catalyst. Its
stability was also corroborated by spectroscopic analyses of
the catalyst recovered after epoxidation. In particular, 1H
and 13C NMR spectra of the
Figure 1. Change in ee with increasing turnover: comparison between 3b
&
^
( )and 4b ( ).
and 1.97(6H) ppm confirmed that no quinone formation
had occurred (Table 2).
Quite similar chemical shifts were observed for the Zn
complex 4c (d=2.64 and 1.40 ppm, respectively, in deuterat-
1
ed pyridine). On the contrary, the H NMR spectrum of the
free base porphyrin 4a in [D5]pyridine revealed methoxy
signals at d=2.37 and 0.47 ppm, respectively. The significant
chemical shift difference of the proximal methoxy groups
can be explained by considering the repulsion between the
metal-coordinated [D5]pyridine and the strap. Thus, the
steric hindrance ascribable to the axial ligand displaces the
handle from the porphyrin center and moves it away from
the corresponding strongly shielding anisotropic cone. Simi-
hexacoordinate iron complex 4
d obtained after reduction of
the catalyst using Na2S2O4 in
the presence of deuterated pyri-
dine revealed diamagnetic FeII
(S=0) porphyrin spectra with
no evidence of strap degrada-
tion. The presence of the me-
Table 2. 1H and 13C chemical shifts of selected signals.
Porphyrins
3a[a]
4a[a]
4a[b]
2.37
0.47
nd
nd
4c[a]
2.04
1.97
61.0
60.0
4c[b]
2.64
1.40
nd
nd
4d[b]
4d[b]Recovered
dH distal OMe (6H)
dH proximal OMe(6H)
dC distal OMe
2.96
À0.65
nd
1.98
À0.51
59.4
2.21
1.97
61.4
60.4
2.21
1.97
61.5
60.4
dC proximal OMe
nd
57.5
[a] NMR spectra were recorded at 258C in CDCl3 or in deuterated pyridine. [b] Chemical shifts were calibrat-
thoxy signals at d=2.21(6H) ed by using residual solvent peaks as reference. nd=not determined.
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Enantioselective Epoxidation of Terminal Olefins
224 230
larly, 13C NMR data of the recovered catalyst 4d clearly in-
dicated the presence of the two methoxy groups at d=60.4
and 61.5 ppm. Complementary UV/Vis spectroscopy and
MALDI-TOF analyses confirmed again the integrity of the
structure: catalyst 4b had not been degraded during the oxi-
dative process. This observation is in total contrast with
other catalysts such as [Mn(salen)][2] or other porphyrinic
systems including binap porphyrins which rapidly de-
grade.[12,13]
In addition to the remarkable stability and efficiency of 4
b, the analytical investigations revealed another unique fea-
ture of the catalyst. Indeed, while catalyst 3b, or more pre-
cisely its derivative 2b mainly afforded S epoxides, catalyst
4b generated the opposite R enantiomers (Table 1). We
tried to rationalize this surprising observation on the basis
of molecular modeling. Preliminary molecular modeling of
the free base porphyrins 2a and 4a revealed several inter-
esting features that might explain the reverse enantioselec-
tivity observed with the homologated catalyst 4b (Figure 2).
proach of the olefin operates on opposite faces (Figure 3). In
2b, the quinone structure may generate enough room to ac-
commodate the approach of the substrate via the Re face,
near the oxidized naphthalene ring. Such an approach indu-
ces the formation of the S epoxide. In the case of 4e, the
methoxy group of the homologated binaphthyl structure
more likely prevents the Re face approach of the olefin on
the proximal methoxy-naphthalene. Thus, it favors the Si
face approach affording the R enantiomer.
In conclusion, we have demonstrated that the C2-symmet-
rical binaphthyl porphyrin 4b constitutes an exceptional cat-
alyst for the asymmetric epoxidation of styrene derivatives.
Indeed, unprecedented enantiomeric excesses and very high
TON were simultaneously obtained for the epoxidation of
terminal olefins. A key role of the proximal methoxy group
was proposed for explaining the reversed enantioselectivities
observed with iron derivatives 3b and 4b. We suggested that
the proximal methoxy group forces the approach of the Si
face of the substrate for epoxidation by the oxoferryl active
site. On the other hand, we ex-
clude p p stacking interactions
as we have already demonstrat-
ed that 2b is a remarkable cata-
lyst for the epoxidation of non-
aromatic tert-butyl- and trime-
thylsilyl ethylenes (82 and 90
% ee were respectively meas-
ured for the latter olefins).
Thus, we were able to synthe-
size a novel oxidizing catalyst
which can discriminate prochi-
ral faces of simple olefins
throughout weak nonbonding
interactions. It appeared that
the binaphthyl handle acts as a
butterfly wing that could prefer-
entially attract the Re or the Si
face of the substrate and move
it near the active site for the
Figure 2. Lowest energy conformations for porphyrins 2a (left) and 4a (right).
oxidation process. Work is in
progress to investigate further
The minimum-energy conformations of the free base por-
phyrins 2a and 4a were calculated by using a molecular me-
chanics conformation search method (Tripos force field in
SYBYL computation).[14] In both cases, molecular modeling
revealed slightly ruffled porphyrin planes.
the potential of catalyst 4b. In particular, we are currently
investigating the use of more environmentally friendly oxi-
dants such as H2O2 or NaOCl. Applications of catalyst 4b in
reactions as different as chiral hydroxylation, and asymmet-
ric cyclopropanation are also underway.
It is noteworthy that the porphyrin plane deformation is
more important when n=1 (porphyrin 4a) than when n=0
(porphyrin 2a). This is in agreement with what has been ob-
served in the case of bridled porphyrins.[15] However, the
major differences between the two structures concern the
geometries of the binaphthyl cavities. In particular, it ap-
pears that the dihedral angles of the binaphthyl handles are
different which may be explained by the absence of the
proximal methoxy group for 2a and a higher flexibility for 4
a. Thus, the dihedral angle between the two naphthyl moiet-
ies is 58 smaller in the case of 2a than in the case of 4a (608
versus 658). This is also confirmed using classical CPK
models of 2b and 4e that show that in both cases the ap-
Experimental Section
General: Information: All reagents were used as supplied commercially
unless otherwise noted. THF and diethyl ether were distilled from
sodium under N2 before use. 5, 6a 6c, aabb-o-TAPP were prepared ac-
cording to literature method.[7c,11] 1H and 13C NMR spectra were per-
formed on a Bruker AC200, ARX400 or DRX500 spectrometers and ref-
erenced to the residual solvent signals. Infrared spectra were recorded on
a Nicolet-Avatar 320 FT-IR. UV/Vis spectra were recorded on UVIKON
923Spectrometer. MS/HRMS were obtained from the University of Lille
on an Applied Biosystems Voyager DE-STR MALDI-TOF MS. Optical
rotation data were measured on a Perkin Elmer Model 343 Polarimeter
227
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E. Rose et al.
FULL PAPER
CDCl3, 298 K): 27.5, 68.1, 125.2, 131.6,
132.8, 133.3, 135.0, 135.8, 136.9, 137.5,
138.1, 141.8, 153.0 ppm; EI/MS: m/z:
392.15 [M + H]+ ; elemental analysis
(%): calcd: C 79.57, H 5.14, N 7.14;
found: C 79.46, H 5.20, N 7.13; [a]D20
À78.7 (c=0.50, THF).
=
6e: Compound 6d (2.6 g, 6.63mmol)
was taken up in aqueous NaOH (8m;
30 mL) and stirred at 1008C for 24 h.
The pale yellow precipitate that had
formed during the reaction was fil-
tered off under vacuum and taken up
in ethyl acetate and water. The aque-
ous solution was acidified until pH 2,
and extracted three times with
AcOEt. The organic layers were com-
bined, dried over MgSO4, filtered, and
evaporated to dryness to afford 6e as
a pale yellow powder (2.56 g; 90%).
1H NMR (200.13MHz, CDCl 3, 298 K):
d=3.23 (s, 6H; OCH3), 3.99 (d,
2J(H,H)=16.7 Hz, 2H; CH2Ph), 4.01
(d, 2J(H,H)=16.7 Hz, 2H; CH2Ph),
7.19 (d, 3J(H,H)=8.1 Hz, 2H; ArH),
7.30 (t, 3J(H,H)=8.4 Hz, 2H; ArH),
7.45 (t, 3J(H,H)=8.4 Hz, 2H; ArH),
7.87 (d, 3J(H,H)=8.1 Hz, 2H; ArH),
7.91 (s, 2H; ArH), 8.75 ppm (2H;
large s, CO2H); 13C NMR (50 MHz,
CDCl3, 298 K): 36.9, 61.0, 125.8, 126.4,
127.3, 128.1, 130.7, 131.7, 132.9, 134.0,
154.1, 179.8 ppm; EI/MS: m/z: 430.08;
elemental analysis (%): calcd: C 69.66,
H 5.17; found: C 69.50, H 5.09; [a]D20
À24.3( c=0.50, THF)
=
6f: Compound 6f was freshly prepared
by refluxing 6e (213mg, 0.495 mmol)
in oxalyl chloride (5 mL) under stir-
ring at 508C for 8 h under N2. Excess
of oxalyl chloride was then removed
by using a water aspirator affording
the crude diacid chloride as a pale
yellow foam. The latter was used in
the following reaction without any fur-
ther purification.
4a: A 500-L two-neck round-bottom
flask equipped with
a stir bar, a
rubber septum, and a nitrogen inlet
was charged with freshly distilled THF
Figure 3. Proposed mechanism for the enantioselective epoxidation with catalysts 2b and 4e.
(150 mL). N,N-Diethylaniline (970 mg,
6.5 mmol) was added to the THF.
Under N2, in a separate flask a solu-
at 589 nm. GC analyses were performed on HRGC MEGA series 9000
chromatographs with flame ionization detector and using a QC3/PBX5
capillary column (25 mî0.5 mm) and chiral capillary column Lipodex-E
(50 mî0.25 mm, id.; 0.125 mm thickness) respectively. Nitrogen was used
as the carrier gas.
tion of aabb-o-TAPP (508 mg, 0.76 mmol) in dry THF (20 mL) was pre-
pared and transferred into two 10 mL syringes. Likewise, a solution of 6f
(705 mg, 1.51 mmol) in dry THF (10 mL) was transferred in a dry 10 mL
syringe. A syringe pump was equipped with the three syringes. The por-
phyrin and the diacid chloride were simultaneously added over 3h at 5
8C and the reaction mixture was allowed to stir at room temperature for
an additional 12 h. THF was removed under reduced pressure and the
residue was directly poured onto a column and the mixture was purified
by column chromatography (SiO2, 15 40 mm, eluent CH2Cl2). The expect-
ed bis-strapped porphyrin 4a was eluted with a mixture CH2Cl2/MeOH:
99/1 as a purple band. Evaporation of the fractions containing the expect-
ed porphyrin afforded 4a as purple powder (350 mg; 31%). 1H NMR
(400.13MHz, CDCl 3, 298 K): d=À2.91 (s, 2H; NHpyr), À0.51 (s, 6H;
OMe), 1.98 (s, 6H; OMe), 2.58 (d, 2J(H,H)=14.0 Hz, 2H; CH2Ph), 3.15
(d, 2J(H,H)=14.0 Hz, 2H; CH2Ph), 3.33 (d, 2J(H,H)=16.8 Hz, 2H;
CH2Ph), 3.68 (d, 2J(H,H)=16.8 Hz, 2H; CH2Ph), 5.80 (d, 3J(H,H)=
8.3Hz, 2H; ArH), 6.20 (d, 3J(H,H)=8.3Hz, 2H; ArH), 6.33 (t,
6d: A solution of 6c (4.27 g, 8.53mmol) and sodium cyanide (1.90 g,
38.8 mmol) in DMSO (20 mL) was stirred at 508C for 36 h. After the re-
action was completed, the reaction mixture was poured into a water/di-
chloromethane (350 mL/350 mL) mixture and extracted. The organic
phases were collected, dried over Na2SO4, filtered, and evaporated to
dryness. The crude residue was purified by column chromatography on
silica gel (SiO2 15 40 mm, eluent CH2Cl2) to yield the pure dicyano deriv-
ative 6d (2.83g; 84%).
1H NMR (200.13MHz, CDCl 3, 298 K): d=3.24 (s, 6H; OCH3), 4.00 (s, 4
H; CH2Ph), 7.15 (d, 3J(H,H)=8.4 Hz, 2H; ArH), 7.30 (t, 3J(H,H)=
8.4 Hz, 2H; ArH), 7.45 (t, 3J(H,H)=8.0 Hz, 2H; ArH), 7.91 (d,
3J(H,H)=8.0 Hz, 2H; ArH), 8.09 ppm (s, 2H; ArH); 13C NMR (50 MHz,
3
3J(H,H)=7.4 Hz, 2H; ArH), 6.77 (t, J(H,H)=8.3Hz, 2H; ArH), 6.84 (t,
228
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Chem. Eur. J. 2004, 10, 224 230

Enantioselective Epoxidation of Terminal Olefins
224 230
3J(H,H)=7.4 Hz, 2H; ArH), 7.02 (d, 3J(H,H)=8.4 Hz, 2H; ArH), 7.13
(t, 3J(H,H)=7.6 Hz, 2H; ArH), 7.21 (d, 3J(H,H)=8.0 Hz, 2H; ArH),
7.40 (s, 2H; ArH), 7.47 (t, 3J(H,H)=7.4 Hz, 2H; ArH), 7.57 (t,
3J(H,H)=7.4 Hz, 2H; ArH), 7.62 (d, 3J(H,H)=8.2 Hz, 2H; ArH), 7.80
(large s, 4H; NH), 7.82 (t, 3J(H,H)=8.2 Hz, 2H; ArH), 7.89 (t,
3J(H,H)=8.0 Hz, 2H; ArH), 8.15 (d, 3J(H,H)=6.9 Hz, 2H; ArH), 8.54
(d, 3J(H,H)=8.4 Hz, 2H; ArH), 8.59 (s, 2H; Hb), 8.65 (d, 3J(H,H)=
5.1 Hz, 2H; Hb), 8.70 (s, 2H; Hb), 8.73(d, 3J(H,H)=5.1 Hz, 2H; Hb),
8.85 ppm (d, 3J(H,H)=7.7 Hz, 2H; ArH); 13C NMR (100 MHz, CDCl3,
298 K): 38.7, 39.3, 57.5, 59.4, 112.6, 113.9, 120.4, 120.9, 121.9, 122.2, 122.6,
123.1, 123.4, 123.7, 124.1, 124.2, 125.3, 125.5, 126.5, 128.2, 128.9, 129.2,
129.3, 129.5, 131.3, 131.7, 133.2, 134.0, 136.8, 137.9, 151.5, 152.8,
168.3ppm; UV/Vis (CH 2Cl2): lmax (e)=424 (320000), 517 (18700), 552
(5820), 592 (5780), 649 nm (3420). MALDI-TOF HRMS: m/z calcd for
tions was calculated based on the consumed PhIO on a QC3/PBX5 capil-
lary column (25 mî0.5 mm).
Acknowledgments
This work was supported by a CNRS K.C. Wong Postdoctoral Fellowship
(Q.Z.R), and by the CNRS (B.A., E.R., and Q.Z.R). We express our
thanks to Dr. R. P. Pandian, Mr. W. Assaf, and H. Lakmini for contribu-
ting to this work. We thank Dr. G. Ricart from the Universitÿ des Scien-
ces et Technologies de Lille for MS data. Q.Z.R. acknowledges Prof. B.
Fan from the Institut de Topologie et de Dynamique des Systõmes, Paris
VII for help with the molecular modeling.
[C96H70N8O8
+
H]+ : 1463.5397, found: 1463.5343; elemental analysis
(%): calcd (M + CH2Cl2): C 75.21, H 4.69, N 7.23; found: C 74.98, H
5.06, N 6.96.
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0.23mmol) were added to glacial acetic acid (5 mL) and brought to
reflux overnight under argon. After this reaction time, UV/Vis monitor-
ing confirmed that the reaction had reached completion. Excess of acetic
acid was then removed under vacuum, and the residue taken in CH2Cl2.
The organic phases were washed with dilute HCl (1m), dried over
Na2SO4, filtered through a pad of NaCl, and evaporated to dryness to
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744 nm (602). MALDI-TOF HRMS: m/z calcd. for [C96H68N8O8Fe]+
:
1517.3707, found: 1517.4563.4c: A 50-mL round-bottom flask equipped
with a stir bar was charged with 4a (20 mg, 14 mmol), CH2Cl2 (5 mL),
and AcONa (5 mg, 0.06 mmol) and was brought to reflux. When the re-
action reached a gentle reflux, 1 mL of a saturated methanolic solution
of Zn(OAc)2¥2H2O (154 g/100 g: w/w) was added. Reflux was maintained
for 1 h. TLC revealed that the reaction was not complete, so an addition-
al 1 mL of a saturated solution of Zn(OAc)2¥2H2O was added, and the
reaction was stirred for another 1 h. After this reaction time, both UV/
Vis spectroscopy and a TLC revealed that the reaction had reached com-
pletion. The reaction mixture was then diluted with CH2Cl2 and washed
with water (3times). After drying over Na 2SO4, the organic phase was fil-
tered and evaporated to dryness. The resulting purple powder was taken
up in CH2Cl2 and purified by column chromatography (SiO2 15 40 mm,
eluent CH2Cl2/MeOH: 1/1) to afford the pure zinc complex 4c in quanti-
tative yield. 1H NMR (200.13MHz, CDCl 3, 298 K): d=1.99 (s, 6H;
OMe), 2.10 (s, 6H; OMe), 2.59 (d, 2J(H,H)=14.0 Hz, 2H; CH2Ph), 3.15
(d, 2J(H,H)=14.0 Hz, 2H; CH2Ph), 3.33 (d, 2J(H,H)=16.0 Hz, 2H;
CH2Ph), 3.20 (d, 2J(H,H)=16.0 Hz, 2H; CH2Ph),), 3.28 (d, 2J(H,H)=
15.0 Hz, 2H; CH2Ph),), 3.61 (d, 2J(H,H)=15.0 Hz, 2H; CH2Ph), 5.63(d,
3J(H,H)=8.0 Hz, 2H; ArH), 5.70 (d, 3J(H,H)=8.0 Hz, 2H; ArH), 6.28
(t, 3J(H,H)=8.4 Hz, 2H; ArH), 6.71 (s, 2H; ArH), 6.84 (t, 3J(H,H)=
7.9 Hz, 2H; ArH), 7.12 (s, 2H; ArH), 7.17 (t, 3J(H,H)=7.4 Hz, 2H;
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ArH), 7.37 (t, J(H,H)=7.4 Hz, 2H; ArH), 7.53(t, 3J(H,H)=7.4 Hz, 4H;
3
ArH), 7.63(t, 3J(H,H)=7.4 Hz, 4H; ArH), 7.79 (t, J(H,H)=8.2 Hz, 4H;
3
ArH), 7.80 (t, 3J(H,H)=8.2 Hz, 4H; ArH), 7.85 (s, 2H; ArH), 8.01 (s, 2
H; ArH), 8.22 (d, 3J(H,H)=7.4 Hz, 2H; ArH), 8.74 (m, 8H; Hb),
8.94 ppm (s, 2H; ArH); 13C NMR (125 MHz, CDCl3, 298 K): 29.8, 40.2,
41.0, 60.0, 61.0, 114.7, 116.0, 120.6, 122.0, 122.8, 122.9, 123.1, 123.2, 123.8,
124.2, 125.2, 125.3, 127.0, 127.5, 127.7, 127.8, 128.5, 129.3, 129.7, 130.3,
130.4, 131.2, 131.7, 132.0, 132.2, 132.7, 133.0, 134.8, 136.8, 138.3, 138.8,
149.4, 150.5, 150.6, 151.0, 153.3, 168.8, 169.9 ppm; UV/Vis (CH2Cl2): lmax
(e)=428 (352670), 553 nm (19910).
General procedure for asymmetric olefin epoxidation:
Epoxidations were carried out using the following standard conditions: A
mixture of the catalyst 4b (1 mmol), olefin (1.0 mmol), and 1,2,4-trichlor-
obenzene (160 mmol, as an internal standard) in freshly distilled and de-
gassed CH2Cl2 (2 mL) were stirred under N2 in an ice-bath in a dry
1.5 cm diameter Schlenk tube. After addition of PhIO (100 mmol, 22 mg),
aliquots were taken, purified by chromatography on a short silica-gel
column and monitored by GC at appropriate intervals. Enantiomeric ex-
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(50 mî0.25 mm, id.; 0.125 mm thickness). The retention times were com-
pared to the retention times of standard racemates. The yield of he reac-
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229
Chem. Eur. J. 2004, 10, 224 230
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¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

E. Rose et al.
FULL PAPER
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Received: June 11, 2003
Revised: September 2, 2003[F5222]
230
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 224 230