Catalysis of oxo transfer to prochiral sulfides by oxovanadium(v) compounds that model the active center of haloperoxidases

Article abstract of DOI:10.1002/chem.200304595

The catalytic properties of a new class of chiral vanadium compounds-[(S,S,S)-VO(OMe)L1] (5), [(S,S)-VO(OMe)L2] (6), [(S,S)-VO(OMe)L3] (7), and [(R,R,R)-VO(OMe)L4] (8), as well as the system VO(OiPr)₃/ (R,R,R)-H₂L4 [H ₂L1=

Full text of DOI:10.1002/chem.200304595

FULL PAPER
Catalysis of Oxo Transfer to Prochiral Sulfides by Oxovanadium(v)
Compounds That Model the Active Center of Haloperoxidases
Gabriella Santoni,[a] Giulia Licini,[b] and Dieter Rehder*[a]
Abstract: The catalytic properties of a
new class of chiral vanadium com-
prochiral faces of the sulfides (methyl
p-tolyl sulfide and benzyl phenyl sul-
fide), to steric implications stemming
from the oxidant (cumyl hydroperoxide
and tert-butyl hydroperoxide), and to
the specific complex used. As an exam-
ple, (S)-methyl p-tolyl sulfoxide was
obtained in a 31% enantiomeric excess
by use of cumyl hydroperoxide as oxi-
dant and complex 5 as the catalyst, after
150 min at 08C and with 100% conver-
sion of the sulfide. The crystal and
molecular structures of 5 and 6 reveal
the close relationship between these
complexes and the active center of
vanadate-dependent haloperoxidases:
the vanadium is in a slightly distorted
trigonal-bipyramidal environment with
the nitrogen and the methoxy group in
the axial positions, and the oxo and
alkoxide functions of L2 and L3 are the
plane. The presence and equilibrium
situation of isomers of the catalysts in
solution has been investigated by 51V
EXSY and variable-temperature multi-
nuclear NMR spectroscopy. An inter-
mediately formed peroxo (ROOÀ) va-
nadium complex was detected by 51V
NMR spectroscopy.
pounds–[(S,S,S)-VO(OMe)L1](
5),
[(S,S)-VO(OMe)L2]( 6), [(S,S)-VO(O-
Me)L3]( 7), and [(R,R,R)-VO(OMe)L4]
(8), as well as the system VO(OiPr)3/
(R,R,R)-H2L4 [H2L1 ˆ (S,S)-bis(2-hy-
droxypropyl)-(S)-1-phenylethylamine,
1; H2L2 ˆ (S,S)-bis(2-hydroxypropyl)-
benzylamine, 2; H2L3 ˆ (S,S)-bis(2-hy-
droxypropyl)isopropylamine),
3;
(H2L4) ˆ (R,R)-bis(2-phenylethanol)-
(R)-1-phenylethylamine, 4]–in the
asymmetric oxidation of prochiral sul-
fides by organic hydroperoxides have
been investigated. Particular attention
has been paid to the factors that guide
the discrimination between the two
Keywords: amino
alcohols
sulfides
¥
¥
oxo-transfer catalysis
sulfoxides ¥ vanadium
¥
bicyclic aromatic sulfides with hydrogen peroxide as oxidant
and the bromoperoxidase from the seaweed Corallina offici-
nalis as catalyst yields the corresponding (S)-sulfoxides with
high enantiomeric excesses (ees), while this enzyme is not able
to oxidize methyl phenyl sulfide at all.[7, 8] If, however, this
reaction is mediated by the bromoperoxidase from the brown
seaweed Ascophyllum nodosum, the R enantiomer of the
sulfoxide is obtained in 91% ee, with a yield of 55%, after
20 h at room temperature under slightly acidic conditions.[4]
The sulfoxide with the opposite configuration was obtained
(30% ee, 45% yield) in the oxidation mediated by the
bromoperoxidase from the red seaweed Corallina pilulifera.[5]
In contrast, use of the chloroperoxidase from the mold
Curvularia inaequalis or of recombinant chloroperoxidases
led to racemic mixtures.[5] This difference in reactivity
suggests a specific orientation of the substrate in the vicinity
of the active sites,[9] even though the molecular structures of
the chloroperoxidase from C. inaequalis[10] and the bromoper-
oxidase from A. nodosum[11] revealed a high degree of amino
acid homology in the active sites, with the only difference
being the replacement of His411 by Phe397. The vanadate
core in these enzymes is covalently bound to the Ne of a
proximal histidine; vanadium is in a trigonal-bipyramidal
array (Scheme 1a), with the apical OH group hydrogen-
Introduction
Vanadate-dependent haloperoxidases are enzymes responsi-
ble for the production of a variety of halogenated compounds
through the initial formation of hypohalous acids as the
3]
halogenating agents.[1 The enzymes are capable of with-
standing temperatures of up to 708C, they remain functional
in the presence of several organic solvents, and–in contrast to
heme peroxidases–they are not inactivated by H2O2 during
catalysis.[4] Like other natural receptors, vanadate-dependent
haloperoxidases are also capable of recognizing substrates
with a specific chirality: it has recently been demonstrated
that these enzymes mediate enantioselective sulfoxidation by
hydrogen peroxide.[5 Thus, the asymmetric oxidation of
8]
[a]Prof. Dr. D. Rehder, Dott.ssa G. Santoni
Institut f¸r Anorganische und Angewandte Chemie der Universit‰t
Hamburg
20146 Hamburg (Germany)
Fax : (‡49)40-42838-2893
E-mail: dieter.rehder@chemie.uni-hamburg.de
[b]Prof. Dr. G. Licini
¬
Universita degli Studi di Padova
Dipartimento di Chimica Organica, 35131 Padova (Italy)
Fax : (‡39)049-8275289
E-mail: giulia.licini@unipd.it
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/chem.200304595
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4700 4708
Results and Discussion
Syntheses: A new class of chiral vanadium complexes
mimicking the active site of the vanadate-dependent haloper-
oxidases was synthesized through the use of enantiopure
amino alcohols (H2L1, H2L2, and H2L3, 1 3), obtained by
treatment of (S)-propene oxide with three different amines
(Scheme 2, (1)), and with H2L4 (4), obtained by treatment
of (R)-(‡)-styrene oxide with (R)-(‡)-phenylethylamine
Scheme 1. The active centers of vanadate-dependent haloperoxidases
from: (a) native A. nodosum bromoperoxidase, (b) the peroxo from of
C. inaequalis chloroperoxidase, and (c) the hydroperoxo intermediate
proposed for the A. nodosum peroxidase.
bonded to a distal His residue.
When a molecule of oxidant
(H2O2) coordinates to the metal
center, a structural rearrange-
ment from a trigonal-bipyrami-
dal geometry to square-pyrami-
dal occurs. In the peroxo form,
vanadium carries an axial oxo
group, while the plane is occu-
pied by a side-on coordinated
peroxide, histidine, and an oxo/
hydroxo ligand (Scheme 1b).[12]
For the turnover, a hydroperoxo
intermediate has been pro-
posed; the resulting asymmetric
side-on coordination of hydro-
peroxide has been suggested on
the basis of 17O NMR studies of
solutions of the A. nodosum per-
oxidase after treatment with
17O-enriched
me 1c).[13] The formation of a
mono-hydroperoxo species
H2O2
(Sche-
plays a fundamental role for
the enzymatic reactivity[14] in
the sense that a positive charge
Scheme 2. Syntheses of the new class of chiral vanadium complexes.
on the peroxo-O provided by
17]
protonation[15
furnishes a fa-
vorable site for the nucleophilic
attack of the substrate to be oxidized.[18] The oxidation of
prochiral sulfides to the corresponding optically active sulf-
oxides is believed to work according to this mechanism (see
also below).
(Scheme 2). Treatment of the amino alcohols with VO(OiPr)3
in dichloromethane resulted in the formation of the com-
plexes [VO(OiPr)L](Scheme 2, (2)) with an asymmetric
environment around the metal center. Transesterification
with methanol (Scheme 2, (3)) yielded [VO(OMe)L]( 5 8).
Compounds 5 and 6 were obtained in crystalline form suitable
for X-ray diffraction analysis.
During the last few years, the synthesis of enantiopure
sulfoxides has received much attention[19] because of the use
22]
of these compounds as chiral auxiliaries,[20
synthetic
intermediates, and bioactive compounds.[23] Several inorganic
chiral vanadium compounds have been employed in the
catalytically conducted oxidation of prochiral sulfides to
chiral sulfoxides (and further to sulfones), usually based on
Structure description: ORTEP plots of 5 and 6 are shown in
Figure 1; Table 1 contains selected bonding parameters. In
both molecules, vanadium is in a somewhat distorted trigonal-
bipyramidal environment (t ˆ 0.75 for 5 and t ˆ 0.66 for 6;
the angular parameter t is 1 for an ideal trigonal-bipyramid
and 0 for an ideal square pyramid), with the doubly bonded
oxo group in the plane. The vanadium center is displaced by
0.2321 ä (5) and by 0.2618 ä (6) from the basal plane towards
the nitrogen atom. The angle between the two apical ligands
and the vanadium center, O2-V1-N1, is 1678. The deviations
of the basal angles from the idealized value of 1208 is more
26]
vanadium systems containing Schiff base ligands.[24 These
reactions have further been extended to thioacetals and
thioketals,[27] and to disulfides.[28] Here, as a contribution to
the elucidation of the chiral recognition mechanism of the
haloperoxidases, we report on a study of the catalytic proper-
ties of new oxovanadium(v) complexes, containing bi- and
trichiral amino-bis(alcoholates) as ligands, in the asymmetric
oxidation of prochiral thioethers.
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D. Rehder et al.
FULL PAPER
Solution studies: In the 51V NMR spectra, the observation of
more than one signal in the range typical of five-coordinate
vanadium complexes with an O4N donor set,[37] with the main
components for compound
6
at d ˆ À420, À447, and
À457 ppm (Figure 2), suggests the presence of isomers in
solution. Variations in the solvent (CH2Cl2, toluene, THF,
2-Me-THF) did not cause variation in the signal pattern or in
Figure 1. Structures of 5 and 6 (ORTEP plots (50% probability level).
Table 1. Selected bond lengths [ä]and bond angles [ 8]for 5 and 6.
Figure 2. 51V NMR spectrum of 6 in CDCl3 at room temperature. See text
for discussion.
[VO(OMe)L1]( 5)
[VO(OMe)L2]( 6)
their ratio; coordination of solvent molecules to the complex
in a sixth position can therefore be excluded. Note that even
the polar alcohols employed in the preparation did not lead to
the formation of a six-coordinate complex. An equilibrium
between structural isomers is possibly responsible for the
signals at d ˆ À420 and À447 (see the discussion for complex
5 below). In addition, dimers and/or oligomers in equilibrium
with the monomer (Scheme 3; dashed lines represent weak
bonds[39]) may provide additional signals in the higher field
region. Alkoxovanadium compounds tend to associate into
À
À
V1 O4
1.6043(11)
V1 O4
1.591(2)
1.792(2)
1.787(3)
1.787(2)
2.338(3)
1.480(3)
1.484(3)
1.493(3)
111.10(16)
101.91(13)
98.05(12)
114.29(15)
127.71(15)
96.74(13)
91.01(11)
77.58(10)
167.06(11)
77.06(11)
À
À
V1 O1
1.7947(11)
1.7991(10)
1.8119(10)
2.2615(11)
1.4813(16)
1.4886(15)
1.5216(16)
114.72(6)
102.26(6)
95.63(5)
117.72(6)
122.26(6)
95.44(5)
90.25(5)
78.98(4)
V1 O1
À
À
V1 O3
V1 O3
À
À
V1 O2
V1 O2
À
À
V1 N1
V1 N1
À
À
N1 C16
N1 C11
À
À
N1 C3
N1 C8
À
À
N1 C15
N1 C1
O4-V1-O1
O4-V1-O3
O1-V1-O3
O4-V1-O2
O1-V1-O2
O3-V1-O2
O4-V1-N1
O1-V1-N1
O3-V1-N1
O2-V1-N1
O4-V1-O1
O4-V1-O3
O3-V1-O1
O4-V1-O2
O2-V1-O1
O3-V1-O2
O4-V1-N1
O1-V1-N1
O3-V1-N1
O2-V1-N1
41]
dimers/oligomers through alkoxo bridges.[38 This notion is
corroborated here by the 51V NMR analyses of solutions of 6
at different concentrations: an increase in concentration
increases the integral intensity of the signal at d ˆ À457 at
the expense of the other signals. For entropic reasons these
equilibria should be directed towards the monomer; we
therefore assign the predominant resonance signal at d ˆ
167.49(5)
78.35(4)
1
À420 to the monomer. The H NMR spectrum (Figure 3)
pronounced in 6, in which the ligand 2 bears a sterically less
demanding benzyl residue instead of a phenylethyl moiety.
This steric influence is also reflected in the two different
seems to validate this thesis; the signals corresponding to
complex 6 have been marked with an asterisk, while those
marked with an arrow should be attributed to the dimeric (or
oligomeric) species. The ratio between monomer and dimer is
the same as found in the 51V NMR spectra.
À
d(V N1) values, of 2.2615(11) ä in 5 and 2.338(3) ä in 6.
Both are surprisingly elongated and reminiscent of
V N(amine) bonds in V and VV complexes with the
IV
À
nitrogen atom trans to a doubly bonded oxo group.[29 For
31]
Further insight into the equilibrium situation was obtained
by a variable-temperature NMR analysis of complex 5, the
complexes with the amine function cis to an oxo group, bond
lengths in the range of 2.13
34]
2.21 ä have been reported.[32
The
upper
limit
about
for
À
d[V N(amine)]is
2.52 ä, as observed in [VO-
(acac)L'], in which H2L' is bis-
(2-hydroxyethyl)-(S/R)-1-phenyl-
ethylamine.[35] The d(V OMe)
À
distances of 1.799 and 1.787 ä
are within the expected
range,[36] as are the bonds to
the remaining functions.
Scheme 3. Equilibrium between the monomer and dimers and/or oligomers.
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Oxo-Transfer to Prochiral Sulfides
4700 4708
adjacent to the nitrogen atom, which apparently slows down
the geometrical rearrangement to the extent to which the two
species in equilibrium can be detected in the NMR spectra.
The signal at lower field should be attributable to the species
5', with reference to data reported in the literature for
trigonal-bipyramidal vanadium complexes with N(amine)
trans to the oxo group.[29] The presence of two isomers is
1
confirmed by the H NMR spectra (Figure 5): the signals at
d ˆ 5.05 and 4.52 assigned to V-OCH3, in an approximate
ratio of 1:1, coalesce at about 280 K (not shown). Partial
ligand dissociation can be excluded on the basis of the
1H NMR pattern. Chemical exchange is further confirmed by
the 51V NMR EXSY spectrum of 5 in CDCl3 solution, taken at
room temperature (Figure 6).
Figure 3. 1H NMR spectrum of 6 in CDCl3 at room temperature. The
resonances indicated by asterisks and arrows are assigned to monomers and
dimers (or oligomers) of 6, respectively (cf. Scheme 3).
Catalytic oxidation of sulfides: Vanadium complexes bearing
amino alcohol ligands have not so far been employed as
catalysts in the enantioselective oxidation of organic sulfides.
There are a few reported examples of vanadium catalysts with
chiral Schiff base ligands, in which the asymmetric component
is supplied by the amine component.[24 26] These catalysts have
usually been employed in situ (i.e., as mixtures of a vanadium
precursor and the ligand), with hydrogen peroxide or alkyl
hydroperoxides as oxidant. In the oxidation reactions report-
ed here, alkyl hydroperoxides (cumyl hydroperoxide (CHP),
and tert-butyl hydroperoxide (TBHP)) have been used,
because the reactions had to be carried out in organic
solvents, due to the water sensitivity of the catalysts. The
reactions have been conducted with the sulfides and oxidants
at 0.1m, and the catalyst at 0.01m concentrations in 1,2-
dichloroethane. The results are summarized in Table 2 for
methyl p-tolyl sulfide and CHP and varying catalysts, and in
Table 3 for complex 5 as the catalyst with varying sulfide and
oxidant. For the overall reaction, see Scheme 5.
1
51V and H NMR spectra of which in chloroform and THF
show broad signals at ambient temperature. Figure 4 shows
the 51V NMR spectra in THF in the 193 to 323 K range,
affirming an exchange process involving the species charac-
terized by the two main signals at d ˆ À411 and À453.
With methyl p-tolyl sulfide and CHP, the reactions pro-
ceeded with a turnover of 100% (related to the oxidant).
Along with the sulfoxide as the main product, obtained with
the same absolute configuration as the catalyst, some sulfone
is also formed. Figure 7 represents the reaction path as a
function of time for complex 5 as the catalyst. The ee (about
31% (S)) remains constant during the complete oxidation
process. The reaction is thus kinetically controlled (i.e., there
is no chiral distinction for the oxidation of the sulfoxide to the
sulfone), contrasting with other catalytic sulfoxidation sys-
tems such as those using amino alcoholates of TiIV and ZrIV.[42]
Compounds 5 and 8–as compared to 6 and 7–contain an
additional chiral center, and this is possibly responsible for the
better chiral discrimination (Table 2). Of the reactions
catalyzed by 6 and 7 (i.e., the complexes with only two chiral
Figure 4. Variable-temperature 51V NMR spectra of 5 in [D8]THF. The
signals at d ˆ À391 and À451 (193 K) [d ˆ À411 and À453 at 292 K]are
taking part in an exchange equilibrium (Scheme 4). The signal at d ꢀÀ 470,
which is particularly broad at low temperatures, presumably corresponds to
a larger (i.e., oligomeric) species of 5 (Scheme 3). The sharpening of the
signals with rising temperature is a consequence of decreasing quadrupolar
relaxation (decreasing molecular correlation time) with increasing temper-
ature.
Beyond 303 K, coalescence is reached. We
suggest an equilibrium between the two
isomers 5 and 5' as shown in Scheme 4,
coming about through a rearrangement in
the coordination sphere through a tetrago-
nal-pyramidal transient. Compounds 5/5'
and 6 differ in as far as in 5/5' there is an
additional methyl group on the carbon atom
Scheme 4. Equilibrium between the two isomers 5 and 5'.
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D. Rehder et al.
FULL PAPER
centers), the oxidation proceeds with a better ee in the case of
6, which is the compound with less steric hindrance.
In an attempt to elucidate the mechanism operative in
chiral recognition, we studied the asymmetric oxidation of
two different sulfides–methyl p-tolyl and benzylphenyl
sulfide–with two peroxides (CHP and TBHP) exhibiting
different steric conditions, in the presence of 5 as the catalyst
(Table 3), in more detail. In the case of the MeSpTol (Table 3,
entries 1 and 3), better results both in terms of turnover and in
ee were obtained with CPH. The bulky tert-butyl group in
TBHP probably creates an intermediate peroxo species that
does not allow the substrate to approach with the appropriate
orientation. If we consider the same oxidant, CHP, but two
different substrates (Table 3, entries 1 and 2), better discrim-
ination between the two prochiral faces of the sulfide is
observed as the two residues on the sulfur are unbalanced,
(i.e., in the case of MeSpTol). This observation is markedly
accentuated with THBP as oxidant (Table 3, entries 3 and 4);
here, the ee drops from 24.8 to 4.7%. The selectivity with
respect to a high percentage of sulfoxide in the sulfoxide/
sulfone mixture is particularly pronounced for catalyst 7 (with
methyl groups on the ethanol arms) and the in situ system
VO(OiPr)3/H2L4 (with phenyl groups on the ethanol arms)
(Table 2, entries 3 and 5). The very short reaction time (30 min
for 100% consumption of the oxidant) in the case of the in situ
system may be accounted for by the better accessibility for the
ligand, the oxidant and/or the substrate in four-coordinate
VO(OiPr)3, although this unprecedented observation, which
may be related to the ™ligand accelerating effect in cataly-
sis∫,[43] still needs to be explored.
Figure 5. 1H NMR spectrum of
Scheme 4. The signals at d ˆ 5.05 and 4.52 correspond to V-OCH3.
5 in [D8]THF. For assignments cf.
A possible mechanism for the catalysis, depicted in
Scheme 6, is based on the proposal that a peroxo intermediate
with the peroxide coordinating to vanadium in the h2 mode is
formed, consistent with what is known of peroxovanadium
Figure 6. Room temperature 51V EXSY spectrum of complex 5 in CDCl3,
at a mixing time of 2 ms, showing the exchange correlation between the
signals at d ˆ À411 and À453 and (less pronounced) the two inner signals
at d ˆ À426 and À444.
47]
complexes.[12, 44
The formation of a peroxo intermediate is corroborated by
51V NMR spectra (Figure 8). This intermediate has been
detected in methanolic solutions of [VO(OiPr)L4], containing
[VO(OMe)L4]( 8) treated with CHP, as well as in solutions
containing the precursor components [VO(OiPr)3 ‡ H2L4]
and CHP. Along with the two main signals for 8 and
[VO(OiPr)L4], respectively, the spectra each show a new
signal at À510, which is only present if the peroxide is added
and is thus assigned to [VO(O2R)L4], formed by exchange of
Table 2. Oxidation of methyl p-tolyl sulfide with CHP in the presence of
varying catalysts.
[a]
Entry SO:SO2
ee [%][b] Turnover [%][c] Time [min]Catalyst
1
2
3
4
5
85:15
72:28
94:6
88:12
94:6
31.2 (S) 100
23.0 (S) 100
11.0 (S) 100
26.0 (R) 100
25.0 (R) 100
150
720
540
120
30
5
6
7
8
VOL4(OiPr)[d]
À
the isopropoxo or methoxo ligand by RO2 . In agreement
[a]determined by GC analysis. [b]Determined by HPLC analysis.
[c]Related to the oxidant. [d]Complex prepared in situ by treatment of
VO(OiPr)3 with H2L4.
with what one would expect,[37] the shielding in six-coordinate
[VO(O2R)L4]is lower than in seven-coordinate monoperoxo-
vanadium complexes by about 100 ppm.[37, 44, 48]
Conclusion
Table 3. Oxidation of alkyl aryl sulfides by organic peroxides in the
presence of catalyst 5.[a]
Three five-coordinate oxovanadium(v) complexes, each con-
taining an O4N donor set consisting of a chiral tridentate
amino-bis(alcoholate), a methoxy group, and a basal oxo
group, have been characterized. The complexes are essentially
trigonal-bipyramidal (t ˆ 0.66 0.75) and so are rare examples
of oxovanadium complexes exhibiting this geometry (for a
Schiff base complex with a comparable t ˆ 0.70 see[49]). The
Entry Sulfide Oxidant SO:SO2 ee [%]( S) Turnover [%]Time [min]
1
2
3
4
MeSpTol CHP
BzSPh CHP
MeSpTol TBHP 100:0
BzSPh TBHP 87:13
85:15
79:21
31.2
23.6
24.8
4.7
100
100
58
150
270
120
120
72
[a]Compare legend to Table 2. CHP ˆ cumyl hydroperoxide; TBHP ˆ tert-
butyl hydroperoxide.
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Oxo-Transfer to Prochiral Sulfides
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Scheme 5. Catalytic oxidation of sulfides.
Figure 7. Time dependence of the oxidation of methyl p-tolyl sulfide with CHP in the presence of catalyst 5.
Scheme 6. Possible mechanism for the catalysis.
complexes model specific features of vanadate-dependent
haloperoxidases, such as the trigonal-bipyramidal O4N coor-
dination of VV and the chiral environment at the active center.
Like most of the native enzymes, the model compounds
enantioselectively catalyze the peroxide oxidation of prochi-
ral sulfides to chiral sulfoxides. In the optimal system in our
series, (S)-methyl p-tolyl sulfoxide has been obtained with an
ee of 31% in the presence of catalyst 5 and CHP as the
oxidant. The reaction times are in general faster (about 2 h),
and the turnover and selectivities (with respect to the
formation of sulfoxide) better than those seen in other
26]
systems containing vanadium-based catalysts.[24
The dy-
namic behavior of our complexes (i.e., equilibria between
stereoisomers and possibly also monomers/oligomers) is
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D. Rehder et al.
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16.2 min (R enantiomer) and 18.7 min (S enantiomer). The retention times
of the benzyl phenyl sulfoxide were 23.9 min (R enantiomer) and 30.2 min
(S enantiomer).
IR spectra were obtained on a Perkin Elmer FT 1720 spectrometer. NMR
spectra were measured on a Bruker AM 360 (at 94.726 MHz for 51V, and
360.134 MHz for 1H) or on
a Varian Gemini 200 instrument (at
52.577 MHz for 51V, 50.285 MHz for 13C, and 199.962 MHz for 1H) with
the usual spectrometer settings. 2D EXSY spectroscopy: the 51V homo-
nuclear exchange (EXSY) experiments were conducted on a Bruker
Avance 400 instrument (at 105.198 MHz) by use of the standard NOE-
SYPH pulse sequence (908 t1 908 Tm 908), 2 ms mixing time. All 51V
NMR chemical shifts are referenced against external VOCl3.
Mass analysis measurements were conducted on a Mariner instrument
(Perspective Biosystem), in the electron spray ionization mode and with a
time-of-flight analyzer (ESI/TOF). The sample concentration was 2 Â
10À5 m in methanol. Mobile phase: methanol; rate 5 mLminÀ1
.
X-ray structure analyses were carried out at 153(2) K with MoKa irradiation
(l ˆ 0.71073 ä, graphite monochromator) on a Smart Apex CCD diffrac-
tometer. Hydrogen atoms were calculated in idealized positions and
included in the last cycles of refinement. Absorption corrections were not
performed. For crystal data and structure refinement see Table 4
Figure 8. 51V NMR spectra of 8 dissolved in CDCl3 at 273 K, treated with
CHP (bottom), and of VO(OiPr)3 ‡ H2L4 ‡ CHP (top). The signal
indicated at À510 belongs to the peroxo complex [VO(O2R)L4], and the
two low-field signals to [VO(OMe)L4]( 8) and [VO(OiPr)L4], respectively.
CCDC-176660 (5) and CCDC-187671 (6) contain the supplementary
likely to be responsible for the relatively inefficient (with
respect to the ee) asymmetric induction. The degree of
enantioselectivity is also influenced by the substrate and the
oxidant in that the less ™symmetrical∫ sulfides (methyl p-tolyl
versus phenyl benzyl sulfide) and the less bulky peroxide
(cumyl versus tert-butyl hydroperoxide) gave the better ee
values. The latter factor suggests the formation of an
intermediate with the hydroperoxide coordinated to the
catalyst center, an intermediate detectable by 51V NMR in
the systems 8 ‡ CHP and VO(OiPr)3 ‡ H2L4 (4) ‡ CHP.
Table 4. Crystal data and structure refinement for 5 and 6.
VO(OMe)L1 (5)
VO(OMe)L2 (6)
empirical formula
formula weight [gmolÀ1]333.29
crystal system
C15H24NO4V
319.27
monoclinic
P2(1)
C14H22NO4V
orthorhombic
P2(1)2(1)2(1)
space group
unit cell dimensions
a [ä]8.2684(3)
b [ä]10.9118(4)
c [ä]8.9816(3)
b [8]95.0470(10)
volume [ä3]807.21(5)
Z
10.1615(10)
13.4671(13)
33.682(3)
4609.3(8)
2
12
Experimental Section
1calcd [gÀ1 cmÀ3]1.371
m [mmÀ1]0.629
F(000)
1.380
0.657
Materials and instrumentation: All solvents and liquid reagents used in this
work were stored under nitrogen over molecular sieves (4 ä). Dichloro-
methane was distilled over CaH2. 1,2-Dichloroethane was treated with
concentrated sulfuric acid (four times with 100 mL of H2SO4 per 1 L of
dichloroethane), washed with water, dried overnight with CaCl2, and
distilled over P2O5. Methanol was distilled over sodium. Cumyl hydro-
peroxide (Fluka, 80% in cumene) was stored at 08C. tert-Butyl hydro-
peroxide (Fluka) was purified by distillation at reduced pressure (b.p. ˆ
338C/16 mm Hg) and stored at 08C. Benzyl phenyl sulfide was prepared
according to reference [43]by alkylation of the corresponding thiol, and its
352
2016
crystal size [mm3]0.30
 0.10  0.10 0.60  0.57  0.41
q range for data collection [8]2.28 to 32.53
2.36 to 27.50
index ranges
À 12 < h < 12
À 13 < h < 11,
À 16 < k < 16
À 13 < l < 13
22075
À 17 < k < 17
À 43 < l < 33
56674
reflections collected
independent reflections, (Rint
completeness to q [%]98.9
data/restraints/parameters
goodness of fit
)
5677 (0.0293)
99.9
5677/1/190
1.024
10570 (0.2201)
10570/0/541
1.061
1
identity was established by H NMR spectroscopy and elemental analysis.
Silica gel 60 (Mecherey Nagel, 230 400 mesh ASTM), [VO(OiPr)3]
(Aldrich), (S)-(À)propene oxide (Fluka), (S)-(À)1-phenylethylamine, iso-
propylamine, 4-methyl-benzophenone (Acros Organics), benzylamine
(Merck), benzophenone (Carlo Erba), methyl p-tolyl sulfide, and bis(n-
butyl) sulfide (Aldrich) were used as obtained. The ligand H2L4 (4) and the
final R ind. [I > 2s(I)]
R1
wR2
R indices (all data)
R1
wR2
0.0311
0.0724
0.0515
0.1146
0.0337
0.0731
À 0.002(12)
0.0576
0.1191
0.048(17)
1
complex (R,R,R)-[VO(OMe)L4]¥ ³2CH3OH (8 ¥ 1³2CH3OH) were prepared
as described previously.[50]
absolute structure param.
largest diff. peak and hole [eäÀ3]0.479 and
The quantitative product analyses for the catalytically conducted sulfide
À0.279 0.773 and À0.512
oxidations were carried out with
a Hewlett Packard 5890 series II
chromatograph, equipped with a capillary column with a FFAP EC-1000
stationary phase (30 m  0.25 mm, film thickness 0.25 mm). The instrument
conditions for the analysis were as follows: initial temperature 558C for
1 min, rate ˆ 158CminÀ1, final temperature 2008C for 30 min. The enantio-
meric excesses of the sulfoxides were determined by HPLC analysis, with a
Shimadzu LC-10AT chromatograph, UV Shimadzu SPD-10A (l ˆ 241 nm)
detector, and a C-R5A Shimadzu chromatopac integrator. The chromato-
graph was fitted with a chiral column packed with Lichrosorb S 100, (R,R)-
diaminocyclohexane DNB spherical 250 Â 4.0 mm. The eluent employed
was a mixture of n-hexane/2-propanol 9:1, flow ˆ 0.6 mLminÀ1, pressure ˆ
17 kgcmÀ2. The retention times of the methyl p-tolyl sulfoxide were
crystallographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (‡44)1223-336033; or deposit@ccdc.cam.uk).
General procedure for the catalytically conducted sulfide oxidations
Oxidation of methyl p-tolyl sulfide (cf. Table 2,and entries 1 and 3 in
Table 3 in the Results and Discussion section): Methyl p-tolyl sulfide
4706
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 4700 4708

Oxo-Transfer to Prochiral Sulfides
4700 4708
(15.48 mg, 0.11 mmol), complex 5 (3.66 mg, 0.01mmol), and benzophenone
(12.75 mg, 0.07mmol) as internal standard were dissolved in anhydrous 1,2-
dichloromethane in a 1 mL flask. The solution was then cooled to 08C.
With stirring and under a nitrogen atmosphere, cumyl hydroperoxide
(20 mL, 0.11 mmol) (Table 2, entry 1) or tert-butyl hydroperoxide (5 ML,
0.11 mmol) was added (Table 3, entry 3). For entries 2 and 3 in Table 2, the
same procedure as for entry 1 was employed, with complex 6 (3.19 mg,
0.01 mmol, entry 2), complex 7 (2.71 mg, 0.01 mmol, entry 3), or complex 8
(5.12 mg, 0.01 mmol, entry 4).
(%) for C9H21NO2 (117.19): C 61.68, H 7.99, N 7.99; found: C 60.98, H 12.03,
N 7.51.
(S,S,S)-[VO(OMe)L1],5 : Ligand 1 (0.5055 g, 2.13 mmol) was dissolved in
1,1-dichloromethane (15 mL) in a double-necked 50 mL round-bottomed
flask. Oxo-tris(isopropoxo)vanadium(v) (0.4954 g, 2.03 mmol) dissolved in
dichloromethane (10 mL) was added dropwise to this solution. During the
addition, the color changed to yellow. After 30 min stirring under nitrogen,
the solvent was removed under vacuum. The product ([VO(OiPr)L1]) was
obtained quantitatively as a yellow-green solid, which was recrystallized
from methanol to yield 5 quantitatively. Crystals were grown by keeping a
concentrated methanolic solution at À208C for about two weeks. 51V NMR
([D8]toluene): d ˆ À421.0, À455.4, À463.1, À473.7 ppm; ([D8]THF): d ˆ
À404.5, À450.9, À456.7, À470.2 ppm; (CDCl3): d ˆ À412.7, À445.4,
À452.3, À460.7 ppm; IR (KBr,): nĈ 2969 and 2929 (n(CH)), 2789
Oxidation of benzyl phenyl sulfide (Table 3,entries 2 and 4) : Benzyl phenyl
sulfide (20.03 mg, 0.11 mmol), complex
5 (3.66 mg, 0.01 mmol), and
4-methyl-benzophenone (20.68 mg, 0.10 mmol) as internal standard were
dissolved in anhydrous 1,2-dichloromethane in a 1 mL flask. After the
mixture had been cooled to 08C, cumyl hydroperoxide (20 mL, 0.11 mmol,
Table 3, entry 2) or tert-butyl hydroperoxide (5 mL, 0.11 mmol, Table 3,
entry 4) was added with stirring, under a nitrogen atmosphere.
À
(n(R2N CH)), 1636 and 1451 (CC ring stretch), 1090 (n(CO)), 968
(n(VO)), 746 and 706 (d(CH) and d(CC)) cmÀ1; MS: m/z (%): 333.9 (42)
‡
‡
[5‡H] , 355.9 (100) [5‡Na] ; elemental analysis calcd (%) for
C15H24NO4V (333.11): C 54.05, H 7.26, N 4.20; found: C 53.31, H 7.12, N
4.06.
After defined intervals of time, 50 mL portions were removed from the
reaction mixtures and immediately quenched by addition to an excess of
bis(n-butyl) sulfide, and the product spectrum was analyzed by GC and
HPLC (determination of the enantiomeric excess; see above).
(S,S)-[VO(OMe)L2],6
: Complex 6 was prepared according to the
procedure described for 5 by treatment of ligand 2 (0.790 g, 3.53 mmol)
with VO(OiPr)3 (0.8227 g, 3.30 mmol). The product, [VO(iPrO)L2], was
obtained as a yellow-green solid, and was recrystallized from methanol to
yield 6 quantitatively. Crystals were grown by keeping a concentrated
methanolic solution at À208C for about two weeks. 1H NMR (CDCl3): d ˆ
Preparation of compounds
(S,S)-Bis(2-hydroxy-propyl)-(S)-1-phenyl-ethylamine,
(PhMeCH)N(CH2CHMeOH)2 (H2L1),1 : (S)-(À)-Propene oxide (1.00 g,
17.2 mmol) and (S)-(À)phenyl-ethylamine (1.04 g, 8.6 mmol) were placed
in a 5 mL round-bottomed flask. The reaction mixture was stirred at 408C
for four days. The crude product obtained was purified by flash
chromatography on silica gel, with hexane/ethyl acetate 1:1 as eluent.
The product was obtained as a pale yellow oil. Yield 1.47 g (72%). 1H NMR
(CDCl3): d ˆ 7.42 7.28 (m, 5H; aromatic), 4.06 3.98 (q, J ˆ 6.8 Hz, 1H;
À
7.40 7.28 (m, 5H; aromatic), 5.55 (m, 1H; CH2CHCH3 OV), 4.99 (m, 1H;
À
À
CH2CHMeO V), 4.87 (s, 3H; CH3O V), 4.75 (d, J ˆ 15.0 Hz, 1H;
NCH2Ph), 4.42 (d, J ˆ 15.0 Hz, 1H; NCH2Ph), 2.88 (m, 4H;
NCH2CHMeO), 1.36 (d, J ˆ 6.1 Hz, 3H; CHCH3OV), 1.27 (d, J ˆ 5.9 Hz,
3H; CHCH3O V) ppm; 13C NMR (CDCl3): d ˆ 133.07, 131.05, and 128.70
À
À
À
(aromatic carbons), 81.10 (CH2CHMeO V), 80.60 (CH2CHMeO V),
À
À
À
À
N CHPh CH3), 3.90 3.74 (m, 2H; CH2 CHCH3 OH), 2.61 2.19 (dd,
À
À
70.76 (CH3O V), 66.83 (NCH2Ph), 62.00 (NCH2CHMeO V), 59.12
À
À
À
J ˆ 13.4 and 2.4 Hz, 2H; N CH2 CHPhOH), 2.58 (b, 2H; CHCH3 OH),
(NCH2CHMeO V), 21.42 (CHCH3O V), 21.24 (CHCH3O V) ppm; 51V
NMR (CDCl3): d (relative integral intensity) ˆ À419.8 (1.0), À447.5 (0.2),
À457.5 (0.2) ppm; IR (KBr): nĈ 3028, 2969, and 2926 (n(CH)), 2867,
À
À
À
À
1.38 (d, J ˆ 6.8 Hz, 3H; NCHPh CH3), 1.08 (d, J ˆ 6.3 Hz, 6H;
CHCH3 OH) ppm; 13C NMR (CDCl3): d ˆ 128.50, 127.78, and 127.27
À
À
À
À
(aromatic carbons), 64.45 (CH2 CHMe OH), 58.10 (N CHPhCH3), 57.95
À
(n(R2N CH)), 1630, 1494, and 1454 (CC ring stretch), 1067 (n(CO)); 9.58
À
À
À
(N CH2 CHPhOH), 20.05 (CHCH3OH), 10.99 (NCHPh CH3) ppm; IR
(NaCl): nĈ 3400 (n(OH)), 3086, 3062, and 3029 (n(CH)), 2855
and 974 (n(VO)), 755 and 707 (d(CH) and d(CC)) cmÀ1; elemental analysis
calcd (%) for C14H22NO4V (319.27): C 52.67, H 6.95, N 4.39; found: C 50.95,
H 6.74, N 4.14.
À
(n(R2N CH)), 1602, 1495, and 1451 (CC ring stretch), 1071 (n(CO)), 738
and 701 (d(CH) and d(CC)) cmÀ1; elemental analysis calcd (%) for
(S,S)-[VO(OMe)L3],7
: Complex 7 was prepared by the procedure
C14H27NO2 (237.33): C 73.80, H 9.56, N 7.81; found: C 73.33, H 9.56, N 7.83.
described for 5, by treatment of ligand 3 (0.790 g, 3.53 mmol) with oxo-
tris(isopropoxo)vanadium(v) (0.8227 g, 3.30 mmol). The primary product,
[VO(iPrO)3L3], was quantitatively transesterificated with methanol to
yield 7 as a yellow oil. Yield ˆ 0.6149g (68.7%). 1H NMR (CDCl3): d ˆ 5.26
(S,S)-Bis(2-hydroxypropyl)benzylamine,(PhCH
2)N(CH2CHMeOH)2
(H2L2),2 : (S)-(À)-Propene oxide (1.66 g, 28.5 mmol) and benzylamine
(1.51 g, 14.3 mmol) dissolved in dichloromethane (5 mL) were placed in a
10 mL round-bottomed flask. The reaction mixture was stirred at 408C for
seven days. The crude product obtained was purified by flash chromatog-
raphy on silica gel, with hexane/ethyl acetate 7:3 as eluent. The product was
obtained as a pale yellow oil. Yield 2.51 g (78.6%). 1H NMR (CDCl3): d ˆ
À
À
(br, 1H; CH2CHCH3 OV), 5.03 (br, 1H; CH2CHMeO V), 4.81 (br, 3H;
À
CH3O V), 3.67 2.18 (m, 5H; NCH2CH and NCH(CH3)2), 1.36 1.33 (d,
À
J ˆ 5.8 Hz, 6H; CH2CHCH3O V), 1.29 1.24 (d, J ˆ 5.8 Hz, 6H;
NCH(CH3)2) ppm; 51V NMR (CDCl3): d (relative integral intensity) ˆ
À418.7 (1), À444.3 (0.1), À454.5 (0.3) ppm; elemental analysis calcd (%)
for C10H22NO4V (271.23 gmolÀ1): C 44.28, H 8.18, N 5.16; found: C 43.71, H
7.74, N 5.07.
À
À
7.35 7.28 (m, 5H; aromatic), 3.94 3.78 (m, 2H; CH2 CHCH3 OH), 3.89
À
À
(d, J ˆ 13.6 Hz, 1H; N CH2Ph), 3.51 (d, J ˆ 13.6 Hz, 1H; N CH2Ph), 2.65
À
À
À
(br, 2H; CHCH3 OH), 2.45 (d, J ˆ 6.1 Hz, 4H; N CH2 CHMeOH), 1.10
(d, J ˆ 6.1 Hz, 6H; CHCH3 OH) ppm; 13C NMR (CDCl3): d ˆ 138.38,
À
À
À
128.94, 128.50, and 127.36 (aromatic carbons), 63.97 (CH2 CHMe OH),
À
À
À
62.07 (N CH2 CHMeOH), 59.76 (N CH2Ph), 20.26 (CHCH3OH); IR
(NaCl): nĈ 3399 (n(OH)), 3085, 3062, and 3027 (n(CH)), 2822
À
(n(R2N CH)). 1602, 1495, and 1453 (CC ring stretch), 1055 (n(CO)), 742
and 699 (d(CH) and d(CC)) cmÀ1; elemental analysis calcd (%) for
Acknowledgement
C13H21NO2 (223.32): C 69.92, H 9.48, N 6.27; found: C 69.63, H 9.43, N 6.52.
This work was supported by the Deutsche Forschungsgemeinschaft (grant
RE 431/13 4), the European Union (COST D12 0027/99), the Ufficio
Formazione post lauream, University of Padova, the Deutsche Akademi-
sche Austauschdienst (grant to G.S.), and the Fonds der Chemischen
Industrie.
(S,S)-Bis(2-hydroxypropyl)isopropylamine,
{(CH3)2CH}N(CH2CHMeOH)2 (H2L3),3 : (S)-(À)-Propene oxide (1.660 g,
28.05 mmol) and isopropylamine (0.845 g, 14.3 mmol) were dissolved in
1,2-dichloromethane (5 mL). The reaction mixture was stirred at 408C for
four days. The crude product was purified as described for 2. Compound 3
was obtained as a pale yellow oil. Yield 1.47 g (71.4%). 1H NMR (CDCl3):
À
À
À
d ˆ 3.79 (br, 2H; CHCH3 OH), 3.72 3.56 (m, 2H; CH2 CHCH3 OH),
[1]R. Wever, Nature 1988, 335, 501; R. Wever, W. Hemrika, Vanadium in
the Environment (Ed.: J. O. Nriagu), Wiley, New York, 1998, 30, 285
305.
[2]A. Butler, J. V. Walker, Chem. Rev. 1993, 93, 1937 1944.
[3]A. Butler, A. H. Baldwin, Structure & Bonding: Metal Sites in Proteins
& Models (Eds.: P. Sadler, H. A. O. Hill, A. Thompson), Springer,
1997, 109 131.
À
2.95 2.75 (heptet, J ˆ 6.6 Hz, 1H; N CH(CH3)2), 2.34 2.06 (m, 4H;
À
À
À
N CH2 CHMeOH), 1.01 0.98 (d, J ˆ 5.86 Hz, 6H; CHCH3 OH), 0.96
À
0.93 (d, J ˆ 6.6 Hz, 3H; N CH(CH3)2), 0.84 0.81 (d, J ˆ 6.6 Hz, 3H;
13
À
À
À
N CH(CH3)2) ppm; C NMR (CDCl3): d ˆ 63.90 (CH2 CHMe OH),
À
À
À
À
57.69 (N CH2 CHMeOH), 50.65 (N CH(CH3)2), 20.42 (N CH(CH3)2),
À
20.07 (CHCH3OH), 15.17 (N CH(CH3)2) ppm; elemental analysis calcd
Chem. Eur. J. 2003, 9, 4700 4708
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4707

D. Rehder et al.
FULL PAPER
[4]H. B. ten Brink, H. E. Schoemaker, R. Wever, Eur. J. Biochem. 2001,
268, 132 138, and references therein.
[29]D. C. Crans, C. Haojiang, O. P. Anderson, M. M. Miller, J. Am. Chem.
Soc. 1993, 115, 6769 6776.
[5]H. B. ten Brink, A. Tuynman, H. L. Dekker, W. Hemrika, Y. Izumi, T.
Oshiro, H. E. Schoemaker, R. Wever, Inorg. Chem. 1998, 37, 6780
6784.
[6]H. B. ten Brink, H. L. Holland, H. E. Schoemaker, H. von Lingen, R.
Wever, Tetrahedron Asymmetry 1999, 10, 4563 4572.
[7]M. A. Andersson, A. Willets, S. G. Allenmark, J. Org. Chem. 1997, 62,
8455 8458.
[8]M. A. Andersson, S. G. Allenmark, Tetrahedron 1998, 54, 15293
15304.
[9]J. S. Martinez, G. L. Carroll, R. A. Tschirret-Guth, G. Altenhoff, R. D.
Little, A. Butler, J. Am. Chem. Soc. 2001, 123, 3289 3294.
[10]A. Messerschmidt, R. Wever, Proc. Natl. Acad. Sci. USA 1996, 93,
392 396.
[30]S. Ooi, M. Nishizawa, K. Matzsumoto, K. Saito, Bull. Chem. Soc. Jpn.
1979, 52, 452 457.
[31]M. Mahroof-Tahir, A. D. Keramidas, R. B. Goldfarb, O. P. Anderson,
M. M. Miller, D. C. Crans, Inorg. Chem. 1997, 36, 1657 1668.
[32]A. D. Keramidas, M. M. Miller, O. P. Anderson, D. C. Crans, J. Am.
Chem. Soc. 1997, 119, 8901 8915.
[33]K. Kawabe, M. Tadokoro, A. Ichimura, Y. Kojima, T. Takino, H.
Sakurai, J. Am. Chem. Soc. 1999, 121, 7937 7938.
[34]Y. Chen, Q. Liu, Y. Deng, H. Zhu, H. F. Chen, D. Liao, E. Gao, Inorg.
Chem. 2001, 40, 3725 3733.
[35]M. Bashirpoor, H. Schmidt, C. Schulzke, D. Rehder, Chem. Ber./
Recueil 1997, 130, 651 657.
[36]I. D. Brown, D. Altermatt, Acta Crystallogr. B 1985, 41, 244 247.
[37]D. Rehder, C. Weidemann, A. Duch, W. Priebsch, Inorg. Chem. 1988,
27, 584 587.
[11]M. Weyand, H.-J. Hecht, M. Kie˚, M.-F. Liaud, H. Vilter, D.
Schomburg, J. Mol. Biol. 1999, 293, 595 611.
[12]A. Messerschmidt, R. Prade, R. Wever, Biol. Chem. 1997, 378, 309
315.
[38]W. Priebsch, D. Rehder, Inorg. Chem. 1990, 29, 3013 3019.
[39]F. Hillerns, F. Olbrich, U. Behrens, D. Rehder, Angew. Chem. 1992,
104, 479 480; Angew. Chem. Int. Ed. Engl. 1992, 31, 447 448.
[40]O. W. Howarth, J. R. Trainor, Inorg. Chim. Acta 1987, 127, L27.
[41]D. C. Crans, F. Jiang, J. Chen, O. P. Anderson, M. M. Miller, Inorg.
Chem. 1997, 36, 1038 1047.
[42]a) F. di Furia, G. M. Licini, G. Modena, R. Motterle J. Org. Chem.
1996, 61, 5175–5177; b) M. Bonchio, G. M. Licini, F. di Furia, S.
Mantovani, G. Modena, W. A. Nugent, J. Org. Chem. 1999, 64, 1326
1330.
œ
¬
[13]M. C asny, D. Rehder, H. Schmidt, H. Vilter, V. Conte, J. Inorg.
Biochem. 2000, 80, 157 169
[14]T. L. Poulus, J. Kraut, J. Biol. Chem. 1980, 255, 8199 8205.
[15]C. Kimblin, X. Bu, A. Butler, Inorg. Chem. 2002, 41, 161 163.
œ
¬
[16]M. C asny, D. Rehder, Chem. Commun. 2001, 10, 921 922.
[17]G. Colpas, B. J. Hamstra, J. W. Kampf, V. L. Pecoraro, J. Am. Chem.
Soc. 1996, 118, 3469 3478.
[18]A. Butler, Coord. Chem. Rev. 1999, 187, 17 35.
[19]H. B. Kagan, Asymmetric Oxidation of Sulfides 2nd ed. (Ed.: I.
Ojima), Wiley-VCH, New York, 2000, ch. 6c.
[43]a) D. J. Berrisford, C. Bolm, K. B. Sharpless, Angew. Chem. 1995, 107,
1159 1171; Angew. Chem. Int. Ed. Engl. 1995, 34, 1059 1070; b) C.
Bolm, Coord. Chem. Rev. 2003, 237, 245 256.
ƒ
[20]M. C. Carren o, Chem. Rev. 1995, 95, 1717.
¬
[21]G. Solladie , Synthesis 1981, 185.
[44]H. Mimoun, P. Chaumette, M. Mignard, L. Saussine, J. Fischer, R.
[22]M. C. Andersen, The Chemistry of Sulfones and Sulfoxides (Eds.: S.
Patai, Z. Rappoport, C. J. M. Stirling), Wiley, Chichester, England,
1988, ch. 3 and ch. 16.
Weiss, Nouv. J. Chim. 1983, 7, 467 475.
¬
¬
[45]M. Siva k, M. Madarova, J. Marek, J. Benko, Chem. Listy 2000, 94,
906 907.
[23]a) H. L. Holland, F. M. Brown, Tetrahedron Asymmetry 1998, 9, 535;
b) V. Conte, F. Di Furia, G. Licini, Appl. Catal. A: General 1997, 157,
335 361, and references therein.
[46]V. Conte, F. di Furia, G. M. Licini, Appl. Catal. 1997, 157, 335 361.
œ
¬
œ
¬
[47]L. Kuchta, M. Siva k, J. Marek, F. Pavelcik, M. Casny, New. J. Chem.
1998, 17, 43 46.
[24]K. Nakajima, M. Kojima, K. Toriumi, K. Saito, J. Fujita, Bull. Chem.
Soc. Jpn. 1989, 62, 760 767.
[48]H. Schmidt, I. Andersson, D. Rehder, L. Pettersson, Chem. Eur. J.
2001, 7, 251 257.
[25]K. Nakajima, M. Kojima, K. Kojima, J. Fujita, Bull. Chem. Soc. Jpn.
1990, 63, 2620 2630.
[49]C. R. Cornman, K. M. Geiser-Bush, S. P. Rowley, P. D. Boyle, Inorg.
Chem. 1997, 36, 6401.
[26]C. Bolm, F. Bienewald, Angew. Chem. 1996, 108, 1767 1769; Angew.
Chem. Int. Engl. 1996, 34, 1657 1659; .
[50]D. Rehder, G. Santoni, G. M. Licini, C. Schulzke, B. Meier, Coord.
Chem. Rev. 2003, 237, 53 63.
[27]C. Bolm, F. Bienewald, Synlett. 1998, 1327 1328.
[28]G. Liu, D. A. Cogan, J. A. Ellman, J. Am. Chem. Soc. 1997, 119, 9913
9914.
Received: November 21, 2002
Revised: May 27, 2003 [F4595]
4708
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www.chemeurj.org
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