Asymmetric oxidation of sulfides by hydrogen peroxide catalyzed by chiral manganese porphyrins in water/methanol solution

Article abstract of DOI:10.1016/j.molcata.2012.12.016

An efficient asymmetric oxidation of sulfides catalyzed by water-soluble chiral manganese porphyrin was carried out in presence of cheap and environmentally benign oxidant H₂O₂ at 25 °C. Prochiral sulfides were converted to respective sulfoxides with up to 100% conversion and up to 57% enantiomeric excess. The present study demonstrated the necessity of water as solvent and imidazole as co-catalyst. Application to the preparation of the optically drug, sulindac, was demonstrated.

Full text of DOI:10.1016/j.molcata.2012.12.016

Journal of Molecular Catalysis A: Chemical 370 (2013) 75–79
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journal homepage: www.elsevier.com/locate/molcata
Asymmetric oxidation of sulfides by hydrogen peroxide catalyzed by chiral
manganese porphyrins in water/methanol solution
a
a
a
a
b
a,∗
Hassan Srour , Joanna Jalkh , Paul Le Maux , Soizic Chevance , Marwan Kobeissi , Gérard Simonneaux
a
UMR 6226, Sciences Chimiques de Rennes, Campus de Beaulieu, Université de Rennes 1, 35042 Rennes, France
Libanese University, Beirut, Lebanon
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 September 2012
Received in revised form
An efficient asymmetric oxidation of sulfides catalyzed by water-soluble chiral manganese porphyrin was
carried out in presence of cheap and environmentally benign oxidant H2O2 at 25 C. Prochiral sulfides were
converted to respective sulfoxides with up to 100% conversion and up to 57% enantiomeric excess. The
present study demonstrated the necessity of water as solvent and imidazole as co-catalyst. Application
to the preparation of the optically drug, sulindac, was demonstrated.
◦
1
3 December 2012
Accepted 30 December 2012
Available online 11 January 2013
©
2013 Elsevier B.V. All rights reserved.
Keywords:
Asymmetric oxidation
Catalytic sulfoxidation
Water-soluble manganese porphyrin
Hydrogen peroxide
Sulindac
1
. Introduction
Metalloporphyrins, widely studied as models of hemes or
cytochrome P-450, have been known to exhibit the catalytic activ-
ity for monooxygenation, proceeding via the formation of a high
valency metal–oxygen complex intermediate [22]. However, to the
best of our knowledge, the asymmetric oxidation of sulfides cat-
alyzed by chiral manganese porphyrin is still unprecedented when
Development of catalytic system for the preparation of optically
active sulfoxides is important in organic synthesis as sulfoxides
constitute chiral synthons for the preparation of biologically active
compounds [1–3]. Among all methods described so far [1,4–6], the
asymmetric oxidation of sulfides by metal catalysts is one of the
most attractive routes to optically active sulfoxides. Catalysis often
permits the use of less toxic reagents, as in the case of oxidation
by hydrogen peroxide. H O is widely accepted as a green oxidant
the oxidant is H O2 although there is one example of sulfoxida-
2
tion with chiral manganese corroles [23] and few examples of
epoxidation reactions have also been previously reported [24,25].
This is quite surprising since the first metalloporphyrin-catalyzed
2
2
because it is relatively nontoxic and breaks down in the environ-
ment into benign byproduct [7–9]. After the pioneering work of
Kagan [10] and Modena [11] on asymmetric sulfoxidation with
organic peroxides, new catalytic systems based on vanadium [12],
iron [13,14], aluminum [15] and titanium [16] have been reported
within the fifteen years, all employing hydrogen peroxide as oxi-
dant. Moreover water which is an inexpensive and environmentally
benign solvent, coupled with H O , can be advantageously used in
oxygenation with H O2 reported the formation of sulfoxide from
2
sulfide [26] and the enzymatic oxidation of sulfides to optically
active sulfoxides catalyzed by peroxidases [27–30] and other heme
proteins [1] have been reported. However, the main obstacle when
using H O is the high activity of transition-metal complexes in the
2
2
catalase reaction and the homolytic cleavage of the peroxidic O O
bond with the formation of the hydroxyl radical [22].
We previously described sulfoxidation reactions with H O2
2
2
2
organic syntheses [9,17]. There are recent and excellent reviews on
catalytic asymmetric sulfoxidation [18–21].
in water/methanol using chiral iron porphyrin as a catalyst in a
preliminary report [31]. In this study, we examine catalytic asym-
metric sulfoxidation reactions by water-soluble optically active
manganese porphyrins using hydrogen peroxide as oxidant in
water/methanol solutions. The synthetic value of our method was
demonstrated by the enantioselective synthesis of the nonsteroidal
anti-inflammatory drug sulindac, which has recently found addi-
tional utility in cancer treatment [32].
∗ Corresponding author. Tel.: +33 2 23236285; fax: +33 2 23235637.
E-mail address: gerard.simonneaux@univ-rennes1.fr (G. Simonneaux).
1
381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2012.12.016

7
6
H. Srour et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 75–79
2
. Experimental
SO Na
3
2.1. General
All reactions were performed under argon and were mag-
netically stirred. Solvents were distilled from appropriate drying
agent prior to use: MeOH from turning Mg. Commercially avail-
able reagents (Acros) were used without further purification unless
otherwise stated. All reactions were monitored by TLC with Merck
pre-coated aluminum foil sheets (Silica gel 60 with fluorescent indi-
cator UV254). Column chromatographies were carried out using
silica gel from Merck (0.063–0.200 mm). UV–Vis spectra were
recorded on a UVIKON XL from Biotech. Gas chromatography anal-
yses were performed on a Varian CP-3380 gas chromatography
equipped with a CP-1177 injector. The enantiomeric excess of
the sulfoxides was determined on a Varian Prostar 218 system
equipped with Chiralcel columns. The optical rotations were deter-
mined on a Perkin Elmer 341 polarimeter.
N Cl
N
N
M
SO Na
3
NaO3S
N
SO Na
3
(
1) M = Mn
(2) M = Fe
Fig. 1. Structure of the manganese and iron catalysts.
2.2. Synthesis and characterization of catalysts
rate = 0.5 ml/min; wavelength = 220 nm; tr (S) = 10.4 min, tr
(
4
R) = 18.0 min.
Under argon, the porphyrin (H )HaltSNa (120 mg, 0.077 mmol)
33] and 2,6-lutidine (83 mg, 0.77 ␮mol) were dissolved in reflux-
ing dimethylformamide (DMF) (25 mL). After waiting for several
2
-Nitrophenyl methyl sulfoxide: HPLC condition: column:
[
Chiralcel OJ-H; eluent n-hexane/isopropanol = 80/20; flow
rate = 0.5 ml/min; wavelength = 220 nm; tr (R) = 54.8 min, tr
minutes to allow the porphyrin to dissolve, MnBr ·4H O (222 mg,
2
2
(S) = 64.8 min.
0
.77 mmol, 10 equiv) was added to the solution. The reaction was
4
-Bromophenyl methyl sulfoxide: HPLC condition: column:
followed by UV–Vis spectroscopy. After refluxing for 2 h, the mix-
ture was allowed to cool to room temperature and evaporated
under vacuum. The crude product was dissolved in a mixture
of hydrochloric acid (5%) and methanol (15 mL), and stirred for
0 min. The solvent was then evaporated and the product was
treated with a cationic exchange resin (Dowex 50) to give a green
Chiralcel OB-H; eluent n-hexane/isopropanol = 50/50; flow
rate = 0.5 ml/min; wavelength = 220 nm; tr (S) = 9.6 min, tr
(R) = 12.0 min.
2
-Bromophenyl methyl sulfoxide: HPLC condition: column:
2
Chiralcel OB-H; eluent n-hexane/isopropanol = 50/50; flow
rate = 0.5 ml/min; wavelength = 220 nm; tr (S) = 9.7 min, tr
solid. Yield = 80%. MALDI-TOF Linear: calculated m/z = 1514.364
(R) = 13.2 min.
−
[
M−4Na+3H] for C84H75MnN O S , found 1514.363.
4
12 4
Benzyl methyl sulfoxide: HPLC condition: column: Chiralcel OB-
H; eluent n-hexane/isopropanol = 70/30; flow rate = 0.5 ml/min;
wavelength = 220 nm; tr (R) = 44.8 min, tr (S) = 48.8 min.
−1
−1
UV–Vis (MeOH): ꢀmax 470 nm (ε = 35.50 cm mM ), 567 nm
−
1
−1
−1
−1
(
ε = 3.47 cm mM ), 600 nm (ε = 2.43 cm mM ).
Benzyl phenyl sulfoxide: HPLC condition: column: Chiralcel OB-
H; eluent n-hexane/isopropanol = 70/30; flow rate = 0.5 ml/min;
wavelength = 220 nm; tr (R) = 35.0 min, tr (S) = 42.7 min.
2
.3. General procedure for asymmetric sulfoxidation
Methyl phenyl sulfoxide. Manganese porphyrin complex 1
(
1.6 mg, 1 ␮mol) and imidazole (1.7 mg, 25 ␮mol) were placed in
3
. Results and discussion
a test tube under argon. The solvent (375 ␮L MeOH + 125 ␮L PBS,
pH 7) was then added via syringe, followed by the sulfide (5 ␮L,
4
added in one portion to the solution. The reaction was followed by
gas chromatography (GC). From GC we knew that the reaction was
over after 2 h with a 100% yield containing 1% sulfone. The solution
was extracted with dichloromethane three times and then dried
3.1. Effect of the proportion of water/methanol in the
2.3 ␮mol). Finally, hydrogen peroxide (1.8 ␮L, 21.2 ␮mol) was
MnHaltS–H O –imidazole system
2
2
The complex 1 (Fig. 1) was used for the catalytic asymmetric
sulfoxidation reactions. The porphyrin was placed in DMF under
argon in the presence of ten equivalents of MnBr ·4H O. Ten equiv-
2
2
over MgSO . The ee was then determined by HPLC to be 33%.
4
alents of 2,6-lutidine were added in order to deprotonate hydrogen
present on the nitrogen of the macrocycle. It was necessary to heat
2
(
.4. Characterization data of sulfoxides and chromatography
HPLC) conditions
◦
to 140 C for the insertion of manganese to occur. The reaction is
controlled by UV–Visible spectroscopy, which shows that it was
over after 2 h. Then, HCl (5%) was added in order to exchange the
bromine by chlorine. Finally, an ion exchange column chromatog-
raphy was done to purify the product. The complex, MnHaltS 1, was
obtained with 80% yield as a black-green solid. It was easily soluble
in water and methanol. The UV–Vis spectrum (Fig. 2) presents a
hypsochromic shift of 50 nm for the Soret band after complexation.
Because of the high solubility of the catalyst in methanol, the
sulfoxidation of phenyl methyl sulfide (see Scheme 1) was first
examined in this solvent at room temperature with imidazole as
co-catalyst and in anaerobic conditions. The results were traces of
the corresponding sulfide and sulfone after 2 h. This reaction was
successfully amplified in the presence of 25% phosphate buffer (pH
7) and using first 0.5 equivalent of H O to avoid the formation of
1
All the sulfoxides have been previously characterized by H NMR
31]. Enantiomeric excesses have been determined by HPLC (see
[
below).
Phenyl methyl sulfoxide: HPLC condition: column: Chiralcel OD-
H; eluent n-hexane/isopropanol = 70/30; flow rate = 0.5 ml/min;
wavelength = 220 nm; tr (R) = 28.2 min, tr (S) = 31.6 min.
Methyl p-tolyl sulfoxide: HPLC condition: column: Chiralcel OD-
H; eluent n-hexane/isopropanol = 90/10; flow rate = 0.5 ml/min;
wavelength = 220 nm; tr (R) = 25.1 min, tr (S) = 27.4 min.
4
-Methoxyphenyl methyl sulfoxide: HPLC condition: column:
Chiralcel OB-H; eluent n-hexane/isopropanol = 50/50; flow
2
2

H. Srour et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 75–79
77
O
S
O
O
S
S
MnHaltS
H O
2
2
X
X
X
MeOH/H O
2
Scheme 1. Catalytic asymmetric oxidation of sulfides by hydrogen peroxide.
Fig. 2. UV–Vis spectrum for MnHaltS (1) and H2HaltS (2).
Fig. 3. Variation of the amount of catalyst (1) during the reaction.
sulfone. The result was a 100% yield and 33% ee. The reaction was
selective and only traces of the sulfone were observed due to over-
oxidation (Table 1, entry 2). Similar results were obtained while
changing the ratio methanol/water from 50/50 (Table 1, entry 3)
to 25/75 (Table 1, entry 4) without an important change in the
ee; however, the percentage of sulfone increases from 3 to 8%
respectively. A “push–pull” mechanism for heterolytic O O bond
cleavage in hydroperoxo manganese porphyrins has been previ-
ously reported by Groves and coworkers [34] underlying the role
of water in these systems. The same reaction was performed only in
water to give a 12% yield containing 18% of the product as a sulfone
3
.2. Influence of sulfide structure on enantiomeric excess
We also investigated the sulfoxidation of various sulfides with
the same catalyst 1 using 1 equiv of H O . Results are summarized
2
2
in Table 2. As shown in Table 2, sulfoxide yields in the range of
7–95% were obtained with enantiomeric excess (ee) as high
5
as 57% for 4-nitrophenyl methyl sulfoxide. Selectivities in all
cases were moderate, although a significant electronic effect on
the substrate could also be discerned. More reactive, electron
rich sulfides were oxidized with lower selectivity, while better
enantioselectivity were obtained with substrate bearing a nitro
group. Small amounts of sulfone (<24%) were also detected. The
(
Table 1, entry 5). This result might be due to the poor solubil-
ity of phenyl methyl sulfide in water. Moreover, a typical reaction
using phenyl methyl sulfide was followed by UV–Vis spectroscopy
in order to measure the oxidative destruction of the catalyst by
Table 2
H O . As shown in Fig. 3, only a partial destruction of the cata-
2
2
Asymmetric oxidation of sulfides catalyzed by MnHaltS–H2O2–imidazole system.a
lyst (30%) occurred in the progress of the reaction. The reaction
apparently ends up after 1h30 when all the H O is consumed.
Yieldb
%)
Eec (%)
Sulfoxide/
sulfone
2
2
Entry
Substrate
(
(config)d
ratiob (%)
1
2
3
4
5
6
7
8
Methyl phenyl sulfide
72
61
95
93
93
57
76
62
34 (S)
28 (S)
16 (S)
57 (S)
32 (S)
7 (S)
97/3
Table 1
2-Bromophenyl methyl sulfide
4-Methoxyphenyl methyl sulfide
4-Nitrophenyl methyl sulfide
4-Bromophenyl methyl sulfide
Benzyl phenyl sulfide
90/10
87/13
87/13
86/14
76/24
98/2
Effect of the proportion of water/methanol on the oxidation of methyl phenyl sulfide
by MnHaltS–H2O2–imidazole system.
a
Entry
Solvent
Yield (%)
Ee (%)
Sulfone (%)
1
2
3
4
5
MeOH
Traces
100
100
100
12
–
33
32
30
–
Traces
1
3
8
Benzyl methyl sulfide
Methyl p-tolyl sulfide
5 (S)
24 (S)
MeOH/PBS (3/1)
MeOH/PBS (1/1)
MeOH/PBS (1/3)
PBS
99/1
a
Reaction conditions: 1 equiv of H2O2 (relative to sulfide) was added in one
portion to a solution of sulfide/imidazole/MnHaltS mixture (1:0.6:0.025) in 0.5 ml
18
◦
of MeOH/PBS (pH 7) (3/1) placed under argon at 25 C and the reaction was stirred
a
for 2 h.
Reaction conditions: 0.5 equiv H2O2 (relative to sulfide) was added in one
portion to a solution of sulfide/imidazole/MnHaltS mixture (1:0.6:0.025) in 0.5 ml of
b
Determined by GC.
Determined by chiral HPLC.
Determined by the sign of optical rotation and to comparison with literature.
◦
c
MeOH/PBS (pH 7) mixture placed under argon at 25 C and the reaction was stirred
for 2 h.
d

7
8
H. Srour et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 75–79
Table 3
Table 5
Effects of the co-catalyst on the oxidation of methyl phenyl sulfide with
MnHaltS–H2O2–imidazole system.
Asymmetric
oxidation
of
methyl
phenyl
sulfide
catalyzed
by
a
a
MnHaltS–H2O2–imidazole system at different pH values.
Entry
Cocatalyst
Yield (%)
Ee (%)
Sulfoxide/sulfone
ratio (%)
Entry
pH
Yield (%)
Ee (%)
Sulfoxide/sulfone
ratio (%)
1
2
3
4
5
6
–
33
35
33
–
25
27
24
29
30
98/2
99/1
–
97/3
99/1
98/2
91/9
98/2
1
2
3
4
4
7
9
82
100
64
33
33
35
32
98/2
99/1
100/0
99/1
Imidazole
NH4OAc
Pyridine
Piperidine
2-Methyl imidazole
NH4OAc
100
Traces
38
80
53
10.5
68
a
Same conditions as Table 2 but at different pH values (see experimental section).
b
7
8
69
62
c
NH4OAc
the presence of H O , at room temperature, using MeOH/PBS as
solvent in a 3:1 ratio. The yield and ee values were observed after
h. The results are summarized in Table 5. We found that a 100%
conversion was observed only at pH 7 (Table 5, entry 2) while at an
acidic pH (pH 4), we observed 82% conversion. In contrast, a larger
negative effect was observed at a basic pH (pH 9 and 10.5) because
2
2
a
Same conditions as Table 2 (see experimental section).
equiv H2O2, solvent: MeOH.
equiv H2O2, solvent: MeOH/PBS (pH 7) (3/1).
b
c
5
5
2
best yield was obtained with 4-methoxyphenyl methyl sulfoxide
95%), however with a low ee (16%). The reaction was performed
in the same conditions but in the absence of H O . No oxidation
(
6
4 and 68% yields were only obtained, respectively (Table 5, entries
3 and 4). The ees were found quite similar (between 32 and 35%).
2
2
occurred which proves that H O2 is necessary for oxidation. It
2
is also important to note the presence of direct oxidation by
hydrogen peroxide (8%) in the absence of catalyst.
3.5. Influence of an excess of oxidant
We have examined the effect of increasing the oxidant/phenyl
methyl sulfide ratio on the yield and ee in hope of increasing the
ee. Table 6 shows a decrease in the yield from 100 (Table 6, entry
3
.3. Influence of the nature and the amount of the co-catalyst
The key role of imidazole in metalloporphyrin-catalyzed oxi-
4
) to 72 (Table 6, entry 5) without an important change in the ee.
dation with H O , evidenced by Mansuy et al. [35] in olefin
◦
2
2
It also shows that at 5 C, increasing the ratio of the oxidant from 1
to 2, provides an increase in the yield from 76 to 98% along with an
increasing in the ee from 33 to 38%. However, 50% of sulfone was
obtained which may suggest the existence of a kinetic resolution
process during the course of the reaction. In order to investigate this
aspect, an experiment was performed under standard asymmetric
sulfide oxidation conditions using racemic sulfoxide as a substrate.
After 2 h, the conversion of sulfoxide to sulfone was 96%. The ee of
epoxidation, is confirmed herein since a weak conversion (33%) was
detected in the absence of this ligand (Table 3, entry 1). Various co-
catalysts, other than imidazole, were investigated on phenyl methyl
sulfide in order to see their effect. Using pyridine, the results were
not satisfactory since only a 38% yield and 25% ee were obtained
(
(
Table 3, entry 4). 2-Methyl imidazole gave 53% yield and 24% ee
Table 3, entry 6). The ammonium acetate was investigated under
different conditions. First, it was tried under the same conditions
as the other co-catalysts. The results were traces of the sulfoxide.
Trying to amplify these results, it was tested with 5 equivalents of
1
4% for the recovered sulfoxide revealed that the sulfoxidation was
indeed weakly enantioselective. Note that the slight increase in the
ee from 34 to 38% may be due to kinetic resolution.
H O , a 62% yield and 30% ee were obtained (Table 3, entry 8). It
2
2
is worth noting that the same reaction with ammonium acetate
in MeOH only gave similar results (Table 3, entry 7). But using
piperidine, better yields were obtained giving 80% yield and 27%
ee (Table 3, entry 5). However, imidazole remained herein the best
co-catalyst (Table 3, entry 2).
3
.6. Preparation of optically active sulindac
Sulindac, or (Z)-5-Fluoro-2-methyl-1-[p-(methylsulfinyl)
benzylidene]indene-3-acetic acid, is an efficient anti-inflammatory
drug mainly used in the treatment of pain, rheumatoid arthritis,
osteoarthritis and acute gouty arthritis [36]. To date, sulindac
has only been administered therapeutically as a racemic mixture
We have also investigated the effect of decreasing the amount
of imidazole from 0.6 to 0.3 equivalents. The yield decreases from
100 to 46% (Table 4). Also, the enantiomeric excess decreases from
33 to 31%. Concerning the amount of sulfone obtained, it is less than
1% in both cases which confirms that no over-oxidation is occurring
[
4]. The first asymmetric synthesis of enantiopure sulindac has
been recently reported by Maguire and co-workers [36] using
stoichiometric quantities of a mixture of Ti(Oi-Pr) , diethyltartrate
4
in these experimental conditions.
◦
and H O (in a 1:2:1 ratio) at −30 C and cumene hydroperoxide
2
as oxidant. Both enantiomers were obtained in moderate yields
3
.4. pH-dependent H O oxidation
2
2
(56% and 54%) but with high enantioselectivities (89% and 90%
ee). Another method reported by Bolm and co-workers [37] is
an enantioselective oxidation of the corresponding sulfide using
To explore whether the pH affects the yield and the ee, phenyl
methyl sulfide was chosen as the substrate at different pH values.
The experiments for pH-dependent oxidation were carried out in
Table 6
Effects of the amount of H2O2 relative to phenyl methyl sulfide on the
Table 4
MnHaltS–H O –imidazole system.a
2
2
Effects of the amount of imidazole relative to methyl phenyl sulfide on the
MnHaltS–H2O2–imidazole system.
a
Entry
Number of
equiv H2O2
Yield (%)
Ee (%)
Sulfoxide/sulfone
ratio (%)
Entry
Number of equiv
imidazole
Yield (%)
Ee (%)
Sulfoxide/sulfone
ratio (%)
b
1
2
1
1.2
2
0.5
1
76
92
98
100
72
33
34
38
33
34
96/4
94/6
50/50
99/1
97/3
b
1
2
3
0.6
0.3
0
100
46
33
33
31
35
99/1
100/0
98/2
3b
4
5
a
a
Same conditions as Table 2 but with different amount of imidazole (number of
equiv relative to sulfide) (see experimental section).
2 2
Same conditions as Table 2 but with different amount of H O .
b
At 5 ◦C.

H. Srour et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 75–79
79
F
F
CO H
CO H
2
2
MnHaltS
MeOH/H O
2
S
S
O
Scheme 2. Asymmetric synthesis of sulindac by hydrogen peroxide.
Table 7
a modest ee varying between 16 and 57% for methyl aryl sul-
fides. This variation was dependent on the sulfide used. We also
showed the essential need for a co-catalyst, particularly imidaz-
ole. As an application, an optically active sulindac molecule was
successfully synthesized for the first time directly from the cor-
responding sulfide by iron and manganese porphyrin catalysts
in water/methanol solutions giving ee up to 82% (iron complex).
Ongoing work includes investigations to specify the role of chiral-
ity in the mechanism in order to enhance the enantiomeric excess,
and investigations of an extended range of substrates particularly
those of pharmaceutical importance.
Asymmetric oxidation of sulindac sulfide catalyzed by (1) and (2).
◦
Yieldb (%)
Eec (%)
Entry
T/ C
Catalyst
Sulfoxide/sulfone
ratiob (%)
1a
25
25
0
1
2
2
2
2
70
100
100
100
100
27
68
74
80
82
100/0
98/2
97/3
96/4
93/7
d
2
3
d
d
4
−20
d,e
5
−20
a
Same conditions as Table 2 (see experimental section).
Determined by NMR analysis on the crude reaction mixture.
Determined by HPLC on a chiral phase.
b
c
d
Reaction conditions: a mixture containing catalyst (1 ␮mol), sulfide (100 ␮mol)
and H2O2 (120 ␮mol) in 1 ml distilled CH3OH under argon was stirred for 1 h.
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e
1
0 ␮mol of 2-methylimidazole was added to the reaction.
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asymmetric oxidations were done on an intermediate compound
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[
[
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[
[
[
lent of H O , methanol/water (3/1) and 0.6 equivalent of imidazole
2
2
at room temperature to obtain the expected optically active sulin-
dac (Scheme 2) (Table 7). The result was a moderate 70% yield
but a low 27% enantiomeric excess. This enantiomeric excess
was determined by HPLC after esterification using 1.5 equivalent
of trimethylsilyldiazomethane in a solution of toluene/distilled
methanol in a ratio of 4:1. Also, the sign of the optical rotation was
determined by a polarimeter to be negative (−), which stands for
an S absolute configuration [36].
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[
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5
[
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[
19] H.B. Kagan, in: T. Toru, C. Bolm (Eds.), Organosulfur Chemistry in Asymmetric
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[
[21] G.E. O’Mahony, P. Kelly, S.E. Lawrence, A.R. Maguire, ARKIVOC (i) (2011) 1–110.
[
[
[
22] B. Meunier, Chem. Rev. 92 (1992) 1411–1456.
On the other hand, a similar asymmetric sulfoxidation reaction
was performed using the hydrosoluble iron porphyrin catalyst 2
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1697–1698.
(
Fig. 1), FeHaltS, which was previously reported by our group [31],
instead of the manganese complex 1. The best reaction conditions
were found by the use of 1.2 equivalents of H O in 1 mL methanol,
[
25] J.P. Collman, V.J. Lee, C.J. Kellen-Yuen, X. Zang, J.A. Ibers, J.I. Brauman, J. Am.
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2
2
[26] S. Oae, Y. Watanabe, K. Fujimori, Tetrahedron Lett. 23 (1982) 1189–1192.
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which gave, when applied to phenyl methyl sulfide, 100% yield and
1% (S) ee. Therefore, these same conditions were applied for the
3
57–358.
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637–1645.
7
[
oxidation of the sulindac sulfide at room temperature. Optically
active sulindac was obtained in 100% yield and 68% enantiomeric
1
[29] M.P.J. van Deurzen, F. van Rantwijk, R.A. Sheldon, Tetrahedron 53 (1997)
13183–13220.
◦
◦
excess. Decreasing the temperature to 0 C and −20 C improved
[
[
30] E.N. Kadnikova, N.M. Kostic, J. Org. Chem. 68 (2003) 2600–2608.
31] P. Le Maux, G. Simonneaux, Chem. Commun. 47 (2011) 6957–6959.
the enantiomeric excess of sulindac to 74 and 82%, respectively
(
Table 7).
[32] T. Takayama, H. Nagashima, M. Maeda, S. Nojiri, M. Hirayama, Y. Nakano, Y.
Takahashi, Y. Sato, H. Sekikawa, M. Mori, T. Sonoda, T. Kimura, J. Kato, Y. Niitsu,
Clin. Cancer Res. 17 (2011) 3803–3811.
4
. Conclusion
[
33] I. Nicolas, S. Chevance, P.L. Maux, G. Simonneaux, Tetrahedron: Asymmetry 21
2010) 1788–1792.
(
[
[
34] N. Jin, D.E. Lahaye, J.T. Groves, Inorg. Chem. 49 (2010) 11516–11524.
35] J.P. Renaud, P. Battioni, J.F. Bartoli, D. Mansuy, J. Chem. Soc. Chem. Commun.
After optimizing the conditions of the H O asymmetric sulfox-
2
2
idation reactions in water/methanol solutions, using a hydrosol-
uble manganese porphyrin as catalyst, various reactions were
performed on phenyl methyl sulfide and its derivatives. These
reactions gave a good yield varying between 38 and 100% and
(
1985) 888–889.
[36] R. Maguire, S. Papot, A. Ford, S. Touhey, R. O’Connor, M. Clynes, Synlett (2001)
1–44.
37] A. Korte, J. Legros, C. Bolm, Synlett (2004) 2397–2399.
4
[