Katsuki-Jacobsen oxidation-epoxidation of α-silyloxy sulfinyl dienes: application to the formal synthesis of (6S,7S,9R,10R)-6,9-epoxynonadec-18-ene-7,10-diol

Article abstract of DOI:10.1016/j.tetlet.2007.07.058

The Katsuki-Jacobsen oxidation-epoxidation of acyclic α-silyloxy sulfinyl dienes, followed by acid-promoted cyclization, leads to 2,5-trans sulfonyl dihydrofurans with good selectivities. As an application, the formal synthesis of (6S,7S,9R,10R)-6,9-epoxy

Full text of DOI:10.1016/j.tetlet.2007.07.058

Tetrahedron Letters 48 (2007) 6500–6504
Katsuki–Jacobsen oxidation–epoxidation of a-silyloxy
sulfinyl dienes: application to the formal synthesis of
(6S,7S,9R,10R)-6,9-epoxynonadec-18-ene-7,10-diol
*
´
Roberto Fernandez de la Pradilla and Alejandro Castellanos
Instituto de Quı´mica Orga´nica, CSIC, Juan de la Cierva, 3, 28006 Madrid, Spain
Received 24 June 2007; accepted 9 July 2007
Available online 13 July 2007
Abstract—The Katsuki–Jacobsen oxidation–epoxidation of acyclic a-silyloxy sulfinyl dienes, followed by acid-promoted cyclization,
leads to 2,5-trans sulfonyl dihydrofurans with good selectivities. As an application, the formal synthesis of (6S,7S,9R,10R)-6,9-
epoxynonadec-18-ene-7,10-diol is reported.
Ó 2007 Elsevier Ltd. All rights reserved.
Substituted tetrahydrofurans are commonly occurring
substructures found in a broad array of natural products
and biologically active molecules like, for instance, Lau-
rencia sesquiterpenes ((ꢀ)-kumausalene), polyether anti-
biotics (pamamycin-607) or Annonaceous acetogenins
(muricatetrocin C).1 Due to the biological relevance of
these molecules and their unique structural features,
considerable effort has been devoted toward the devel-
opment of methods for the stereoselective construction
of substituted tetrahydrofurans.2
In a one-pot sequence, the resulting monoepoxides,
5a–d/6a–d were treated with catalytic CSA to afford
good yields of predominantly 2,5-cis mixtures of sulfo-
nyl dihydrofurans 7a–d/8a–d that were difficult to sepa-
rate by chromatography. Silylation of these mixtures
with TBDMSCl in the presence of imidazol allowed
for a straightforward separation of both diastereomers
by column chromatography.
In view of the low selectivities associated with the use of
m-CPBA, we decided to explore other alternatives.
Thus, epoxidation of substrate 3a under Payne condi-
tions occurred with no changes in selectivity (60:40)
and lower yield.6 Similarly, the reaction of diene 3a
with CF3CO3H,7 led just to sulfonyl diene 4a. After
these disappointing results we chose to explore enantio-
selective epoxidation conditions with our a-hydroxy
dienyl sulfoxides. Unfortunately Shi’s epoxidation using
commercially available D-Epoxone resulted in recovered
starting material.8 Katsuki–Jacobsen epoxidation,9
using the commercially available catalysts developed
by Jacobsen (R,R)-JC and (S,S)-JC,10 seemed to be a
good option primarily due to the excellent results ob-
tained by Fuchs for cyclic dienyl sulfones.11 It should
be mentioned that acyclic dienyl sulfones were not good
substrates for this chemistry.11a
In recent years, we have been studying in depth the
nucleophilic and electrophilic epoxidation of a-hydroxy
dienyl sulfoxides as versatile routes to highly functional-
ized sulfinyl and sulfonyl tetrahydrofurans.3 Scheme 1
shows an outline of our strategy that entails lithiation
of the mixture of dienes 1E/Z,4 and condensation with
freshly distilled aldehydes followed by chromatographic
separation to afford dienols 2 and 3.5 These diastereo-
mers were interconverted by a Mitsunobu protocol.
The treatment of the chosen diastereomers 3a–d,
prepared as described above, with m-CPBA in toluene
resulted in a fast oxidation at sulfur to produce sulfones
4a–d, followed by a slow epoxidation at the distal dou-
ble bond with low stereochemical control.
Despite the fact that terminal olefins have led to worse
selectivities than substituted olefins in Katsuki–Jacobsen
epoxidations, we decided to explore the Jacobsen epox-
idation of a-hydroxy dienyl sulfoxides 3a–d (Scheme 1)
Keywords: Sulfoxides; Katsuki–Jacobsen epoxidation; Tetrahydro-
furans.
*
Corresponding author. Tel.: +34 91 562 29 00; fax: +34 91 564 48
53; e-mail: iqofp19@iqog.csic.es
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.07.058

R. Ferna´ndez de la Pradilla, A. Castellanos / Tetrahedron Letters 48 (2007) 6500–6504
6501
OH
O
S
PO
O
S
1.5-2.5 equiv chlorosilane
3.0-5.0 equiv Et3N
OH
O
S
OH
O
S
Mitsunobu
60%
O
S
1) LDA
R
-Tol
R
-Tol
p
p
0.05 equiv DMAP
R
-Tol
R
-Tol
p
m
p
3a-d
-Tol
-CPBA
p
DMF, 0 °C-rt
16 h to 3 days
2) RCHO
3a
3b
, R = -Pent
n
i
R = -Pent, 98%
n
Mitsunobu
50%
, R = -Pr
, R = -Pent, P = TBDMS, (60%)a
(39%)b
3a
, R = -Pent
11a
11b
n
i
n
3c, R = Ph
3d
2a (45)
3a (55)
, R = -Pent, P = TES, (89%)a
1
E/Z
3b
, R = -Pr
n
, R = -Bu
t
3c, R = Ph
11c, R = -Pent, P = -Bu Si, (63%)a
n
i
3
OH
OH
, R = -Pent, P = Bu Si, (64%)a
(15%)b
(40%)b
3d
, R = -Bu
t
11d
n
n
i
3
(60:40 to 78:22)
S
S
, R = -Pent, P = Hex Si, (48%)a
S
S
11e
11f, R = -Pr, P = Bu Si, (375%)a
CSA
R
R
O
3
a
, R = Ph, P = Bu3Si, (60%)
(31%)b
11g
OH
H
OH
R
R
O
O
a
Yields of pure products after column chromatography.
H
H
H
b Recovered starting material after column chromatography.
2.0 equiv Bu3SiCl
7a-d
8a-d
4a-d
5a-d/6a-d
7a/8a, R = n-Pent, (60:40), 77%
7b/8b, R = i-Pr, (60:40), 84%
7c/8c, R = Ph, (67:33), 76%
7d/8d, R = t-Bu, (78:22), 74%
OH
O
S
Bu3SiO
-Pent
O
S
4.0 equiv Et3N
0.05 equiv DMAP
-Pent
-Tol
p
-Tol
p
n
n
DMF, 0 °C-rt, 4 days
S
S
67%
TBDMSCl
n
7a/8a
2a
12a
OTBDMS
OTBDMS
-Pent
-Pent
n
O
H
O
H
H
H
Scheme 2. Silylation reactions.
9a
Separable mixture 10a
Scheme 1. Preparation of starting materials and sulfonyl dihydro-
furans (S = SO2p-Tol).
deprotection. Performing sequential additions of re-
agents improved the conversions and yields of these
epoxidations. In spite of the moderate yield (60%), the
use of a TBDMS group (entry 1, substrate 11a) sup-
posed an increase in trans selectivity producing after
desilylation and cyclization a 71:29 ratio favoring the
2,5-trans isomer 8a. This result represents a considerable
improvement relative to the substrate with the free OH
using catalyst (R,R)-JC. In contrast, the treatment of
11a with m-CPBA in toluene led to an equimolar mix-
ture of diastereomeric vinyl oxiranes.
and sulfone 4a,12 under the conditions reported by
Fuchs, hoping that the combined effects of the allylic
stereocenter and the chiral catalyst would lead to a use-
ful stereocontrol. These experiments resulted in a fast
oxidation at sulfur to their corresponding a-hydroxy
dienyl sulfones, followed by a slow distal epoxidation.
Subsequent treatment of the intermediate monoepoxides
with catalytic CSA afforded the expected sulfonyl
dihydrofurans with a modest increase of 2,5-trans selec-
tivity (ca 60:40). Details on these experiments will be
included in a forthcoming full account on this chemistry.
The use of a TES group (entry 2, substrate 11b)
increased slightly the selectivity (77:23) with catalyst
(R,R)-JC. Similarly, the i-Bu3Si group (entry 3) led to
a 90:10 ratio of dihydrofurans. With Bu3Si derivative,
11d, and (R,R)-JC catalyst, a 90:10 selectivity was
observed (entry 4) with excellent yield. To clarify the
role of the sulfoxide in the process, this protocol was
applied to sulfone 13d (entry 5) with comparable results.
Thus, it appears that the sulfoxide moiety does not exert
a significant influence on the stereochemical outcome of
the process. Then we decided to check the effect of a
Hex3Si group and the selectivity was again found to be
90:10 (entry 6). Finally, the scope of the methodology
was tested with substrates 11f (R = i-Pr), and 11g
(R = Ph), (Table 1, entries 7 and 8) bearing a Bu3Si
protecting group. In both cases the selectivity measured
was 90:10.
With these preliminary results in hand, we decided to
modify our substrates seeking to improve the selectivity
of the process. The presence of bulky groups in the sub-
strates has been shown to be important for improving
the enantioselectivities in these epoxidations.13 There-
fore, introducing different silyl ethers on the hydroxyl
group of our substrates seemed to be an interesting
and accessible transformation. This goal was accom-
plished with commercially available chlorosilanes,
Et3N, DMAP in DMF to render silyl ethers 11a–g from
hydroxy dienyl sulfoxides 3a–c (Scheme 2). It should be
pointed out that TIPS and TBDPS derivatives could not
be prepared under these conditions leading to recovered
starting materials. The unoptimized yields of these pro-
tections ranged from moderate (60–63%) to good (89%),
with recovery of starting material in some cases. With
substrate 3d (R = t-Bu), no reaction was observed per-
haps due to its considerable steric hindrance. The pro-
tection of alcohol 2a with R configuration in the allylic
center to afford silyl ether 12a is also shown in Scheme 2.
These results suggest that bulky silyl ethers at the allylic
position are acting like directing groups increasing the
anti selectivity in the epoxidation presumably due to
their steric hindrance that blocks a face of the diene
(see Scheme 3). The enhanced selectivity found for silyl
ethers bearing longer alkyl chains is noteworthy (com-
pare entries 4 and 2).
Table 1 summarizes the results for the epoxidation and
cyclization of silyloxy derivatives 11a–g. The crude mix-
tures were filtered through silica gel, treated with TBAF
in THF to cleave the silyl ether and then cyclized in the
presence of CSA. In the early experiments that did not
reach completion, silyloxy sulfonyl dienes 13 were pres-
ent in the crude mixtures; these led to dienes 4 upon
Table 2 shows the experiments carried out with sub-
strate 12a with R configuration at the allylic position.
Catalyst (R,R)-JC gave a 60:40 selectivity favoring
epoxidation by the face that produces 2,5-trans
dihydrofurans after cyclization. With catalyst (S,S)-JC,

6502
Table 1. Jacobsen epoxidation of (S)-silyloxy sulfinyl and sulfonyl dienes
PO PO PO
R. Ferna´ndez de la Pradilla, A. Castellanos / Tetrahedron Letters 48 (2007) 6500–6504
HO
(R,R)-JC
-TolO S
p
2
NH4OAc, H2O2
S
SO -Tol
2p
SO -Tol
2p
SO -Tol
2p
TBAF
CSA
R
R
R
R
S
CH2Cl2:MeOH, 0 °C
OH
R
O
H
H
O
8a-d
11a-g S
13d (S = SO -Tol)
(
= SO -Tol)
p
13a-g
14a-g
4a-d
2p
Entry
1
Substrate
P
Sulfur oxidation state
Conditions
Yielda
11a R = n-Pent
TBDMS
SOp-Tol
5% (R,R)-JC
30% 4a + 60% 8a (71:29)
35% 4a + 60% 8a (77:23)
24% 4a + 73% 8a (90:10)
89% 8a (90:10)
1.0 equiv NH4OAc
8.0 equiv H2O2
2 days
2
3
4
5
6
7
8
11b R = n-Pent
11c R = n-Pent
11d R = n-Pent
13d R = n-Pent
11e R = n-Pent
11f R = i-Pr
TES
SOp-Tol
SOp-Tol
SOp-Tol
SO2p-Tolc
SOp-Tol
SOp-Tol
SOp-Tol
5% (R,R)-JC
1.0 equiv NH4OAc
8.0 equiv H2O2
2 days
i-Bu3Si
Bu3Si
Bu3Si
Hex3Si
Bu3Si
Bu3Si
10% (R,R)-JC
2.0 equiv NH4OAc
16.0 equiv H2O2
3 days
20% (R,R)-JC
4.0 equiv NH4OAc
32.0 equiv H2O2
6 days
15% (R,R)-JC
3.0 equiv NH4OAc
24.0 equiv H2O2
6 days
97% 14a (90:10)b
25% (R,R)-JC
5.0 equiv NH4OAc
40.0 equiv H2O2
6 days
90% 8a (90:10)
15% (R,R)-JC
3.0 equiv NH4OAc
24.0 equiv H2O2
6 days
95% 8b (90:10)
11g R = Ph
20% (R,R)-JC
4.0 equiv NH4OAc
32.0 equiv H2O2
5 days
95% 8c (90:10)
a Yields of pure products after column chromatography.
b Mixture that was not desilylated/cyclized. Data taken from the 1H NMR spectrum of the crude products.
c Sulfone 13d was obtained by oxidation with 1.5 equiv MMPP in MeOH (2 h, 71%) from sulfoxide 11d.
the selectivity increased to 86:14. In both cases, yields
of the final product ent-8a were good after four addi-
tions of reagents. Thus, it appears that the stereochemi-
cal outcome of the process is primarily controlled by
the substrate. The optical purity of dihydrofurans 8a
and ent-8a was secured by formation of their TBDMS
ethers, separation and comparison of their optical rota-
tion data with data measured for samples obtained with
m-CPBA.
(R
,R
) and (
MnV
S,S)
PO
SO -Tol
2p
R
S
H
R
H
O
-TolO S
p
2
O
OP
13
P = TBDMS, TES, -Bu Si, Bu Si, Hex Si
As an application of this study and following the interest
of the group in the synthesis of natural products con-
taining substituted THF rings, we report here the formal
synthesis of the marine epoxy lipid (6S,7S,9R,10R)-6,9-
epoxynonadec-18-ene-7,10-diol and our approach is
14
-
anti
i
3
3
3
Scheme 3. Proposed favored approximation of the oxo-complex to the
diene system.

R. Ferna´ndez de la Pradilla, A. Castellanos / Tetrahedron Letters 48 (2007) 6500–6504
Table 2. Jacobsen epoxidation of (R)-silyloxy sulfinyl dienes
6503
Bu3SiO
O
S
Bu3SiO
-Pent
n
-TolO S
p
SO -Tol
2p
2
-Pent
-Tol
p
n
R
(
R
,
R
)-JC or (
S,S)-JC
TBAF
CSA
NH4OAc, H2O2
OH
-Pent
n
O
H
CH2Cl2:MeOH, 0 °C
H
O
12a
ent-14a
ent-8a
Entry
1
Substrate
Conditions
Yielda
12a
20% (R,R)-JC
98% ent-8a (60:40)
4.0 equiv NH4OAc
32.0 equiv H2O2
11 days
2
12a
20% (S,S)-JC
4.0 equiv NH4OAc
32.0 equiv H2O2
11 days
89% ent-8a (86:14)
a Yields of pure products after column chromatography.
Bu3SiO
-Pent
O
S
Bu3SiO
-Pent
n
Jacobsen
epoxidation
Deprotection-
Cyclization
TolO S
2
p-
-TolO S
p
2
SO -Tol
2p
90:10
OH
-Tol
n
p
i
OTBDMS
-Pent
n
O
Pent
n-
O
H
H
H
H
O
90:10
11a
(3 steps)
14a
8a
10a
ii
HO
Pent
BzO
O
HO
-TolO S
p
1 step
2
n-
(6 ,7
Williams, D. R. J. Am. Chem. Soc.
O
iv
H
iii
H
H
OH
OTBDMS
OTBDMS
Pent
n-
O
H
Pent
S
S,9R
,10
R
)-6,9-Epoxynonadec-18-ene-7,10-diol
n-
O
H
Pent
n-
O
H
O
H
H
H
1984
,
106, 2641-2644.
17
16
15
Scheme 4. Formal synthesis of (6S,7S,9R,10R)-6,9-epoxynonadec-18-ene-7,10-diol. Key: (i) TBDMSCl, ImH, DMAP, CH2Cl2, 0 °C to rt, 90%; (ii)
KOOt-Bu, THF, ꢀ40 to 0 °C, 97%; (iii) (a) MgI2, Et2O, 0 °C to rt, 97%; (b) L-Selectride, THF, ꢀ78 °C, 100% (85:15); (iv) (a) PhCO2H, DCC,
DMAP, CH2Cl2, 0 °C to rt, 92%; (b) Dowex, MeOH, rt, 96%; (c) (COCl)2, DMSO, Et3N, CH2Cl2, ꢀ70 °C, 80%.
shown in Scheme 4.14 Since its isolation and because of
its peculiar substitution this natural product has been
studied in depth and it has been the target of several syn-
thetic efforts.15
step by Williams, by addition of the appropriate Grig-
nard reagent.
In conclusion, silylation of a-hydroxy dienyl sulfoxides
allows for a selective Katsuki–Jacobsen oxidation
and distal epoxidation. Subsequent deprotection and
cyclization leads to 2,5-trans substituted sulfonyl
dihydrofurans with good yield and selectivity. The opti-
mization and extension of this protocol to more substi-
tuted dienes is currently being investigated in our
laboratories. In addition, this process has been applied
to a formal synthesis of a marine natural product that
illustrates also the usefulness of our reductive cleavage
of sulfonyl oxiranes with MgI2.
As described above, Jacobsen epoxidation of silyloxy
sulfinyl diene 11a gave a 90:10 mixture of monoepoxides
14a that after deprotection/cyclization afforded an
inseparable mixture of sulfonyl dihydrofurans 8a that
was transformed into the readily separable tert-butyl di-
methyl silyl ethers. Nucleophilic epoxidation of 2,5-trans
diastereomer 10a with KOOt-Bu,3 gave sulfonyl oxirane
15 as a single isomer and in excellent yield.16 Reductive
cleavage of the sulfonyl oxirane with freshly prepared
MgI2,17 followed by reduction of the resulting ketone
with L-Selectride afforded alcohol 16 with good
stereoselectivity (85:15). After separation by chromato-
graphy, the secondary alcohol was protected as a benzo-
ate and then the silyl ether was cleaved with Dowex resin
in good yield for the two steps. Swern oxidation of the
primary alcohol afforded aldehyde 17, that had identical
spectral data to that in the literature.15a This intermedi-
ate has been transformed into the natural product in one
Acknowledgments
This research was supported by DGI MEC (CTQ2006-
04522/BQU) and C.M. (S-SAL-0249-2006). We thank
JANSSEN-CILAG for generous additional support,
CSIC-FSE for a doctoral fellowship to A.C., and Dr.
Alma Viso (IQOG, CSIC) for fruitful discussions.

6504
R. Ferna´ndez de la Pradilla, A. Castellanos / Tetrahedron Letters 48 (2007) 6500–6504
manganese (III), (S,S)-JC. (a) Jacobsen, E. N.; Zhang, W.;
References and notes
Muci, A. R.; Ecker, J. R.; Deng, L. J. Am. Chem. Soc.
1991, 113, 7063–7064; For epoxidations of dienes
and enynes, see: (b) Lee, N. H.; Jacobsen, E. N.
Tetrahedron Lett. 1991, 32, 6533–6536; (c) Chang, S.;
Lee, N. H.; Jacobsen, E. N. J. Org. Chem. 1993, 58, 6939–
6941.
1. (a) Suzuki, T.; Koizumi, K.; Suzuki, H.; Kurosawa, E.
Chem. Lett. 1983, 1639–1642; (b) Faul, M.; Huff, B. E.
Chem. Rev. 2000, 100, 2407–2474; (c) Alali, F. Q.; Liu,
X.-X.; McLaughlin, J. L. J. Nat. Prod. 1999, 62, 504–540.
2. For reviews see: (a) Boivin, T. L. B. Tetrahedron 1987, 43,
11. (a) Hentemann, M. F.; Fuchs, P. L. Tetrahedron Lett.
1997, 38, 5615–5618; (b) Chen, Y.; Evarts, J. B., Jr.;
Torres, E.; Fuchs, P. L. Org. Lett. 2002, 4, 3571–3574; (c)
Evarts, J.; Torres, E.; Fuchs, P. L. J. Am. Chem. Soc.
2002, 124, 11093–11101; (d) Torres, E.; Chen, Y.; Kim, I.
C.; Fuchs, P. L. Angew. Chem., Int. Ed. 2003, 42, 3124–
3131; (e) El-Awa, A.; Fuchs, P. Org. Lett. 2006, 8, 2905–
2908.
`
3309–3362; (b) Harmange, J.-C.; Figadere, B. Tetrahe-
dron: Asymmetry 1993, 4, 1711–1754; (c) Elliot, M. C. J.
Chem. Soc., Perkin Trans. 1 2002, 2301–2323; (d) Wolfe, J.
P.; Hay, M. B. Tetrahedron 2007, 63, 261–290.
´
3. (a) Fernandez de la Pradilla, R.; Montero, C.; Priego, J.;
´
Martınez-Cruz, L. A. J. Org. Chem. 1998, 63, 9612–9613;
(b) Fernandez de la Pradilla, R.; Manzano, P.; Montero,
´
´
´
C.; Priego, J.; Martınez-Ripoll, M.; Martınez-Cruz, L. A.
J. Org. Chem. 2003, 68, 7755–7767; For metal-catalyzed
oxidation and epoxidation of related substrates, see: (c)
12. Sulfone 4a was obtained by oxidation of sulfoxide 3a with
1.5 equiv MMPP in MeOH (2 h, 78%).
´
13. Jacobsen, E. N.; Deng, L.; Furukawa, Y.; Martınez, L. E.
´
´
Fernandez de la Pradilla, R.; Castellanos, A.; Fernandez,
J.; Lorenzo, M.; Manzano, P.; Mendez, P.; Priego, J.;
Tetrahedron 1994, 50, 4323–4334.
´
14. Warren, R. G.; Wells, R. J.; Blount, J. F. Aust. J. Chem.
1980, 33, 891.
´
Viso, A. J. Org. Chem. 2006, 71, 1569–1575; (d) Fernandez
´
´
de la Pradilla, R.; Fernandez, J.; Viso, A.; Fernandez, J.;
15. (a) Williams, D. R.; Harigaya, Y.; Moore, J. L.; D’sa, A.
J. Am. Chem. Soc. 1984, 106, 2641–2644; (b) Hatakeyama,
S.; Sakurai, K.; Saijo, K.; Takano, S. Tetrahedron Lett.
1985, 26, 1333–1336; (c) Gurjar, M. K.; Mainkar, P. S.
Heterocycles 1990, 31, 407–410; (d) Chikashita, H.;
Nakamura, Y.; Uemura, H.; Itoh, K. Chem. Lett. 1993,
477–480; (e) Capon, R. J.; Barrow, R. A.; Skene, C.;
Rochfort, S. Tetrahedron Lett. 1997, 38, 7609–7612; (f)
Wang, Z.-M.; Shen, M. J. Org. Chem. 1998, 63, 1414–
1418; (g) Mori, Y.; Sawada, T.; Furukawa, H. Tetrahedron
´
Gomez, A. Heterocycles 2006, 68, 1579–1584.
4. Available in one step by the procedure of Craig: Craig, D.;
Daniels, K.; MacKenzie, A. R. Tetrahedron 1993, 49,
11263–11304.
5. (a) Posner, G. H.; Mallamo, J. P.; Miura, K.; Hulce, M.
Pure Appl. Chem. 1981, 53, 2307–2314; (b) Cheng, H.-C.;
Yang, T.-H. Tetrahedron Lett. 1990, 31, 673–676; (c)
´
Solladie, G.; Moine, G. J. Am. Chem. Soc. 1984, 106,
6097–6098; (d) Fawcett, J.; House, S.; Jenkins, P. R.;
Lawrence, N. J.; Russell, D. R. J. Chem. Soc., Perkin
Trans. 1 1993, 67–73.
´
Lett. 1999, 40, 731–734; (h) Garcıa, C.; Soler, M. A.;
´
Martın, V. S. Tetrahedron Lett. 2000, 41, 4127–4130; (i)
6. Payne, G. B. Tetrahedron 1962, 18, 763–765.
7. (a) Lee, K.-W.; Choi, H.; Lee, B.-H.; Choi, B.-S.; Chang,
J.-H.; Kim, Y.-K.; Lee, J.-H.; Heo, T.; Nam, D.-H.; Shin,
H. Synlett 2005, 3136–3138; (b) Wiktelius, D.; Berts, W.;
Jensen, A. J.; Gullbo, J.; Saitton, S.; Cso¨regh, I.; Luth-
man, K. Tetrahedron 2006, 62, 3600–3601.
´
´
´
Garcıa, C.; Martın, T.; Martın, V. S. J. Org. Chem. 2001,
66, 1420–1428.
16. Sulfonyl oxiranes are versatile synthetic intermediates. For
leading references, see: (a) Mori, Y.; Takase, T.; Noyori,
R. Tetrahedron Lett. 2003, 44, 2319–2322; (b) Inoue, M.;
Yamashita, S.; Tatami, A.; Miyazaki, K.; Hirama, M. J.
Org. Chem. 2004, 69, 2797–2804; (c) Furuta, H.; Hase, M.;
Noyori, R.; Mori, Y. Org. Lett. 2005, 7, 4061–4064; (d)
8. (a) Frohn, M.; Dalkiewicz, M.; Tu, Y.; Wang, Z.-X.; Shi,
Y. J. Org. Chem. 1998, 63, 2948–2953; (b) Burke, C. P.;
Shi, Y. Angew. Chem., Int. Ed. 2006, 45, 4475–4478.
9. For reviews, see: (a) Katsuki, T. Synlett 2003, 281–297; (b)
McGarrigle, E. M.; Gilheany, D. G. Chem. Rev. 2005, 105,
1563–1602.
´
´
Dıez, D.; Templo Beneitez, M.; Gil, M. J.; Moro, R. F.;
Marcos, I. S.; Garrido, N. M.; Basabe, P.; Urones, J. G.
Synthesis 2005, 565–568.
10. (R,R)-N,N0-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohex-
anediaminomanganese (III), (R,R)-JC and (S,S)-N,N0-
Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamino-
´
17. Fernandez de la Pradilla, R.; Alhambra, C.; Castellanos,
´
A.; Fernandez, J.; Manzano, P.; Montero, C.; Urena, M.;
˜
Viso, A. J. Org. Chem. 2005, 70, 10693–10700.