Enantioselective epoxidation of tertiary allylic alcohols by chiral dihydroperoxides

Article abstract of DOI:10.1016/j.tet.2013.01.032

gem-Dihydroperoxides were successfully used for the enantioselective epoxidation of tertiary and primary allylic alcohols. Epoxides derived from tertiary alcohols were obtained in yields up to 71% with ee's up to 52%.

Full text of DOI:10.1016/j.tet.2013.01.032

Tetrahedron 69 (2013) 2446e2450
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Enantioselective epoxidation of tertiary allylic alcohols by chiral
dihydroperoxides
a
a
a
a,b,
*
€
€
Alexander Bunge , Hans-Jurgen Hamann , Dennis Dietz , Jurgen Liebscher
a
€
€
Institut fur Chemie, Humboldt-Universitat zu Berlin, Brook-Taylor-Straße 2, D-12489 Berlin, Germany
b National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca 5, Romania
a r t i c l e i n f o
a b s t r a c t
Article history:
gem-Dihydroperoxides were successfully used for the enantioselective epoxidation of tertiary and pri-
mary allylic alcohols. Epoxides derived from tertiary alcohols were obtained in yields up to 71% with ee’s
up to 52%.
Received 21 November 2012
Received in revised form 3 January 2013
Accepted 9 January 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Available online 18 January 2013
Dedicated to Erhard Matthes on the occa-
sion of his 90th birthday
Keywords:
gem-Dihydroperoxides
Enantioselective epoxidation
Allylic alcohols
Thujone
Glycidols
1. Introduction
hand there is a continuous interest to find oxygen-transferring re-
agents, which are more environmentally friendly, such as hydrogen
It is a general understanding that asymmetric epoxidation of al-
lylic alcohols is a solved problem thanks to the famous asymmetric
KatsukieSharpless epoxidation.1,2 This synthesis works with tert-
butylhydroperoxide as oxygen source and diethyl tartrate and tita-
nium alkoxides as catalysts in the presence of molecular sieves.3 It
provides excellent enantioselectivities and can also be performed at
large scale in industries.4 However, there are still limitations due to
structural restrictions in the allylic alcohols. While primary allylic
alcohols are superb substrates and kinetic resolution of racemic
secondary allylic alcohols can also be achieved by the Sharpless
epoxidation protocol, tertiary allylic alcohols do not react under
these conditions.5 There are few reports of asymmetric epoxidations
of tertiary allylic alcohols. Wang et al. observed enantioselectivities
of 60e87%, but substrates were limited to 1,1-disubstituted alkenes.6
Takano et al. saw good enantioselectivities in tertiary allylic alcohols
that were part of 2-alkene-1,4-diol frameworks.7 Spivey et al. ach-
ieved the desymmetrization of tertiary bisallylic pentadienols using
a Zr(IV)-based catalyst.8 However, none of the previous approaches
addressed the 1,2-disubstituted alkene core, that is, the most com-
mon substrate framework for asymmetric epoxidation. On the other
peroxide.9
Since gem-dihydroperoxides (DHP) 1 can be synthesized from
hydrogen peroxide and a carbonyl compound 2, gem-DHPs have
been in the focus of several recent research activities concerning
oxygen transfer (Scheme 1). After transferring oxygen from gem-
DHPs 1 to a substrate the parent carbonyl compound 2 formed can
be recycled and reused.
The interest in gem-dihydroperoxides 1 has led to a number of
methods for their synthesis, usually starting from the respective
carbonyl compound 2, a corresponding ketal or an enol ether. Some
of these syntheses have been reviewed by Iskra et al.,10 others were
published recently by Terent’ev,11 Das,12,13 Dussault,14 Azarifar,15,16
Wu,17 and Itoh.18 Primary aliphatic gem-DHPs were not obtained
by these methods, but were reported very recently by us.19 With
the synthesis protocol described there it was also possible to obtain
a number of gem-dihydroperoxides from ketones, which were
impossible to get by other methods previously described.20
A different approach to gem-DHPs 1 uses ozonolysis of enol
ethers or alkenes 3 in the presence of ethereal hydrogen peroxide
solution (Scheme 1). This method has, however, been described
only sporadically in the literature.21e23
As far as the application of gem-DHPs as oxygen transferring
reagents is concerned the cyclohexane-1,1-dihydroperoxide-me-
diated WeitzeScheffer-epoxidation of chalcones has to be
* Corresponding author. Tel.: þ40 264 584037; fax: þ40 264 420042; e-mail
address: liebscher@chemie.hu-berlin.de (J. Liebscher).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.01.032

A. Bunge et al. / Tetrahedron 69 (2013) 2446e2450
2447
R2
2.2. Epoxidation
R2
O3, H2O2 (eth.)
R2
H2O2(70%), CSA
R1
OOH
OOH
R1
R1
O
These hydroperoxides 1 were screened in the epoxidation of 2-
methyl-4-phenylbut-3-en-2-ol 4d26 as an example of a tertiary
allylic alcohol (Scheme 2). Reaction conditions for asymmetric ep-
oxidation were at first chosen similar to those of the Sharpless
epoxidation. The results obtained are shown in Table 1.
1j-n
1a-i
3
2
1
OOH
OOH
OOH HOO
OOH
OOH
O
O
OOH
OOH
O
DHP 1, Ti(OiPr)4,
1a
1´c
19%
1d
41%
1b
57%
Ph
58%
OH
Ph
OH
DCM, -20 °C, 3 d
OH
OOH
5d
OOH
OOH
4d
OOH
OOH
Scheme 2. Asymmetric epoxidation of tertiary allylic alcohol 4d.
OOH
1f
60%
1e
35%
1g
55%
Table 1
Epoxidation of tertiary allylic alcohol 4d with various gem-dihydroperoxides 1a
OH
Entry
DHP 1
Conversion
of 4d (%)
ee of 5d (%)
Sign of
optical rotationb
H
H
1
2
3
4
5
6
7
8
1a
1b
10c
1d
1e
1f
1g
1h
1i
42
23
6
0
31
13
7
35
0
15
8
7
7
2
18
28
3
H
H
HOO
HOO
þ
þ
þ
þ
H
H
HOO
HOO
H
1h
82%
1i
31%
H
5
22
40
4
64
60
28
7
71
6
24
O
OH
ꢀ
ꢀ
ꢀ
þ
þ
þ
þ
ꢀ
OH
9
OH
OOH
OOH
1m
39%
OH
OOH
OOH
1l
89%
O
10
11
12
13
14
1j
1k
1l
OOH
OOH
O
OOH
OOH
OOH
1´n
21%
1j
62%
1k
68%
1m
10n
Scheme 1. gem-Dihydroperoxides 1 (yields in parentheses) synthesized from carbonyl
compounds 2 or by ozonolysis of alkenes 3.
a
Reaction conditions: ꢀ20 ꢁC, 3 d, DCM, DHP:Ti(OiPr)4:4d¼1:1:1.
b
In chloroform.
mentioned.24 Furthermore, this gem-DHP was used by Ven-
kateswarlu et al. in selective oxidation of sulfides to sulfoxides.25 In
the course of our research we found gem-DHPs able to enantiose-
lectively epoxidize 3-substituted 1,4-naphthoquinones,20 which
often gave only low enantioselectivities in previously reported
epoxidations.
With this background we wanted to check the hitherto un-
known suitability of gem-dihydroperoxides 1 for the epoxidation of
allylic alcohols. We surmised that optically active dihydroper-
oxides, which proved to be successful in the enantioselective ep-
oxidation of naphthoquinones of the vitamin K-type20 could also be
used in the enantioselective transformation of allylic alcohols into
corresponding epoxides, in particular tertiary members.
It turned out that all gem-dihydroperoxides 1 were able to ep-
oxidize the allylic alcohol 4d. However, the yields were often un-
satisfactory. Significant enantioselectivity could be observed in
some cases (see entries 2, 5, and 13). As in our previous in-
vestigations in the epoxidation of naphthoquinones20 the geminal
dihydroperoxide 1e performed best with respect to enantiose-
lectivity (entry 5).
It appeared that a hydroxy-group properly situated in the gem-
DHP 1 can have a significant positive effect on enantioselectivity,
most likely due to increased rigidity of an assumed complex tran-
sition state, as can be seen by comparing substrates 1e and 1m
(entry 5 and 13, favorable position) with 1j (entry 10, lack of OH
group), 1k, 1l (entries 11, 12, unfavorable position). The position of
a methyl group next to the gem-dihydroperoxide moiety can also
strongly affect enantioselectivity (compare 1b, entry 2 with 1d,
entry 4). As a result of the screening shown in Table 1 we decided to
use compound 1e in further optimizations. Since the addition of
molecular sieves, which is important in the Sharpless epoxidation
did not result in a significant effect on the outcome of the reaction
in our cases the experiments were performed without it.
Conversion of the substrate 4d was quite low (Table 1, entry 5)
with DHP 1e, therefore a primary allylic alcohol (4b) was used for
optimization studies (Scheme 3).
2. Results and discussion
2.1. Synthesis of gem-dihydroperoxides
Several gem-dihydroperoxides 1aen were synthesized as ep-
oxidizing reagents. Hydroperoxides 1aei were obtained according
to previous literature from the corresponding ketones 2.20 For the
synthesis of hydroperoxides 1jen we found that ozonolysis of
alkenes 3jen in the presence of hydrogen peroxide (Scheme 1) can
be a powerful tool. In particular, terpene-based DHPs 1 cannot be
generated by alternative methods or request multiple steps
starting from ketones 2. Interestingly, ozonolysis of isopulegone
3n did not give the dihydroperoxide, but the hemiacetal structure
10n instead. 1d, 1g, 1jem, and 10n have not yet been reported in
the literature.
As can be seen in Table 2, solvents can play an important role in
conversion and ee. Too nonpolar (hexane) or too polar (acetonitrile)
solvents decreased both conversion and ee, while medium polar
solvents gave at least comparable conversions. Although N,N-
dimethylformamide (DMF) provided the highest ee (58%),

2448
A. Bunge et al. / Tetrahedron 69 (2013) 2446e2450
These conditions were now applied in the epoxidation of vari-
ous primary and tertiary allylic alcohols (Scheme 4).
OH
OOH
OOH
O
, catalyst,
solvent
1e
OH
OH
Cl
Cl
5b
4b
Scheme 3. Variation of reaction conditions in the asymmetric epoxidation of 4b with
gem-dihydroperoxide 1e.
Scheme 4. Asymmetric epoxidation of allylic alcohols 4 using DHP 1e.
Table 2
Dependence of conversion and ee of epoxidation of 4b on solventsa
Highest enantioselectivities were observed with the primary
cinnamyl alcohols 4a, b and c (Table 3, entries 1, 2, 3). However,
these substrates were epoxidized in much higher enantioselectiv-
ities before under Sharpless conditions.29,31,32 In contrast, none of
the tertiary allylic alcohols 4 (R1¼Me) has yet been described to be
epoxidized enantioselectively, neither by Sharpless nor by any
other epoxidation method. Allylic alcohols 4 and their corre-
sponding epoxides 5 were sometimes difficult to separate by col-
umn chromatography. Thus, in case of 5e, the yield could only be
determined from the mixture of 4e and 5e by 1H NMR measure-
ments. It turned out that no side reactions occurred in the case of
tertiary allylic alcohols, while some decomposition took place with
primary allylic alcohols explaining the low yields, as also described
for Sharpless epoxidations.33
Solvent
Conversion of 4b (%)
ee (5b) (%)
Hexane
21
54
61
14
50
68
28
28
14
26
31
20
20
35
27
58
Toluene
Diethyl ether
THF
Ethyl acetate
DCM
Acetonitrile
DMF
a
Reaction conditions: ꢀ20 ꢁC, 3 d, 1e: Ti(OiPr)4:4b¼1:1:1.
dichloromethane (DCM) turned out to be an optimum regarding
speed of reaction, conversion, and ee. Apparently complexation of
DMF with the titanium catalyst gives rise to a particularly favorable
transition state. To our knowledge nothing similar has been ob-
served for the Sharpless epoxidation or similar reaction types.
Variation of reaction time in DCM resulted in a slight decrease in
enantioselectivities (from 39% after 1 h to 35% after 72 h), while the
conversion grew to 82% at 24 h (37% ee) with partial decomposition
occurring at this time. Choice of reaction temperature is crucial,
because conducting the reaction at 0 ꢁC yielded only racemic
product with notably increased decomposition, whereas at room
temperature no epoxide 5b was detected anymore. Performing the
reaction at ꢀ78 ꢁC gave only a minor increase of ee to 39% but
drastically reduced conversions.
Table 3
Enantioselective epoxidation of various allylic alcohols 4a with DHP 1eb
Entry
Epoxide 5c
R
R1
Yield (%)
ee (%)
1
2
3
4
5
6
7
8
5a
5b
5c
5d
5e
5f
Ph
H
H
H
Me
Me
Me
Me
Me
43
35
43
60d,e
57d,e
68d,f
46e
32
4-CleC6H4
1-C10H7
Ph
4-CleC6H4
1-C10H7
Phe(CH2)2e
H
64
21g
50
40f
5g
5h
22
50e
52
71h
a
Substrates 4 were obtained according or analogous to known syntheses.26e28
Reaction conditions: ꢀ20 ꢁC, 1 d, 1e: Ti(OiPr)4:4¼1:1:1.
Solvent for 4aec: DMF, for 4deh: DCM.
b
c
Without the application of Ti(OiPr)4 product 5 was not observed.
Change of the amount of Ti(OiPr)4 from 1 equiv to 2 or 0.5 equiv
yielded worse results in both conversion and ee. Decrease of the
ratio of oxidant to 50% was unfavorable while doubling of the
amount of oxidant afforded a significant increase of conversion
(93%), whereas enantioselectivity remained almost unchanged
(36%).
d
e
f
Configuration of major enantiomer (2R, 3R).29,30
Sign of optical rotation in CHCl3 þ.
Sign of optical rotation in CHCl3 ꢀ.
g
h
Only isolated as mixture.
Product highly volatile, not isolated, yield determined by GC.
Testing of some metal catalysts different from Ti(OiPr)4 did not
result in an improvement of the epoxidation of 4b. Ti(OiBu)4 gave
worse results, while others (VO(acac)2, MoO2(acac)2) blocked the
reaction or gave racemates (H4WO5). We assume that Ti(OiPr)4
plays a similar rule like in the Sharpless epoxidation, namely it
complexes the allylic alcohol and the gem-dihydroperoxide in
a rigid transition state. Since gem-dihydroperoxides have two
hydroperoxy moieties capable of complexation with titanium it is
essential that one of the both is more exposed in such a way that it
can easily bind to titanium. This would also explain to some extent
To simplify the reaction procedure a combination of DHP
preparation and epoxidation was attempted circumventing any
purification of the DHP 1e by column chromatography (Scheme 5).
OH
O
OH
O
O
1. H2O2, H+
+
OH
2. 4d, Ti(OiPr)4,
the effect of the configuration of the a-methyl group in gem-DHPs
DCM, molecular sieves
1b and 1d. The additional hydroxyl group found in the gem-DHP 1e
is likely also to be complexed to the titanium thus covering the
reaction site more selectively from one direction.
5d
2e
2e
Scheme 5. Simplified epoxidation of 4d.
To resume, best reaction conditions for primary allylic alcohol
4b were found to be DMF as solvent, 2 equiv of the oxidant 1e,
1 equiv of Ti(OiPr)4, ꢀ20 ꢁC, and 24 h reaction time. Unfortunately,
DMF gave no conversion of tertiary allylic alcohols, so that DCM was
used as solvent in those cases.
Since this reaction mixture still contained hydrogen peroxide,
molecular sieves were added to remove it.20 It turned out that 5d was
obtained in 55% yield with only a slightly lower enantioselectivity of

A. Bunge et al. / Tetrahedron 69 (2013) 2446e2450
2449
44% as compared with the application of separately prepared 1e. It
was possible to re-obtain ketone 2e in 70% yield, proving the possi-
bility of recycling and reusing the ketone.
hydrogen peroxide (2 mL) and camphorsulfonic acid monohydrate
(25 mg, 0.1 mmol) the biphasic system was left to stir over night
(16 h). The mixture was diluted with water (30 mL), extracted with
diethyl ether (3ꢂ20 mL), and the combined organic layers washed
with saturated NaHCO3-solution (20 mL), dried (Na2SO4), and the
solvent evaporated under reduced pressure. After purification by
column chromatography (silica gel, DCM/MeOH, 99:1 or CyH/
EtOAc, 7:3) the desired DHP 1 was obtained.
3. Conclusion
In summary, we have demonstrated that gem-dihydroperoxides
1 can be successfully used in enantioselective epoxidation of allylic
alcohols. This methodology represents the best way to epoxidize
tertiary allylic alcohols affording ee’s of up to 52%. For primary al-
lylic alcohols it cannot compete with the superb Sharpless epoxi-
dation. Combination of the synthesis of the gem-dihydroperoxides
1 from corresponding ketones 2 with subsequent application in
epoxidation of allylic alcohols is possible with recycling of the
starting ketone.
4.3. General procedure for preparation of gem-dihydroper-
oxides 1jen by ozonolysis
The corresponding alkene 3 (3 mmol) was dissolved in 20 mL of
an ethereal solution of hydrogen peroxide (ca. 3 M, 60 mmol) and
a small quantity of Sudan red was added. At ꢀ78 ꢁC an ozone
stream was blown through the solution until the color disappeared.
The reaction mixture was washed with brine (ice cold, 20 mL),
dried (Na2SO4), and the solvent carefully evaporated under vacuum.
Purification was done by column chromatography (CyH/EtOAc or
DCM/MeOH).
4. Experimental
4.1. General
TLC analysis was performed on Merck silica gel 60 F254 plates
and visualized with UV illumination or stained with phosphomo-
lybdic acid in EtOH (5%, v/v) or N,N0-dimethyl-4-phenyl-
endiamoniumdichloride-solution in MeOH/H2O/HOAc (peroxides).
Column chromatography was conducted with Merck silica gel
60 (400e639 mesh). 1H NMR and 13C NMR spectra were recorded at
300 (500) and 75 (125) MHz, respectively, on a Bruker AMX 300,
DPX 300 or Avance III 500.
4.4. General procedure for epoxidation (analytical scale)
Dihydroperoxide 1 (0.02 mmol) was dissolved in dry solvent
(DCM, 5 mL) under argon. After cooling to ꢀ40 to ꢀ50 ꢁC a 0.2 M
solution of (Ti(OiPr)4) (100
mL, 0.02 mmol) in DCM was added. After
stirring at this temperature for 30 min a 0.2 M DCM solution of the
allylic alcohol 4 (100 L, 0.02 mmol) was added. The solution was
m
Chemicals used were purchased from Aldrich, Acros or Merck
and were used without further purification. Hydrogen peroxide
was donated by Solvay Interox GmbH. Essential oil of Thuja occi-
dentalis was purchased from Baccararose, Sonsbeck (Germany).
stirred for additional 60 min at this temperature and afterward
stored in a freezer at ꢀ30 ꢁC. After 72 h, the reaction mixture was
poured onto water (20 mL) and extracted with DCM (2ꢂ20 mL); the
combined organic phases were dried (Na2SO4) and the solvent was
evaporated. The reaction mixture was analyzed by HPLC on a chiral
column (See Supplementary data).
(þ)-
b
-Thujone 2d34 (from hydroxymethylthujone20), hydroperox-
ides 1aei,20 (ꢀ)-pinocamphone,26,35 (ꢀ)-isopulegone 3n,26
(þ)-neoisopulegol 3m,36 the allyl alcohols 4b,c27 (via DIBAL re-
duction of the unsaturated ethyl esters), and 4deg27,28 (via MeMgI-
addition to the unsaturated ethyl esters) as well as the racemic
epoxides 5beg26 were synthesized according or analogous to
known procedures. Asymmetric epoxidations were carried out
under an argon atmosphere. NMR-spectra of the hydroperoxides
should be measured as fast as possible after dissolving the samples
in the deuterated solvent, for we found them to at least partially
decompose quite often. In some cases, benzene-d6 or CD3CN as
a solvent helped to prevent the decomposition. CDCl3 should be
taken from a relatively fresh bottle, as the decomposition products
of the solvent seem to promote decomposition of the samples as
well.
4.5. General procedure for epoxidation (preparative scale)
3,3-Dihydroperoxy-4-(hydroxymethyl)-b-thujane 1e (93 mg,
0.4 mmol) in dry DCM or DMF (20 mL) were combined with
Ti(OiPr)4 (56.8 mg, 0.2 mmol) and the allylic alcohol 4 (0.2 mmol) in
dry DCM (1 mL) under the same conditions as in the analytical scale
(vs). The solution was stirred for additional 60 min and then stirring
continued in a cryostat (ꢀ20 ꢁC). After keeping the reaction mixture
at ꢀ20 ꢁC for 24 h it was diluted with DCM (40 mL), washed with
a saturated NaHCO3-solution (60 mL), and the aqueous phase re-
extracted with DCM (40 mL). The combined organic layers were
washed again with a saturated solution of NaHCO3 (40 mL), dried
(Na2SO4), and the solvent was evaporated. The residue was purified
by column chromatography (15 g silica gel, CyH/ethyl acetate, 9:1
or DCM/ethyl acetate, 99.5:0.5), in some cases several times.
HPLC: HPLC was done on a system consisting of high pressure
gradient system 322 (Kontron), UV-detector DAD K-2800 (Knauer),
chiral detector IBZ Messtechnik, injection ventile 7125 (10
Rheodyne).
mL,
HRMS spectra were measured either on an ESI-MS-device LTQ-
FT-ICR-MS (Thermo Finnigan (HU-Berlin)) or on a Waters Acquity
UPLC/MS (LCT Premier XE Mass spectrometer).
Optical rotation was measured on a PerkineElmer 241 Polar-
imeter, at 589 nm wavelength.
Acknowledgements
We wish to thank Dipl.-Ing. Angela Thiesies for NMR measure-
ments. We further thank Solvay Interox GmbH for donation of
hydrogen peroxide.
The determination of absolute configuration was taken from the
literature by comparing optical rotation.
Supplementary data
Caution: 70% hydrogen peroxide and peroxidic compounds are
potentially explosive and should be handled with precautions
(shields, fume hoods, avoidance of transition metal salts).
Characterization of hitherto unknown gem-DHP 1, preparation
and characterization of allylic alcohols 2 and their epoxides 5,
combined procedure for synthesis of 5d. Supplementary data as-
sociated with this article can be found in the online version, at
http://dx.doi.org/10.1016/j.tet.2013.01.032. These data include MOL
files and InChiKeys of the most important compounds described in
this article.
4.2. General procedure for preparation of gem-DHPs 1d,g
The corresponding ketone 2 (10 mmol) was dissolved in diethyl
ether (2 mL) and cooled in an ice bath. After addition of 70%

2450
A. Bunge et al. / Tetrahedron 69 (2013) 2446e2450
19. Bunge, A.; Hamann, H. J.; Liebscher, J. Tetrahedron Lett. 2009, 50, 524.
References and notes
20. Bunge, A.; Hamann, H. J.; McCalmont, E.; Liebscher, J. Tetrahedron Lett. 2009, 50,
4629.
21. Kim, H. S.; Tsuchiya, K.; Shibata, Y.; Wataya, Y.; Ushigoe, Y.; Masuyama, A.;
Nojima, M.; McCullough, K. J. Perkin Trans. 1 1999, 1867.
22. Kim, H. S.; Nagai, Y.; Ono, K.; Begum, K.; Wataya, Y.; Hamada, Y.; Tsuchiya, K.;
Masuyama, A.; Nojima, M.; McCullough, K. J. J. Med. Chem. 2001, 44, 2357.
23. Ghorai, P.; Dussault, P. H.; Hu, C. H. Org. Lett. 2008, 10, 2401.
24. Jakka, K.; Liu, J. Y.; Zhao, C. G. Tetrahedron Lett. 2007, 48, 1395.
25. Selvam, J. J. P.; Suresh, V.; Rajesh, K.; Babu, D. C.; Suryakiran, N.; Venkateswarlu,
Y. Tetrahedron Lett. 2008, 49, 3463.
26. Autorenkollektiv. Organikum, 22nd ed.; Wiley VCH: 2004.
27. Bouziane, A.; Helou, M.; Carboni, B.; Carreaux, F.; Demerseman, B.; Bruneau, C.;
Renaud, J. L. Chem.dEur. J. 2008, 14, 5630.
28. Inguimbert, N.; Coric, P.; Dhotel, H.; Bonnard, E.; Llorens-Cortes, C.; De Mota,
N.; Fournie-Zaluski, M. C.; Roques, B. P. J. Pept. Res. 2005, 65, 175.
29. Medina, E.; VidalFerran, A.; Moyano, A.; Pericas, M. A.; Riera, A. Tetrahedron:
Asymmetry 1997, 8, 1581.
30. Sarabia, F.; Chammaa, S.; Garcia-Castro, M.; Martin-Galvez, F. Chem. Commun.
2009, 5763.
1. Pfenninger, A. Synthesis 1986, 89.
2. Johnson, R. A.; Sharpless, B. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.;
Wiley-VCH: New York, NY, 2000; p 231.
3. Katsuki, T.; Sharpless, K. B. J. Am. Chem. Soc. 1980, 102, 5974.
4. Breuer, M.; Ditrich, K.; Habicher, T.; Hauer, B.; Kesseler, M.; Sturmer, R.; Zelinski,
T. Angew. Chem., Int. Ed. 2004, 43, 788.
5. Sharpless, B. In Comprehensive Organic Synthesis; Trost, B., Ed.; Pergamon:
Oxford, 1993; p 417.
6. Wang, B.; Wong, O. A.; Zhao, M. X.; Shi, Y. J. Org. Chem. 2008, 73, 9539.
7. Takano, S.; Iwabuchi, Y.; Ogasawara, K. Tetrahedron Lett. 1991, 32, 3527.
8. Spivey, A. C.; Woodhead, S. J.; Weston, M.; Andrews, B. I. Angew. Chem., Int. Ed.
2001, 40, 769.
9. Kamata, K.; Yonehara, K.; Sumida, Y.; Yamaguchi, K.; Hikichi, S.; Mizuno, N.
Science 2003, 300, 964.
10. Zmitek, K.; Zupan, M.; Iskra, J. Org. Biomol. Chem. 2007, 5, 3895.
11. Terent’ev, A. O.; Platonov, M. M.; Ogibin, Y. N.; Nikishin, G. I. Synth. Commun.
2007, 37, 1281.
12. Das, B.; Krishnaiah, M.; Veeranjaneyulu, B.; Ravikanth, B. Tetrahedron Lett. 2007,
31. Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J.
Am. Chem. Soc. 1987, 109, 5765.
48, 6286.
13. Das, B.; Veeranjaneyulu, B.; Krishnaiah, M.; Balasubramanyam, P. J. Mol. Catal. A
2008, 284, 116.
32. Woodard, S. S.; Finn, M. G.; Sharpless, K. B. J. Am. Chem. Soc. 1991, 113, 106.
33. Katsuki, T.; Martin, V. Asymmetric Epoxidation of Allylic Alcohols: the Kat-
sukieSharpless Epoxidation Reaction; John Wiley & Sons: 2004.
34. Brieskorn, C. H.; Schwack, W. Tetrahedron Lett. 1980, 21, 255.
35. Brieskorn, C. H.; Ryu, C. K. Arch. Pharm. (Weinheim, Ger.) 1985, 318, 261.
36. Moreira, J. A.; Correa, A. G. Tetrahedron: Asymmetry 2003, 14, 3787.
14. Ghorai, P.; Dussault, P. H. Org. Lett. 2008, 10, 4577.
15. Azarifar, D.; Khosravi, K.; Soleimanei, F. Synthesis 2009, 2553.
16. Azarifar, D.; Khosravi, K.; Soleimanei, F. Molecules 2010, 15, 1433.
17. Li, Y.; Hao, H. D.; Zhang, Q.; Wu, Y. K. Org. Lett. 2009, 11, 1615.
18. Tada, N.; Cui, L.; Okubo, H.; Miura, T.; Itoh, A. Chem. Commun. 2010, 1772.