Titanium cis-1,2-Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide

Article abstract of DOI:10.1002/cctc.201601154

We report a new and readily accessible class of titanium salalen complexes derived from cis-1,2-diaminocyclohexane (cis-DACH) and fluorinated salicylic aldehyde derivatives. With aqueous hydrogen peroxide as the oxidant, these complexes catalyze the epoxidation of terminal, nonconjugated olefins in high yields with high enantioselectivities. We furthermore discovered that the addition of certain acidic or basic co-catalysts significantly accelerated the epoxidation. For example, in the presence of 1 mol % Ti catalyst and 1 mol % pentafluorobenzoic acid, 1-octene epoxidation (95 % ee) was completed at room temperature within 8 h. The catalytic process was compatible with many functional groups (e.g., ethers, esters, halides, nitriles, and nitro groups), whereas free hydroxy groups appeared to slow down the reaction to some extent. Catalyst recycling was possible.

Full text of DOI:10.1002/cctc.201601154

Accepted Article
Title: Titanium cis-1,2-Diaminocyclohexane Salalen Catalysts of
Outstanding Activity and Enantioselectivity for the Asymmetric
Epoxidation of Non-Conjugated Terminal Olefins with H2O2
Authors: Albrecht Berkessel, Markus Lansing, Hauke Engler, Tobias M.
Leuther, and Jörg M. Neudörfl
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201601154
Link to VoR: http://dx.doi.org/10.1002/cctc.201601154
A Journal of
www.chemcatchem.org

10.1002/cctc.201601154
ChemCatChem
COMMUNICATION
Titanium cis-1,2-Diaminocyclohexane (cis-DACH) Salalen
Catalysts of Outstanding Activity and Enantioselectivity for the
Asymmetric Epoxidation of Non-Conjugated Terminal Olefins
with H2O2**
Markus Lansing,[a] Hauke Engler,[a] Tobias M. Leuther,[a] Jörg-M. Neudörfl,[a,b] and Albrecht Berkessel*[a]
Abstract: We report a new and readily accessible class of titanium
salalen complexes derived from cis-1,2-diaminocyclohexane (cis-
DACH) and fluorinated salicylic aldehyde derivatives. With aqueous
hydrogen peroxide as oxidant, these complexes effect the epoxid-
ation of terminal, non-conjugated olefins in high yield and high
enantioselectivity. We furthermore discovered that addition of certain
acidic or basic co-catalysts significantly accelerates the epoxidation.
For example, in the presence of 1 mol% Ti-catalyst and 1 mol%
pentafluorobenzoic acid, 1-octene epoxidation (95 % ee) is complet-
ed at RT within 8 h. The catalytic process is compatible with many
functional groups (e.g. ethers, esters, halides, nitriles, nitro groups),
while free hydroxyl groups appear to slow down the reaction to some
extent. Catalyst recycling is possible.
building block largely increases the catalyst's stability against
oxidative degradation under the reaction conditions.[3,4] We
observed that ligands as simple as cis-2a and cis-2b (Figure 1),
at loadings as low as 1 mol%, are able to effect e.g. 1-octene
epoxidation with 82% yield and 95% ee.[4] The combination of
the cis-DACH substructure with the axially chiral binaphthyl motif
led to a new (stereo)isomeric salalen ligands, the screening of
which resulted in the identification of the examples cis-3a,b
shown (Figure 1).[5] The Ti-complexes derived from cis-3a,b
effect the asymmetric epoxidation of 1-octene, too, and again
with high yields and enantioselectivities, at low catalyst load-
ings.[5]
trans-
cis-DACH
DACH
N
O
N
O
In 2005, Katsuki et al. introduced titanium salalen complexes as
novel and highly enantioselective catalysts for the asymmetric
epoxidation of a variety of non-functionalized olefins (both con-
jugated and non-conjugated), using hydrogen peroxide as the
oxidant.[1] Salalen ligands are mono-reduced salens, carrying
one imine and one amine functionality. For example, the catalyst
trans-1 (Figure 1) which is based on trans-1,2-diaminocyclohex-
ane (trans-DACH) was reported to effect the epoxidation of 1,2-
dihydronaphthalene with quantitative yield and over 99% ee.
Even more remarkably, the epoxidation of 1-octene and vinyl
cyclohexane were reported to proceed with 85% yield / 82% ee,
and 72% yield / 95% ee, respectively. 1-Octene in particular is a
terminal olefin notoriously difficult to epoxidize asymmetrically -
in 2005/2007, the epoxide yields/enantioselectivities achieved by
Katsuki et al. were the highest ever reported.[1]
H
Ti
NH
N
Ph Ph
OH HO
O
R
R
cis-2a: R = Ph
cis-2b: R = c-hexyl
2
trans-1, Katsuki's Ti-trans-DACH
salalen complex
this work:
cis-DACH
NH
N
NH
N
OH HO
Ph
OH HO
R
C6F5
C6F5
cis-3a: R = Ph
cis-3b: R = c-hexyl
cis-4h
Our own work in this area has focused on (i) the simpli-
fication of the salalen ligand structure, and at the same time (ii)
on increasing catalyst stability and performance.[2] In 2013, we
reported that the switching from trans-DACH to cis-DACH as
Figure 1. Katsuki's trans-DACH Ti-salalen complex trans-1, and our cis-DACH
derived salalen ligands cis-2a,b, cis-3a,b, and cis-4j.[1,4,5]
Clearly, the preparation of ligands such as cis-3a,b requires
significantly more steps than that of cis-2a or cis-2b.[6] It was
therefore our aim to achieve catalyst performance as good as, or
preferably even better than those provided by ligands cis-3a,b
with simpler ligand architectures. An equally important issue to
be addressed was the still relatively long reaction time, typically
in the order of 30-100 h.[4,5] Given the overall beneficial effect of
the cis-DACH backbone, we decided to retain this structural
element and to focus our study on the further modification of the
salicylic aldehyde moieties. As one example from the Ti-salan
area pointed to the positive influence of CF3-substitution, we
decided to investigate the effect of methylation and in particular
fluorination in a more general sense.[7] In this article, we disclose
the identification and outstanding performance of the simple
[a]
M. Lansing, H. Engler, T. M. Leuther, Dr. J.-M. Neudörfl,
Prof. Dr. A. Berkessel*
Cologne University, Department of Chemistry, Organic Chemistry
Greinstrasse 4, 50939 Cologne (Germany)
E-mail: berkessel@uni-koeln.de
Homepage: http://www.berkessel.de
[b]
Dr. J.-M. Neudörfl, X-Ray crystallography
[**]
Support by the Fonds der Chemischen Industrie (Kekulé doctoral
fellowship to H.E.) and by SusChemSys[12] is gratefully
acknowledged. We thank Sarwar Aziz for his help with the
preparation of the ligand cis-4h.
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601154
ChemCatChem
COMMUNICATION
bis(pentafluorophenyl) salalen ligand cis-4h (Figure 1) which
more than fulfilled both of the above mentioned expectations,
and defines a new level of performance for the catalytic asym-
metric epoxidation of terminal olefins with hydrogen peroxide.
enantioselectivity. Introduction of a CF3-group ortho to the
phenolic hydroxy functions again proved deleterious to catalyst
activity (cis-4g, entry 7). Up to this point, ortho-tolyl (cis-4b) and
ortho-CF3-phenyl (cis-4c) substitution proved optimal. Note that
similar observations had been made by Katsuki et al. for salan-
ligands.[8]
Table 1. Evaluation of the modified cis-DACH salalen ligands cis-4a-h in the
catalytic asymmetric epoxidation of 1-octene (5a).[a]
Our next approach focused on the fluorination of the ortho-
phenyl substituents in ligand cis-2a ("R" in Figure 1), and the bis-
pentafluorophenyl variant of cis-2a is represented by the ligand
cis-4h (Table 1, entries 8,9). We were delighted so see that both,
the catalytic activity and the enantioselectivity of this readily
available ligand by far exceed that of all other salalen ligands
reported: after only 45 h reaction time, (S)-1-octene epoxide
[(S)-6a] was formed in quantitative yield, and with 94% ee (Table
1, entry 8). In fact, 90% conversion of 1-octene (5a) was
achieved already after 18 h reaction time (Table 1, entry 9). For
comparison, the trans-DACH derived ligand trans-4h was pre-
pared and tested as well. The results shown for trans-4h in entry
10 of Table 1 prove the superiority of cis-DACH ligand cis-4h.
The X-ray crystal structures of the dimeric Ti µ-dioxo and
µ-oxo-µ-peroxo complexes derived from ligand cis-4h are shown
in Figure 2.[9] As is the case for other salalens, anti-configurated
dimeric Ti complexes are found in the crystal, with the ligand cis-
4h coordinating the Ti-ion in cis-β mode.[4,5]
ligand cis-4a-h, trans-4h (10 mol%)
Ti(OiPr)4 (10 mol%)
H3C
H3C
1,2-dichloroethane, RT
O
5a
(S)-6a
H
ligand cis-4a-h:
4a: R1 = R2 = H
4e: R1 = F, R2 = H
4f: R1 = R2 = F
4g: R1 = H, R2 = CF3
4h: R1= H, R2 = C6F5
4b: R1 = H, R2 = (2-Me)Ph
4c: R1 = H, R2 = (2-CF3)Ph
4d: R1 = H, R2 = (3,5-CF3)Ph
NH
N
R1
OH HO
R1
R2
R2
Entry[a]
Ligand
Time [h]
Conv. [5a]
Yield [(S)-
6a] (%)[b]
ee [(S)-
(%)[b]
6a] (%)[b]
1
2
cis-4a
cis-4b
cis-4c
cis-4d
cis-4e
cis-4f
48
48
48
82
40
48
42
45
18
18
51
77
47
75
82
85
89
93
84
83
67
94
94
84[c]
3
64
62
4
28
28
5
46
44
6
66
63
7
cis-4g
cis-4h
cis-4h
trans-4h
35
9
8
quant
90
quant.
89
9
10
74
74
(cis-4h)2Ti2O2
[a] All reactions were performed at
a molar ratio of substrate/ligand/
Ti(OiPr)4/30% aq. H2O2 of 1:0.1:0.1:1.5, [substrate] = 0.2 mol L-1; [b] determin-
ed by GC on chiral stationary phase (see Supporting Information for analytical
details). [c]: The (R)-enantiomer of the epoxide was formed predominantly.
NH
N
OH HO
C6F5
C6F5
Table 1 summarizes the results achieved with our set of modi-
fied cis-DACH salalen ligands, using 1-octene (5a) as the test
substrate. Ligand cis-4a, derived from unsubstituted salicylic
aldehyde, represents the "reference point" of this study. Ortho-
tolyl substituents (cis-4b, entry 2) improved both the catalyst act-
ivity and enantioselectivity. With ligands cis-4c-h, we intended to
survey the effects of fluorination on catalyst performance and
selectivity. In the ligand cis-4c, the ortho-tolyl substituent present
in cis-4b is modified to its fluorinated analog ortho-(trifluoro-
methyl)phenyl.[9] The comparison of entries 2 and 3 of Table 1
reveals that fluorination at this position results in somewhat
lower activity, but higher enantioselectivity. Introduction of a
second trifluoromethyl group in ligand cis-4d [R2 = 3,5-bis(tri-
fluoromethyl)phenyl] increases the enantioselectivity further, but
once again, the catalyst activity is reduced (entry 4).[9] Fluorin-
ation of the parent ligand cis-4a para to the phenolic hydroxyl
groups leads to cis-4e (entry 5). The effect of this modification
on catalytic activity and enantioselectivity is negligible (compare
entries 1 and 5 of Table 1). Additional ortho fluorination (cis-4f,
entry 6) resulted in a minor increase of activity and did not affect
ligand cis-4h
(cis-4h)2Ti2O3
Figure 2. X-ray crystal structures of the bis-µ-oxo- (top) the µ-oxo-µ-peroxo-
titanium complexes (bottom) derived from the cis-salalen ligand cis-4h.
With the highly active and selective ligand cis-4h in hand, we
set out to gather information on its substrate scope, and the
results of our study are summarized in Table 2. As shown in
entries 1-5, non-functionalized terminal olefins are excellent sub-
strates, and even propene (5d) is epoxidized with 92% ee. The
values obtained for 5-bromopentene (5f, entry 6) show that
halide substitution is well tolerated, as is the ether functionality
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601154
ChemCatChem
COMMUNICATION
Table 2. Substrate scope of the asymmetric epoxidation catalyzed by Ti-
of the substrates 5g to 5l (entries 7-12). The allyl diethers 5j and
5k (entries 10,11) afforded lower yields, moderate diastereo-
selectivities (RR/SS : RS = 7-9:1), but high enantiopurity (up to
>99% ee) of the main di-epoxide product, due to double stereo-
differentiation. When the racemic mono-epoxide of diallyl ether
(rac-5l, entry 12) was used as the substrate, the homochiral
diepoxide and the meso-product were formed in almost equal
amounts (1.1:1), confirming that the catalyst overrides the
substrate control. Again, the homochiral di-epoxide was formed
in high enantiopurity (95% ee). The 1,ω-diolefin 1,5-hexadiene
(5m, entry 13) behaves as an excellent substrate in the sense
that it is converted to its di-epoxide in good yield and high
diastereoselectivity (18:1), affording the main di-epoxide product
in virtually enantiopure form. As exemplified by the benzoate 5n
(entry 14), the ester functionality is well tolerated. In contrast,
electron-withdrawing groups such as neighboring carbonyl
functions (as in the case of the allyl ketone 5o, or the acrylate 5p,
entries 15,16) prevent the epoxidation of the C=C double bond.
In the 5-hexenyl acrylate (5p), there is a clear discrimination of
the substrate's two C-C double bonds, with the terminal, non-
conjugated one being epoxidized with the "usual" high enantio-
selectivity, while the acrylate moiety remains untouched (entry
16). As observed before with other salalen ligands,[4,5] the pres-
ence of alcohol OH in the substrate appears to somewhat slow
down the epoxidation, but the very high enantioselectivity is
retained [e.g. 5-hexenol (5q), entry 17]. Finally, the substrates
5r-t give an impression of the catalysts action upon the three
possible forms of disubstituted olefins: for the internal cis-olefin
5r, a high epoxide yield at somewhat reduced ee (84%, entry
18) resulted. Similar yields, but almost no enantioselectivity are
typical for trans-olefins such as trans-2-octene (5s, entry 19).
Extremely slow conversion and low ee was the result for the 2,2-
disubstituted substrate olefin 5t (entry 20).
salalen complex of ligand cis-4h.[a]
ligand
cis-4h:
ligand cis-4h (10 mol%)
Ti(OiPr)4 (10 mol%)
R1
R2
R3
R4
NH
OH HO
C6F5
N
R3
R4
R1
R2
O
1,2-dichloroethane, RT
5a-t
6a-t
C6F5
Substrate olefins 5a-t:
5a: R = n-hexyl
5b: R = n-octyl
5c: R = n-butyl
5d: R = methyl
5e: R = c-hexyl
O
Bn
R
O
Br
5g
5f
5a-e
R
5h: R = CN; 5i: R = NO2
O
O
O
rac-5l
O
5j
5m
5k
O
O
O
O
HO
CH3
O
O
5o
5p
5q
5n
CH3
H3C
H3C
H3C
CH3
5t
5r
5s
CH3
Entry[a]
Olefin
Reaction
time [h]
Conv.
(%)[b]
Epoxide
Epoxide ee
(%)[b]
yield
(%)[b]
1
2
5a
5b
5c
5d
5e
5f
45
45
45
45
45
40
45
45
45
40
45
45
45
45
100
42
45
45
40
45
quant.
quant.
quant.
n.d.
quant.
quant.
62[c]
56[d]
quant.
quant.
63
94
96
3
94
4
92 [d]
94
5
quant.
quant.
93
6
95
7
5g
5h
5i
95
8
80
75
96
9
90
87
96
34/34[e]
51/14[e]
40
88/>99 (dr 9:1)[e,f,g]
In the course of our reaction optimization, we observed that
the addition of carboxylic acids as co-catalysts results in a quite
remarkable acceleration. From a broader screening of acid and
bases as co-catalysts (see Supporting Information), pentafluoro-
benzoic acid, tetra-n-butylammonium hydrogensulfate (TBAHS)
and 2,6-di-tert-butylpyridine emerged as the most beneficial
additives. Figure 3 displays the time courses of 1-octene (5a)
epoxidation, in the presence and absence of these three addi-
tives. Overall, addition of the co-catalysts results in a shortening
of the reaction time for full olefin conversion from ca. 45 h to ca.
10
11
12
13
14
15
16
17
18
19
20
5j
89
5k
rac-5l
5m
5n
5o
5p
5q
5r
64
87/>99 (dr 7:1)[e,f]
49
95 (dr 1.1:1)[f]
quant.
quant.
n.d
69
>99 (dr 18:1)[f,g]
97
93
n.d.
92[h]
93
trace
40
65
58
34
quant.
94
93
84
5s
5t
85
4
n.d.
trace
15
[a] All reactions were performed at
a molar ratio of substrate/ligand/
Ti(OiPr)4/30% aq. H2O2 of 1:0.1:0.1:1.5, unless noted otherwise, [substrate] =
0.2 mol L-1; [b] determined by GC or HPLC on chiral stationary phase (see
Supporting Information for analytical details); [c] losses of material due to the
high volatility of substrate olefin 5c and product epoxide 6c; [d] reaction was
run with a ligand/Ti(OiPr)4/30% aq. H2O2 ratio of 1:1:15 at 0 oC under a
propene atmosphere; yield based on H2O2; [e] values refer to mono- and
diepoxide product; [f] dr: RR/SS : RS; [g] reaction was performed with a
substrate/ligand/Ti(OiPr)4/30% aq. H2O2 ratio of 1:0.1:0.1:3.0; [h] epoxidation
exclusively at the non-conjugated C=C double bond.
Figure 3. Effect of the additives pentafluorobenzoic acid, tetra-n-butyl-
ammonium hydrogensulfate (TBAHS), and 2,6-di-tert-butylpyridine on the time
course of 1-octene (5a) epoxidation; 10 mol% of additive were used, all other
reaction conditions as in Tables 1,2.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601154
ChemCatChem
COMMUNICATION
1.00 equiv), pentafluorobenzoic acid (6.80 mg, 32.1 mmol, 0.005
equiv) 360 µl DCE, and 0.5 mL aq. hydrogen peroxide (0.50 mL
50% w/w, 8.8 mmol, 1.47 equiv) were added, and the mixture
was stirred at room temperature for 10 h. After filtering through a
short pad of silica/MnO2 (to deactivate excess H2O2), the phases
were separated, and the aqueous phase was extracted with
DCM. The combined organic phases were dried over MgSO4,
and the solvent was removed under reduced pressure.
Purification by flash column chromatography (silica, DCM)
afforded 753 mg of the epoxide 6b (4.83 mmol, 81%, 96% ee)
as a colorless liquid.
8 h. At the same time, both the yield and the enantiomeric purity
of the product epoxide [(S)-6a] remained unchanged. We
furthermore observed that the epoxidation proceeds faster at
higher substrate concentrations, which in turn allowed for lower-
ing of the catalyst loading. When the olefin concentration is
raised to ca. 6 mol L-1, and using TBAHS as co-catalyst, the
epoxidation of 1-octene (5a) reaches completion within 8 h in the
presence of 1 mol% catalyst/additive, while the epoxide is form-
ed in unaltered enantiopurity (95% ee). As shown exemplarily in
eq. 1, 1-decene (5b) is fully converted to its epoxide (96% ee)
within 10 h, with as little as 0.5 mol% catalyst/pentafluorobenzo-
ic acid as additive. Under these conditions, the catalyst can even
be recovered and recycled by simple removal of all volatiles in
vacuo (see Supporting Information for experimental details).
Keywords: asymmetric catalysis · epoxidation · hydrogen
peroxide · titanium · cis-DACH
[1]
a) K. Matsumoto, Y. Sawada, B. Saito, K. Sakai, T. Katsuki, Angew.
Chem. 2005, 117, 5015-5019; Angew. Chem. Int. Ed. 2005, 44, 4935-
4939; b) Y. Sawada, K. Matsumoto, T. Katsuki, Y. Sawada, K. Matsu-
moto, T. Katsuki, Angew. Chem. 2007, 119, 4643-4645; Angew. Chem.
Int. Ed. 2007, 46, 4559-4561.
0.5 mol% ligand cis-4h
0.5 mol% Ti(OiPr)4
0.5 mol% C6F5COOH
n-octyl
(1)
O
n-octyl
H
6b, quant. (GC)
isolated yield: 735 mg, 81%,
5b, 841 mg
aq. H2O2, DCE, RT, 10 h
96% ee
[2]
a) A. Berkessel, M. Brandenburg, E. Leitterstorf, J. Frey, J. Lex, M.
Schäfer, Adv. Synth. Catal. 2007, 349, 2385-2391; b) A. Berkessel, M.
Brandenburg, M. Schäfer, Adv. Synth. Catal. 2008, 350, 1287-1294.
A. Berkessel, M.-C. Ong, M. Nachi, J.-M. Neudörfl, ChemCatChem
2010, 2, 1215-1218.
In conclusion, we report a new generation of cis-DACH
salalen ligands for the Ti-catalyzed asymmetric epoxidation of
terminal olefins with hydrogen peroxide, based on the introduct-
ion of fluorine substituents adjacent to the ligands' phenolic
metal binding sites. Best results were achieved with the
bis(pentafluorophenyl)-substituted ligand cis-4h in the presence
of e.g. pentafluorobenzoic acid or tetra-n-butylammonium hydro-
gensulfate (TBAHS) as co-catalysts. With this novel catalyst
system, the highly enantioselective epoxidation of non-con-
jugated terminal in particular, and additionally of cis-1,2-
disubstituted olefins can be achieved in high yields and within
short reaction times. Potential applications of this epoxidation
method are manifold, for example in the area of natural product
synthesis[10] or pharmaceutical chemistry.[11] The mechanistic
aspects of this novel and highly efficient epoxidation catalysis
are currently under investigation in our laboratory, and will be
reported in due course.
[3]
[4]
[5]
[6]
A. Berkessel, T. Günther, Q. Wang, J.-M. Neudörfl, Angew. Chem.
2013, 125, 8625-8629; Angew. Chem. Int. Ed. 2013, 52, 8467-8471.
Q. Wang, J.-M. Neudörfl, A. Berkessel, Chem. Eur. J. 2015, 21, 247-
254.
Our cis-DACH salalen ligands are typically prepared by the two-step
route described in ref. 4, starting from enantiopure mono-N-alloc cis-
DACH (ref. 3) and the corresponding salicylic aldehydes. The ease of
accessibility of the latter therefore largely affects the overall practical
value of the ligand synthesis.
[7]
[8]
K. Matsumoto, Y. Sawada, T. Katsuki, Synlett 2006, 3545-3547.
E. P. Talsi, T. V. Rybalova, K. P. Bryliakov, J. Mol. Catal. A: Chemical
2016, 421, 131-137.
[9]
CCDC 1451975 [(cis-4c)2Ti2O2], CCDC 1451974 [(cis-4d)2Ti2O2],
CCDC 1451973 [(cis-4h)2Ti2O2] and 1451976 [(cis-4h)2Ti2O3] contain
the supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.uk/data_request/cif.
Experimental Section
[10] W. Francke, S. Schulz in Comprehensive Natural Products II, Vol. 4,
153-223, Elsevier, 2010.
Preparative Ti-salalen catalyzed asymmetric epoxidation of
1-decene (5b):
[11] D. Zelaszczyk, K. Kiec-Kononowicz, Curr. Med. Chem. 2005, 14, 53-65.
[12] The project "Sustainable Chemical Synthesis (SusChemSys)" is co-
financed by the European Regional Development Fund (ERDF) and the
state of North Rhine-Westphalia, Germany, under the Operational
Programme "Regional Competitiveness and Employment" 2007 - 2013.
In a 5 ml vial, 20.2 mg (30.8 µmol, 0.005 equiv) of ligand cis-4h,
and 8.4 mg Ti(OiPr)4 (30 µmol, 0.005 equiv) were dissolved in
1.5 mL of DCM and stirred under argon at RT for 1 h. The sol-
vent was removed under reduced pressure, and the residue was
dried in vacuo for 1 h. 1-Decene (5b, 841 mg, 6.01 mmol,
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601154
ChemCatChem
COMMUNICATION
COMMUNICATION
cis-
DACH
Markus Lansing, Hauke Engler, Tobias
M. Leuther, Jörg-M. Neudörfl, and
Albrecht Berkessel*
H3C
+ 1.3 equiv aq. H2O2 (30%)
NH
N
in situ complexation with
Ti(OiPr)4
1 mol% n-Bu4NHSO4
OH HO
Page No. – Page No.
C6F5
C6F5
Titanium cis-1,2-Diaminocyclohexane
(cis-DACH) Salalen Catalysts of Out-
standing Activity and Enantioselectivity
for the Asymmetric Epoxidation of Non-
Conjugated Terminal Olefins with H2O2
H3C
O
ligand, 1 mol%
H
quant., 95% ee
Nine-to-fivers. The titanium complex of the cis-DACH salalen ligand shown effects
the asymmetric epoxidation of terminal, non-conjugated olefins with unprecedented
efficiency and excellent selectivity. In the presence of acid/base co-catalysts, olefins
such as 1-octene are epoxidized in high yield and enantioselectivity, within a few
hours at room temperature, using aqueous H2O2 as terminal oxidant.
This article is protected by copyright. All rights reserved.