Proton-Promoted and Anion-Enhanced Epoxidation of Olefins by Hydrogen Peroxide in the Presence of Nonheme Manganese Catalysts

Article abstract of DOI:10.1021/jacs.5b11579

We report a remarkable Br?nsted acid effect in the epoxidation of olefins by nonheme manganese catalysts and aqueous hydrogen peroxide. More specifically, a mononuclear nonheme manganese complex bearing a tetradentate N4 ligand, Mn^II(Dbp-MCP)(OTf)₂ (Dbp-MCP = (1R,2R)-N,N′-dimethyl-N,N′-bis((R)-(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine; OTf^- = CF₃SO₃^-), is a highly efficient catalyst in the epoxidation of olefins by aqueous H₂O₂ in the presence of H₂SO₄ (1-3 mol %). The yields of epoxide products as well as the chemo- and enantioselectivities increase dramatically in the presence of H₂SO₄; no formation of epoxides is observed in the absence of H₂SO₄. In addition, the product yields and enantioselectivities are dependent significantly on the manganese catalysts and Br?nsted acids. The catalytic epoxidation of olefins by other oxidants, such as peracids, alkyl hydroperoxides, and iodosylbenzene, is also affected by the presence of H₂SO₄; product yields and enantioselectivities are high and similar irrespective of the oxidants in the presence of H₂SO₄, suggesting that a common epoxidizing intermediate is generated in the reactions of [Mn^II(Dbp-MCP)]²⁺ and the oxidants. Mechanistic studies, performed with ¹⁸O-labeled water (H₂¹⁸O) and cumyl hydroperoxide, reveal that a high-valent manganese-oxo species is formed as an epoxidizing intermediate via O-O bond heterolysis of Mn-OOH(R) species. The role of H₂SO₄ is proposed to facilitate the formation of a high-valent Mn-oxo species and to increase the oxidizing power and enantioselectivity of the Mn-oxo oxidant in olefin epoxidation reactions. Density functional theory (DFT) calculations support experimental results such as the formation of a Mn(V)-oxo species as an epoxidizing intermediate.

Full text of DOI:10.1021/jacs.5b11579

Subscriber access provided by Deakin University Library
Article
Proton-Promoted and Anion-Enhanced Epoxidation of Olefins by
Hydrogen Peroxide in the Presence of Nonheme Manganese Catalysts
Chengxia Miao, Bin Wang, Yong Wang, Chungu Xia, Yong-Min Lee, Wonwoo Nam, and Wei Sun
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b11579 • Publication Date (Web): 31 Dec 2015
Downloaded from http://pubs.acs.org on January 3, 2016
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the
course of their duties.

Page 1 of 10
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Proton-Promoted and Anion-Enhanced Epoxidation of Olefins
by Hydrogen Peroxide in the Presence of Nonheme Manganese
Catalysts
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Chengxia Miao,† Bin Wang,‡ Yong Wang,† Chungu Xia,† Yong-Min Lee,‡ Wonwoo Nam,‡,* and Wei Sun†,*
† State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of
Sciences, Lanzhou 730000, China
‡ Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
ABSTRACT: We report a remarkable Brønsted acid effect in the epoxidation of olefins by nonheme manganese catalysts and aqueous hydrogen
peroxide. More specifically, a mononuclear nonheme manganese complex bearing a tetradentate N4 ligand, MnII(Dbp-MCP)(OTf)2 (Dbp-
MCP = (1R,2R)-N,N’-dimethyl-N,N’-bis((R)-(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine; OTf– = CF3SO3 ), is a
–
highly efficient catalyst in the epoxidation of olefins by aqueous H2O2 in the presence of H2SO4 (1 – 3 mol%). The yields of epoxide products
as well as the chemo- and enantioselectivities increase dramatically in the presence of H2SO4; no formation of epoxides is observed in the
absence of H2SO4. In addition, the product yields and enantioselectivities are dependent significantly on the manganese catalysts and Brønsted
acids. The catalytic epoxidation of olefins by other oxidants, such as peracids, alkyl hydroperoxides, and iodosylbenzene, is also affected by the
presence of H2SO4; product yields and enantioselectivities are high and similar irrespective of the oxidants in the presence of H2SO4, suggesting
that a common epoxidizing intermediate is generated in the reactions of [MnII(Dbp-MCP)]2+ and the oxidants. Mechanistic studies, performed
with 18O-labeled water (H2 O) and cumyl hydroperoxide, reveal that a high-valent manganese-oxo species is formed as an epoxidizing
18
intermediate via O-O bond heterolysis of Mn-OOH(R) species. The role of H2SO4 is proposed to facilitate the formation of a high-valent Mn-
oxo species and to increase the oxidizing power and enantioselectivity of the Mn-oxo oxidant in olefin epoxidation reactions. Density functional
theory (DFT) calculations support experimental results such as the formation of a Mn(V)-oxo species as an epoxidizing intermediate.
INTRODUCTION
reported a highly enantioselective epoxidation of α-substituted
styrenes by a nonheme iron complex and H2O2 in the presence of N-
protected amino acids.9 Although the role(s) of the carboxylic acids in
the nonheme metal complex-catalyzed epoxidation reactions by H2O2
has yet to be understood, it has been proposed that protonation of the
hydroperoxide ligand by the coordinated carboxylic acid in metal-
hydroperoxo intermediates facilitates the O-O bond cleavage,
generating high-valent metal-oxo species as reactive epoxidizing
intermediates.7 Indeed, involvement of the high-valent metal-oxo
intermediates in the catalytic epoxidation reactions has been
supported experimentally and theoretically.7c,8h,10
Development of highly efficient and selective oxidation reactions
under mild conditions is of current interest in the communities of
synthetic organic, oxidation, and bioinorganic/biomimetic chemistry.
In particular, catalytic (asymmetric) epoxidation reactions using earth-
abundant transition metals (e.g., Fe and Mn) and environmentally
benign oxidants (e.g., H2O2) have been attracted much attention
recently to develop oxidation methods with low cost and low toxicity
considerations, since epoxides are highly useful building blocks for a
number of subsequent transformations in organic synthesis.1,2 In this
context, bioinspired catalytic olefin epoxidation reactions utilizing
nonheme iron and manganese complexes bearing polydentate N-
donor ligands as catalysts and aqueous H2O2 as a terminal oxidant have
been intensively investigated recently.2 As a result, a number of highly
efficient catalytic epoxidation reactions using the biomimetic
nonheme iron and manganese catalysts and aqueous H2O2 oxidant
have been reported;3-8 a common feature in these reactions is the use
of carboxylic acids as additives to improve the catalytic activity and
stereo- and enantioselectivities. More recently, Costas and co-workers
In biomimetic studies, it has been shown that the O-O bond
activation of metal-hydroperoxo species is affected markedly by the
protonation of the hydroperoxide ligand (Scheme 1A), resulting in the
generation of highly reactive metal-oxo species as active oxidants in
oxidation reactions.11 Further, it has been demonstrated recently that
the reactivity of metal-oxo complexes in oxidation reactions increased
significantly by binding of Lewis and Brønsted acids (Scheme 1B),
resulting from the change of the reduction potentials and oxidizing
1
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 10
1
2
3
power of the metal-oxo complexes.12,13 The effects of Lewis and
4
5
6
7
8
9
Brønsted acids have also been demonstrated in catalytic oxidation
reactions.14 Thus, we have envisioned that protons play important roles
not only in the formation of metal-oxo species via the O-O bond
cleavage of metal-hydroperoxo species but also in the increase of the
reactivity of the metal-oxo species in the olefin epoxidation reactions
by nonheme metal catalysts and H2O2 (Scheme 1).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. Proton effects on (A) the hydroperoxide O-O bond cleavage
and (B) the reactivity of metal-oxo species.
As alluded above, understanding the effects of protons on the
catalytic oxidation reactions by nonheme metal catalysts and H2O2 and
the reactivity of nonheme metal-oxo complexes in oxidation reactions
is of importance in developing efficient catalytic systems.2,12 We
therefore attempted the epoxidation of olefins by aqueous H2O2
catalyzed by mononuclear nonheme manganese complexes in the
presence of Brønsted acids. Herein, we report for the first time that the
Figure 1. (A) ORTEP-III diagram of 1 (CCDC-917216), showing the
20% probability displacement ellipsoids. Hydrogen atoms are omitted for
epoxidation of olefins by mononuclear nonheme manganese clarity (see Tables S1 and S2 in SI for crystallographic data). Atom colors
are aquamarine for Mn, blue for N, red for O, gray for C, yellow for S, and
pink for F. (B – E) Schematic structures of (B) MnII(Dbp-MCP)(OTf)2
(1), (C) MnII(P-MCP)(OTf)2 (2, P-MCP = N,N’-dimethyl-N,N’-bis-
complexes and aqueous H2O2 is affected dramatically by the presence
of a catalytic amount of sulfuric acid; the yields of epoxide products as
well as the chemo- and enantioselectivities are very high in the
presence of H2SO4, whereas no formation of epoxides is observed in
the absence of H2SO4. We also show that both the proton and anions
of Brønsted acids play key roles in determining the catalytic activity
and chemo- and enantioselectivities of the manganese catalysts in the
olefin epoxidation reactions. Detailed mechanistic aspects, such as the
nature of the epoxidizing intermediate and the O-O bond cleavage
mechanism, are discussed as well.
(phenyl-2-pyridinylmethyl)cyclohexane-1,2-diamine),
(D)
MnII(MCP)(OTf)2 (3), and (E) MnII(PDP)(OTf)2 (4, PDP = N,N’-
bis(2-pyridinylmethyl)-2,2’-bipyrrolidine)).
carried out in the absence of Brønsted acids, no epoxide formation was
observed (Table 1, entry 1). Interestingly, when the identical reaction
was carried out in the presence of a small amount of H2SO4 (i.e., 6 equiv
to 1) (eq 1), we observed the formation of cyclooctene oxide with a
RESULTS AND DISCUSSION
Synthesis and Characterization of MnII(Dbp-MCP)(OTf)2 (1). A
linear tetradentate N4 ligand, (1R,2R)-N,N’-dimethyl-N,N’-bis((R)-
(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-
diamine (Dbp-MCP; see Experimental Section and Figure S1 in
Supporting Information (SI) for NMR spectra), was prepared by
high yield (Table 1, entry 2). This result indicates that the H2SO4
additive plays an important role in generating an efficient epoxidizing
species in the reaction of 1 and H2O2 (vide infra). We also found that
the product yields obtained in the olefin epoxidation were dependent
on the Brønsted acids added, such as H3PO4, HClO4, CF3SO3H, HCl,
and acetic acid (Table 1, entries 3 – 7), indicating that the anion of
Brønsted acids is an important factor that controls the catalytic activity
of 1. It is noteworthy that the epoxidation reaction using acetic acid
(e.g., carboxylic acid) afforded only a small amount of epoxide product
(Table 1, entry 7).3-8 In addition, no epoxidation occurred when an
introducing
a
3,5-di-tert-butylbenzene group into the 2-
pyridinylmethyl positions of (R,R)-MCP (MCP = N,N’-dimethyl-
N,N’-bis(2-pyridinylmethyl)cyclohexane-1,2-diamine), and the
MnII(Dbp-MCP)(OTf)2 complex (1, see Figure 1A) was synthesized
by reacting equimolar amounts of Dbp-MCP and Mn(OTf)2 (OTf– =
–
CF3SO3 ) under an Ar atmosphere in CH3CN (see Experimental
Section and Figure S2 in SI for detailed experimental procedures).5a
The X-ray crystal structure reveals that the Dbp-MCP ligand adopts a
cis-α topology coordinating a Mn atom (Figure 1A; Tables S1 and S2
in SI for crystallographic data).15,16
2–
inorganic salt containing SO4 (e.g., Na2SO4) was used instead of
H2SO4 (Table 1, entry 8). However, a significant amount of epoxide
product (73%) was obtained in the reaction using NaHSO4 as an
additive (Table 1, entry 9). The latter results further demonstrate that
proton is an essential component for the catalytic epoxidation reaction
by 1 and H2O2.
Catalytic Activities of Manganese(II) Complexes (1 – 4) in the
Epoxidation of Olefins. The manganese complex 1 was tested as a
catalyst in the epoxidation of cyclooctene by aqueous H2O2 in the
absence and presence of Brønsted acids. First, when the reaction was
2
ACS Paragon Plus Environment

Page 3 of 10
Journal of the American Chemical Society
1
2
3
2–
Table 1. Catalytic epoxidation of olefins by 1 and H2O2 in the presence
of H2SO4 or under other reaction conditionsa
H2O2 is determined by the presence of both proton and SO4 anion
(i.e., H2SO4) and the structure of the Mn catalysts.
4
5
6
7
8
yield (%)b,c
NR
The catalytic activity of 1 was then examined in the epoxidation of
other olefins, such as cyclic olefins (e.g., cyclohexene), cis- and trans-
olefins, and terminal olefin (Table 1, entries 10 – 14). In the
epoxidation of cyclohexene, cyclohexene oxide was the sole product
with no formation of allylic oxidation products, such as cyclohexenol
and cyclohexenone (Table 1, entry 10), suggesting that no
autooxidation is involved in the epoxidation of olefins by 1 and H2O2
in the presence of H2SO4. In the epoxidation of cycloheptene,
cycloheptene oxide was yielded as the sole product (Table 1, entry 11).
We also found that the olefin epoxidation by 1 and H2O2 was highly
stereospecific; cis- and trans-2-heptenes were oxidized to their
corresponding cis- and trans-2-heptene oxides, respectively, and no
epimerized products were detected in these reactions (Table 1, entries
12 and 13); it is notable that the product yield in the trans-2-heptene
epoxidation was lower than that in the cis-2-heptene epoxidation.
Finally, 1-octene, which is a less reactive terminal olefin,17 was also
oxidized to the corresponding epoxide with a high yield (Table 1, entry
14). The results described above demonstrate that a highly reactive
and stereoselective epoxidizing intermediate is generated in the
reaction of 1 and H2O2 in the presence of H2SO4.
entry
substrate
additive
none
1
2
3
4
5
6
7
8
9
H2SO4
H3PO4
HClO4
CF3SO3H
HCl
91(3)
Trace
17(3)
30(4)
NR
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
AcOH
Na2SO4
NaHSO4
8(2)
NR
73(3)
10
11
H2SO4
H2SO4
87(3)
92(4)
Asymmetric Epoxidation by 1. Since 1 is a chiral complex, this
manganese catalyst was examined in the asymmetric epoxidation of
olefins by H2O2 in the presence of H2SO4. As the results are shown in
Table 2, the epoxidation of chalcone derivatives by 1 (0.20 mol%) and
H2O2 (1.5 equiv to substrate) in the presence of H2SO4 (5 equiv to 1)
afforded high yields of epoxide products with excellent
enantioselectivities (>97% enantiomeric excess (ee) values; Table 2,
entries 1, 3 and 4; see also Figure S3 in SI). In the case of a chalcone
derivative with an electron-donating substituent (e.g., p-Me), a
moderate yield of epoxide product with an 86% ee value was obtained
(Table 2, entry 5). Interestingly, in a gram scale reaction (eq 2), we
12
13
14
H2SO4
H2SO4
H2SO4
90(2)
45(4)
90(3)
a Reaction conditions: olefin (0.25 mmol), catalyst (1, 0.50 mol%), and
additive (3.0 mol%) in CH3CN (1.0 mL) were added into a Schlenk tube
at –20 oC. Then, 50% H2O2 (1.5 equiv) in CH3CN (0.50 mL) was added
to the reaction solution over a period of 1 h using a syringe pump. b Yields
were obtained by GC analysis using decane or nitrobenzene as an
c
internal standard. NR stands for no reaction. Product yields are based
on the amounts of substrate used.
We also examined the catalyst effect in the olefin epoxidation
reactions. When the epoxidation of cyclooctene by H2O2 was carried
out using simple Mn salts (e.g., MnSO4 or Mn(OTf)2) in the absence
and presence of H2SO4, no formation of epoxide was observed (Table
S3 in SI, entries 1 – 4). Then, to investigate the structural effect of
manganese catalysts, the epoxidation of cyclooctene by H2O2 was
carried out using several manganese catalysts in the presence of H2SO4
(2 – 4; see Figure 1). In these reactions, the yields of cyclooctene oxide
were 76% for 2, 37% for 3, and 11% for 4 (Table S3 in SI, entries 5 – 7);
the product yields are much lower than that obtained in the reaction
with 1 as a catalyst. These results indicate that the structure of the
manganese catalysts is another important factor that determines the
efficiency of the olefin epoxidation by H2O2. Taken together, 1 is a
highly efficient catalyst in the epoxidation of olefins by aqueous H2O2,
and the efficiency of the olefin epoxidation by the Mn catalyst and
obtained a similar product yield (93%) with an excellent
enantioselectivity (97%), indicating that the present epoxidation
protocol can be adapted for large scale applications. 2 (see Figure 1C),
which is an analogue of 1, also provided an excellent ee value (95%),
but the product yield was lower than that obtained in the reaction with
1 (Table 2, entry 2). Similarly, 3 and 4 afforded low product yields but
with high ee values (e.g., ~90%) were obtained under the optimized
reaction conditions, respectively (Table S4, entries 13 and 14). When
H2SO4 was omitted or replaced by other Brønsted acids, such as H3PO4,
HClO4 and CF3SO3H, in the epoxidation of chalcone, the product
yields and ee values were much lower (e.g., <50%) than those obtained
with H2SO4 (Table S4 in SI), demonstrating again that the SO42– anion
is a vital component determining the enantioselectivity of the Mn
catalyst as well as the catalytic activity.
3
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 10
1
2
3
4
Table 2. Asymmetric epoxidation of olefins by 1 and H2O2 in the presence
Table 3. Asymmetric epoxidation of chalcone by various oxidants
a
a
of H2SO4
catalyzed by 1 in the absence and presence of H2SO4
5
6
7
8
entry
oxidant
H2SO4
no
yield (%)b
38(3)
87(3)
18(2)
56(3)
8(2)
ee (%)c
37(3)
95(2)
45(3)
97(2)
30(3)
96(2)
68(4)
97(2)
entry
substrate
yield (%)
ee (%)
1
2
3
4
5
6
7
8
m-CPBA
9
yes
no
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
2b
3
R = H
94(3)
57(2)
89(4)
90(3)
61(3)
97(2)
95(2)
98(2)
98(2)
86(3)
t-BuOOH
Cumyl-OOH
PhIO
R = H
yes
no
R = o-Cl
R = m-Cl
R = p-Me
4
yes
no
33(3)
25(3)
78(4)
5
yes
a
Reaction conditions: oxidant (1.2 equiv) was added into a reaction
6
7
R = CN
56(4)
45(4)
92(2)
94(3)
solution containing chalcone (0.25 mmol) and 1 (0.20 mol%) in the
absence and presence of H2SO4 (1.0 mol%) in CH3CN (1.5 mL) at –20
oC. Total reaction time was 2.0 h. b Isolated yields are reported. c The ee
values were determined by HPLC equipped with a Daicel OD-H
column.
R = NO2
asymmetric epoxidation reactions by H2O2 are determined by the
presence of the proton and SO42– anion.
8c
9c
R = OMe
R = OEt
R = OBn
48(4)
55(4)
57(5)
95(3)
95(2)
97(2)
The asymmetric olefin epoxidation by 1 was also investigated using
various oxidants, such as m-chloroperoxybenzoic acid (m-CPBA),
tert-butyl hydroperoxide (t-BuOOH), cumyl hydroperoxide (Cumyl-
OOH), and iodosylbenzene (PhIO), in the absence and presence of
H2SO4. As we have observed in the H2O2 reactions (vide supra), not
only the product yields but also the ee values were affected significantly
by the presence of H2SO4 in the epoxidation of chalcone by 1 and the
oxidants (Table 3); both the product yields and the ee values were low
in the absence of H2SO4, even in the reactions of single oxygen atom
donors such as m-CPBA and PhIO. Most importantly, the ee values
were virtually the same irrespective of the oxidants in the presence of
H2SO4 (Table 2, entry 1 and Table 3, entries 2, 4, 6, and 8), suggesting
that a common epoxidizing intermediate (e.g., a high-valent Mn-oxo
species) was generated in the reactions of H2O2, m-CPBA, t-BuOOH,
Cumyl-OOH, and PhIO in the presence of H2SO4 (vide infra).
10c
11d
80(3)
58(3)
60(2)
66(3)
12d
a
Reaction conditions: olefin (0.25 mmol), 1 (0.20 mol%), and H2SO4
(1.0 mol%) in CH3CN (1.0 mL) were added into the Schlenk tube at –20
oC. Then, 50% H2O2 (1.5 equiv to substrate) in CH3CN (0.50 mL) was
added to the reaction solution over a period of 1 h using a syringe pump.
Total reaction time was 2.0 h. Isolated yields are reported, and the ee
values were determined by HPLC with a Daicel OD-H, OJ-H or IC
column. b 2 instead of 1 was used as a catalyst. c Reaction was carried out
with 1 (1.0 mol%) and H2SO4 (3.0 mol%) at 0 C. 1 (0.50 mol%) and
H2SO4 (3.0 mol%) were used, and the yields and ee values were
determined by GC with a CP-Chirasil-Dex CB column.
o
d
Mechanistic Studies to Elucidate the Role(s) of H2SO4. We then
investigated the nature of the epoxidizing intermediate formed in the
reaction of 1 and H2O2 in the presence of H2SO4. It has been proposed
that the reactions of nonheme iron(II) and manganese(II) complexes
bearing N4 ligands, such as TPA7a and PDP,7b with H2O2 in the
presence of carboxylic acids generate Fe(V)- and Mn(V)-oxo species,
respectively, via O-O bond heterolysis of presumed M(III)-OOH
precursors (Scheme 2A).10 We therefore conducted mechanistic
studies to elucidate the nature of the epoxidizing intermediate and the
O-O bond cleavage mechanism in the reactions of 1 and ROOH (e.g.,
R = H and Cumyl). First, we carried out the reaction of 1 with cumyl
In the case of chromenes, the product yields were moderate, but the
enantioselectivities were high (Table 2, entries 6 and 7; Figure S4 in
SI). In the epoxidation of methyl cinnamate, ethyl cinnamate, and
benzyl cinnamate, we also obtained high ee values with moderate
epoxide yields (Table 2, entries 8 – 10; Figure S5 in SI). In contrast,
the ee values were moderate in the epoxidation of styrene and cis-β-
methylstyrene (Table 2, entries 11 and 12). Thus, the results described
above clearly indicate that 1 is an efficient enantioselective catalyst and
both the catalytic activity and the enantioselectivity of 1 in the
4
ACS Paragon Plus Environment

Page 5 of 10
Journal of the American Chemical Society
1
2
3
hydroperoxide and analyzed product(s) derived from the
4
5
6
7
8
9
decomposition of the cumyl hydroperoxide to distinguish homolytic
vs heterolytic O-O bond cleavage pathways (Scheme 2B).18 In this
reaction, cumyl alcohol was produced quantitatively in the presence of
H2SO4 (see Figures S6 and S7 in SI), suggesting that a Mn(III)-
alkylperoxo species is converted to a Mn(V)-oxo species via a
heterolytic O-O bond cleavage pathway (Scheme 2B, pathway a). On
the contrary, acetophenone was yielded as a major product when the
reaction was performed in the absence of H2SO4 (~90% yield based on
the amount of Cumyl-OOH), indicating that O-O bond homolysis is a
predominant pathway (Scheme 2B, pathway b). We therefore
conclude that one possible role of H2SO4 is to control the O-O bond
cleavage pathway to form a Mn-oxo intermediate (vide infra), such as
the heterolytic and homolytic O-O bond cleavage of Mn-OOR in the
presence and absence of H2SO4, respectively (Scheme 2B, pathways a
and b).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 3. (A) A proposed mechanism for the use of 18O-labeled water
experiment to probe the intermediacy of a high-valent Mn-oxo species in
the catalytic epoxidation of olefins by 1 and H2O2. (B) A reaction scheme
showing the source of oxygen found in epoxide product.
the same amount of 18O derived from the Cumyl-18O18OH oxidant
(Figures S8 and S9 in SI), demonstrating that the source of oxygen
atom in the products was the cumyl hydroperoxide oxidant, not
molecular oxygen (Scheme 3B).
Consistent with the experimental results, density functional theory
(DFT) calculations on the formation of Mn(V)-oxo complex (6) from
its precursor, Mn(III)-OOH complex (5), revealed that the
conversion of 5 to 6 occurs via a heterolytic O-O bond cleavage step
(Figures 2 and 3; see also Tables S5 and S6 in SI). The difference
between the ground state of Mn(III)-OOH in quintet spin state and
the triplet state is 7.0 kcal mol-1, which is consistent with the previous
theoretical and experimental results of [(TMC)Mn(III)-OOH]2+
(TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetra-decane).20
During the O-O bond elongation, a spin inversion occurs that leads the
reaction to occur on a triplet transition state (3TS56); thus, the O-O
bond cleavage shows two-state reactivity. The spin of OH group in the
Scheme 2. (A) A proposed mechanism for the formation of metal-oxo
intermediates in the reaction of a nonheme metal(II) complex and H2O2.
(B) Heterolytic and homolytic O-O bond cleavage mechanisms in the
presence and absence of H2SO4, respectively, in the reaction of 1 and
ROOH.
To support the intermediacy of a high-valent Mn-oxo species in
the catalytic epoxidation reactions, we carried out an 18O-labeled water
experiment in the epoxidation of styrene by 1 and H2O2 in the presence
of H2SO4 (Scheme 3A, pathways a and c).4c,10b,12a,19 In some cases,
although a high-valent metal-oxo species is generated as an epoxidizing
intermediate, we would not observe 18O-incorporation from H2 O
18
into the epoxide product due to a slow 18O-exchange between a metal-
18
oxo species and H2 O (Scheme 3A, competition between pathways a
and b).4c,10b,19 In the present study, a significant amount of 18O-
18
incorporation from H2 O into the styrene oxide was observed in the
epoxidation of styrene by 1 and H2O2 in the presence of H2SO4 (~30%
18
18
based on 95% O-enriched H2 O) (Figure S8 in SI), demonstrating
unambiguously that a high-valent Mn-oxo species was indeed formed
as an epoxidizing intermediate in the reaction of 1 and H2O2 in the
presence of H2SO4. This result is in sharp contrast to the previous
reports in the oxidation of organic substrates by H2O2 catalyzed by
nonheme manganese complexes in the presence of excess amounts of
carboxylic acids; no 18O-incorporation from H2 O into the products in
18
Figure 2. Energy profiles (in kcal mol-1) for the conversion of
Mn(III)(OOH) (5) to Mn(V)-Oxo (6). Energies were calculated at the
18
the latter reactions was ascribed to the blocking of H2 O coordination
–
to the Mn site by the carboxylic acids.4c,5c In a separate study, when 18O-
labeled cumyl hydroperoxide (Cumyl-18O18OH) was used as a
terminal oxidant, the epoxide and cumyl alcohol products contained
level of UB3LYP/def2-TZVPP//TZVP(MnOOH, N, HSO4 ), 6-
31G*(C and H in the nonheme ligand). Zero-point energies (ZPE) and
solvation were taken into account.
5
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 3. Key geometric information of the transformation 5 to 6. Values outside of parentheses are the triplet ones and values inside of parenthesis are
the quintet ones. Length is in Å unit and imaginary frequency is in cm-1 unit. Hydrogen atoms in the ligand are omitted for clarity. Calculations were
done at the UB3LYP/B1 level in solvent.
Mn-O-OH moiety is nearly zero (-0.07) (Table S6 in SI) on 3TS56, and
EXPERIMENTAL SECTION
–
3
the hydrogen-removed SO4 moiety contains no spin on TS56 either,
thus, O-O cleavage is heterolytic. The nascent manganese-oxo species
36 lies 1.7 kcal mol-1 lower than 55 and is a Mn(V)-oxo species.
Materials. All chemicals were purchased from Aldrich, Alfa Aesar, and
TCI with the maximum purity available, and used as received unless
otherwise indicated. Solvents were dried according to published
procedures and distilled under argon prior to use.21 All reactions were
performed under an Ar atmosphere using dried solvent and standard
CONCLUSION
A large number of reports have been published using carboxylic acids
as additives to improve the catalytic activity and enantioselectivity of
metal complexes in the (asymmetric) epoxidation of olefins by
aqueous H2O2.3-8 In the present study, we have reported an unexpected
novel effect of sulfuric acid in the catalytic (asymmetric) epoxidation
of olefins by aqueous H2O2 catalyzed by a nonheme manganese
complex bearing a tetradentate N4 ligand; the product yields and ee
Schlenk techniques unless otherwise noted. H2 O (95% 18O-enriched)
18
and 18O2 (98% 18O-enriched) were purchased from ICON Services Inc.
(Summit, NJ, USA). Cumyl-18O18OH (90% 18O-enriched) was
synthesized by reacting cumene and 18O2 in hexane at 85 °C according
to literature methods.22 m-CPBA (77%) was obtained from Aldrich
and purified by washing with phosphate buffer (pH 7.2) and
recrystallized from n-hexane/ether to remove the free carboxylic acid.
Final purity was >98%. Ligands, (R,R)-MCP, (R,R)-P-MCP, and
(R,R)-PDP, and their manganese complexes, MnII(MCP)(OTf)2,
MnII(P-MCP)(OTf)2, and MnII(PDP)(OTf)2 were prepared according
to the known methods.5a,17
2–
values were exceedingly high when both the proton and SO4 anion
were present in the catalytic reactions. The role(s) of H2SO4 was
proposed to facilitate the formation of a high-valent Mn-oxo species via
heterolytic O-O bond cleavage of a presumed Mn(III)-OOH
precursor and to increase the oxidizing power and enantioselectivity of
the Mn-oxo oxidant in olefin epoxidation reactions. The involvement
of the Mn-oxo species as an epoxidizing intermediate, which was
formed via O-O bond heterolysis in the presence of protons, was
evidenced experimentally by carrying out isotopically labeled water
experiments. In addition, there should be a proton effect on the
increase of the reactivity of the Mn-oxo species in the epoxidation of
olefins, as we have demonstrated in our previous studies on the effects
of Lewis and Brønsted acids on the oxidation of organic substrates by
nonheme iron- and manganese-oxo complexes.12a,13 We have also
shown that the enantioselectivity increased dramatically by the
Synthesis of Dbp-MCP Ligand and Its Mn(II) Complex. Dbp-MCP
ligand was prepared by introducing a 3,5-di-tert-butylbenzene group
into the 2-pyridinylmethyl positions of (R,R)-MCP (Figure S2 in SI).5a
A solution of ligand (1.46 g, 5.0 mmol; Figure S2 in SI, ligand a) in Et2O
was added dropwise to a vigorously stirred Grignard reagent (50 mmol)
in Et2O (20 mL) at room temperature and the reaction mixture was
stirred for 24 h. Then, saturated NH4Cl was added to quench the
reaction, and the organic phase was dried over anhydrous Na2SO4 and
purified by column chromatography on silica gel (petroleum
ether/EtOAc = 3:1) to afford the corresponding ligand (Figure S2 in
SI, ligand b) with 70% isolated yield. To a solution of ligand b (0.50
mmol) in THF (15 mL) was added NaH (ca. 60% in oil, 60 mg, 2.5
2–
presence of SO4 anion in the asymmetric epoxidation reactions.
Future studies will be focused on understanding the exact role of the
o
mmol) at 0 C. After stirring for 1 h, CH3I (2.1 mmol) was added to
2–
SO4 anion in increasing the enantioselectivity of the manganese
the resulting solution, and the reaction solution was stirred for 4 h. The
reaction mixture was quenched by distilled water and extracted with
CH2Cl2. The organic phase was dried over anhydrous Na2SO4. The
crude product was purified by chromatography on silica gel
catalyst, by synthesizing a manganese complex coordinating a sulfate
anion and using it directly in stoichiometric asymmetric epoxidation
reactions.
6
ACS Paragon Plus Environment

Page 7 of 10
Journal of the American Chemical Society
1
2
3
(petroleum ether/EtOAc = 3:1) to afford the ligand Dbp-MCP with mg/mL in CH3CN) were added to a Schlenk tube in CH3CN (1.0 mL).
4
5
6
7
8
9
84% isolated yield (0.29 g) (see Figure S2 in SI).
Then, 1.5 equiv of 50% H2O2 (diluted in 0.50 mL of CH3CN) was
added dropwise via a syringe pump over 1 h. After the reaction mixture
was stirred for the given time at –20 C, the reaction solution was
subjected to silicon column or GC to determine the product yield. The
ee values were determined by GC or HPLC equipped with chiral
columns.
MnII(Dbp-MCP)(OTf)2 (1) was prepared by adding Mn(CF3SO3)2
(0.10 mmol) to a solution of Dbp-MCP (0.10 mmol) under an Ar
atmosphere in CH3CN (1.0 mL). The reaction mixture was stirred for
1 day and diethyl ether was carefully layered on the solution over 2 days.
The off-white crystals was isolated and washed with cold ether.
o
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Gram-scale Reaction for the Asymmetric Epoxidation of Chalcone by
1. Chalcone (1.0 g, 4.8 mmol), 1 (0.20 mol%), and H2SO4 (1.0 mol%)
were added into a Schlenk tube containing 20 mL CH3CN, and the
resulting mixture was cooled to –20 oC. Then, 50% H2O2 (1.5 equiv to
substrate) was added dropwise over a period of 1 h via a syringe pump.
The isolated yield was 93% and the ee value, which was determined by
HPLC equipped with a Daicel OD-H, was 97%.
Dbp-MCP: [α]2D0 = −78.1 (c = 0.1, CHCl3); H NMR (400 MHz,
1
CDCl3) in ppm: δ = 8.48 (d, J = 4.2 Hz, 2H), 8.06 (d, J = 7.9 Hz, 2H),
7.79 (t, J = 7.6 Hz, 2H), 7.28 (s, 4H), 7.23 (s, 2H), 7.16-7.10 (m, 2H),
4.86 (s, 2H), 2.29 (d, J = 7.9 Hz, 2H), 2.18 (s, 6H), 1.86 (d, J = 11.6
Hz, 2H), 1.46 (s, 2H), 1.23 (s, 36H), 1.00 (d, J = 8.0 Hz, 2H), 0.65 (t,
J = 9.2 Hz, 2H). 13C NMR (100 MHz, CDCl3) in ppm: δ= 164.7, 150.3,
148.9, 139.5, 136.5, 123.6, 121.8, 121.7, 121.0, 77.2, 76.0, 59.2, 34.8,
31.4, 25.3, 24.2. Dbp-MCP ligand: HRMS calcd. for [Dbp-MCP+H]+:
701.5517, found: 701.5514. MnII(Dbp-MCP)(OTf)2 (1): HRMS
calcd. for [MnII(Dbp-MCP)(OTf)]+: 904.4332, found: 904.4325.
Anal. Calcd. for C50H68F6MnN4O6S2∙H2O: C 56.01, H 6.58, N 5.23.
found C 55.93, H 6.65, N 5.18.
Instrumentation. 1H and 13C NMR spectra were recorded on a Bruker
AVANCE III 400 MHz spectrometer. All NMR spectra were recorded
at room temperature and were indirectly referenced to TMS using
residual solvent signals as internal standards. High resolution mass
spectra (HRMS) were obtained on a Bruker Daltonics micrOTOF-Q
IITM mass spectrometer with an ESI source. Elemental analyses were
conducted with a Vario EL cube Elemental analyzer. Product analysis
was performed with Agilent Technologies 6890N gas chromatograph
(HP-5 column, 30 m × 0.32 mm × 0.25 μm film thickness) with a flame
ionization detector and Thermo Finnigan (Austin, Texas, USA)
FOCUS DSQ (dual stage quadrupole) mass spectrometer interfaced
with Finnigan FOCUS gas chromatograph (GC-MS). High
Performance Liquid Chromatography (HPLC) analysis was
performed on Waters-Breeze (2487 Dual λ Absorbance Detector and
1525 Binary HPLC Pump) or DIOMEX Pump Series P580 equipped
with a variable wavelength UV-200 detector. Chiralpak OD-H, OJ-H
and IC were purchased from Daicel Chemical Industries, LTD. HPLC
equipped with SunFire C18 5μm (4.6 mm × 25 mm column) was also
used. Column chromatography was generally performed on silica gel
(200 – 300 mesh) and TLC inspections were on silica gel GF254 plates.
Decayed Products of Cumyl Hydroperoxide in Catalytic Reactions.
The products obtained in the catalytic oxidation of chalcone (0.20 M)
by 1 (2.0 mM) and cumyl hydroperoxide (20 mM) in the absence and
presence of H2SO4 (10 mM) at room temperature were analyzed by
HPLC equipped with SunFire C18 5μm (4.6 mm × 25 mm column).
Water and methanol were used as mobile phase. In the presence of
H2SO4 (10 mM), cumyl alcohol (2-phenylpropan-2-ol) was formed as
a sole product with >99% yield based on the amount of cumyl
hydroperoxide used (see Figure S7 in SI), whereas, in the absence of
H2SO4, acetophenone (~90% yield based on the amount of the cumyl
hydroperoxide used) was formed as a major product with a small
amount of cumyl alcohol (~10%).
18O-Labeled Experiments. An acetonitrile solution of H2O2 (40 mM)
was added to a solution containing 1 (2.0 mM), H2SO4 (12 mM),
styrene (2.0 × 102 mM), and H2 O (20 μL) under inert atmosphere in
18
CH3CN at room temperature. The reaction solution was stirred for 1
min at room temperature and then analyzed by GC-MS. The 16O and
18O compositions in styrene oxide were analyzed by comparing the
relative abundances at m/z = 119 for styrene oxide-16O and at m/z =
121 for styrene oxide-18O (Figure S8 in SI).
DFT Calculations. The spin-unrestricted B3LYP functional23 was
employed with two basis sets: (i) The TZVP basis set24a for MnOOH,
N and atoms of sulfuric acid (H2SO4), and 6-31G* basis set for the rest
atoms of the supporting ligand of 2, which was used instead of 1 for
more efficient calculations. This basis set is denoted as B1 and is used
to optimize the transition states and minima; (ii) The Def2-TZVPP
basis set24b for all atoms, denoted as B2, used for single point energy
corrections. Transition states were ascertained by vibrational
frequency analysis to possess only one imaginary frequency. All
optimizations and single point calculations were performed with
solvation included using the self-consistent reaction field (SCRF)
calculations in the conductor-like polarizable continuum model
(CPCM); the dielectric constant corresponding to acetonitrile solvent
(ε = 35.688) was used. DFT calculations were performed with the
Gaussian 09 suite of quantum chemical packages.25
Catalytic Epoxidation of Olefins by 1. Reaction conditions for the
catalytic epoxidation of simple olefins are as follows: substrate (0.25
mmol), MnII(Dbp-MCP)(OTf)2 (1) (1.5 mL, 1.3 × 10−3 mmol, 0.87
mg/mL in CH3CN), and H2SO4 (0.30 mL, 7.5 × 10−3 mmol, 2.45
mg/mL in CH3CN) were added to a Schlenk tube in CH3CN (1.0 mL).
Then, 1.5 equiv of 50% H2O2 (diluted in 0.50 mL of CH3CN) was
added dropwise via a syringe pump over 1 h. After the reaction mixture
o
was stirred for the given time at –20 C, the reaction solution was
subjected to GC analysis to determine the product yield.
Asymmetric Epoxidation of Olefins by 1. Reaction conditions for the
asymmetric epoxidation of olefins are as follows: substrate (0.25
mmol), MnII(Dbp-MCP)(OTf)2 (1) (0.60 mL, 5.0 × 10−4 mmol, 0.87
mg/mL in CH3CN), and H2SO4 (0.10 mL, 2.5 × 10−3 mmol, 2.45
ASSOCIATED CONTENT
Supporting Information. The Supporting Information is available free of
charge on the ACS Publications website at DOI: 10.1021/jacs.5b11579.
7
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 10
1
2
3
4
2011, 353, 885. (c) Lyakin, O. Y.; Ottenbacher, R. V.; Bryliakov, K. P.; Talsi, E.
P. ACS Catal. 2012, 2, 1196.
Full crystallographic data are also available from the Cambridge
Crystallographic Data Centre (CCDC-917216).
(7) (a) Mas-Ballesté, R.; Que, L., Jr. J. Am. Chem. Soc. 2007, 129, 15964. (b)
Wang, Y.; Janardanan, D.; Usharani, D.; Han, K.; Que, L., Jr.; Shaik, S. ACS
Catal. 2013, 3, 1334. (c) Oloo, W. N.; Meier, K. K.; Wang, Y.; Shaik, S.; Münck,
E.; Que, L., Jr. Nat. Commun. 2014, 5, 3046.
5
6
7
8
Figures S1 – S9, Tables S1 – S6 and the coordinates of DFT calculated
structures (PDF). Crystallographic data for MnII(Dbp-MCP)(OTf)2,
compound 1 (CIF).
(8) (a) Francis, M. B.; Jacobsen, E. N. Angew. Chem., Int. Ed. 1999, 38, 937.
(b) Anilkumar, G.; Bitterlich, B.; Gelalcha, F. G.; Tse, M. K.; Beller, M. Chem.
Commun. 2007, 289. (c) Gelalcha, F. G.; Bitterlich, B.; Anilkumar, G.; Tse, M.
K.; Beller, M. Angew. Chem., Int. Ed. 2007, 46, 7293. (d) Gelalcha, F. G.;
Anilkumar, G.; Tse, M. K.; Brückner. A.; Beller, M. Chem.−Eur. J., 2008, 14,
7687. (e) Yeung, H.-L.; Sham, K.-C.; Tsang, C.-S.; Lau, T.-C.; Kwong, H.-L.
Chem. Commun. 2008, 3801. (f) Bruynee, F.; Letondor, C.; Bastürk, B.;
Gualandi, A.; Pordea, A.; Stoeckli-Evans, H.; Neier, R. Adv. Synth. Catal. 2012,
354, 428. (g) Yazerski, V. A.; Orue, A.; Evers, T.; Kleijn, H.; Gebbink, R. J. M.
K. Catal. Sci. Technol. 2013, 3, 2810. (h) Ansari, A.; Kaushik, A.; Rajaraman,
G. J. Am. Chem. Soc. 2013, 135, 4235. (i) Dai, W.; Li, J.; Li, G.; Yang, H.; Wang,
L.; Gao, S. Org. Lett. 2013, 15, 4138. (j) Maity, N. C.; Bera, P. K.; Ghosh, D.;
Abdi, S. H. R.; Kureshy, R. I.; Khan, N. H.; Bajaj, H. C.; Suresh, E. Catal. Sci.
Technol. 2014, 4, 208. (k) Dai, W.; Li, G.; Chen, B.; Wang, L.; Gao, S. Org. Lett.
2015, 17, 904.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
AUTHOR INFORMATION
Corresponding Author
* E-mail: wwnam@ewha.ac.kr; wsun@licp.cas.cn
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We acknowledge financial support of this work from the National Natural
Science Foundation of China (21473226 and 21133011 to W.S.) and the
NRF of Korea through CRI (NRF-2012R1A3A2048842 to W.N.) and
GRL (NRF-2010-00353 to W.N.).
(9) Cussó, O.; Ribas, X.; Lloret-Fillol, J.; Costas, M. Angew. Chem., Int. Ed.
2015, 54, 2729.
REFERENCES
(10) (a) Prat, I.; Mathieson, J. S.; Güell, M.; Ribas, X.; Luis, J. M.; Cronin, L.;
Costas, M. Nat. Chem. 2011, 3, 788. (b) Ottenbacher, R. V.; Samsonenko, D.
G.; Talsi, E. P.; Bryliakov, K. P. ACS Catal. 2014, 4, 1599. (c) Lyakin, O. Y.;
Zima, A. M.; Samsonenko, D. G.; Bryliakov, K. P.; Talsi, E. P. ACS Catal. 2015,
5, 2702.
(11) (a) van Eldik, R. Coord. Chem. Rev. 2007, 251, 1649. (b) Nam, W.; Han,
H. J.; Oh, S.-Y.; Lee, Y. J.; Choi, M.-H.; Han, S.-Y.; Kim, C.; Woo, S. K.; Shin,
W. J. Am. Chem. Soc. 2000, 122, 8677. (c) Traylor, T. G.; Traylor, P. S. in
Active Oxygen in Biochemistry (Eds.: Valentine, J. S.; Foote, C. S.; Greenberg,
A.; Liebman, J. F.), Blackie Academic and Professional, Chapman & Hall,
London, 1995, pp. 84‒187. (d) Almarsson, O.; Bruice, T. C. J. Am. Chem. Soc.
1995, 117, 4533. (e) Yang, S. J.; Nam, W. Inorg. Chem. 1998, 37, 606.
(12) (a) Nam, W.; Lee, Y.-M.; Fukuzumi, S. Acc. Chem. Res. 2014, 47, 1146.
(b) Chen, Z.; Yin, G. Chem. Soc. Rev. 2015, 44, 1083. (c) Neu, H. M.; Baglia,
R. A.; Goldberg, D. P. Acc. Chem. Res. 2015, 48, 2754.
(13) (a) Chen, J.; Yoon, H.; Lee, Y.-M.; Seo, M. S.; Sarangi, R.; Fukuzumi, S.;
Nam, W. Chem. Sci. 2015, 6, 3624. (b) Park, J.; Lee, Y.-M.; Nam, W.;
Fukuzumi, S. J. Am. Chem. Soc. 2013, 135, 5052. (c) Park, J.; Morimoto, Y.;
Lee, Y.-M.; Nam, W.; Fukuzumi, S. J. Am. Chem. Soc. 2012, 134, 3903. (d)
Park, J.; Lee, Y.-M.; Ohkubo, K.; Nam, W.; Fukuzumi, S. Inorg. Chem. 2015,
54, 5806. (e) Park, J.; Morimoto, Y.; Lee, Y.-M.; Nam, W.; Fukuzumi, S. Inorg.
Chem. 2014, 53, 3618. (f) Yoon, H.; Lee, Y.-M.; Wu, X.; Cho, K.-B.; Sarangi,
R.; Nam, W.; Fukuzumi, S. J. Am. Chem. Soc. 2013, 135, 9186. (g) Chen, J.;
Lee, Y.-M.; Davis, K. M.; Wu, X.; Seo, M. S.; Cho, K.-B.; Yoon, H.; Park, Y. J.;
Fukuzumi, S.; Pushkar, Y. N.; Nam, W. J. Am. Chem. Soc. 2013, 135, 6388. (h)
Zaragoza, J. P. T.; Baglia, R. A.; Siegler, M. A.; Goldberg, D. P. J. Am. Chem.
Soc. 2015, 137, 6531. (i) Baglia, R. A.; Dürr, M.; Ivanović-Burmazović, I.;
Goldberg, D. P. Inorg. Chem. 2014, 53, 5893. (j) Leeladee, P.; Baglia, R. A.;
Prokop, K. A.; Latifi, R.; de Visser, S. P.; Goldberg, D. P. J. Am. Chem. Soc.
2012, 134, 10397.
(14) (a) Chen, Z.; Yang, L.; Choe, C.; Lv, Z.; Yin, G. Chem. Commun. 2015,
51, 1874. (b) Zhang, Z.; Coats, K. L.; Chen, Z.; Hubin, T. J.; Yin, G. Inorg.
Chem. 2014, 53, 11937. (c) Dong, L.; Wang, Y.; Lv, Y.; Chen, Z.; Mei, F.; Xiong,
H.; Yin, G. Inorg. Chem. 2013, 52, 5418. (d) Du, H.; Lo, P.-K.; Hu, Z.; Liang,
H.; Lau, K.-C.; Wang, Y.-N.; Lam, W. W. Y.; Lau, T.-C. Chem. Commun. 2011,
47, 7143. (e) Taktak, S.; Ye, W.; Herrera, A. M.; Rybak-Akimova, E. V. Inorg.
Chem. 2007, 46, 2929. (f) Yiu, S.; Man, W.-L.; Lau, T.-C. J. Am. Chem. Soc.
(1) (a) Lane, B. S.; Burgess, K. Chem. Rev. 2003, 103, 2457. (b) Wong, O.
A.; Shi, Y. Chem. Rev. 2008, 108, 3958. (c) Enthaler, S.; Junge, K.; Beller, M.
Angew. Chem., Int. Ed. 2008, 47, 3317. (d) Que, L., Jr.; Tolman, W. B. Nature
2008, 455, 333. (e) De Faveri, G.; Ilyashenko, G.; Watkinson, M. Chem. Soc.
Rev. 2011, 40, 1722. (f) Darwish, M.; Wills, M. Catal. Sci. Technol. 2012, 2,
243. (g) Srour, H.; Le Maux, P.; Chevance, S.; Simonneaux, G. Coord. Chem.
Rev. 2013, 257, 3030. (h) Gopalaiah, K. Chem. Rev. 2013, 113, 3248. (i) Davis,
R. L.; Stiller, J.; Naicker, T.; Jiang, H.; Jørgensen, K. A. Angew. Chem., Int. Ed.
2014, 53, 7406. (j) Zhu, Y.; Wang, Q.; Cornwall, R. G.; Shi, Y. Chem. Rev. 2014,
114, 8199. (k) Wang, C.; Yamamoto, H. Chem.−Asian J. 2015, 10, 2056.
(2) (a) Fingerhut, A.; Serdyuk, O. V.; Tsogoeva, S. B. Green Chem. 2015,
17, 2042. (b) Oloo, W. N.; Que, L., Jr. Acc. Chem. Res. 2015, 48, 2612. (c)
Cussó, O.; Ribas, X.; Costas, M. Chem. Commun. 2015, 51, 14285. (d) Codola,
Z.; Lloret-Fillol, J.; Costas, M. Prog. Inorg. Chem. 2014, 59, 447. (e) Gelalcha,
F. G. Adv. Synth. Catal. 2014, 356, 261. (f) Bryliakov, K. P.; Talsi, E. P. Coord.
Chem. Rev. 2014, 276, 73. (g) Lyakin, O. Y.; Ottenbacher, R. V.; Bryliakov, K.
P.; Talsi, E. P. Top. Catal. 2013, 56, 939. (h) Talsi, E. P.; Bryliakov, K. P. Coord.
Chem. Rev. 2012, 256, 1418.
(3) White, M. C.; Doyle, A. G.; Jacobsen, E. N. J. Am. Chem. Soc. 2001, 123,
7194.
(4) (a) Gómez, L.; Garcia-Bosch, I.; Company, A.; Sala, X.; Fontrodona, X.;
Ribas, X.; Costas, M. Dalton Trans. 2007, 5539. (b) Garcia-Bosch, I.; Company,
A.; Fontrodona, X.; Ribas, X.; Costas, M. Org. Lett. 2008, 10, 2095. (c) Garcia-
Bosch, I.; Ribas, X.; Costas, M. Adv. Synth. Catal. 2009, 351, 348. (d) Garcia-
Bosch, I.; Gómez, L.; Polo, A.; Ribas, X.; Costas, M. Adv. Synth. Catal. 2012,
354, 65. (e) Cussó, O.; Garcia-Bosch, I.; Ribas, X.; Lloret-Fillol, J.; Costas, M.
J. Am. Chem. Soc. 2013, 135, 14871. (f) Cussó, O.; Garcia-Bosch, I.; Font, D.;
Ribas, X.; Lloret-Fillol, J.; Costas, M. Org. Lett. 2013, 15, 6158.
(5) (a) Wu, M.; Wang, B.; Wang, S.; Xia, C.; Sun, W. Org. Lett. 2009, 11,
3622. (b) Wu, M.; Miao, C.-X.; Wang, S.; Hu, X.; Xia, C.; Kühn, F. E.; Sun, W.
Adv. Synth. Catal. 2011, 353, 3014. (c) Wang, B.; Wang, S.; Xia, C.; Sun, W.
Chem.–Eur. J. 2012, 18, 7332. (d) Wang, B.; Miao, C.; Wang, S.; Xia, C.; Sun,
W. Chem.–Eur. J. 2012, 18, 6750. (e) Wang, X.; Miao, C.; Wang, S.; Xia, C.;
Sun, W. ChemCatChem, 2013, 5, 2489.
(6) (a) Ottenbacher, R. V.; Bryliakov, K. P.; Talsi, E. P. Inorg. Chem. 2010,
49, 8620. (b) Ottenbacher, R. V.; Bryliakov, K. P.; Talsi, E. P. Adv. Synth. Catal.
8
ACS Paragon Plus Environment

Page 9 of 10
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
2008, 130, 10821. (g) Lam, W. W. Y.; Yiu, S.; Lee, J. M. N.; Yau, S. K. Y.; Kwong, (20) So, H.; Park, Y. J.; Cho, K.-B.; Lee, Y.-M.; Seo, M. S.; Cho, J.; Sarangi, R.;
H.-K.; Lau, T.-C.; Liu, D.; Lin, Z. J. Am. Chem. Soc. 2006, 128, 2851. (h) Yiu, Nam, W. J. Am. Chem. Soc. 2014, 136, 12229.
S.-M.; Wu, Z.-B.; Mak, C.-K.; Lau, T.-C. J. Am. Chem. Soc. 2004, 126, 14921.
(21) Armarego, W. L. F.; Chai, C. L. L. Purification of Laboratory Chemicals.
(15) (a) Aldrich-Wright, J. R.; Vagg, R. S.; Williams, P. A. Coord. Chem. Rev. 6th edn, Pergamon Press, Oxford, U.K. 2009.
1997, 166, 361. (b) Knof, U.; von Zelewsky, A. Angew. Chem., Int. Ed. 1999, (22) Finn, M. G.; Sharpless, K. B. J. Am. Chem. Soc. 1991, 113, 113.
38, 302.
(23) (a) Becke, A. D. J. Chem. Phys. 1992, 96, 2155. (b) Becke, A. D. J. Chem.
(16) CCDC-917216 contains the supplementary crystallographic data for Phys. 1992, 97, 9173. (c) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (d) Lee,
this paper. These data can be obtained free of charge from the Cambridge C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.
(24) (a) Schaefer, A.; Horn, H.; Ahlrichs, R. J. Chem. Phys. 1992, 97, 2571.
(17) (a) Murphy, A.; Dubois, G.; Stack, T. D. P. J. Am. Chem. Soc. 2003, 125, (b) Schaefer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. 1994, 100, 5829. (c)
5250. (b) Murphy, A.; Pace, A.; Stack, T. D. P. Org. Lett. 2004, 6, 3119. (c) Weigend, F.; Ahlrichs, R. Phys. Chem. Chem. Phys. 2005, 7, 3297.
Murphy, A.; Stack, T. D. P. J. Mol. Catal. A: Chem. 2006, 251, 78. (d) Chen, M. (25) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
S.; White, M. C. Science 2007, 318, 783.
Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.;
(18) (a) Tano, T.; Sugimoto, H.; Fujieda, N.; Itoh, S. Eur. J. Inorg. Chem. Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.;
2012, 4099. (b) Coggins, M. K.; Martin-Diaconescu, V.; DeBeer, S.; Kovacs, J. Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
A. J. Am. Chem. Soc. 2013, 135, 4260. (c) Hong, S.; Lee, Y.-M.; Cho, K.-B.; Seo, Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven,
M. S.; Song, D.; Yoon, J.; Garcia-Serres, R.; Clémancey, M.; Ogura, T.; Shin, T.; Montgomery, J. A. Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.;
W.; Latour, J.-M.; Nam, W. Chem. Sci. 2014, 5, 156. (d) Ma, L.; Pan, Y.; Man, Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.;
W.-L.; Kwong, H.-K.; Lam, W. W. Y.; Chen, G.; Lau, K.-C.; Lau, T.-C. J. Am. Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.;
Chem. Soc. 2014, 136, 7680. (e) Nam, W.; Han, H. J.; Oh, S.-Y.; Lee, Y. J.; Choi, Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo,
M.-H.; Han, S.-Y.; Kim, C.; Woo, S. K.; Shin, W. J. Am. Chem. Soc. 2000, 122, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
8677.
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.;
(19) (a) Seo, M. S.; In, J.-H.; Kim, S. O.; Oh, N. Y.; Hong, J.; Kim, J.; Que, L., Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.;
Jr.; Nam, W. Angew. Chem., Int. Ed. 2004, 43, 2417. (b) Meunier, B.; Bernadou, Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.
J. Top. Catal. 2002, 21, 47. (c) Lee, K. A.; Nam, W. J. Am. Chem. Soc. 1997, Gaussian 09, revision D.01; Gaussian, Inc.: Wallingford, CT, 2009.
119, 1916. (d) Bernadou, J.; Fabiano, A.-S.; Robert, A.; Meunier, B. J. Am.
Chem. Soc. 1994, 116, 9375. (e) Nam, W.; Valentine, J. S. J. Am. Chem. Soc.
1993, 115, 1772.
9
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 10 of 10
1
2
3
4
Table of Contents Graphic
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
10
ACS Paragon Plus Environment