Highly efficient Ir-catalyzed asymmetric hydrogenation of benzoxazinones and derivatives with a Br?nsted acid cocatalyst

Article abstract of DOI:10.1039/c8sc05797d

The Ir-catalyzed highly efficient asymmetric hydrogenation of benzoxazinones and derivatives was successfully developed with N-methylated ZhaoPhos L5 as the ligand, which may display a new activation mode with a single anion-binding interaction among the

Full text of DOI:10.1039/c8sc05797d

Chemical
Science
View Article Online
View Journal
EDGE ARTICLE
Highly efficient Ir-catalyzed asymmetric
hydrogenation of benzoxazinones and derivatives
Cite this: DOI: 10.1039/c8sc05797d
with a Brønsted acid cocatalyst†
Zhengyu Han,a Gang Liu,a Rui Wang,a Xiu-Qin Dong
All publication charges for this article
have been paid for by the Royal Society
of Chemistry
a
ab
*
*
and Xumu Zhang
The Ir-catalyzed highly efficient asymmetric hydrogenation of benzoxazinones and derivatives was
successfully developed with N-methylated ZhaoPhos L5 as the ligand, which may display a new
activation mode with a single anion-binding interaction among the substrate, cocatalyst Brønsted acid
and ligand. This synthetic approach afforded a series of chiral dihydrobenzoxazinones and derivatives
with excellent results (>99% conversion, 88–96% yields, 91–>99% ee, up to 40 500 TON). A key to
success is the utilization of a strong Brønsted acid as the cocatalyst, such as hydrochloric acid, to form
a possible single anion-binding interaction with the substrate and catalyst, which greatly contributed to
the improvement of reactivity and enantioselectivity. Importantly, a creative and efficient synthetic route
was developed to construct the important intermediate for the potential IgE/IgG receptor modulator
through our catalytic methodology system.
Received 28th December 2018
Accepted 3rd March 2019
DOI: 10.1039/c8sc05797d
rsc.li/chemical-science
hydrogenation of benzoxazinones via
a relay iron/chiral
Introduction
Brønsted acid catalysis with good to excellent enantioselectivi-
ties.7e However, the reactivity of most catalytic systems is not
very high with less than 2000 TON (turnover numbers). It is well
known that the substrate activation strategy with noncovalent
interactions has been widely used in the eld of asymmetric
organic catalysis, which played an important role in greatly
improving the reactivity and stereoselectivity.8,9 The thiourea
motif as the hydrogen bonding donor can recognize suitable
guest molecules, which usually works on the direct activation of
neutral substrates bearing hydrogen bonding acceptor
groups.10 Compared with the hydrogen bonding interaction, the
anion-binding ion-pairing strategy did not draw much attention
until recent development in organocatalysis.9b–d,11 In 2013, our
Chiral dihydrobenzoxazinones and derivatives are important
and unique building blocks in the biologically active molecule
discovery process (Fig. 1).1 Chiral dihydrobenzoxazinone deriv-
atives A are potential IgE/IgG receptor modulators for the
treatment of autoimmune diseases.2 Chiral 1,2,3,4-tetrahy-
droquinoxaline compounds B–C and 2,3-dihydro-3,8-diphe-
nylbenzo[1,4]oxazine D are disclosed as active and promising
cholesteryl ester transfer protein inhibitors.3–6
Taking into account the growing importance of these
compounds, great attention had been paid to the development
of efficient enantioselective synthetic methodologies. Among
various synthetic approaches for the construction of these
chiral dihydrobenzoxazinones and derivatives,7 the direct
asymmetric hydrogenation of prochiral benzoxazinones and
derivatives was paid great attention with the advantages of high
atom economy, a relatively simple procedure and easy work-up.
Zhou and co-workers realized Ru-catalyzed biomimetic asym-
metric hydrogenation of benzoxazinones and derivatives in the
presence of chiral phosphoric acid through the NAD(P)H
mode.7c In 2015, Beller and co-workers described asymmetric
aKey Laboratory of Biomedical Polymers, Engineering Research Center of Organosilicon
Compounds & Materials, Ministry of Education, College of Chemistry and Molecular
Sciences, Wuhan University, Wuhan, Hubei, 430072, P. R. China. E-mail:
xiuqindong@whu.edu.cn
bDepartment of Chemistry, Shenzhen Grubbs Institute, Southern University of Science
and Technology, Shenzhen, Guangdong, 518055, P. R. China. E-mail: zhangxm@sustc.
edu.cn
Fig. 1 Selected examples of bioactive compounds containing the
† Electronic supplementary information (ESI) available: See DOI:
10.1039/c8sc05797d
framework of chiral dihydrobenzoxazinones and derivatives.
This journal is © The Royal Society of Chemistry 2019
Chem. Sci.

View Article Online
Chemical Science
Edge Article
Table 1 Optimization of reaction conditions for asymmetric hydro-
genation of 3-phenyl-2H-benzo[b][1,4]oxazin-2-one (1a)a
group successfully developed a series of bifunctional bisphos-
phine–thiourea ligands, which extended the powerful
hydrogen-bonding and anion-binding activation strategy in
organocatalysis to transition-metal-catalyzed asymmetric
hydrogenation, and a variety of functionalized substrates had
been hydrogenated well.12 Herein, we successfully realized Ir-
catalyzed highly enantioselective hydrogenation of prochiral
benzoxazinones and derivatives using N-methylated ZhaoPhos
L5 as the ligand, which may exhibit a single anion-binding
activation mode among the substrate, cocatalyst Brønsted acid
hydrochloric acid and ligand. A variety of hydrogenation prod-
ucts, chiral dihydrobenzoxazinones and derivatives, can be
obtained with excellent results (>99% conversion, 88–96%
yields, 91–>99% ee), and our catalytic system displayed
extremely high activity with up to 40 500 TON (Scheme 1). In
addition, a highly efficient synthetic route was successfully
developed to prepare the important intermediate for the
potential IgE/IgG receptor modulator with our asymmetric
hydrogenation methodology as the key reaction step.
Entry
Metal precursor
Solvent
Conv.b (%)
eec (%)
1
2
3
4
5
6
7
8
9
Rh(NBD)2BF4
[Rh(COD)Cl]2
[Ir(COD)Cl]2
[Ir(COD)Cl]2
[Ir(COD)Cl]2
[Ir(COD)Cl]2
[Ir(COD)Cl]2
[Ir(COD)Cl]2
[Ir(COD)Cl]2
Toluene
Toluene
Toluene
CH2Cl2
THF
1,4-Dioxane
CHCl3
63
71
90
97
>99
60
95
95
55
82
64
94
93
98
95
95
93
94
Ethyl acetate
CH3CN
a
Reaction conditions: 0.05 mmol 1a in 1.0 mL solvent, S/C ¼ 100, 45
b
atm H2, 1.0 equiv. HCl (4 M in dioxane), 25 ꢀC, 24 h. Determined by
1H NMR analysis. Determined by HPLC analysis using a chiral
c
stationary phase.
Results and discussion
Inspired by the powerful performance of the ligand ZhaoPhos
L1 in Rh-catalyzed asymmetric hydrogenation of iminium salts,
isoquinoline hydrochloride and N-unprotected indoles,12b,d,e,g
we initially investigated the hydrogenation of model substrate
>99% conversions, 93–98% ee, Table 1, entries 4–9). And the
hydrogenation product 2a can be obtained with the best result
in THF (>99% conversion, 98% ee, Table 1, entry 5).
A series of bisphosphine–(thio)urea ligands (Fig. 2) were
then applied to this Ir-catalyzed asymmetric hydrogenation of 3-
phenyl-2H-benzo[b][1,4]oxazin-2-one 1a in THF. Full conver-
sions and excellent enantioselectivities can be obtained in the
presence of ZhaoPhos L1 and N-methylated ZhaoPhos L5, and
N-methylated ZhaoPhos L5 provided higher enantioselectivity
(>99% conversion, 98–99% ee, Table 2, entries 1 and 5). The
ligand L2 containing one triuoromethyl group and ligand L3
without any triuoromethyl group on the phenyl ring provided
poor conversions and excellent enantioselectivities (33–45%
conversions, 97% ee, Table 2, entries 2 and 3). The ligand L4
displayed very poor reactivity and enantioselectivity, which
changed the thiourea motif to the urea motif (11% conversion,
13% ee, Table 2, entry 4). In addition, no reaction was observed
in the presence of ligand L6 without the thiourea motif (Table 2,
entry 6). This indicated that the thiourea motif may make
3-phenyl-2H-benzo[b][1,4]oxazin-2-one
1a
catalyzed
by
Rh(NBD)2BF4/ZhaoPhos L1 in toluene with 1.0 equiv. HCl (4 M
in dioxane) as the additive, affording the hydrogenation product
2a with 63% conversion and 82% ee (Table 1, entry 1). Other
metal precursors were then screened, and [Ir(COD)Cl]2 was
proved to be the best with 90% conversion and 94% ee (Table 1,
entry 3). Solvents played an important role in asymmetric
reactions, and always affected the reactivity and enantiose-
lectivity. This asymmetric hydrogenation was then conducted in
different solvents. Moderate to high conversions and excellent
enantioselectivities were observed in CH2Cl2, tetrahydrofuran
(THF), 1,4-dioxane, CHCl3, ethyl acetate (EA) and CH3CN (55–
Scheme 1 Ir-catalyzed asymmetric hydrogenation of benzoxazinones
and derivatives, and the possible activation mode.
Fig. 2 The structure of bisphosphine ligands.
Chem. Sci.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Edge Article
Chemical Science
Table 2 Screening a series of bisphosphine–(thio)urea ligands for Table 3 Investigation of the effect of the Brønsted acid cocatalysta
asymmetric hydrogenation of 3-phenyl-2H-benzo[b][1,4]oxazin-2-
one (1a)a
x
Entry Acid
pKa (in H2O)b (equiv.) Conv.c (%) eed (%)
Entry
Ligand
Conv.b (%)
eec (%)
1
2
3
4
5
6
7
8
CF3SO3H
CF3COOH
H3PO4
HCOOH
CH3COOH 4.76
HCl
HCl
HCl
HCl
HCl
HCl
HCl
ꢁ14
1.0
1.0
1.0
1.0
1.0
2.0
1.0
0.5
0.1
0.01
0
>99
>99
95
30
21
>99
>99
>99
>99
>99
NR
>99
99
84
81
58
57
99
99
99
99
95
NA
99
1
2
3
4
ZhaoPhos L1
L2
L3
L4
L5
L6
>99
45
33
98
97
97
13
99
NA
98
99
ꢁ0.25
2.12
3.77
11
5
>99
NR
65
ꢁ8
ꢁ8
ꢁ8
ꢁ8
ꢁ8
ꢁ8
ꢁ8
6
7d
8d
ZhaoPhos L1
L5
>99
9
10
11
12e
a
Reaction conditions: 0.05 mmol 1a in 1.0 mL THF, S/C ¼ 100, 45 atm
H2, 1.0 equiv. HCl (4 M in dioxane), 25 ꢀC, 24 h. Determined by 1H
b
1.0
c
NMR analysis. Determined by HPLC with a chiral stationary phase.
d
a
30 atm H2, S/C ¼ 500, 16 h.
Reaction conditions: 0.05 mmol substrate 1a in 1.0 mL THF, 30 atm
b
H2, 25 ꢀC; S/C ¼ 100, 16 h. The pKa data are available from Evans's
pKa table. Conversion was determined by 1H NMR analysis. ee was
c
d
e
determined by HPLC with a chiral stationary phase. S/C ¼ 1000. NR
a great contribution to activate our substrate through anion-
binding interactions. When the catalyst loading is decreased
from 1.0 mol% to 0.2 mol%, full conversion and excellent
enantioselectivity can be obtained with ligand L5 (>99%
conversion, 99% ee, Table 2, entry 8). Interestingly, it is better
than ZhaoPhos L1 (65% conversion, 98% ee, Table 2, entry 7 vs.
entry 8). It is possible that a single anion-binding interaction in
a precise position is sufficient in this asymmetric reaction,
which is different from previous reports.11,12b,d,e,g
is no reaction, NA is not available.
formation of anion-binding activation among the substrate,
Brønsted acid and ligand. To our delight, this asymmetric
hydrogenation still proceeded smoothly with the same result
even when catalyzed by only the 0.1 mol% [Ir(COD)Cl]2/ligand
L5 catalyst with 1.0 equiv. HCl (4 M in dioxane) (Table 3, entry
12).
A series of representative Brønsted acids were then deeply
inspected in this Ir/ligand L5-catalyzed asymmetric hydroge-
nation of 3-phenyl-2H-benzo[b][1,4]oxazin-2-one 1a, and we
found that there is a signicant correlation between the reac-
tivity, enantioselectivity and acid strength of the Brønsted acid.
When hydrochloric acid, HCl (4 M in dioxane), was switched to
We then continued to investigate the substrate generality of
this Ir-catalyzed asymmetric hydrogenation of prochiral ben-
zoxazinones using N-methylated ZhaoPhos L5 as the ligand.
These reaction results are summarized in Table 4. A series of
prochiral benzoxazinones were hydrogenated smoothly in this
catalytic system to prepare various chiral dihydrobenzox-
azinones with excellent results (>99% conversion, 88–96%
yields, 91–>99% ee). The benzoxazinone substrates with
different substituents on the benzo ring (1b–1e) were hydroge-
nated well with >99% conversion, 93–95% yields and >99% ee.
In addition, regardless of the position or electronic properties of
the substituents on the phenyl ring of the benzoxazinone
substrates (1f–1j), the corresponding hydrogenation products
(2f–2j) were obtained with 88–95% yields and >99% ee. The
naphthyl substituted substrates with bulky steric hindrance
(1k–1l) were obtained smoothly with excellent results (91–95%
yields, 97–>99% ee). It is worth noting that the heteroaromatic
substrate 3-(thiophen-3-yl)-2H-benzo[b][1,4]oxazin-2-one (1m)
was well tolerated to produce the desired product (2m) with
96% yield and >99% ee. Moreover, the alkyl substrates (1n–1p)
were hydrogenated smoothly with excellent results (>99%
conversion, 91–95% yields, and 91–98% ee).
a
strong acid, CF3SO3H, this hydrogenation proceeded
smoothly to provide the same result with full conversion and
99% ee (Table 3, entries 1 and 7). CF3COOH and H3PO4 gave
high conversions and good enantioselectivities (95–>99%
conversions, 81–84% ee, Table 3, entries 2 and 3). As expected,
the weaker acids HCOOH and AcOH afforded poor reactivities
and enantioselectivities (21–30% conversions, 57–58% ee, Table
3, entries 4–5). In addition, the amount of Brønsted acid HCl
was further investigated in this asymmetric hydrogenation. We
found that the amount of HCl had little effect on the reactivity
and enantioselectivity, and the reaction results remained
excellent, when the amount of HCl was gradually reduced from
2.0 equiv. to 0.01 equiv. (>99% conversion, 95–99% ee, Table 3,
entries 6–10). However, no reaction was observed in the absence
of the cocatalyst HCl (Table 3, entry 11), which showed that HCl
was involved in this transformation with great importance.
These results also displayed that the acid strength of the
Brønsted acid cocatalyst is very important to achieve excellent
results in this asymmetric hydrogenation, which may affect the
Encouraged by the success of the Ir/N-methylated ZhaoPhos
L5-catalyzed asymmetric hydrogenation of prochiral benzox-
azinones, the asymmetric hydrogenation of several
This journal is © The Royal Society of Chemistry 2019
Chem. Sci.

View Article Online
Chemical Science
Edge Article
Table 4 Substrate scope study of Ir-catalyzed asymmetric hydroge- Table 5 Substrate scope study for Ir-catalyzed asymmetric hydro-
nation of benzoxazinonesa
genation of quinoxalinones and 4-phenyl-1H-benzo[b][1,4]diazepin-
2(3H)-onea
Entry
R
R0
n
Sub. Prod. Conv.b (%) Yieldc (%) eed (%)
1
2
3
H
H
Ph
Et
0
0
0
1
1
3a
3b
3c
3d
3d
4a
4b
4c
4d
4d
>99
>99
>99
>99
>99
90
91
91
91
93
>99
99
98
>99
>99
Me Ph
H
H
4
Ph
Ph
5e
a
Unless otherwise noted, all reactions were carried out with a [Ir(COD)
Cl]2/ligand L5/substrate 3 (0.05 mmol) ratio of 0.5 : 1.1 : 1000 in 1.0 mL
THF at room temperature under 30 atm H2 for 16 h. b Determined by 1H
c
d
NMR analysis. Isolated yield. Determined by HPLC analysis using
a chiral stationary phase. e S/C ¼ 5000.
asymmetric hydrogenation with very low catalyst loading under
40 atm H2. These results are summarized in Table 6. The
hydrogenation product 2a can be obtained with full conversion,
91% yield and 99% ee when the catalyst loading is decreased
from 0.1 mol% (S/C ¼ 1000) to 0.01 mol% (S/C ¼ 10 000) (Table
6, entries 1 and 2). Our catalytic system still exhibited high
activity and excellent enantioselectivity with further diminution
of the catalyst loading to 0.0025 mol% (S/C ¼ 40 000), affording
the product 2a with excellent results (>99% conversion, 89%
yield and 99% ee, Table 6, entry 3). In addition, good conversion
and excellent enantioselectivity can be obtained even in the
presence of 0.002 mol% (S/C ¼ 50 000) catalyst (81% conver-
sion, TON ¼ 40 500, 72% yield, 99% ee, Table 6, entry 4).
The deuterium-labeling experiment was conducted to verify
the hydrogen atom source of the hydrogenation product dihy-
drobenzoxazinone. As shown in Scheme 2, the asymmetric
hydrogenation of 3-phenyl-2H-benzo[b][1,4]oxazin-2-one 1a
a
Unless otherwise noted, all reactions were carried out with a [Ir(COD)
Cl]2/ligand L5/substrate 1 (0.05 mmol) ratio of 0.5 : 1.1 : 1000 in 1.0 mL
THF with 1.0 equiv. HCl (4 M in dioxane) at room temperature under 30
atm H2 for 16 h. Conversion was determined by 1H NMR analysis, ee was
determined by HPLC with a chiral stationary phase, and the yield was
isolated yield.
quinoxalinones was subsequently explored. As shown in Table
5, the asymmetric hydrogenation of quinoxalinones (3a–3c)
proceeded efficiently, affording the desired products (4a–4c)
with >99% conversion, 90–91% yields and 98–>99% ee (Table 5,
entries 1–3). To our delight, the hydrogenation of benzo-seven-
membered cyclic imine 4-phenyl-1H-benzo[b][1,4]diazepin-
2(3H)-one (3d) proceeded smoothly to obtain the hydrogenation
product (4d) with excellent results (>99% conversion, 91% yield,
>99% ee, Table 5, entry 4). In addition, our catalytic system
displayed extremely high activity in this asymmetric hydroge-
nation, and when the catalyst loading was reduced from 0.1
mol% to 0.02 mol% (S/C ¼ 5000), the asymmetric hydrogena-
tion of benzo-seven-membered cyclic imine (3d) can be nished
with >99% conversion, 93% yield and >99% ee (Table 5, entry 5).
In order to further investigate the high activity of this Ir/N-
methylated ZhaoPhos L5 catalytic system, the model substrate
3-phenyl-2H-benzo[b][1,4]oxazin-2-one 1a was applied in this
Table 6 High TON experimenta
Entry
S/C
Time (h)
Conv.b (%)
Yieldc (%)
eed (%)
1
2
3
4
1000
16
48
72
72
>99
>99
>99
81
93
91
89
72
99
99
99
99
10 000
40 000
50 000
a
Reaction conditions: substrate 1a (5.0 mmol) in 20.0 mL THF, 40 atm
H2, 1.0 equiv. HCl (4 M in dioxane), 25 ꢀC. b Conversion was determined
by 1H NMR analysis. c Isolated yield. d ee was determined by HPLC with
a chiral stationary phase.
Chem. Sci.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Edge Article
Chemical Science
stored in basophils and tissue mast cell granules to cause
allergic effects. Our catalytic hydrogenation methodology
showed great synthetic application. As shown in Scheme 3, 7-
((2-chloro-5-uoropyrimidin-4-yl)amino)-3-methyl-2H-benzo[b]
[1,4]oxazin-2-one 1q was efficiently obtained within four steps
using the easily commercially available 2-amino-5-nitrophenol
as the starting material.14 The Ir-catalyzed asymmetric hydro-
genation of compound 1q was efficiently accomplished to
obtain the chiral compound 2q with 92% yield and 91% ee,
which is the key intermediate to construct the potential IgE/IgG
receptor modulator for the treatment of autoimmune diseases.2
Scheme 2 Deuterium-labeling experiment.
proceeded in the presence of DCl in D2O, and the product 2a
without deuterium was obtained. This observation displayed
that the hydrogen atom of the hydrogenation product was from
H2 and not HCl to a great extent.
A series of asymmetric reductions of model substrate 3-
phenyl-2H-benzo[b][1,4]oxazin-2-one 1a were performed using
ligand L5 with varying ee values. As shown in Fig. 3, there is no
nonlinear effect in this transformation, which indicated that
there should be no catalyst self-aggregation or ligand–substrate
agglomeration in this catalytic system.13
Conclusions
In summary, the Ir-catalyzed asymmetric hydrogenation of
benzoxazinones and derivatives was successfully developed
with N-methylated ZhaoPhos L5 as the ligand through a new
anion-binding activation strategy. A series of chiral dihy-
drobenzoxazinones and derivatives were obtained with excel-
lent results (88–96% yields, 91–>99% ee, up to 40 500 TON). The
utilization of a strong Brønsted acid, such as hydrochloric acid
even at a small catalytic amount, as the cocatalyst is very
important to form a single anion-binding interaction with the
substrate and ligand L5, which strongly improved the reactivity.
Moreover, a highly efficient synthetic route was developed to
construct the key intermediate to synthesize a potential IgE/IgG
receptor modulator through our catalytic methodology system.
IgE/IgG is one of the most important immunoglobulins,
which are associated with the release of vasoactive amines
Conflicts of interest
There are no conicts to declare.
Acknowledgements
Fig. 3 Investigation of the nonlinear effect of the hydrogenation of
substrate 1a using ligand L5 with different ee values.
We are grateful for nancial support from the National Natural
Science Foundation of China (Grant No. 21432007 and
21502145), Wuhan Morning Light Plan of Youth Science and
Technology (Grant No. 2017050304010307), Shenzhen Nobel
Prize Scientists Laboratory Project (Grant No. C17783101) and
the Fundamental Research Funds for and the Central Univer-
sities (Grant No. 2042018kf0202). The Program of Introducing
Talents of Discipline to Universities of China (111 Project) is
also appreciated.
Notes and references
1 (a) F. Grant, S. Bartulis, L. Brogley, M. S. Dappan, R. Kasar,
A. Khan, M. Neitzel, M. A. Pleiss, E. D. Thorsett and
J. Tucker, PCT Int. Appl. WO 2003093245 A1, 2003; (b)
Z. Jones, R. Groneberg, M. Drew and C. T. Eary, U.S. Pat.,
20050282812, 2005; (c) D.-S. Su and M. G. Bock, U.S. Pat.
ˇ
Appl. Publ. US 20050020591 A1, 2005; (d) J. Ilas,
ˇ
P. S. Anderluh, M. S. Dolenc and D. Kikelj, Tetrahedron,
2005, 61, 7325–7348; (e) C. J. Abraham, D. H. Paull,
M. T. Scerba, J. W. Grebinski and T. Lectka, J. Am. Chem.
Soc., 2006, 128, 13370–13371; (f) D. V. Smil, S. Manku,
Y. A. Chantigny, S. Leit, A. Wahhab, T. P. Yan, M. Fournel,
Scheme 3 Synthetic application for the construction of the key
intermediate of biologically active molecules.
This journal is © The Royal Society of Chemistry 2019
Chem. Sci.

View Article Online
Chemical Science
Edge Article
C. Maroun, Z. Li, A.-M. Lemieux, A. Nicolescu, J. Rahil,
Chem. Soc., 2004, 126, 10558–10559; (e) D. J. Maher and
S. J. Connon, Tetrahedron Lett., 2004, 45, 1301–1305; (f)
H. Huang and E. N. Jacobsen, J. Am. Chem. Soc., 2006, 128,
7170–7171; (g) M. P. Lalonde, Y. Chen and E. N. Jacobsen,
Angew. Chem., Int. Ed., 2006, 45, 6366–6370; (h)
M. S. Taylor and E. N. Jacobsen, Angew. Chem., Int. Ed.,
2006, 45, 1520–1543; (i) X. Yu and W. Wang, Chem.–Asian
J., 2008, 3, 516–532; (j) P. M. Pihko, Hydrogen Bonding in
Organic Synthesis, Wiley, 2009.
´
S. Lefebvre, A. Panetta, J. M. Besterman and R. Deziel,
Bioorg. Med. Chem. Lett., 2009, 19, 688–692; (g) M. Rueping,
M. Stoeckel, E. Sugiono and T. Theissmann, Tetrahedron,
2010, 66, 6565–6568.
2 (a) R. Singh, A. Argade, D. G. Payan, J. Clough, H. Keim,
S. Bhamidipati, C. Sylvain and H. Li, WO2004014382 A1,
2004; (b) R. Singh, A. Argade, D. G. Payan, J. Clough,
H. Keim, S. Bhamidipati, C. Sylvain and H. Li, US
7517886B2, 2009.
3 A. Kuhl, P. Kolkhof, L. Telan, J. G. Peters, K. Lustig, R. Kast,
K. Muenter, J. P. Stasch and H. Tinel, WO 2005028451, 2005.
4 S. Fleischer, S. Zhou, S. Werkmeister, K. Junge and M. Beller,
Chem.–Eur. J., 2013, 19, 4997–5003.
5 C. T. Eary, Z. S. Jones, R. D. Groneberg, L. E. Burgess,
D. A. Mareska, M. D. Drew, J. F. Blake, E. R. Laird,
11 (a) Z. Zhang and P. R. Schreiner, Chem. Soc. Rev., 2009, 38,
1187–1198; (b) C. Zhao, C. A. Sojdak, W. Myint and
D. Seidel, J. Am. Chem. Soc., 2017, 139, 10224–10227; (c)
K. Eichstaedt, J. Jaramillo-Garcia, D. A. Leigh, V. Marcos,
S. Pisano and T. A. Singleton, J. Am. Chem. Soc., 2017, 139,
9376–9381; (d) A. E. Wendlandt, P. Vangal and
E. N. Jacobsen, Nature, 2018, 556, 447–451.
D. Balachari, M. O'Sullivan, A. Allen and V. Marsh, Bioorg. 12 Selected examples: (a) Q. Zhao, S. Li, K. Huang, R. Wang and
Med. Chem. Lett., 2007, 17, 2608–2613.
X. Zhang, Org. Lett., 2013, 15, 4014–4017; (b) Q. Zhao, J. Wen,
R. Tan, K. Huang, P. Metola, R. Wang, E. V. Anslyn and
X. Zhang, Angew. Chem., Int. Ed., 2014, 53, 8467–8470; (c)
Z. Han, P. Li, Z. Zhang, C. Chen, Q. Wang, X.-Q. Dong and
X. Zhang, ACS Catal., 2016, 6, 6214–6218; (d) J. Wen,
R. Tan, S. Liu, Q. Zhao and X. Zhang, Chem. Sci., 2016, 7,
3047–3051; (e) P. Li, Y. Huang, X. Hu, X.-Q. Dong and
X. Zhang, Org. Lett., 2017, 19, 3855–3858; (f) X. Li, C. You,
Y. Yang, Y. Yang, P. Li, G. Gu, L. W. Chung, H. Lv and
X. Zhang, Chem. Sci., 2018, 9, 1919–1924; (g) J. Wen,
X. Fan, R. Tan, H.-C. Chien, Q. Zhou, L. W. Chung and
X. Zhang, Org. Lett., 2018, 20, 2143–2147; (h) X. Yin,
Y. Huang, Z. Chen, Y. Hu, L. Tao, Q. Zhao, X.-Q. Dong and
X. Zhang, Org. Lett., 2018, 20, 4173–4177.
6 A. Wang, C. P. Prouty, P. D. Pelton, M. Yong, K. T. Demarest,
W. V. Murray and G.-H. Kuo, Bioorg. Med. Chem. Lett., 2010,
20, 1432–1435.
7 (a) R. I. Storer, D. E. Carrera and D. W. C. Macmillan, J. Am.
Chem. Soc., 2006, 128, 84–86; (b) X. Chen, Y. Zheng, C. Shu,
W. Yuan, B. Liu and X. Zhang, J. Org. Chem., 2011, 76,
9109–9115; (c) Q.-A. Chen, K. Gao, Y. Duan, Z.-S. Ye, L. Shi,
Y. Yang and Y.-G. Zhou, J. Am. Chem. Soc., 2012, 134, 2442–
2448; (d) J. L. Nunez-Rico and A. Vidal-Ferran, Org. Lett.,
2013, 15, 2066–2069; (e) L.-Q. Lu, Y. Li, K. Junge and
M. Beller, J. Am. Chem. Soc., 2015, 137, 2763–2768; (f)
Y. Zhang, R. Zhao, R. L.-Y. Bao and L. Shi, Eur. J. Org.
Chem., 2015, 3344–3351; (g) X. Zhang, B. Xu and M.-H. Xu,
Org. Chem. Front., 2016, 3, 944–948.
13 (a) D. Guillaneux, S.-H. Zhao, O. Samuel, D. Rainford and
H. B. Kagan, J. Am. Chem. Soc., 1994, 116, 9430–9439; (b)
C. Girard and H. B. Kagan, Angew. Chem., Int. Ed., 1998,
37, 2922–2959.
8 Comprehensive Asymmetric Catalysis, ed. E. N. Jacobsen, A.
Pfaltz and H. Yamamoto, Springer, Berlin, 1999.
9 For reviews, see: (a) R. R. Knowles and E. N. Jacobsen, Proc.
Natl. Acad. Sci. U. S. A., 2010, 107, 20678–20685; (b) 14 (a) S. Yan, L. Ye, M. Liu, J. Chen, J. Ding, W. Gao, X. Huang
R. J. Phipps, G. L. Hamilton and F. D. Toste, Nat. Chem.,
2012, 4, 603–614; (c) K. Brak and E. N. Jacobsen, Angew.
Chem., Int. Ed., 2013, 52, 534–561; (d) M. Mahlau and
B. List, Angew. Chem., Int. Ed., 2013, 52, 518–533.
and H. Wu, RSC Adv., 2014, 4, 16705–16709; (b) D.-J. Zhang,
W.-F. Sun, Z.-J. Zhong, R.-M. Gao, H. Yi, Y.-H. Li, Z.-G. Peng
and Z.-R. Li, Molecules, 2014, 19, 925–939; (c) Y. C. Teo,
S. N. Riduan and Y. Zhang, Green Chem., 2013, 15, 2365–
2368; (d) Y. Kamada, N. Sakai, S. Sogabe, K. Ida, H. Oki,
K. Sakamoto, W. Lane, G. Snell, M. Iida, Y. Imaeda,
J. Sakamoto and J. Matsui, J. Med. Chem., 2017, 60, 4358–
4368.
10 (a) M. S. Sigman and E. N. Jacobsen, J. Am. Chem. Soc., 1998,
120, 4901–4902; (b) A. G. Wenzel and E. N. Jacobsen, J. Am.
Chem. Soc., 2002, 124, 12964–12965; (c) T. Okino,
Y. Hoashi and Y. Takemoto, Tetrahedron Lett., 2003, 44,
2817–2821; (d) M. S. Taylor and E. N. Jacobsen, J. Am.
Chem. Sci.
This journal is © The Royal Society of Chemistry 2019