Spiro indane-based phosphine-oxazolines as highly efficient P,N ligands for enantioselective Pd-catalyzed allylic alkylation of indoles and allylic etherification

Article abstract of DOI:10.3390/molecules24081575

A series of indane-based phosphine-oxazoline ligands with a spirocarbon stereogenic center were examined for palladium-catalyzed asymmetric allylic alkylation of indoles. Under optimized conditions, high yields (up to 98%) and enantioselectivities (up to

Full text of DOI:10.3390/molecules24081575

molecules
Article
Spiro Indane-Based Phosphine-Oxazolines as
Highly Efficient P,N Ligands for Enantioselective
Pd-Catalyzed Allylic Alkylation of Indoles and
Allylic Etherification
Zhongxuan Qiu, Rui Sun, Kun Yang and Dawei Teng *
State Key laboratory Base of Eco-chemical Engineering, College of Chemical Engineering, Qingdao University of
Science and Technology, Qingdao 266042, China; qiuzhognxuan21@163.com (Z.Q.); sunruiqdao@163.com (R.S.);
yang802597641kun@163.com (K.Y.)
* Correspondence: dteng@qust.edu.cn; Tel.: +86-532-8402-2879
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
ꢀꢁꢂꢃꢄꢅꢆ
Received: 29 March 2019; Accepted: 20 April 2019; Published: 21 April 2019
Abstract: A series of indane-based phosphine-oxazoline ligands with a spirocarbon stereogenic center
were examined for palladium-catalyzed asymmetric allylic alkylation of indoles. Under optimized
conditions, high yields (up to 98%) and enantioselectivities (up to 98% ee) were obtained with a broad
scope of indole derivatives. The ligand was determined to be the most efficient P,N-ligand for this
reaction. Moreover, the ligand was also efficient for Pd-catalyzed asymmetric allylic etherification
with hard aliphatic alcohols as nucleophiles.
Keywords: asymmetric synthesis; indole; phosphine-oxazoline; spiro; palladium
1. Introduction
As a typical heterocyclic structural subunit, the indole scaffold is highly prevalent in biological
compounds, pharmaceuticals, natural products and material science [1–5]. Notably, a variety of
biologically active indole derivatives and indole-based drugs are enantiopure. Therefore, the synthesis
and functionalization of chiral indole derivatives is meaningful. It is found that many 3-substitued
indoles are important intermediates of natural products, such as (
(Figure 1). Because of the biologically significant activities, including treatment of migraine headaches,
antagonists, antiviral activity and agonist, functionalization of indoles on C-3 position has attracted
−
)-agroclavine and ( )-aurantioclavine
−
much attention [
6
]. Enantioselective alkylation of indoles at the C-3 position by the Friedel–Crafts
10]. However, high catalyst
reaction with Lewis acid as the catalyst has been explored extensively [
7
–
loading (10 %mol) is usually needed to obtain satisfactory yields and enantioselectivites.
Recently, palladium-catalyzed allylic alkylation has been proven to be an attractive strategy
to achieve enantiopure 3-substituted indoles [11–14] and diligent efforts have been made to
develop novel and efficient chiral palladium-complexes using the asymmetric allylic alkylation
of indoles as the model reaction. Chan reported that chiral ferrocenyl P/S ligands demonstrated
good catalytic performance [15]. Hoshi reported that high yields and good enantioselectivities
were obtained with sulphur-MOP ligands [16]. A phosphine ligand developed by Mino afforded
89% yields and 80% enatioselectivities with narrow substrate scope [17]. Other ligands such as
phosphoramidite-thioether [18], phosphoramidite-terminal olefin [19], phosphine olefin [20,21],
and helicenylphosphine ligands [22] were also reported as efficient catalysts.
The P,N-ligands are an important class of ligands and have successfully been applied in a large
scope of reactions because the steric and electronic characters of ligands can be finely tuned [23 24].
However, for the asymmetric allylic alkylation of indole, P,N ligands were not as effective as other ligands
,
Molecules 2019, 24, 1575; doi:10.3390/molecules24081575
www.mdpi.com/journal/molecules

Molecules 2019, 24, 1575
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mentioned above. The reaction only afforded < 10% ee using iPr-phosphine-oxazoline (iPr-PHOX) as
the ligand [15]. Hence, design of highly active and selective P/N ligands is still desirable.
Figure 1. Selected natural products containing the indole moieties.
Spiro phosphine-oxazoline ligands exhibit impressive catalytic performance in many cases
by taking advantage of the chelating units of PHOX (phosphine-oxazoline ligands) and the
spiro backbone. So far, there are four kinds of spiro phosphine-oxazoline ligands reported,
including SIPHOX (spirobiindane-based phosphine-oxzoline ligands) by Zhou [25–30], SpinPHOX
(spiro[4.4]-1,6-nonadiene-based phosphine-oxazoline ligands) by Ding [31
(hexamethyl-1,1’-spirobiindane phosphine-oxazoline ligands) by Lin [35] and SMI-PHOX
(an abbreviation for spiro mono-indane-based phosphine-oxazoline ligands L1 L4 in Scheme 1)
by us [36 37]. Compared with the other three ligands, SMI-PHOX ligands possess potentially distinct
–34], HMSI-PHOX
–
,
features: (i) first spiro indane-based phosphine-oxazoline ligand with non-C2-symmetric skeleton
in asymmetric metal catalysis; (ii) better stability and higher rigidity; (iii) only one chiral center
avoiding the complex stereochemistry; (iv) modularity by changing easily accessible carboxylic acid
and ClPR2
[36]. Because of the aforementioned properties, SMI-PHOX ligands have demonstrated
2
excellent catalytic performance in several asymmetic reactions [36,37]. Therefore, we envisaged that they
would be efficient chiral ligands for an indole C3-allylic alkylation reaction. As a result, high catalytic
activities and enantioselectivities were obtained when these spiro phosphine-oxazoline ligands were
used. We here disclose a detailed account of the Pd-catalyzed asymmetric allylic alkylation of indoles
using a series of highly rigid spiro phosphine-oxazolines as chiral ligands.
Scheme 1. Spiro-backbone-based phosphine-oxazoline ligands.

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2. Results and Discussion
The chiral phosphine-oxazoline ligands L1
–
L4 were synthesized according to the literature [36].
We investigated the ability of four representative spiro phosphine-oxazoline ligands L1–L4 for
palladium-catalyzed asymmetric allylic alkylation of indole. The reaction of indole (1a) with
1,3-diphenyl-2-propenyl acetate (2a) as the model reaction was examined in the presence of
[Pd(C3H5)Cl]2 (2.0 mol%) and ligand (4.0 mol%, Pd/ligand = 1/1) in toluene at room temperature using
Cs2CO3 (2 equivalent) as the base. The results were summarized in Table 1. The reactions gave the
corresponding product 3a in high yields (87%–95%) and enantioselectivities (87–96% ee) with the use
of ligands L1, L2 and L4 (entry 1, 2, 4). However, yield and enantioselectivity slightly decreased in the
presence of ligand L3 with a phenyl substitution on the oxazoline ring (entry 3). Taking into account
the catalytic activity and enantioselectivity, ligand L1 was chosen as the optimal ligand for further
intensive study.
a
Table 1. Evaluation of ligands for Pd-catalyzed allylic alkylation of indoles.
Yield b (%)
ee c,d (%)
Entry
Ligand
T (◦C)
Time (h)
1
2
3
4
L1
L2
L3
L4
25
25
25
25
12
12
24
12
95
87
70
94
96
91
80
87
a
Unless otherwise noted, reactions were performed with 1a (0.3 mmol), 2a (0.36 mmol), [Pd(C3H5c)Cl]2 (2 mol%),
b
Ligand (4 mol%), Cs2CO3 (0.6 mmol) in toluene (1.5 mL) at room temperature (r.t.). Isolated yield. The ee values
were determined by chiral high-performance liquid chromatography (HPLC) with the N-Boc-protected derivative
d
of 3a
.
The absolute configurations were assigned as S via comparison of specific rotations with the literature
data [20].
The reaction was investigated under various conditions using the ligand L1. The results are
summarized in Table 2. It was shown that solvents have a great influence on the reaction activity
and enantioselectivity (entries 1–8). High yield (95%) and excellent enantioselectivity (96% ee) were
obtained with toluene as the solvent (entry 1). When the reaction was carried out in xylenes and
mesitylene, the enantioselectivities slightly decreased (entries 2 and 3). With dichloromethane and ethyl
acetate as solvents, the entioselectivities decreased to around 80% ee (entries 4 and 5). Using acetonitrile,
tetrahydrofuran or N,N-dimethylformamide as the solvents, low yields and entioselectivities were
obtained (entries 6–8). Toluene was proved to be the best choice. We next changed the base for the
reaction in toluene besides of Cs2CO3 (entries 9 and 10). Using K2CO3 as the base, product 3a was
obtained with a slight decrease in enantioselectivity (89% ee) (entry 9). But the yield of 3a decreased to
65%. With Na2CO3, the enantioselectivity of the reaction dramatically decreased to 15% ee (entry 10).
Subsequent optimization of temperature indicated that the reaction afforded lower yield of 3a at 0 ◦C
and lower enantioselectivity at 40 ◦C than that at room temperature (entries 11 and 12). Compared
to the results shown in entry 1, a slight decrease of yields and enantioselectivities was observed by
changing the ratio of indole to 1,3-diphenyl-2-propenyl acetate from 1:1.2 to 1.2:1 (entries 13 and 14).
Accordingly, the optimal reaction conditions were established as follows: 2 mol% [Pd(C3H5)Cl]2,
4 mol% of ligand L1, 2.0 equivalents of Cs2CO3 in toluene at room temperature with the molar ratio of
1a to 2a being 1:1.2.
With the optimized conditions in hand, we examined the substrate scope with various indoles
1a
–1o and allylic acetates 2a–2e. As shown in Table 3, the reaction exhibited high tolerance of various
substituted indoles. All reactions gave high yields and enantioselectivities either with substituents

Molecules 2019, 24, 1575
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in the C2 position or in the phenyl ring. With 2-substituted indoles 1b
–
1c, the reactions proceeded
smoothly to obtain the desired products 3b and 3c with 85–89% yields and 86–96% ee. C4, C5,
C6 and C7-substituted indoles 1d 1o underwent the reactions smoothly to give the corresponding
products 3d 3o in consistently high yields (86%–98%) and enantioselectivities (83–98% ee) with either
–
–
electron-donating groups (Me, MeO, BnO) or electron-withdrawing (Cl, Br) groups in the phenyl
ring. The electronic properties of the substituents in the phenyl ring of the indoles have no obvious
effect on the reaction. As for the 1,3-diarylallyl acetate components, the substrates bearing either
electron-donating (OMe) or electron-withdrawing (NO2) substituents at the para position of the benzene
ring underwent the reaction smoothly to give the corresponding products in good yield with excellent
ee values (Table 3, 3p–3s). To summarize Table 3, the ligand L1 exhibits superior catalytic performance
for allylic alkylation reaction of 1,3-diaryl-2-propenyl acetate and indoles.
a
Table 2. Optimization of reaction conditions for Pd-catalyzed allylic alkylation of indoles.
Yield b (%)
ee c,d (%)
Entry
Solvent
Base
Time (h)
T (◦C)
1
2
3
4
5
6
7
8
9
10
11
12
13 g
14 h
toluene
xylenes
mesitylene Cs2CO3
CH2Cl2
EtOAc
CH3CN
THF
Cs2CO3
Cs2CO3
12
12
12
12
12
24
24
48
12
12
12
12
12
12
25
25
25
25
25
25
25
25
25
25
0
95
86
84
76
74
96
94
90
83
84
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
Na2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
47
49
19
3
N.R. e
65
N.D. f
89
DMF
toluene
toluene
toluene
toluene
toluene
toluene
76
70
84
91
15
90
79
94
40
25
25
90
95
a
Unless otherwise noted, reactions were performed with 1a (0.3 mmol), 2a (0.36 mmol), [Pd(C3H5)Cl]2 (2 mol%),
b
c
L1 (4 mol%), base (0.6 mmol) in solvent (1.5 mL) at a certain temperature. Isolated yield. The ee values were
determined by chiral HPLC with the N-Boc-protected derivative of 3a
as S via comparison of specific rotations with the literature data [20]. No reaction. Not detected. The molar
ratio of 1a to 2a was 1:1. The molar ratio of 1a to 1b was 1.2:1.
d
.
The absolute configurations were assigned
e
f
g
h
Encouraged by the excellent results achieved in the asymmetric allylic alkylation of
indole, we successfully extended the current catalytic system to Pd-catalyzed asymmetric allylic
etherification [38–41] by directly utilizing relatively hard aliphatic alcohols as nucleophiles (Table 4).
We were pleased to find that the protocol is applicable to aromatic rings of benzylicalcohols with
different electronic and steric natures. For example, a wide variety of benzylic alcohols bearing
electron-donating (MeO) or electron-withdrawing (Br) groups at ortho-, meta-, or para-positions
were well tolerated, and afforded the corresponding products 5a–5e in consistently high yields and
enantioselectivities with dichloromethane (DCM) as the solvent (Table S1). When the aryl group
was changed to naphthyl and aromatic heterocycle, good yields and ee values were also observed
(5f and 5g). Notably, spiro phosphine-oxazoline ligand L1 also worked efficiency in the asymmetric
allylic etherification of simple aliphatic alcohols, including primary and secondary alcohols, which led
to the formation of the desired products in excellent enantioselectivities (5h–5j, 93–99% ee).

Molecules 2019, 24, 1575
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a
Table 3. Substrate scope of asymmetric allylic alkylation of indoles.
Yield b (%)
Ee c,d (%)
Entry
R1
R2
Ar
Product
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
H
H
H
H
Me
Ph
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
95
89
85
93
95
96
98
97
95
92
90
94
90
86
90
92
85
91
87
96
96
86
84
92
95
98
96
92
93
93
93
83
84
94
94
90
95
97
4-Me
4-MeO
5-Me
5-MeO
5-BnO
5-Cl
5-Br
6-Me
6-Cl
7-Me
7-MeO
7-Cl
H
4-MePh
4-MeOPh
4-ClPh
4-NO2Ph
H
H
H
3s
a
Unless otherwise noted, reactions were performed with
1
(0.3 mmol), 2 (0.36 mmol), [Pd(C3H5)Cl]2 (2 mol%),
b
c
L1 (4 mol%), Cs2CO3 (0.6 mmol) in toluene (1.5 mL) at room temperature. Isolated yield. The ee values were
determined by chiral HPLC with the N-Boc-protected derivative of
d
3
.
The absolute configurations were assigned
as S via comparison of specific rotations with the literature data [20].
a
Table 4. Substrate scope of asymmetric allylic etherification.
Yield b (%)
99
ee c,d (%)
Entry
4
Product
5a
1
2
3
4
4a
4b
4c
98
97
91
94
5b
5c
5d
97
93
95
4d
5
6
7
8
9
4e
4f
4g
4h
4i
5e
5f
5g
5h
5i
93
97
86
98
97
96
93
94
94
99
95
93
10
4j
5j
a
Unless otherwise noted, reactions were performed with 2a (0.3 mmol),
4 (0.9 mmol), [Pd(C3H5)Cl]2 (2 mol%),
L1 (4 mol%), Cs2CO3 (0.9 mmol) in DCM (2 mL) at 0oC. b Isolated yield. Determined by HPLC using a chiral
column. The absolute configurations were assigned as S via comparison of specific rotations with the literature
c
d
data [42].

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3. Materials and Methods
3.1. General Information
All solvents were purified and dried according to standard methods prior to use. All air and
moisture sensitive manipulations were carried out with standard Schlenk techniques under argon.
Commercially available reagents were used without further purification. Melting points were recorded
1
on a RY-1 microscopic melting apparatus and uncorrected. H- and 13C-nuclear magnetic resonance
(NMR) spectra were recorded on a Bruker Avance 500 spectrometer (Bruker, Rheinstetten, Germany).
Chemical shifts were reported in parts per million (δ) relative to tetramethylsilane (TMS). High resolution
mass spectrometry (HRMS) were performed on an Ultima Global spectrometer (Waters, Milford, MA,
USA) with an electrospray ionization (ESI) source. HPLC was performed on a Shimadzu LC-20 Liquid
Chromatograph ( Shimadzu, Kyoto, Japan) using chiralcel OD-H, AD-H and OJ-H columns. Ligands
L1–L4 were prepared according to the reported procedure [36].
3.2. General Procedure for the Pd-Catalyzed Asymmetric Allylic Alkylation of Indoles
Ligand L1 (5.0 mg, 4 mol%) and [Pd(C3H5)Cl]2 (2.2 mg, 2 mol%) were dissolved in toluene
(1.0 mL) in a Schlenk tube under Ar. After 0.5 h of stirring at room temperature, allylic acetate
2
(0.36 mmol) dissolved in toluene (0.5 mL) was added, followed by indole (0.3 mmol), and Cs2CO3
1
(195 mg, 0.6 mmol). The mixture was stirred at room temperature for 12 h and then was diluted
with CH2Cl2 and washed with saturated NH4Cl (aq). The organic layers were dried over MgSO4
and filtered, and the solvents were evaporated in vacuo. The residue was purified by flash column
chromatography, eluting with petroleum ether and ethyl acetate to afford the corresponding product 3.
◦
1
(S,E)-3-(1,3-diphenylallyl)-1H-indole (3a) [15]: Yellow solid (m.p. 121–123 C), 95% yield. H-NMR
(500 MHz, CDCl3) 7.98 (brs, 1H), 7.45 (d, J = 8.0 Hz, 1H), 7.39–7.19 (m, 12H), 7.04 (t, 7.4 Hz, 1H),
6.91 (s, 1H), 6.76 (dd, J = 15.8, 7.4 Hz, 1H), 6.47 (d, J = 15.8 Hz, 1H), 5.14 (d, J = 7.4 Hz, 1H); 13C-NMR
(125 MHz, CDCl3) 143.3, 137.4, 136.6, 132.5, 130.5, 128.4, 128.3, 127.1, 126.7, 126.3, 126.2, 122.5, 122.0,
δ
δ
119.8, 119.3, 118.6, 111.0, 46,1.
(S,E)-3-(1,3-diphenylallyl)-2-methyl-1H-indole (3b) [15]: Yellow solid (m.p. 39–41 ◦C), 89% yield. 1H-NMR
(500 MHz, CDCl3)
(t, J = 7.3 Hz, 1H), 7.00 (t, J = 7.5 Hz, 1H), 6.88 (dd, J = 15.8, 7.2 Hz, 1H), 6.45 (d, J = 15.8 Hz, 1H), 5.17
(d, J = 7.2 Hz, 1H), 2.40 (s, 3H); 13C-NMR (125 MHz, CDCl3)
143.4, 137.5, 135.3, 132.1, 131.6, 130.5,
128.4, 128.3, 128.2, 127.9, 127.0, 126.2, 126.1, 120.9, 119.4, 119.2, 112.8, 110.2, 45.0, 12.4.
δ 7.83 (brs, 1H), 7.40–7.36 (m, 5H), 7.31–7.28 (m, 5H), 7.23–7.21 (m, 2H), 7.12
δ
1
(S,E)-3-(1,3-diphenylallyl)-2-phenyl-1H-indole (3c) [15]: Yellow solid (m.p. 40–42 ◦C), 85% yield. H-NMR
(500 MHz, CDCl3) 8.09 (brs, 1H), 7.53 (d, J = 7.4 Hz, 2H), 7.45–7.31 (m, 9H), 7.26–7.24 (m, 4H),
7.19–7.14 (m, 3H), 6.99 (t, J = 7.6 Hz, 1H), 6.90 (dd, J = 15.8, 7.3 Hz, 1H), 6.40 (d, J = 15.8 Hz, 1H), 5.27
(d, J = 8.4 Hz, 1H); 13C-NMR (125 MHz, CDCl3)
143.4, 137.4, 136.2, 135.5, 132.9, 132.2, 131.0, 128.7,
δ
δ
128.6, 128.5, 128.4, 128.2, 128.1, 128.0, 127.8, 127.0, 126.2, 126.0, 122.0, 121.1, 119.6, 113.8, 110.8, 45.1.
◦
(S,E)-3-(1,3-diphenylallyl)-4-methyl-1H-indole (3d) [17]: White solid (m.p. 172–174 C), 93% yield.
1H-NMR (500 MHz, CDCl3)
δ
8.00 (brs, 1H), 7.35 (d, J = 7.4 Hz, 2H), 7.32–7.26 (m, 6H), 7.25–7.18
(m, 3H), 7.07 (t, J = 7.5 Hz, 1H), 6.86 (d, J = 2.2 Hz, 1H), 6.81 (d, J = 7.0 Hz, 1H), 6.75 (dd, J = 15.8, 6.6 Hz,
1H), 6.25 (d, J = 15.8 Hz, 1H), 5.46 (d, J = 6.4 Hz, 1H), 2.53 (s, 3H); 13C-NMR (125 MHz, CDCl3)
144.1,
δ
137.6, 137.1, 134.0, 131.2, 130.8, 129.0, 128.6, 127.2, 126.4, 125.7, 123.6, 122.3, 121.4, 119.1, 109.1, 46.6, 20.5.
1
(S,E)-3-(1,3-diphenylallyl)-4-methoxy-1H-indole (3e): Yellow oil, 95% yield. H-NMR (500 MHz, CDCl3)
δ
7.96 (brs, 1H), 7.36 (d, J = 7.6 Hz, 2H), 7.31–7.25 (m, 6H), 7.19–7.16 (m, 2H), 7.07 (t, J = 8.0 Hz, 1H), 6.96
(d, J = 8.2 Hz, 1H), 6.83 (d, J = 1.8 Hz, 1H), 6.77 (dd, J = 15.8, 7.2 Hz, 1H), 6.45 (d, J = 7.8 Hz, 1H), 6.35
(d, J = 15.8 Hz, 1H), 5.55 (d, J = 7.2 Hz, 1H), 3.73 (s, 3H); 13C-NMR (125 MHz, CDCl3)
δ 154.8, 144.7,
138.1, 137.9, 134.0, 129.9, 128.5, 128.4, 128.0, 126.8, 126.2, 125.7, 122.9, 121.1, 119.3, 117.0, 104.3, 100.0,
55.0, 46.3. HRMS (ESI): calcd for C24H21NNaO [M + Na]+: 362.1515, found 362.1510.

Molecules 2019, 24, 1575
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1
(S,E)-3-(1,3-diphenylallyl)-5-methyl-1H-indole (3f) [15]: White solid (m.p. 113–114 ◦C), 96% yield. H-NMR
(500 MHz, CDCl3) 7.90 (brs, 1H), 7.38–7.26 (m, 8H), 7.25–7.19 (m, 4H), 7.01 (d, 8.2 Hz, 1H), 6.86 (s, 1H),
6.73 (dd, J = 15.8, 7.3 Hz, 1H), 6.44 (d, J = 15.8 Hz, 1H), 5.11 (d, J = 7.2 Hz, 1H), 2.38 (s, 3H); 13C-NMR
δ
(125 MHz, CDCl3)
46.1, 21.6.
δ
143.6, 137.7, 135.0, 132.8, 130.6, 128.6, 127.2, 126.4, 123.8, 122.9, 119.5, 118.2, 110.9,
1
(S,E)-3-(1,3-diphenylallyl)-5-methoxy-1H-indole (3g) [15]: Colorless oil, 98% yield. H-NMR (500 MHz,
CDCl3)
δ
7.90 (brs, 1H), 7.38–7.19 (m, 11H), 6.89–6.83 (m, 3H), 6.74 (dd, J = 15.8, 7.4 Hz, 1H), 6.47
154.0, 143.5,
(d, J = 15.8 Hz, 1H), 5.09 (d, J = 7.3 Hz, 1H), 3.72 (s, 3H); 13C-NMR (125 MHz, CDCl3)
δ
137.7, 132.7, 132.0, 130.8, 128.7, 128.6, 127.4, 127.3, 126.6, 126.5, 123.6, 118.6, 112.4, 111.9, 102.0, 56.0, 46.4.
1
(S,E)-5-(benzyloxy)-3-(1,3-diphenylallyl)-1H-indole (3h) [15]: Colorless oil, 97% yield. H-NMR (500 MHz,
CDCl3)
δ
7.82 (brs, 1H), 7.37–7.17 (m, 16H), 6.92–6.88 (m, 2H), 6.82 (s, 1H), 6.70 (dd, J = 15.8, 7.4 Hz, 1H),
152.9,
6.43 (d, J = 15.8 Hz, 1H), 5.04 (d, J = 7.3 Hz, 1H), 4.93 (s, 2H); 13C-NMR (125 MHz, CDCl3)
δ
143.3, 137.6, 137.5, 132.4, 131.9, 130.5, 128.5, 127.7, 127.6, 127.2, 126.4, 126.3, 123.5, 118.3, 112.9, 111.8,
103.4, 70.8, 46.2.
1
(S,E)-5-chloro-3-(1,3-diphenylallyl)-1H-indole (3i) [15]: Yellow oil, 95% yield. H-NMR (500 MHz, CDCl3)
δ 8.01 (brs, 1H), 7.38–7.20 (m, 12H), 7.13–7.11 (m, 1H), 6.94 (s, 1H), 6.69 (dd, J = 15.8, 7.3 Hz, 1H), 6.43
(d, J = 15.8 Hz, 1H), 5.07 (d, J = 7.3 Hz, 1H); 13C-NMR (125 MHz, CDCl3)
δ 143.0, 137.4, 135.0, 132.1,
130.9, 128.6, 128.5, 128.0, 127.3, 126.6, 126.4, 125.2, 124.0, 122.5, 119.3, 118.6, 112.2, 46.0.
(S,E)-5-bromo-3-(1,3-diphenylallyl)-1H-indole (3j) [15]: Colorless oil, 92% yield. 1H-NMR (500 MHz,
CDCl3)
(d, J = 2.2 Hz, 1H), 6.69 (dd, J = 15.8, 7.3 Hz, 1H), 6.42 (d, J = 15.8 Hz, 1H), 5.05 (d, J = 7.3 Hz, 1H);
13C-NMR (125 MHz, CDCl3)
142.8, 137.2, 135.2, 132.0, 130.7, 128.4, 128.3, 127.2, 126.5, 126.3, 125.0,
123.8, 122.2, 118.4, 112.7, 112.5, 45.8.
δ 8.00 (brs, 1H), 7.53 (s, 1H), 7.36 (d, J = 7.6 Hz, 2H), 7.32–7.28 (m, 5H), 7.26–7.19 (m, 5H), 6.90
δ
1
(S,E)-3-(1,3-diphenylallyl)-6-methyl-1H-indole (3k) [20]: Yellow oil, 90% yield. H-NMR (500 MHz, CDCl3)
δ 7.85 (brs, 1H), 7.37–7.17 (m, 11H), 7.14 (s, 1H), 6.86–6.83 (m, 2H), 6.74 (dd, J = 15.8, 7.4 Hz, 1H), 6.45
(d, J = 15.8 Hz, 1H), 5.09 (d, J = 7.4 Hz, 1H), 2.43 (s, 3H); 13C-NMR (125 MHz, CDCl3)
δ 143.4, 137.5,
137.1, 132.6, 131.8, 130.4, 128.4, 128.3, 127.1, 126.3, 124.6, 121.9, 121.1, 119.5, 118.4, 111.0, 46.2, 21.6.
1
(S,E)-6-chloro-3-(1,3-diphenylallyl)-1H-indole (3l) [20]: Yellow oil, 94% yield. H-NMR (500 MHz, CDCl3)
δ
8.01 (brs, 1H), 7.38–7.28 (m, 10H), 7.26–7.20 (m, 2H), 7.00 (dd, J = 8.5, 1.8 Hz, 1H), 6.91 (d, J = 2.0 Hz,
1H), 6.72 (dd, J = 15.8, 7.4 Hz, 1H), 6.44 (d, J = 15.8 Hz, 1H), 5.09 (d, J = 7.4 Hz, 1H); 13C-NMR (125 MHz,
CDCl3) 143.0, 137.2, 137.0, 132.1, 130.8, 128.5, 128.4, 128.0, 127.3, 126.6, 126.3, 125.4, 123.3, 120.8, 120.2,
δ
118.9, 111.1, 46.1.
(S,E)-3-(1,3-diphenylallyl)-7-methyl-1H-indole (3m) [19]: Yellow oil, 90% yield. 1H-NMR (500 MHz, CDCl3)
δ
7.89 (brs, 1H), 7.41–7.30 (m, 9H), 7.28-7.22 (m, 2H), 7.03–6.98 (m, 2H), 6.92 (s, 1H), 6.78 (dd, J = 15.8,
7.3 Hz, 1H), 6.49 (d, J = 15.8 Hz, 1H), 5.16 (d, J = 7.2 Hz, 1H), 2.50 (s, 3H); 13C-NMR (125 MHz, CDCl3)
δ
143.4, 137.5, 136.2, 132.5, 130.5, 128.4, 128.3, 127.1, 126.3, 122.6, 122.3, 120.2, 119.6, 119.1, 117.6, 46.2, 16.5.
1
(S,E)-3-(1,3-diphenylallyl)-7-methoxy-1H-indole (3n): Yellow oil, 86% yield. H-NMR (500 MHz, CDCl3)
δ
8.21 (brs, 1H), 7.37-7.17 (m, 10H), 7.03 (d, J = 8.0 Hz, 1H), 6.95-6.88 (m, 2H), 6.74 (dd, J = 15.8, 7.4 Hz,
1H), 6.63 (d, J = 7.6 Hz, 1H), 6.44 (d, J = 15.8 Hz, 1H), 5.10 (d, J = 7.4 Hz, 1H), 3.94 (s, 3H); 13C-NMR
(125 MHz, CDCl3)
δ 146.1, 143.5, 137.5, 132.6, 130.5, 128.4, 128.2, 127.1, 122.2, 119.8, 119.1, 112.7, 101.9,
55.3, 46.3. HRMS (ESI): calcd for C24H21NNaO [M+Na]+: 362.1515, found 362.1516.
(S,E)-7-chloro-3-(1,3-diphenylallyl)-1H-indole (3o): Yellow solid (m.p. 81–82 ◦C), 90% yield. 1H-NMR
(500 MHz, CDCl3)
δ 8.23 (brs, 1H), 7.38–7.28 (m, 9H), 7.24–7.17 (m, 3H), 6.98–6.94 (m, 2H), 6.73
(dd, J = 15.8, 7.3 Hz, 1H), 6.45 (d, J = 15.8 Hz, 1H), 5.11 (d, J = 7.3 Hz, 1H); 13C-NMR (125 MHz, CDCl3)
δ 143.0, 137.3, 133.9, 132.1, 130.9, 128.5, 128.4, 128.3, 127.3, 126.6, 126.4, 123.3, 121.5, 120.3, 119.9, 118.6,
116.6, 46.2. HRMS (ESI): calcd for C23H18ClNNa [M + Na]+: 366.1020, found 366.1018.

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(S,E)-3-(1,3-di-p-tolylallyl)-1H-indole (3p) [19]: Yellow oil, 92% yield. 1H-NMR (500 MHz, CDCl3)
δ
7.97 (brs, 1H), 7.46 (d, J = 8.0 Hz, 1H), 7.37 (d, J = 8.1 Hz, 1H), 7.28–7.02 (m, 10H), 6.91 (s, 1H), 6.70
(dd, J = 15.8, 7.4 Hz, 1H), 6.44 (d, J = 15.8 Hz, 1H), 5.09 (d, J = 7.2 Hz, 1H), 2.35 (s, 3H), 2.33 (s, 3H);
13C-NMR (125 MHz, CDCl3)
δ
140.7, 137.0, 136.8, 136.0, 135.0, 132.0, 130.4, 129.4, 129.3, 128.6, 127.0,
126.4, 122.8, 122.2, 120.1, 119.6, 119.2, 111.3, 46.0, 21.3.
1
(S,E)-3-(1,3-bis(4-methoxyphenyl)allyl)-1H-indole (3q) [43]: Yellow oil, 85% yield. H-NMR (500 MHz,
CDCl3) 7.98 (s, 1H), 7.43–7.28 (m, 4H), 7.24 (d, J = 8.2 Hz, 2H), 7.16 (t, J = 7.6 Hz, 1H), 7.02 (t, J = 7.6 Hz,
1H), 6.89 (s, 1H), 6.85–6.81 (m, 4H), 6.56 (dd, J = 15.8, 7.3 Hz, 1H), 6.36 (d, J = 15.8 Hz, 1H), 5.05
(d, J = 7.3 Hz, 1H), 3.78 (s, 6H); 13C-NMR (125 MHz, CDCl3)
158.9, 158.1, 136.7, 135.8, 130.8, 130.4,
δ
δ
129.7, 129.5, 127.5, 126.9, 122.6, 122.0, 120.0, 119.4, 119.2, 113.9, 113.8, 111.2, 55.3, 55.2, 45.4.
(S,E)-3-(1,3-bis(4-chlorophenyl)allyl)-1H-indole (3r) [19]: Yellow oil, 91% yield. 1H-NMR (500 MHz, CDCl3)
δ
8.05 (brs, 1H), 7.39 (d, J = 8.2 Hz, 2H), 7.30–7.19 (m, 9H), 7.06 (t, J = 7.5 Hz, 1H), 6.92 (s, 1H), 6.69 (dd,
J = 15.8, 7.2 Hz, 1H), 6.38 (d, J = 15.8 Hz, 1H), 5.11 (d, J = 7.2 Hz, 1H); 13C-NMR (125 MHz, CDCl3)
δ
141.8, 136.9, 135.9, 133.1, 132.8, 132.4, 130.0, 129.9, 128.9, 128.8, 127.7, 126.7, 122.8, 122.5, 119.9, 119.8,
118.2, 111.4, 45.7.
1
(S,E)-3-(1,3-bis(4-nitrophenyl)allyl)-1H-indole (3s): Yellow oil, 87% yield. H-NMR (500 MHz, CDCl3)
δ
8.23–8.11 (m, 5H), 7.50–7.32 (m, 6H), 7.22 (t, J = 7.4 Hz, 1H), 7.06 (t, J = 7.5 Hz, 1H), 6.98 (s, 1H), 6.90
(dd, J = 15.8, 7.2 Hz, 1H), 6.5 (d, J = 15.8 Hz, 1H), 5.28 (d, J = 8.0 Hz, 1H); 13C-NMR (125 MHz, CDCl3)
δ 150.2, 146.8, 143.4, 136.7, 135.7, 130.0, 129.4, 127.0, 126.2, 124.0, 123.9, 122.8, 122.7, 119.9, 119.2, 116.2,
111.6, 46.1. HRMS (ESI): calcd for C23H17N3NaO4 [M + Na]+: 422.1111, found 422.1110.
3.3. General Procedure for the N-Boc Protection of Alkylated Indoles
To a solution of
3 (0.15 mmol) and DMAP (0.9 mg, 0.0075 mmol) in CH2Cl2 (3 mL) was added
(Boc)2O (49 mg, 0.225 mmol), and the solution was stirred for 0.5 h at room temperature. The resulting
mixture was evaporated under reduced pressure and purified by flash column chromatography
(elution with n-hexane/EtOAc = 30:1) to afford the N-Boc-protected alkylated indole (Boc-3).
(S,E)-tert-butyl 3-(1,3-diphenylallyl)-1H-indole-1-carboxylate (Boc-3a) [15]: Colorless oil. 99% yield and
96% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.4 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 13.2 min for (S)-isomer (major), tr = 16.0 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ
8.12 (brs, 1H), 7.39–7.21 (m, 13H), 7.14 (t, J = 7.6 Hz, 1H), 6.72
(dd, J = 15.8, 7.4 Hz, 1H), 6.46 (d, J = 15.8 Hz, 1H), 5.06 (d, J = 7.4 Hz, 1H), 1.68 (s, 9H); 13C-NMR
(125 MHz, CDCl3) 150.0, 142.1, 137.3, 135.8, 131.4, 131.3, 129.9, 128.6, 128.5, 128.4, 127.4, 126.8, 126.4,
δ
124.4, 123.8, 123.1, 122.5, 120.2, 115.3, 83.7, 46.0, 28.3.
(S,E)-tert-butyl 3-(1,3-diphenylallyl)-2-methyl-1H-indole-1-carboxylate (Boc-3b) [15]: Colorless oil. 99%
yield and 96% ee, determined by chiral HPLC analysis (Chiralcel OJ-H hexane/isopropanol, 99:1 v/v,
0.3 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 37.2 min for (R)-isomer (minor), tr = 50.1 min
1
for (S)-isomer (major). H-NMR (500 MHz, CDCl3)
δ 8.14 (d, J = 8.4 Hz, 1H), 7.39 (d, J = 7.5 Hz,
2H), 7.34–7.27 (m, 7H), 7.23–7.19 (m, 3H), 7.07 (t, J = 7.5 Hz, 1H), 6.83 (dd, J = 15.8, 7.4 Hz, 1H), 6.48
(d, J = 16.0 Hz, 1H), 5.20 (d, J = 7.4 Hz, 1H), 2.62 (s, 3H), 1.70 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
150.7, 142.3, 137.2, 136.0, 134.0, 131.5, 130.5, 128.9, 128.5, 128.3, 128.0, 127.2, 126.3, 123.1, 122.2, 119.5,
119.1, 115.3, 83.6, 44.5, 28.3, 14.3.
(S,E)-tert-butyl ◦ 3-(1,3-diphenylallyl)-2-phenyl-1H-indole-1-carboxylate
(Boc-3c) [15]: White solid
(m.p. 153–155 C). 98% yield and 86% ee, determined by chiral HPLC analysis (Chiralcel AD-H
hexane/isopropanol, 99:1 v/v, 0.8 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 5.1 min for (S)-isomer
1
(major), tr = 13.4 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ 8.29 (d, J = 8.6 Hz, 1H),
7.42–7.36 (m, 5H), 7.33–7.17 (m, 12H), 7.10 (t, J = 7.8 Hz, 1H), 6.77 (dd, J = 15.8, 7.6 Hz, 1H), 6.32
(d, J = 15.8 Hz, 1H), 4.85 (d, J = 7.6 Hz, 1H), 1.22 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
150.4, 142.8,

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137.6, 137.2, 136.9, 134.5, 131.9, 130.9, 130.3, 128.7, 128.5, 128.4, 128.2, 128.1, 127.5, 126.6, 124.5, 122.8,
121.5, 121.2, 115.6, 83.3, 45.1, 27.8.
(S,E)-tert-butyl ◦ 3-(1,3-diphenylallyl)-4-methyl-1H-indole-1-carboxylate (Boc-3d) [18]: White solid
(m.p. 137–139 C). 98% yield and 84% ee, det◦ermined by chiral HPLC analysis (Chiralcel OD-H
hexane/isopropanol, 99:1 v/v, 0.7 mL/min, 25 C, UV 254 nm), Retention times: tr = 7.1 min for
1
(S)-isomer (major), tr = 8.5 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
8.07 (brs, 1H),
7.38 (d, J = 7.4 Hz, 2H), 7.35–7.25 (m, 8H), 7.24–7.19 (m, 2H), 6.94 (d, J = 7.3 Hz, 1H), 6.73 (dd, J = 15.8,
6.6 Hz, 1H), 6.31 (d, J = 15.8 Hz, 1H), 5.37 (d, J = 6.6 Hz, 1H), 2.50 (s, 3H), 1.68 (s, 9H); 13C-NMR
(125 MHz, CDCl3)
δ 149.9, 142.8, 137.4, 136.4, 132.7, 131.3, 131.2, 128.9, 128.6, 127.4, 126.7, 126.5, 125.0,
124.9, 124.4, 123.5, 113.2, 83.7, 46.6, 28.3, 27.5, 20.4.
(S,E)-tert-butyl 3-(1,3-diphenylallyl)-4-methoxy-1H-indole-1-carboxylate (Boc-3e): Colorless oil. 99% yield
and 92% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v,
0.7 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 7.8 min for (S)-isomer (major), tr = 11.6 min for
1
(R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ 7.73 (brs, 1H), 7.37 (d, J = 7.5 Hz, 2H), 7.30–7.27
(m, 7H), 7.20 (t, J = 7.8 Hz, 3H), 6.73 (dd, J = 15.8, 7.4 Hz, 1H), 6.60 (d, J = 8.0 Hz, 1H), 6.37 (d, J = 15.8 Hz,
1H), 5.46 (d, J = 7.4 Hz, 1H), 3.70 (s, 3H), 1.66 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
154.3, 150.0, 143.5,
137.7, 137.3, 132.9, 130.5, 128.5, 128.2, 127.1, 126.4, 126.1, 125.3, 123.4, 122.6, 119.6, 108.3, 103.8, 93.7, 55.2,
46.5, 28.3. HRMS (ESI): calcd for C29H29NNaO3 [M + Na]+: 462.2040, found 462.2033.
(S,E)-tert-butyl ◦ 3-(1,3-diphenylallyl)-5-methyl-1H-indole-1-carboxylate
(Boc-3f) [15]: White solid
(m.p. 151–152 C). 98% yield and 95% ee, determined by chiral HPLC analysis (Chiralcel OD-H
hexane/isopropanol, 99:1 v/v, 0.7 mL/min, 25 ◦C, ultraviolet (UV) 254 nm), Retention times: tr = 7.5 min
1
for (S)-isomer (major), tr = 8.9 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ 7.96 (brs, 1H),
7.37–7.27 (m, 9H), 7.25–7.19 (m, 2H), 7.12–7.09 (m, 2H), 6.68 (dd, J = 15.8, 7.3 Hz, 1H), 6.42 (d, J = 15.8 Hz,
1H), 5.01 (d, J = 7.3 Hz, 1H), 2.35 (s, 3H), 1.65 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
150.0, 142.2, 137.3,
134.0, 131.9, 131.4, 131.3, 130.1, 128.6, 128.5, 127.4, 126.7, 126.4, 125.8, 123.9, 122.8, 119.9, 114.9, 83.5, 45.9,
28.3, 21.5.
(S,E)-tert-butyl 3-(1,3-diphenylallyl)-5-methoxy-1H-indole-1-carboxylate (Boc-3g) [15]: Yellow oil. 98%
yield and 98% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v,
0.7 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 8.0 min for (S)-isomer (major), tr = 10.2 min for
1
(R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
7.99 (brs, 1H), 7.39–7.22 (m, 11H), 6.91 (dd, J = 9.0,
2.4 Hz, 1H), 6.78 (d, J = 2.3 Hz, 1H), 6.69 (dd, J = 15.8, 7.4 Hz, 1H), 6.46 (d, J = 15.8 Hz, 1H),
5.00 (d, J = 7.3 Hz, 1H), 3.73 (s, 3H), 1.67 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
155.8, 155.0, 142.2,
137.4, 131.5, 131.3, 130.9, 128.8, 128.7, 128.6, 127.6, 126.9, 126.6, 124.7, 123.0, 116.1, 112.9, 103.3, 83.7, 55.8,
46.2, 28.4, 27.6.
(S,E)-tert-butyl 5-(benzyloxy)-3-(1,3-diphenylallyl)-1H-indole-1-carboxylate (Boc-3h) [15]: Colorless oil. 99%
yield and 96% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v,
0.35 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 34.3 min for (S)-isomer (major), tr = 38.3 min for
1
(R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ 8.00 (brs, 1H), 7.38–7.30 (m, 13H), 7.28–7.22 (m, 3H),
6.99 (dd, J = 9.0, 2.2 Hz, 1H), 6.86 (d, J = 2.2 Hz, 1H), 6.69 (dd, J = 15.8, 7.4 Hz, 1H), 6.45 (d, J = 15.8 Hz,
1H), 4.98 (d, J = 5.0 Hz, 3H), 1.67 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
154.9, 150.0, 142.2, 137.4, 131.5,
131.3, 130.9, 128.8, 128.7, 128.6, 128.0, 127.7, 127.6, 126.9, 126.6, 124.7, 123.0, 116.2, 113.9, 104.7, 83.7, 70.8,
46.2, 28.4.
(S,E)-tert-butyl 5-chloro-3-(1,3-diphenylallyl)-1H-indole-1-carboxylate
(Boc-3i) [15]: White solid
(m.p. 54–56 ◦C). 99% yield and 92% ee, determined by chiral HPLC analysis (Chiralcel OD-H
◦
hexane/isopropanol, 99:1 v/v, 0.7 mL/min, 25 C, UV 254 nm), Retention times: tr = 8.2 min for
1
(S)-isomer (major), tr = 9.0 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
8.02 (brs, 1H),
7.37–7.27 (m, 10H), 7.24–7.20 (m, 2H), 6.64 (dd, J = 15.8, 7.3 Hz, 1H), 6.42 (d, J = 15.8 Hz, 1H),

Molecules 2019, 24, 1575
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4.98 (d, J = 7.3 Hz, 1H), 1.65 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
149.6, 141.7, 137.1, 134.2, 131.6,
131.1, 130.8, 128.7, 128.6, 128.4, 128.2, 127.5, 127.0, 126.4, 125.1, 124.6, 122.5, 119.6, 116.4, 84.2, 45.8, 28.2.
(S,E)-tert-butyl 5-bromo-3-(1,3-diphenylallyl)-1H-indole-1-carboxylate
(Boc-3j) [15]: White solid
(m.p. 72–73 ◦C). 96% yield and 93% ee, determined by chiral HPLC analysis (Chiralcel OD-H
◦
hexane/isopropanol, 99:1 v/v, 0.7 mL/min, 25 C, UV 254 nm), Retention times: tr = 8.2 min for
1
(S)-isomer (major), tr = 8.8 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
7.99 (brs, 1H),
7.46 (s, 1H), 7.38–7.36 (m, 4H), 7.33–7.27 (m, 6H), 7.26–7.21 (m, 2H), 6.67 (dd, J = 15.8, 7.3 Hz, 1H), 6.43
(d, J = 15.8 Hz, 1H), 4.99 (d, J = 7.3 Hz, 1H), 1.65 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
149.4, 141.5,
137.0, 134.5, 131.5, 131.4, 130.7, 128.6, 128.4, 128.2, 127.4, 127.2, 126.8, 126.3, 124.8, 122.5, 122.3, 116.6,
115.8, 84.1, 45.6, 28.1.
(S,E)-tert-butyl 3-(1,3-diphenylallyl)-6-methyl-1H-indole-1-carboxylate (Boc-3k): White solid (m.p. 121–123 ◦C).
99% yield and 93% ee, de◦termined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol,
99:1 v/v, 0.7 mL/min, 25 C, UV 254 nm), Retention times: tr = 7.2 min for (S)-isomer (major),
1
tr = 8.2 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
7.97 (brs, 1H), 7.37–7.18 (m, 12H),
6.96 (d, J = 8.0 Hz, 1H), 6.69 (dd, J = 15.8, 7.4 Hz, 1H), 6.44 (d, J = 15.8 Hz, 1H), 5.01 (d, J = 7.4 Hz, 1H),
2.44 (s, 3H), 1.65 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
150.0, 142.2, 137.3, 136.3, 134.4, 131.3, 131.2,
128.6, 128.5, 128.4, 127.6, 127.4, 126.7, 126.4, 123.9, 123.1, 123.0, 119.7, 115.6, 83.5, 46.0, 28.2, 22.0. HRMS
(ESI): calcd for C29H29NNaO2 [M + Na]+: 446.2091, found 446.2093.
(S,E)-tert-butyl 6-chloro-3-(1,3-diphenylallyl)-1H-indole-1-carboxylate (Boc-3l): Colorless oil. 98% yield and
93% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.7 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 8.5 min for (S)-isomer (major), tr = 9.2 min for (R)-isomer
(minor). 1H-NMR (500 MHz, CDCl3)
δ
8.14 (brs, 1H), 7.36–7.19 (m, 12H), 7.10 (dd, J = 8.3, 1.7 Hz,
1H), 6.67 (dd, J = 15.8, 7.4 Hz, 1H), 6.43 (d, J = 15.8 Hz, 1H), 5.00 (d, J = 7.3 Hz, 1H), 1.66 (s, 9H);
13C-NMR (125 MHz, CDCl3)
171.2, 149.5, 141.8, 137.1, 136.2, 131.5, 130.9, 130.4, 128.7, 128.6, 128.4,
δ
127.5, 126.9, 126.4, 124.3, 123.0, 122.9, 120.9, 115.6, 84.3, 60.4, 45.9, 28.2, 21.1, 14.2. HRMS (ESI): calcd for
C28H26ClNNaO2 [M + Na]+: 466.1544, found 466.1547.
(S,E)-tert-butyl ◦3-(1,3-diphenylallyl)-7-methyl-1H-indole-1-carboxylate (Boc-3m) [19]: White solid
(m.p. 123–124 C). 99% yield and 83% ee, det◦ermined by chiral HPLC analysis (Chiralcel OD-H
hexane/isopropanol, 99:1 v/v, 0.7 mL/min, 25 C, UV 254 nm), Retention times: tr = 7.6 min for
1
(S)-isomer (major), tr = 8.9 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ 7.39–7.28
(m, 9H), 7.26–7.18 (m, 3H), 7.09–7.04 (m, 2H), 6.71 (dd, J = 15.8, 7.4 Hz, 1H), 6.45 (d, J = 15.8 Hz, 1H),
5.03 (d, J = 7.4 Hz, 1H), 2.64 (s, 3H), 1.63 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
149.6, 142.0, 137.2,
135.4, 131.2, 131.1, 131.0, 128.4, 128.3, 127.6, 127.2, 126.5, 126.3, 125.9, 125.3, 122.8, 122.4, 117.6, 83.2, 45.8,
28.0, 22.1.
(S,E)-tert-butyl 3-(1,3-diphenylallyl)-7-methoxy-1H-indole-1-carboxylate (Boc-3n): Colorless oil. 95% yield
and 84% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v,
0.7 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 21.4 min for (S)-isomer (major), tr = 49.0 min for
1
(R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ 7.37 (d, J = 7.5 Hz, 2H), 7.32–7.26 (m, 7H), 7.25–7.21
(m, 2H), 7.07 (t, J = 7.9 Hz, 1H), 6.96 (d, J = 7.8 Hz, 1H), 6.80 (d, J = 7.9 Hz, 1H), 6.69 (dd, J = 15.8,
7.4 Hz, 1H), 6.43 (d, J = 15.8 Hz, 1H), 5.01 (d, J = 7.4 Hz, 1H), 3.93 (s, 3H), 1.62 (s, 9H); 13C-NMR
(125 MHz, CDCl3)
δ 150.0, 148.4, 142.2, 137.3, 132.8, 131.4, 131.3, 128.6, 127.4, 126.7, 126.5, 126.4, 125.2,
123.5, 122.4, 112.8, 106.9, 83.3, 55.8, 46.0, 28.1. HRMS (ESI): calcd for C29H29NNaO3 [M+Na]+: 462.2040,
found 462.2043.
(S,E)-tert-butyl 7-chloro-3-(1,3-diphenylallyl)-1H-indole-1-carboxylate (Boc-3o): Colorless oil. 99% yield and
94% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.7 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 11.6 min for (S)-isomer (major), tr = 17.3 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ
7.36–7.27 (m, 10H), 7.26–7.21 (m, 3H), 7.06 (t, J = 7.8 Hz, 1H),
6.67 (dd, J = 15.8, 7.4 Hz, 1H), 6.43 (d, J = 15.8 Hz, 1H), 5.00 (d, J = 7.4 Hz, 1H), 1.63 (s, 9H); 13C-NMR

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(125 MHz, CDCl3)
δ
149.1, 141.7, 137.0, 133.2, 132.7, 131.5, 130.8, 128.6, 128.5, 128.4, 127.4, 127.3,
126.8, 126.5, 126.4, 123.4, 122.4, 120.4, 118.7, 84.5, 45.8, 27.9. HRMS (ESI): calcd for C28H26ClNNaO2
[M + Na]+: 466.1544, found 466.1539.
(S,E)-tert-butyl 3-(1,3-di-p-tolylallyl)-1H-indole-1-carboxylate (Boc-3p) [19]: Colorless oil. 99% yield and
94% ee, determined by chiral HPLC analysis (Chiralcel AD-H hexane/isopropanol, 99:1 v/v, 0.5 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 12.0 min for (S)-isomer (major), tr = 14.1 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ
8.13 (brs, 1H), 7.38 (d, J = 8.2 Hz, 2H), 7.31–7.27 (m, 3H), 7.24–7.22
(m, 2H), 7.16–7.11 (m, 5H), 6.67 (dd, J = 15.8, 7.4 Hz, 1H), 6.43 (d, J = 15.8 Hz, 1H), 5.01 (d, J = 7.7 Hz,
1H), 2.35 (s, 3H), 2.34 (s, 3H), 1.69 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
150.1, 139.4, 137.2, 136.3, 136.0,
134.7, 131.1, 130.6, 130.1, 129.4, 129.3, 128.5, 126.4, 124.5, 123.9, 123.5, 122.6, 120.4, 115.4, 83.8, 45.7,
28.4, 21.3.
(S,E)-tert-butyl 3-(1,3-bis(4-methoxyphenyl)allyl)-1H-indole-1-carboxylate (Boc-3q): Yellow oil. 85% yield
and 90% ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v,
0.7 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 17.5 min for (S)-isomer (major), tr = 19.3 min for
1
(R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
8.08 (s, 1H), 7.33–7.74 (m, 5H), 7.22 (d, J = 8.6 Hz,
2H), 7.11 (t, J = 7.5 Hz, 1H), 6.82 (t, J = 9.2 Hz, 4H), 6.51 (dd, J = 15.8, 7.2 Hz, 1H), 6.34 (d, J = 15.8 Hz,
1H), 4.95 (d, J = 7.2 Hz, 1H), 3.78 (s, 6H), 1.65 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
159.1, 158.3, 150.0,
134.4, 130.4, 130.1, 130.0, 129.4, 127.5, 124.3, 123.7, 123.6, 122.4, 120.2, 115.3, 113.9, 83.7, 55.3, 55.2, 45.1,
28.3. HRMS (ESI): calcd for C30H31NNaO4 [M + Na]+: 492.2145, found 492.2150.
(S,E)-tert-butyl 3-(1,3-bis(4-chlorophenyl)allyl)-1H-indole-1-carboxylate (Boc-3r) [19]: White solid
◦
(m.p. 65–67 C). 99% yield and 95% ee, dete◦rmined by chiral HPLC analysis (Chiralcel OD-H
hexane/isopropanol, 99:1 v/v, 0.7 mL/min, 25 C, UV 254 nm), Retention times: tr = 8.6 min for
1
(S)-isomer (major), tr = 11.7 min for (R)-isomer (minor). H-NMR (500 MHz, CDCl3)
δ
8.11 (brs, 1H),
7.36 (s, 1H), 7.32–7.23 (m, 10H), 7.14 (t, J = 7.5 Hz, 1H), 6.64 (dd, J = 15.8, 7.2 Hz, 1H), 6.37 (d, J = 15.8 Hz,
1H), 5.01 (d, J = 7.2 Hz, 1H), 1.68 (s, 9H); 13C-NMR (125 MHz, CDCl3)
δ
150.0, 140.5, 136.0, 135.6, 133.3,
132.8, 131.5, 130.7, 129.9, 129.7, 129.0, 128.9, 127.8, 124.7, 124.0, 122.7, 122.4, 120.1, 115.5, 84.1, 45.4, 28.4.
(S,E)-tert-butyl 3-(1,3-bis(4-nitrophenyl)allyl)-1H-indole-1-carboxylate (Boc-3s): Yellow oil. 87% yield
and 97% ee, determined by chiral HPLC analysis (Chiralcel AD-H hexane/isopropanol, 93:7 v/v,
1.0 mL/min, 25 ◦C, UV 254 nm), Retention times: tr = 43.5 min for (R)-isomer (minor), tr = 54.4 min
for (S)-isomer (major). 1H-NMR (500 MHz, CDCl3)
δ
8.21–8.12 (m, 5H), 7.50 (d, J = 7.2 Hz, 4H), 7.42
(s, 1H), 7.33 (t, J = 7.6 Hz, 1H), 7.24–7.14 (m, 2H), 6.85 (dd, J = 15.8, 7.2 Hz, 1H), 6.51 (d, J = 15.8 Hz,
1H), 5.21 (d, J = 7.2 Hz, 1H), 1.68 (s, 9H); 13C-NMR (125 MHz, CDCl3)
148.7, 147.1, 142.9, 134.3,
δ
130.7, 129.3, 129.0, 127.0, 124.9, 124.1, 122.8, 120.6, 119.5, 115.6, 84.3, 45.8, 28.2. HRMS (ESI): calcd for
C28H25N3NaO6 [M + Na]+: 522.1636, found 522.1632.
3.4. General Procedure for the Pd-Catalyzed Asymmetric Allylic Etherification
Ligand L1 (5.0 mg, 4 mol%) and [Pd(C3H5)Cl]2 (2.2 mg, 2 mol%) were dissolved in DCM (1.0 mL)
in a Schlenk tube under Ar. After 0.5 h of stirring at room temperature, allylic acetate 2a (0.3 mmol)
dissolved in DCM (0.5 mL) was added, followed by alcohol 4 (0.9 mmol) dissolved in DCM (0.5 mL) and
Cs2CO3 (195 mg, 0.9 mmol). The mixture was stirred at 0 ◦C for 5 h and then was diluted with CH2Cl2
and washed with saturated NH4Cl (aq). The organic layers were dried over MgSO4 and filtered, and
the solvents were evaporated in vacuo. The residue was purified by flash column chromatography,
eluting with petroleum ether and ethyl acetate to afford the corresponding product 5.
(S,E)-(3-(benzyloxy)prop-1-ene-1,3-diyl)dibenzene (5a) [44]: Colorless oil. 99% yield and 98% ee, determined
by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.5 mL/min, 25 ◦C, UV 254 nm),
1
Retention times: tr = 12.2 min for (S)-isomer (major), tr = 13.4 min for (R)-isomer (minor). H-NMR
(500 MHz, CDCl3) δ 7.46–7.30 (m, 14H), 7.27–7.23 (m, 1H), 6.66 (d, J = 15.9 Hz, 1H), 6.38 (dd, J = 15.9,

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7.0 Hz, 1H), 5.04 (d, J = 7.0 Hz, 1H), 4.62–4.57 (m, 2H); 13C-NMR (125 MHz, CDCl3)
δ
141.0, 138.2, 136.5,
131.4, 130.2, 129.6, 128.4, 128.3, 127.6, 127.4, 126.9, 126.5, 81.5, 70.0.
(S,E)-(3-((4-methoxybenzyl)oxy)prop-1-ene-1,3-diyl)dibenzene (5b) [44]: Colorless oil. 97% yield and 97%
ee, determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.5 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 18.0 min for (S)-isomer (major), tr = 23.8 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ
7.44 (d, J = 7.6 Hz, 2H), 7.38 (t, J = 7.6 Hz, 4H), 7.32–7.29 (m, 5H),
7.23 (t, J = 7.2 Hz, 1H), 6.91 (d, J = 8.5 Hz, 2H), 6.63 (d, J = 15.9 Hz, 1H), 6.36 (dd, J = 15.9, 7.0 Hz, 1H),
5.01 (d, J = 7.0 Hz, 1H), 4.51 (s, 2H), 3.82 (s, 3H); 13C-NMR (125 MHz, CDCl3)
δ 159.1, 141.2, 136.6, 131.4,
130.4, 130.3, 129.3, 128.5, 127.6, 126.9, 126.5, 113.7, 81.2, 69.7, 55.2.
(S,E)-(3-((4-bromobenzyl)oxy)prop-1-ene-1,3-diyl)dibenzene (5c) [44]: Colorless oil. 93% yield and 91% ee,
determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 95:5 v/v, 0.5 mL/min, 25 ◦C,
UV 254 nm), Retention times: tr = 10.2 min for (S)-isomer (major), tr = 11.2 min for (R)-isomer (minor).
1H-NMR (500 MHz, CDCl3)
δ 7.47 (d, J = 8.3 Hz, 2H), 7.42-7.36 (m, 6H), 7.31–7.27 (m, 3H), 7.25–7.23
(m, 3H), 6.61 (d, J = 15.9 Hz, 1H), 6.32 (dd, J = 15.9, 7.1 Hz, 1H), 4.97 (d, J = 7.1 Hz, 1H), 4.55–4.48
(m, 2H); 13C-NMR (125 MHz, CDCl3)
127.0, 126.7, 121.4, 81.9, 69.4.
δ 140.9, 137.5, 136.5, 131.8, 131.5, 130.1, 129.4, 128.7, 128.6, 127.9,
(S,E)-(3-((3-bromobenzyl)oxy)prop-1-ene-1,3-diyl)dibenzene (5d) [45]: Colorless oil. 95% yield and 94% ee,
determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.5 mL/min, 25 ◦C,
UV 254 nm), Retention times: tr = 14.3 min for (S)-isomer (major), tr = 15.9 min for (R)-isomer (minor).
1H-NMR (500 MHz, CDCl3)
δ 7.54 (s, 1H), 7.44–7.39 (m, 7H), 7.33–7.29 (m, 4H), 7.26–7.21 (m, 2H), 6.65
(d, J = 15.9 Hz, 1H), 6.36 (dd, J = 15.9, 7.1 Hz, 1H), 5.02 (d, J = 7.0 Hz, 1H), 4.58 (q, J = 12.2 Hz, 2H);
13C-NMR (125 MHz, CDCl3)
82.1, 69.4.
δ 140.9, 136.5, 131.8, 130.6, 130.0, 128.6, 127.9, 127.0, 126.7, 126.1, 122.6,
(S,E)-(3-((2-bromobenzyl)oxy)prop-1-ene-1,3-diyl)dibenzene (5e) [46]: Colorless oil. 93% yield and 93%
ee, determined by chiral HPLC analysis (Chiralcel OJ-H hexane/isopropanol, 99:1 v/v, 0.3 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 73.1 min for (S)-isomer (major), tr = 81.9 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ 7.69 (d, J = 7.7 Hz, 1H), 7.64 (d, J = 7.9 Hz, 1H), 7.57–7.47
(m, 6H), 7.45–7.39 (m, 4H), 7.35–7.24 (m, 2H), 6.80 (d, J = 15.9 Hz, 1H), 6.47 (dd, J = 15.9, 7.0 Hz, 1H),
5.17 (d, J = 7.1 Hz, 1H), 4.76 (q, J = 13.1 Hz, 2H); 13C-NMR (125 MHz, CDCl3)
δ 141.0, 137.9, 136.6,
132.9, 132.5, 131.8, 130.0, 129.2, 128.9, 128.6, 127.8, 127.4, 126.9, 126.7, 82.4, 69.8.
(S,E)-2-(((1,3-diphenylallyl)oxy)methyl)naphthalene (5f) [40]: Colorless oil. 97% yield and 94% ee,
determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 98:2 v/v, 1.0 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 7.3 min for (S)-isomer (major), tr = 10.2 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ
7.84–7.79 (m, 4H), 7.51–7.45 (m, 5H), 7.40–7.37 (m, 4H), 7.32–7.28
(m, 3H), 7.23 (t, J = 7.3 Hz, 1H), 6.66 (d, J = 15.9 Hz, 1H), 6.39 (dd, J = 15.9, 7.0 Hz, 1H), 5.06 (d, J = 7.0 Hz,
1H), 4.74 (s, 2H); 13C-NMR (125 MHz, CDCl3)
141.2, 136.7, 136.0, 133.4, 133.1, 131.7, 130.3, 128.6,
δ
128.2, 128.0, 127.8, 127.7, 127.1, 126.7, 126.5, 126.1, 125.9, 125.8, 81.7, 70.3.
(S,E)-2-(((1,3-diphenylallyl)oxy)methyl)pyridine (5g) [44]: Colorless oil. 86% yield and 94% ee, determined
by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.8 mL/min, 25 ◦C, UV 254 nm),
1
Retention times: tr = 25.0 min for (S)-isomer (major), tr = 36.8 min for (R)-isomer (minor). H-NMR
(500 MHz, CDCl3) δ 8.56 (d, J = 4.6 Hz, 1H), 7.74–7.71 (m, 1H), 7.58 (d, J = 7.8 Hz, 1H), 7.49 (d, J = 7.4 Hz,
2H), 7.40 (t, J = 7.4 Hz, 4H), 7.32 (t, J = 7.6 Hz, 3H), 7.25 (t, J = 7.3 Hz, 1H), 7.21–7.19 (m, 1H), 6.72
(d, J = 15.8 Hz, 1H), 6.40 (dd, J = 15.8, 7.1 Hz, 1H), 5.11 (d, J = 7.1 Hz, 1H), 4.78 (dd, J = 34.2, 13.5 Hz,
2H); 13C-NMR (125 MHz, CDCl3)
122.1, 121.2, 82.5, 71.1.
δ 158.7, 148.9, 140.7, 136.4, 131.7, 129.8, 128.4, 127.7, 126.8, 126.5,
(S,E)-(3-ethoxyprop-1-ene-1,3-diyl)dibenzene (5h) [44]: Colorless oil. 98% yield and 99% ee, determined
by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.5 mL/min, 25 ◦C, UV 254 nm),

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Retention times: tr = 9.2 min for (S)-isomer (major), tr = 10.4 min for (R)-isomer (minor). 1H-NMR
(500 MHz, CDCl3) 7.42–7.35 (m, 6H), 7.31–7.27 (m, 3H), 7.22 (t, J = 7.3 Hz, 1H), 6.63 (d, J = 15.9 Hz,
δ
1H), 6.34 (dd, J = 15.9, 7.1 Hz, 1H), 4.93 (d, J = 7.1 Hz, 1H), 3.61–3.56 (m, 1H), 3.52–3.48 (m, 1H),
1.27 (t, J = 7.0 Hz, 3H); 13C-NMR (125 MHz, CDCl3)
δ 141.6, 136.7, 131.2, 130.7, 128.5, 127.7, 127.6, 126.9,
126.6, 82.6, 64.0, 15.4.
(S,E)-(3-(but-3-en-1-yloxy)prop-1-ene-1,3-diyl)dibenzene (5i) [44]: Colorless oil. 97% yield and 95% ee,
determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99.2:0.8 v/v, 0.4 mL/min,
25 ◦C, UV 254 nm), Retention times: tr = 10.3 min for (S)-isomer (major), tr = 12.1 min for (R)-isomer
1
(minor). H-NMR (500 MHz, CDCl3)
δ
7.40–7.34 (m, 6H), 7.30–7.26 (m, 3H), 7.22 (t, J = 7.4 Hz, 1H), 6.62
(d, J = 15.9 Hz, 1H), 6.31 (dd, J = 15.9, 7.0 Hz, 1H), 5.90–5.81 (m, 1H), 5.11–5.02 (m, 2H), 4.92 (d, J = 7.0 Hz,
1H), 3.60–3.56 (m, 1H), 3.50–3.46 (m, 1H), 2.43 (q, J = 6.8 Hz, 2H); 13C-NMR (125 MHz, CDCl3)
δ 141.4,
136.6, 135.3, 131.3, 130.5, 128.5, 127.7, 127.6, 126.8, 126.6, 116.3, 82.7, 68.0, 34.4.
(S,E)-2-((1,3-diphenylallyl)oxy)-2,3-dihydro-1H-indene (5j) [41]: Colorless oil. 96% yield and 93% ee,
determined by chiral HPLC analysis (Chiralcel OD-H hexane/isopropanol, 99:1 v/v, 0.5 mL/min, 25 ◦C,
UV 254 nm), Retention times: tr = 13.7 min for (S)-isomer (major), tr = 14.8 min for (R)-isomer
(minor). 1H-NMR (500 MHz, CDCl3)
δ 7.45–7.36 (m, 6H), 7.32–7.30 (m, 3H), 7.26–7.15 (m, 5H),
6.65 (d, J = 15.9 Hz, 1H), 6.37 (dd, J = 15.9, 7.0 Hz, 1H), 5.12 (d, J = 6.9 Hz, 1H), 4.55–4.51 (m, 1H),
3.25–3.02 (m, 4H); 13C-NMR (125 MHz, CDCl3)
126.5, 126.3, 124.5, 80.9, 77.9, 39.5.
δ 141.4, 140.8, 136.5, 131.1, 130.6, 128.4, 127.5, 126.8,
4. Conclusions
SMI-PHOX ligand exhibited good catalytic performance in Pd-catalyzed asymmetric allylic
alkylation reactions of indoles with 1,3-diaryl-2-propenyl acetate. The reactions afforded the
corresponding products with high yields (up to 98%) and enantioselectivities (up to 98% ee) for
a broad scope of indole derivatives. SMI-PHOX ligand was determined to be the most efficient
P,N-ligand for this reaction. Furthermore, SMI-PHOX ligand was also efficient for Pd-catalyzed
asymmetric allylic etherification with hard aliphatic alcohols as nucleophiles. Up to 99% yield and
99% ee were obtained. Further applications of these ligands in other asymmetric transformations are
currently under development in our laboratory.
Supplementary Materials: The supplementary materials including NMR spectra and HPLC traces of the
compounds are available online.
Author Contributions: Conceptualization, D.T. and Z.Q.; methodology, Z.Q. and R.S.; formal analysis, Z.Q. and
K.Y.; investigation, Z.Q. and R.S.; resources, D.T.; data curation, Z.Q.; writing—original draft preparation, D.T.
and Z.Q.; writing—review and editing, D.T.; supervision, D.T. and Z.Q. All authors read and approved the
final manuscript.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds are available from the authors.
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