Efficient and Divergent Synthesis of Medium-Sized Lactams through Zinc-Catalyzed Oxidative Cyclization of Indoly Ynamides?

Article abstract of DOI:10.1002/cjoc.201900478

An efficient zinc-catalyzed oxidative cyclization of readily available indoly ynamides has been developed, enabling rapid and practical access to a diverse array of valuable medium-sized lactams in mostly good to excellent yields with wide substrate scope. In addition, such an asymmetric synthesis has also been explored by employing the chiral substrate.

Full text of DOI:10.1002/cjoc.201900478

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: Efficient and Divergent Synthesis of Medium-Sized Lactams through Zinc-
Catalyzed Oxidative Cyclization of Indoly Ynamides
Authors: Hang-Hao Li, Si-Han Ye, Yang-Bo Chen, Wen-Feng Luo, Peng-Cheng Qian,*
and Long-Wu Ye*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.201900478.
The final Version of Record (VoR) of it with formal page numbers will soon be
published online in Early View: http://dx.doi.org/10.1002/cjoc.201900478.
ISSN 1001-604X • CN 31-1547/O6
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Chinese Journal
of Chemistry
zinc, cyclization, ynamides, oxidation, heterocycles
Report
CJC
中
国 化 学 - An International Journal
Efficient and Divergent Synthesis of Medium-Sized Lactams through
Zinc-Catalyzed Oxidative Cyclization of Indoly Ynamides
Hang-Hao Li,a Si-Han Ye,a Yang-Bo Chen,a Wen-Feng Luo,b Peng-Cheng Qian,*,b and Long-Wu Ye*,a,c
a State Key Laboratory of Physical Chemistry of Solid Surfaces and Key Laboratory for Chemical Biology of Fujian Province, College of Chemistry and
Chemical Engineering, Xiamen University, Xiamen 361005, China
b Institute of New Materials & Industry Technology, College of Chemistry & Materials Engineering, Wenzhou Uni-versity, Wenzhou 325035, China
c State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
Cite this paper: Chin. J. Chem. 2019, 37, XXX—XXX. DOI: 10.1002/cjoc.201900XXX
Summary of main observation and conclusion An efficient zinc-catalyzed oxidative cyclization of readily available indoly ynamides has been developed,
enabling rapid and practical access to a diverse array of valuable medium-sized lactams in mostly good to excellent yields with wide substrate scope. In
addition, such an asymmetric synthesis has also been explored by employing the chiral substrate.
efficient synthetic methods have been developed based on this
Background and Originality Content
Medium-sized lactams, especially the indole-fused
medium-sized lactams such as Paullone and its derivatives and
strategy.[5] In this regard, our group recently disclosed that such
an N-oxide oxidation of ynamides could be achieved via non-noble
metal catalysis presumably by a Lewis acid-catalyzed SN2’ pathway,
Balasubramide, are important structural motifs found in a large
which is distinctively different from the relevant oxidative gold
number of natural products and bioactive molecules (Figure 1).[1]
catalysis. And importantly, the unwanted overoxidation could be
However, the formation of these scaffolds is generally difficult
completely suppressed in this type of non-noble metal catalysis.
owing to entropic effects and transannular interactions.[2] To date,
As a result, this strategy has been widely utilized into the
reported methods for their synthesis are very limited, and most of
them are limited to the noble metal catalysis.[3] Therefore, the
development of novel strategies for their construction is highly
desired, especially those with high efficiency and flexibility.
synthesis of a variety of five- and six-membered lactams[6] and
α-functionalized amides (Scheme 1a).[7]
Inspired by these results and our recent work on the catalytic
construction of medium-sized lactams,[8] we envisioned that the
synthesis of indole-fused medium-sized lactams might be
O
achieved through
oxidation/C–H functionalization of indoly ynamides (Scheme
1b).[9,10] Herein, we describe the realization of such
non-noble metal-catalyzed
ynamide
R
NH
*
R
a
NH
zinc-catalyzed oxidative cyclization of indoly ynamides, leading to
the rapid and practical construction of a diverse range of valuable
medium-sized lactams in mostly good to excellent yields with
broad substrate scope. Moreover, such an asymmetric synthesis
has also been achieved by employing the chiral substrate.
NH
au one:
en au one:
s er au one:
N
O
=
H
H
P
ll
R
=
r
an m o c a en
ti it ti
K
Al t
p
p
ll
ll
R
R
B
NO2
g
t
=
N
H
N
O
O
NH
OH
N
H
Ph
-
+
a asu ram
b l
id
)
e
an ro era ve ac v
tip lif ti ti ity
b
(
Figure 1 Indole-fused seven- and eight-membered lactams in natural
products and bioactive molecules.
Over the past decade, the generation of presumable α-oxo
gold carbenoid intemediates via gold-catalyzed intermolecular
alkyne oxidation by an N–O bond oxidant has attracted significant
research attention because this protocol avoids to use the
hazardous, not easily obtainable, and potentially explosive α-diazo
carbonyls as precursors for carbene generation.[4] Thus, numerous
This article has been accepted for publication and undergone full peer review but has not been
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differences between this version and the Version of Record. Please cite this article as doi:
10.1002/cjoc.201900478
This article is protected by copyright. All rights reserved.

First author et al.
Report
Scheme 1 Non-noble metal-catalyzed intermolecular ynamide oxidation by
an N–O bond oxidant
Entry
1
Catalyst
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
Oxidant (R)
3a (2-Br)
Conditions
DCE, 80 oC, 12 h
Yieldb
27%
-
-
-
α
a
rev ous wor : s n es s o ve an s x mem ere an
unc ona ze am es
P
i
k
y th
i
f fi
d
i
b
d
d
f
ti
li
d
id
)
R2
O
PG
M
[
-
]
2
3b (2-Cl)
DCE, 80 oC, 12 h 35%
DCE, 80 oC, 4 h
32%
R2
PG
R2
N
R1
or
O
R
N
R1
o
x
id
e
N
N
n
u
N
PG
3
3c (3,5-Cl2)
,
=
n
w
ith
ex erna
t
u
or
l N H N TMS
)
u
1 2
(
)
(
-
-
-
s wor
:
n
me um s ze
n
m m
r
m
s
es s o
i
se e
v n
a
e
e
e e ac a
s
Thi
k
di
i
d
b
y th
f
d
ight
b
d
)
l
t
)
(
4
Zn(OTf)2 3d (2,6-Br2) DCE, 80 oC, 0.5 h 54%
R2
O
s
O
M
N
R2
R2
s
M
5
Zn(OTf)2
Zn(OTf)2
Cu(OTf)2
Sc(OTf)3
Zn(OTf)2
3e (2,6-Cl2) DCE, 80 oC, 0.5 h 58%
DCE, 80 oC, 12 h
<5%
R1
.
t
N
.
ca
t
)
n
Z
R1
R1
II
( ) (
n
Z II
( ) (
ca
s
N
n
M
)
-
-
ox
e
ox
e u v
q i
e
N
id
q i
N
id
N
N
N
e u v
2
(
6
2
(
3f
)
)
PG
PG
exam es
PG
exam es
20
pl
25
pl
=
=
n
n
-
-
2
3
e
e
7
3e (2,6-Cl2) DCE, 80 oC, 0.5 h 36%
3e (2,6-Cl2) DCE, 80 oC, 0.5 h 39%
3e (2,6-Cl2) DCE, 80 oC, 0.5 h 92%
46 97 yi ld
68 99% yi ld
%
-
♦
♦
♦
va ua e me um s ze ac ams
bl di d l
ox a ve c c za on
id ti
y li ti
w
id
e su s ra e sco e
l
i
t
b t
t
p
-
♦
♦
♦
rac ca s n es s
p
eas access
ily ibl
e
recursors
non no e me a ca a s s
bl
t l t ly i
p
ti
y th
l
i
8
9c
10d
11
12
13c
Results and Discussion
NaBArF
3e (2,6-Cl2)
3e (2,6-Cl2)
3e (2,6-Cl2)
3e (2,6-Cl2)
DCE, 80 oC, 1 h
DCE, 80 oC, 12 h 10%
76%
4
The 2-indoly ynamide 1a was chosen as the model substrate
for our initial study, hoping to synthesize the more challenging
indole-fused eight-membered lactams (Table 1). To our delight,
the envisioned indole-fused eight-membered lactam 2a was
indeed formed in 27% yield (Table 1, entry 1) when the reaction
was performed under the previously optimized reaction
conditions (10 mol % of Zn(OTf)2, 2 equiv of 2-bromopyridine
N-oxide 3a, DCE, 80 °C).[6d] We then examined different N-oxides
(Table 1, entries 2–6), and found that the use of
2,6-dichloropyridine N-oxide 3e as oxidant could lead to a
significantly improved yield (Table 1, entry 5). Further screening of
MsOH
Tf2NH
DCE, 80 oC, 1 h
69%
Zn(OTf)2
DCE, 60 oC, 1 h
86%
a Reaction conditions: 1a (0.1 mmol), catalyst (0.01 mmol), N-oxide (0.2
mmol), DCE (2 mL), 60-80 °C, 0.5−12 h, in vials. b Measured by 1H NMR
using diethyl phthalate as the internal standard. c 20 mol % of NaBArF4 was
used as additive. d 20 mol % of NaBArF4 was used.
[7b]
other non-noble metals such as Cu(OTf)2 and Sc(OTf)3 failed to
improve the reaction yield (Table 1, entries 7–8). Gratifyingly, the
desired product 2a could be formed in 92% by employing 20 mol %
of NaBArF as additive (Table 1, entry 9). NaBArF here may
enhance the acidity and/or solubility of the zinc complex, thus
leading to the improved reactivity.[6b] Somewhat surprisingly, the
use of 20 mol % of NaBArF4 as sole catalyst also led to the desired
product in 76% yield (Table 1, entry 10).[6a,6b] Of note, Brønsted
acids such as MsOH and Tf2NH failed to further improve the
reaction (Table 1, entries 11–12)[11] and the reaction at 60 oC gave
to a slightly decreased yield (Table 1, entry 13).
Under the optimized reaction conditions (Table 1, entry 9), the
reaction scope of this oxidative cyclization was then explored and
the results are outlined in Table 2. The reaction took place
efficiently with an array of Ms-substituted indoly ynamides 1 and
4
4
the desired indole-fused eight-membered lactams
2 were
obtained in mostly good to excellent yields. Ynamides with
electron-donating groups such as methyl and methoxy and
electron-withdrawing groups such as F, Cl, Br, CHO, COCH3, CO2Me,
and even CN and NO2, were well tolerated under this zinc catalysis,
leading to the desired tricyclic heterocycles 2b–2k in 72–99%
yields. In addition, the reaction also proceeded satisfactorily with
ynamides bearing various meta-substituted aryl groups, furnishing
the desired products 2l–2p in 72–97% yields. Moreover, a variety
of substituted indoly ynamides were also suitable substrates for
this reaction to afford the corresponding products 2q–2w in 68–
95% yields. Finally, it was found that Ts- and Bs-substituted indolyl
ynamides were also compatible with this transformation, thus
delivering the desired 2x (96%) and 2y (80%) respectively. Instead,
low efficiency was observed in case of methyl- or
benzyl-substituted indolyl ynamides, which is distinctively
different from our previous proctol.[6d] The molecular structure of
2a was further confirmed by X-ray diffraction (Figure 2).[12] Of
note, our attempts to extend the reaction to the styryl- and
Table 1 Optimization of reaction conditionsa
O
Ph
s
M
Ph
N
ca a
mo
t ly t 1
l
0
%
s
(
)
reac on con ons
ti
diti
s
M
N
3
or
N
O
N
N
N
O
s
M
s
M
e
R
M
-
a
a
e
a
2
1
3
3
3f
www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
This article is protected by copyright. All rights reserved.

Running title
Chin. J. Chem.
alkyl-substituted ynamides 1z–1aa and terminal ynamide 1ab only
Besides the formation of eight-membered lactams, this
oxidative cyclization was also viable for the construction of
seven-merbered lactams. As depicted in Table 3, the reaction
proceeded smoothly and the anticipated products 5 were formed
in moderate to excellent yields under the above optimized
reaction conditions. First, we investigated different N-substituted
indolyl ynamides. Besides the Ms group, Ts and Bs substituted
indolyl ynamides also gave the desired products 5b–5c in 57–84%
yields. Then, an incredible variety of aryl-substituted indolyl
ynamides (R2 = Ar) were screened, and the corresponding lactams
5d–5m were obtained in 46–97% yields. Further investigation of
different substituents on the indole moiety demonstrated that
both electron-donating groups and electron-withdrawing groups
gave a complex mixture of products.[13,14]
Table 2 Synthesis of indole-fused eight-membered lactams 2a
R2
O
s
M
N
R2
n
mo
mo
Z
Tf 10
l
l
O
%
%
(
)
(
)
)
R1
R1
a
rF2
N BA
20
q
s
M
(
N
3
4
e
e u
v
i
3
2
(
)
.
N
N
,
,
D
E 80 o 0 5 h
C
C
P
G
P
G
2
1
e
e
O
M
M
O
s
s
M
N
O
O
s
s
M
N
M
N
Ph
Table 3 Synthesis of indole-fused seven-membered lactams 5a
R2
O
N
M
,
R2
N
N
s
M
n
mo
mo
u v
i
)
Z
Tf 10
l
l
O
%
%
(
)
(
)
)
s
M
s
,
N
M
%
R1
R1
a
rF2
,
,
c
2
N BA
2
0
s
M
(
2
4
a
2
N
2
2b
72
81
90
%
%
e
e
q
3
(
N
N
.
,
,
,
2d
,
=
=
R
R
F 89
D
C
E
80 oC 0
5 h
%
R
P
G
P
G
,
,
O
e
s
O
2
Cl 94
%
M
N
s
,
=
M
N
e
2l
R
,
M
=
72
e
4
5
%
,
,
=
r
2f
R
B
86
%
,
m
R
2
2
2
X
OM 76
,
%
,
,
=
=
2g
2h
R
R
=
CHO 97
%
,
=
n
R
F 97
,
%
,
,
e
CO2M 85
,
%
,
=
=
o
R
R
Cl 73
%
,
R
,
5d
,
=
=
=
=
=
2i
R
CN 99
%
e
82
%
,
,
R
R
M
r
O
N
M
2p
B
73
%
N
M
,
,
=
,
e
5
,
e
2
j
R
COM 89
,
=
NO2 99
%
e
M
O
7
Ph
O
9
%
s
M
s
s
,
,
a
5
P
,
,
,
,
,
=
=
=
s
M
2k
R
%
N
s
s
s
5f R
M
T
B
86
84
F
6
4
%
G
%
%
%
N
,
,
,
r
5b
5g R
B
C
P
G
G
56
%
,
,
,
c
5
5h R
P
5
7
H
O 50
%
46
%
O
O
O
s
s
s
M
N
s
M
M
N
,
,
,
=
=
N
e
5i
5
j
R
R
M
N 50
CO2
Ph
Ph
N
Ph
N
s
M
,
P
G
C
%
e
M
R
N
M
N
N
e
M
O
O
O
s
M
s
M
Ph
s
M
e
M
R
s
M
s
M
,
r
,
=
=
N
2
R
l 68
C
B
%
,
,
2t
N
N
2q
92
95
%
%
,
,
s
2
r
R
71
%
N
e
M
N
N
s
M
O
O
s
O
s
M
N
s
M
N
M
N
s
M
s
M
Ph
Ph
Ph
,
,
=
5l
5
R
l 54
C
%
%
,
,
n
5
5k
77
%
e
M
51
%
,
,
=
m
r
R
B
53
N
M
N
N
R
O
O
O
s
s
M
e
P
G
=
=
M
Ph
Ph
Ph
s
M
s
M
s
M
,
,
,
,
,
,
,
=
=
u
v
x
s
s
2
2
2
N
N
N
R
R
F 76
P
G
T
B
%
%
G
96%
,
w
2
74
%
,
e
M
l
C
l 75
C
2
y P
80
%
N
N
N
s
M
a Reaction conditions: 1 (0.2 mmol), Zn(OTf)2 (0.02 mmol), NaBArF (0.04
mmol), 3e (0.4 mmol), DCE (4 mL), 80 °C, 0.5 h, in vials; isolated yields are
reported.
l
C
4
s
s
M
M
,
,
,
o
5
7
1
5p 7
4
5q
%
%
80
%
O
O
O
Ph
Ph
s
M
Ph
s
M
s
M
N
N
N
e
M
r
B
N
N
N
s
s
M
,
s
96%
s
M
e
M
M
,
,
5t 7
2%
r
5
5
84%
a Reaction conditions: 4 (0.2 mmol), Zn(OTf)2 (0.02 mmol), NaBArF (0.04
mmol), 3e (0.4 mmol), DCE (4 mL), 80 °C, 0.5 h, in vials; isolated yields are
4
Figure 2 Structure of compound 2a in its crystal.
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

First author et al.
Report
reported.
Ph
Et
O
s
M
N
n
mo
mo
u v
i
)
Z
Tf 10
l
O
%
Ph
(
)
(
)
)
rF2
s
N
M
Et
a
N BA
20
l
%
(
4
3
( )
e
e
q
3
2
(
,
,
E 80 o 15
i
N
m n
D
C
C
s
M
N
s
M
. .
.
,
,
7
=
a
7
a
8
r
:
2 5 1
9 %
ee
ee
)
7
75
%
d
(
9 %
(
)
According to the above experimental observations and
previous studies,[6,7] a plausible reaction pathway to rationalize
the formation of eight-membered lactam 2a is presented in
Scheme 2. First, nucleophilic attack of N-oxide 3e occurs on the
Zn-activated ynamide 1a to afford the vinyl zinc alkene
intermediate B. Subsequently, an intramolecular cyclization of B
leads to the formation of dearomatic intermediate C via a
presumable SN2’ pathway[16] with the release of pyridine. Finally,
intermediate C, which is in equilibrium with its tautomer enolate
D, undergoes aromatization and demetallation, delivering the
desired lactam 2a and regenerating the zinc catalyst.
Figure 3 Structure of compound 5a in its crystal.
were well tolerated, producing the desired 5n–5s in 71–96% yields.
Of note, the reaction even occurred efficiently for the
styryl-substituted ynamide to afford the corresponding
seven-membered lactam 5t in 72% yield. The molecular structure
of 5a was also confirmed by X-ray diffraction (Figure 3).[12] Once
again, attempts to extend the reaction to the terminal ynamide 4u,
which might lead to the valuable Paullone and its derivatives,
were unsuccessful.[14]
Moreover, this reaction was also extended to the
aryl-tethered indoly ynamide 4v and electron-rich alkoxy
arene-substituted ynamide 4w, as depicted in Eqs. 1–2. Under the
above standard reaction conditions, the oxidative cyclization of 4v,
followed by NaBH4 reduction, delivered the desired indole-fused
seven-membered N-heterocycle 6v in 40% yield (2 steps). In
addition, the oxidative cyclization of 4w, followed by deprotection,
Scheme 2 Plausible reaction mechanism
O
Ph
s
M
Ph
N
s
M
N
3
n
Z
[
]
N
N
a
2
s
M
s
M
a
1
could
give
the
corresponding
alkoxy
arene-fused
seven-membered lactam 6w in 52% yield (2 steps). Notably, this
structural motif can be found in various bioactive molecules and
may be of medicinal interest.[15] Finally, attempts to extend the
reaction to 3-indolyl ynamide 4x only gave a complex mixture of
products.
n
Ph
O
Z
O
[
]
Ph
Ph
n
Z
[
]
n
Z
Ph
[
]
s
s
M
M
H
H
N
3
N
3
Ph
s
M
s
M
N
3
N
s
M
N
s a
n ar con ons
N
N
1
)
t
d
d
diti
1
( )
s
D
s
M
M
C
N
a
e u v
4
q i
(
4
2
)
N BH
)
N
M
,
,
s
M
r
m n
THF t 10
i
A
N
s
s
v
M
4
Ph
,
v
4
s e s
t
p
6
2
(
0%
)
O
n
Z
N
[
]
N
]
[
]
[
Ph
s
N M
e
M O
O
s an ar con ons
diti
Ph
1
t
d
d
O
e
N
[ ]
3
)
e
M O
3
2
( )
N
e
M O
n
a
n
u v
NH
a
a e e
e
N
2
N / phth l
10 q i
(
)
)
-
,
,
78 o THF 10
i
M
m n
s
e
M O
C
s
T
B
,
w
4
w
6
s e s
2
t
p
52
%
(
)
Conclusions
We then considered the possibility of extending this reaction
In conclusion, we have developed an efficient zinc-catalyzed
oxidative cyclization of indoly ynamides, enabling facile access to
a diverse array of valuable medium-sized lactams in mostly good
to excellent yields with wide substrate scope. Moreover, such an
asymmetric synthesis has also been realized by employing the
chiral substrate. The use of readily available substrates, non-noble
metal as catalyst and a simple procedure render this method
highly practical in organic synthesis. Further synthetic applications
of this oxidative cyclization for the preparation of the relevant
for the preparation of chiral medium-sized lactams starting from
the chiral indolyl ynamides. According to Ellman’s method, the
chiral indoly ynamide 7a could be readily synthesized with
excellent enantiomeric excess. As shown in Eq. 3, this oxidative
zinc catalysis proceeded smoothly with the ethyl-substituted
ynamide 7a, allowing the facile synthesis of highly functionalized
chiral tricyclic lactam 8a in 75% yield, albeit with moderate
diastereoselectivity (d.r. = 2.5:1). Importantly, the enantiomeric
excess (ee) was well maintained in this case.
www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
This article is protected by copyright. All rights reserved.

Running title
Chin. J. Chem.
natural products and bioactive molecules are under investigation
in our laboratory.
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Experimental
NaBArF (0.04 mmol, 35.6 mg) and Zn(OTf)2 (0.02 mmol, 7.3
4
mg) were added to a mixture of the indolyl ynamide 1 or 4 (0.20
mmol) and 2,6-dichloropyridine N-oxide 3e (60.0 mg, 0.40 mmol)
in DCE (4 mL) at room temperature. Then, the reaction mixture
was stirred at 80 °C and the progress of the reaction was
monitored by TLC. The reaction typically took 0.5 h. Upon
completion, the mixture was concentrated and the residue was
purified by chromatography on silica gel (eluent: hexanes/ethyl
acetate) to afford the desired lactam product 2 or 5.
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Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
Acknowledgement
We are grateful for financial support from the National
Natural Science Foundation of China (21572186, 21622204 and
21772161), the Natural Science Foundation of Fujian Province of
China (2019J02001), the President Research Funds from Xiamen
University (20720180036), NFFTBS (No. J1310024), PCSIRT, and
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&
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www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
This article is protected by copyright. All rights reserved.

Running title
Chin. J. Chem.
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For the structures of compounds 1z–1ab and compounds 4u and 4x,
see:
(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2019
Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
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Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

First author et al.
Report
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Text for Table of Contents. We report an efficient zinc-catalyzed oxidative cyclization of indoly
ynamides, enabling rapid and practical access to a diverse array of valuable medium-sized lactams
in mostly good to excellent yields with wide substrate scope. In addition, such an asymmetric
synthesis has also been explored by employing the chiral substrate.
Hang-Hao Li, Si-Han Ye, Yang-Bo Chen,
Wen-Feng Luo, Peng-Cheng Qi-an,* Long-Wu
Ye*
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Chin. J. Chem. 2019, 37, XXX－XXX
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