CuI/Cu(OTf)2/DMSO system-catalyzed intramolecular oxidative cyclization of (o-alkynyl)arylketones: Efficient synthesis of 1,4-naphthoquinones

Article abstract of DOI:10.1016/j.tet.2019.05.066

A concise and efficient method for the synthesis of 1,4-naphthoquinones has been successfully developed involving a CuI/Cu(OTf)₂/DMSO system-catalyzed intramolecular oxidative cyclization of (o-alkynyl)arylketones. The present protocol provided a novel approach to access functionalized 1,4-naphthoquinones from non-naphthoquinone precursors with good selectivity and functional group tolerance.

Full text of DOI:10.1016/j.tet.2019.05.066

Accepted Manuscript
CuI/Cu(OTf) /DMSO system-catalyzed intramolecular oxidative cyclization of (o-
2
alkynyl)arylketones: Efficient synthesis of 1,4-naphthoquinones
Bingwei Zhou, Qian Liu, Heng Wang, Hongwei Jin, Yunkui Liu
PII:
S0040-4020(19)30628-3
https://doi.org/10.1016/j.tet.2019.05.066
TET 30387
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 8 April 2019
Revised Date: 24 May 2019
Accepted Date: 31 May 2019
Please cite this article as: Zhou B, Liu Q, Wang H, Jin H, Liu Y, CuI/Cu(OTf) /DMSO system-catalyzed
2
intramolecular oxidative cyclization of (o-alkynyl)arylketones: Efficient synthesis of 1,4-naphthoquinones,
Tetrahedron (2019), doi: https://doi.org/10.1016/j.tet.2019.05.066.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
CuI/Cu(OTf)2/DMSO system-catalyzed
intramolecular oxidative cyclization of (o-
alkynyl)arylketones: efficient synthesis of 1,4-
naphthoquinones
Leave this area blank for abstract info.
Bingwei Zhou, Qian Liu, Heng Wang, Hongwei Jin, Yunkui Liu
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering,
Zhejiang University of Technology, Hangzhou 310014, China

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
CuI/Cu(OTf)2/DMSO system-catalyzed intramolecular oxidative cyclization of (o-
alkynyl)arylketones: efficient synthesis of 1,4-naphthoquinones
Bingwei Zhou, Qian Liu, Heng Wang, Hongwei Jin and Yunkui Liu
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou
310014, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A concise and efficient method for the synthesis of 1,4-naphthoquinones has been
successfully developed involving a CuI/Cu(OTf)2/DMSO system-catalyzed intramolecular
oxidative cyclization of (o-alkynyl)arylketones. The present protocol provided a novel
approach to access functionalized 1,4-naphthoquinones from non-naphthoquinone
precursors with good selectivity and functional group tolerance.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
1,4-naphthoquinones
Copper catalysis
Annulation
Selectivity
Tandem reaction
1. Introduction
wastes, and/or low efficiency in the formation of the desired
products.
1,4-Naphthoquinones are found frequently in natural
products as well as synthetic molecules and exhibit various
biological activities.1,2 Besides, they are also very useful
intermediates in organic synthesis.3 Therefore, much effort has
been made to develop efficient methods for their preparation in
the past decades.4-12 Traditional methods for the synthesis of
Alternatively, a more promising and efficient approach to 1,4-
naphthoquinones is probably the construction of them
O
O
R1
R2
OMe
R2
R3
(CO)5Cr
+
R1
MLn
+
annulation
oxidation
1,4-naphthoquinones
usually
relied
on
preformed
naphthoquinone derivatives.4-8 This kind of strategy includes
transition metal-catalyzed cross-coupling of naphthoquinones[4]
or halonaphthoquinones5 with organometallic reagents (mostly
boronic reagents), naphthoquinone-derived boronic esters or
stannyl reagents with halides,6 and more challengingly, non-
prefunctionalized naphthoquinones with arenes.7 In addition,
such strategy also includes the alkylation or arylation of
naphthoquinones involving various radical transfer processes.8
All these reactions have attractive features for the construction
of 1,4-naphthoquinones. However, most of these reactions
suffered from one or more limitations such as the requirement
of tedious prefunctionalization of the starting materials, the use
of expensive catalysts, the production of large amount of salt
(a)
(b)
O
R2
O
O
R3
R2
(f) This work
R1
CuCl2, H2O, O2
(c)
R''
R'
R3
Cat. CuI/Cu(OTf)2
DMSO
R1
O
heating
X
(d)
R2
R1
(e)
R2
O
O
+
R1
CO2Me
O
OH
Scheme 1. Previous Work on the synthesis of parent phenanthridine-6-
carbonitrile scaffold.
Corresponding author. Tel.: fax: +86057188334137; e-mail addresses: ykuiliu@zjut.edu.cn (Y. Liu), jhwei828@zjut.edu.cn (H. Jin)

2
Tetrahedron
from non-naphthoquinone precursors due to the atom- and
in developing efficient copper-catalyzed tandem reactions,14
ACCEPTED MANUSCRIPT
step-economy manner. However, this kind of strategy for the
construction of 1,4-naphthoquinones remains very challenging
and only limited success has been reported in the past years
(Scheme 1).9-13 For example, the annulation of Fischer carbene
complexes with alkynes, known as Dötz benzannulation
reaction,9a represents the early findings for the construction 1,4-
naphthoquinones from non-naphthoquinone precursors
(Scheme 1a).9 Later, the cyclization of phthaloyl transition metal
complexes (M = Co, Fe etc.) and alkynes also enabled the direct
formation of 1,4-naphthoquinones (Scheme 1b).10 In 2011, Li et
al11 reported an efficient transformation of 1,6-enynes into 1,4-
herein, we report a CuI/Cu(OTf)2/DMSO system-catalyzed
oxidative cyclization of (o-alkynyl)arylketones leading to the
direct and efficient synthesis of 1,4-naphthoquinones from non-
naphthoquinone precursors (Scheme 1f).
2. Results and discussion
For the initial study, we selected o-phenylethynyl
acetophenone 1a as the model substrate for the optimization of
reaction conditions (Table 1). When 1a was allowed to react
with CuI (10 mol %) in DMSO in a flask at 130 oC for 8 h, 2-phenyl
1,4-naphthoquinone 2a was isolated in 38% GC yield (Table 1,
Entry 1). A series of other copper salts including CuCl, CuBr,
CuCN, Cu(OAc)2, and CuCl2 were investigated, respectively, but
all gave low catalytic efficiency (Table 1, Entry 2). We then tried
naphthoquinones involving
a
Cu(II)-catalyzed oxidative
carbocyclization (Scheme 1c). In 2015, Mal et al12 described a
demethoxycarbonylative annulation of 3-nucleofugal phthalides
with α-substituted acrylates to provide a succinct route to 1,4-
naphthoquinones (Scheme 1d). The ring opening of the
cyclobutenones under high temperatures could also give 1,4-
naphthoquinones (Scheme 1e).13 As part of our research interest
Table 1. Optimization of reaction conditionsa
Entry
Catalyst I (10 mol%)
Catalyst II (10 mol%)
Base
Solvent
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
solvente
DMSO
DMSO
DMSO
DMSO
Yield (%)b
38
1
CuI
--
--
2
Copper saltsc
--
<10
17
--
3
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
PdCl2
--
4
Pd(CF3COO)2
Ni(OTf)2
20
--
5
48
--
6
CuSO4·9H2O
Cu(OAc)2
47
--
7
27
--
8
CuCl2
56
--
9
Cu(BF4)2·H2O
Cu(OTf)2
36
--
10
11
12
13
14
15
16
17
18
19
20
21
85(70)d
--
Cu(OTf)2
10
--
--
CuOTf (10 and 20 mol%)
Cu(OTf)2 (5 mol%)
Cu(OTf)2 (20 mol%)
Cu(OTf)2
<10
55
--
--
CuI
--
CuI
54
--
CuI (5 mol%)
47
--
CuI (20 mol%)
Cu(OTf)2
57
--
CuI
CuI
CuI
CuI
CuI
Cu(OTf)2
0
--
Cu(OTf)2
34f
--
Cu(OTf)2
Na2CO3
KHCO3
31
Cu(OTf)2
27
Cu(OTf)2
78g
--
aReaction conditions: 1a (0.2 mmol), catalyst I (10 mol % based on 1a), catalyst II (10 mol % based on 1a), base (1.0 equiv), solvent (2.0 mL), 130 ºC for 8 h
unless otherwise noted.
bGC yield by using anisole as an internal standard.
cOther copper salts were tested including CuCl, CuBr, CuCN, Cu(OAc)2, and CuCl2, respectively.
dIsolated yield.
eTested solvents include acetonitrile, DMF, and 1,2-dichloroethane.
fThe reaction was run under an argon atmosphere.
gThe reaction temperature is 110 ºC.
to use combined catalytic systems. Through screening a range
of combined catalytic systems, we finally found that the
CuI/Cu(OTf)2 system exhibited excellent catalytic effectiveness
and afforded 2a in 85% yield (Table 1, Entries 10 vs 3-9). A single

3
use of CuI or Cu(OTf)2 only resulted in a lower yield of 2a,
suggesting that the combination of CuI with Cu(OTf)2 played a
key role in enhancing the catalytic efficiency (Table 1, Entries 10
vs, 1, 11). The single use of Cu(I)OTf (10 mol % and 20 mol %) as
the catalyst was investigated, but the reaction gave low yields
of 2a (Table 1, Entry 12). The use of 10 mol % of CuI and
Cu(OTf)2 was just suitable for getting satisfactory yield of 2a,
while either an excessive or a deficient use of one copper
catalyst (CuI or Cu(OTf)2) resulted in a reduced yield of 2a (Table
1, Entries 13-16 vs 10). A series of other solvents were surveyed
for the reaction, and all failed to give the desired product 2a
(Table 1, Entry 17), indicating that DMSO is indispensable for
the reaction. Control experiments showed that the reaction
gave much lower yield of 2a when the reaction was carried out
under an argon atmosphere (Table 1, Entry 18). Attempts to add
some bases to the reaction only gave a lower yield of 1a (Table
1, Entries 19, 20). Decreasing the reaction temperature (110 ºC)
had no positive effect on the yield of 2a (Table 1, Entry 21). In
the reaction, no benzil derivatives (formed from the oxidation
of the alkyne moiety in 1a were detected, indicating that the
reaction exhibited excellent chemoselectivity.15
gave better yields of desired products than those bearing
ACCEPTED MANUSCRIPT
electron-deficient ones (2b, 2d, 2e, vs 2f-2j, Table 2). Note that
substrates possessing o-arylethynyl units generally reacted
more smoothly and gave better yields of 2 than those
containing o-alkylethynyl motifs (2a-2k vs 2t, Table 2). Next, a
variety of (o-alkynyl)acetophenones
1
with different
substituents (R2) on the aromatic ring A were examined under
the standard reaction conditions. Again it was found that
substrates bearing electron-donating substituents on the ring A
worked better for the reaction than those substituted with
electron-withdrawing groups (2l vs 2n; 2p vs 2q, Table 2). In
addition, an attempt to use other (o-alkynyl)arylketones for the
synthesis of 2,3-disubstituted naphthoquinones was also tried.
For example, when 1-(2-(phenylethynyl)phenyl)propan-1-one
1u was subjected to the standard reaction conditions, 2,3-
disubstituted naphthoquinone 2u could be obtained in 43%
yield.
To gain insight into the mechanism of the
CuI/Cu(OTf)2/DMSO system-catalyzed oxidative cyclization of (o-
alkynyl)arylketones, several mechanistic experiments were
done (Scheme 2). Firstly, we envisioned that the reaction might
undergo 1,2-diketonization toward alkynyl moiety in the
presence of transition metal and DMSO15 to give 1,2-diketone
intermediates. Thus, 1,2-diketone 314a was synthesized and
subjected to the standard reaction conditions. To our
disappointment, the reaction failed to afford 1,4-
naphthoquinone 2a while the starting material was recovered
(Scheme 2a), suggesting that 1,2-diketoes are not likely the
possible intermediates. Furthermore, the addition of TEMPO, a
radical scavenger,16 to the reactants showed no much effect on
the final outcome (Scheme 2b), suggesting that a radical
pathway is not likely involved in the reaction. MS analysis of the
reaction mixture based on the substrate 1a showed that Me2S
was produced (m/z = 62 [M]+, see the Supporting Information),
which suggested that DMSO provided the oxygen atom to form
one carbonyl group in 2a and further converted to Me2S.
Table 2. The CuI/Cu(OTf)2 system-catalyzed oxidative
cyclization of (o-alkynyl)arylketones 1 for the synthesis of
2.a,b
aReaction conditions: 1 (0.2 mmol), CuI (10 mol % based on 1), Cu(OTf)2 (10
mol % based on 1), DMSO (2.0 mL), 130 ºC for 8 h.
Scheme 2. Preliminary mechanistic studies.
bIsolated yield.
cThe reaction gave low conversion and most of the starting materials were
recovered.
According to the above experiments and previous literature,15,17-
20
a possible mechanism for the CuI/Cu(OTf)2/DMSO system-
With the optimized reaction conditions in hand, we then
synthesized a range of (o-alkynyl)acetophenones 1 so as to
investigate the reaction scope (Table 2). Firstly, the effect of
functional groups in the alkyne moiety of 1 (R1) on the outcome
of the reaction was studied. It was found that substrates with
alkyne moieties containing electron-rich aryl rings generally
catalyzed oxidative cyclization of 1a is proposed in Scheme 3.
The coordination of CuI with the C-C triple bond in 1a followed
by the nucleophilic addition of DMSO to the triple bond yielded
an intermediate A and released iodine anion.15,17,18 Cu(OTf)2-
catalyzed keto-enol tautomerism of intermediate A in the
presence of iodine anion afforded intermediate B and HI. Under

4
Tetrahedron
the oxidative conditions, reaction of DMSO with HI would
(100-200 mesh) using petroleum ether-EtOAc (6:1) as eluent to
give pure 2.
ACCEPTED MANUSCRIPT
release I2.19 Intramolecular cyclization of intermediate B
followed by iododecupration of the resulting intermediate C
would afford intermediate D.15,17,20 Elimination of HI in D may
finally give 2a.19
4.3.1 2-phenylnaphthalene-1,4-dione (2a)22. Purification by
column chromatography (petroleum ether/EtOAc, 6/1) as a
yellow solid (32.8 mg, 70%); m.p. 107-109 ºC (lit.22 mp 108-110
1
ºC); IR (neat): ν = 1650 (C=O) cm-1, 1589 (C=C) cm-1; H NMR
(CDCl3, 500 MHz): δ 8.20−8.18 (m, 1H), 8.13−8.11 (m, 1H), 7.79-
7.78 (m, 2H), 7.60-7.58 (m, 2H), 7.50-7.48 (m, 3H), 7.09 (s, 1H);
13C NMR (CDCl3, 125 MHz): δ 185.0, 184.3, 148.1, 135.2, 133.8,
133.8, 133.4, 132.5, 132.1, 130.0, 129.4, 128.4, 127.0, 125.9.
4.3.2 2-(p-tolyl)naphthalene-1,4-dione (2b)8g. Purification by
column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (31.2 mg, 63%); m.p. 100-102 ºC (lit.8g m.p.
102-104 ºC); IR (neat): ν = 1652 (C=O) cm-1, 1586 (C=C) cm-1; 1H
NMR (CDCl3, 500 MHz): δ 8.21-8.19 (m, 1H), 8.14-8.13 (m, 1H),
7.80−7.78 (m, 2H), 7.51 (d, J = 8.0 Hz, 2H), 7.30 (d, J = 8.0 Hz,
2H), 7.09 (s, 1H), 2.44 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ
185.2, 184.6, 148.2, 140.5, 134.7, 133.80, 133.75, 132.7, 132.3,
130.6, 129.4, 129.3, 127.1, 126.0, 21.4.
Scheme 3. Proposed mechanism for the oxidative cyclization of 1a
4.3.3 2-(o-tolyl)naphthalene-1,4-dione (2c). Purification by
column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (23.3 mg, 47%); m.p. 70-72 ºC; IR (neat): ν =
3. Conclusion
1
1662 (C=O) cm-1, 1596 (C=C) cm-1; H NMR (CDCl3, 500 MHz): δ
In summary, we described a direct and efficient method for
the preparation of 1,4-naphthoquinones
8.19-8.15 (m, 2H), 7.81-7.79 (m, 2H), 7.39-7.36 (m, 1H), 7.32-
7.27 (m, 2H), 7.20 (dd, J1 = 7.5 Hz, J2 = 1.0 Hz, 1H), 6.95 (s, 1H),
2.25 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ 185.2, 184.0, 150.7,
136.9, 136.2, 133.90, 133.87, 133.82, 132.3, 132.2, 130.4, 129.4,
129.2, 127.0, 126.1, 125.8, 20.4; HRMS (ESI) for C17H13O2
[M+H]+: calcd. 249.0916, found 249.0923.
involving
a
CuI/Cu(OTf)2/DMSO system-catalyzed tandem oxidative
annulation of (o-alkynyl)arylketones. The present method for
the construction of 1,4-naphthoquinones has several
advantages including the use of inexpensive copper catalyst,
simple operation, no need to use preformed naphthoquinone
precursors, and easy availability of the starting materials.
4.3.4 2-(m-tolyl)naphthalene-1,4-dione (2d). Purification by
column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (36.2 mg, 73%); m.p. 124-126 ºC; IR (neat): ν =
1
1664 (C=O) cm-1, 1588 (C=C) cm-1; H NMR (CDCl3, 500 MHz): δ
4. Experimental section
4.1 General methods
8.19-8.17 (m, 1H), 8.13-8.11 (m, 1H), 7.79-7.76 (m, 2H), 7.37-
7.35 (m, 3H), 7.30-7.28 (m, 1H), 7.06 (s, 1H), 2.42 (s, 3H); 13C
NMR (CDCl3, 125 MHz): δ 185.2, 184.5, 148.4, 138.2, 135.2,
133.9, 133.8, 133.4, 132.5, 132.1, 130.9, 130.0, 128.4, 127.1,
126.6, 126.0, 21.5; HRMS (ESI) for C17H13O2 [M+H]+: calcd.
249.0916, found 249.0925.
Unless otherwise stated, all reagents were purchased from
commercial suppliers and used without purifications. Melting
points are uncorrected. The 1H and 13C NMR spectra were
recorded on a spectrometer at 25 °C in CDCl3 at 500 MHz and
125 MHz, respectively, with TMS as internal standard. Chemical
shifts (δ) are expressed in ppm and coupling constants J are
given in Hz. The IR spectra were recorded on an FT-IR
spectrometer. GC-MS experiments were performed with EI
source; high resolution mass spectra (HRMS) were obtained on
a TOF MS instrument with ESI or EI source.
4.3.5
Purification
2-(4-methoxyphenyl)naphthalene-1,4-dione
by column chromatography
(2e)23.
(petroleum
ether/EtOAc, 10/1) as a pale yellow solid (37.5 mg, 71%); m.p.
129-130 ºC (lit.23 m.p. 131-131.5 ºC; IR (neat): ν = 1665 (C=O)
cm-1, 1594 (C=C) cm-1; 1H NMR (CDCl3, 500 MHz): δ 8.19-8.17 (m,
1H), 8.13-8.11 (m, 1H), 7.78-7.76 (m, 2H), 7.59 (dd, J1 = 7.0 Hz, J2
= 2.0 Hz, 2H), 7.05 (s, 1H), 7.01 (dd, J1 = 6.5 Hz, J2 = 2.0 Hz, 2H),
3.22 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ 185.2, 184.8, 161.4,
147.4, 133.77, 133.75, 132.7, 132.2, 131.1, 127.0, 125.9, 125.7,
114.1 (2C), 55.4.
4.2 Preparation of the starting material (o-
alkynyl)arylketones 1
Alkynyl)arylketones (1) were synthesized from the
corresponding o-bromoarylketones and alkynes via Sonogashira
cross-coupling according to the literature procedure.21
4.3.6
Purification
2-(4-chlorophenyl)naphthalene-1,4-dione
by column chromatography
(2f)23.
(petroleum
ether/EtOAc, 10/1) as a pale yellow solid (33.8 mg, 63%); m.p.
170-172 ºC (lit.23 m.p. 173-174 ºC); IR (neat): ν = 1667 (C=O)
cm-1, 1590 (C=C) cm-1; 1H NMR (CDCl3, 500 MHz): δ 8.20-8.18 (m,
1H), 8.14-8.12 (m, 1H), 7.80-7.79 (m, 2H), 7.54 (dd, J1 = 7.0 Hz, J2
= 2.0 Hz 2H), 7.46 (dd, J1 = 6.5 Hz, J2 = 2.0 Hz, 2H), 7.07 (s, 1H);
13C NMR (CDCl3, 125 MHz): δ 184.9, 184.1, 146.9, 136.4, 135.2,
133.98, 133.96, 132.3, 132.0, 131.7, 130.8, 128.8, 127.1, 126.0.
4.3 Typical experimental procedure for the synthesis of 1,4-
naphthoquinones 2
To a 25-mL flask, (o-alkynyl)arylketones 1 (0.2 mmol), CuI
(3.8 mg, 10 mol % based on 1), Cu(OTf)2 (7.2 mg, 10 mol %
based on 1), and DMSO (2 mL) were added. The solution was
then stirred at 130 ºC for 8 h. After completion of the reaction
as indicated by TLC, the mixture was extracted with CH2Cl2 (3×10
mL). The combined organics were concentrated under reduced
pressure. After evaporation of the solvent under vacuum, the
residue was purified by column chromatography on silica gel
4.3.7 2-(2-chlorophenyl)naphthalene-1,4-dione (2g). Purification
by column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (27.3 mg, 51%); m.p. 118−120 ºC; IR (neat): ν =
1
1662 (C=O) cm-1, 1583 (C=C) cm-1; H NMR(CDCl3, 500 MHz): δ

5
8.20-8.16 (m, 2H), 7.82-7.81 (m, 2H), 7.52 (dd, J = 7.5 Hz, J =
(s, 1H), 3.98 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ 185.0, 183.1,
ACCEPTED MANUSCRIPT
1
2
1.0 Hz, 1H), 7.44-7.38 (m, 2H), 7.31 (dd, J1 = 7.5 Hz, J2 = 2.0 Hz,
1H), 7.02 (s, 1H); 13C NMR (CDCl3, 125 MHz): δ 184.9, 183.1,
148.2, 137.4, 134.0, 133.9, 133.17, 133.16, 132.2, 132.1, 130.64,
130.60, 129.8, 127.1, 126.8, 126.2; HRMS (ESI) for C16H10ClO2
[M+H]+: calcd. 269.0369, found 269.0360.
164.2, 147.1, 136.4, 134.8, 134.1, 132.0, 130.8, 129.6, 128.7,
125.9, 120.7, 109.2, 56.0; HRMS (ESI) for C17H12ClO3 [M+H]+:
calcd. 299.0475, found 299.0467.
4.3.14 6-fluoro-2-phenylnaphthalene-1,4-dione (2n). Purification
by column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (14.1 mg, 28%); m.p. 98-100 ºC; IR (neat): ν =
4.3.8 2-(3-chlorophenyl)naphthalene-1,4-dione (2h). Purification
by column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (26.2 mg, 49%); m.p. 145-147 ºC; IR (neat): ν =
1693 (C=O) cm-1, 1668 (C=O) cm-1; H NMR (CDCl3, 500 MHz): δ
1
8.24 (dd, J1 = 8.5 Hz, J2 = 5.0 Hz, 1H), 7.77 (dd, J1 = 8.5 Hz, J2 = 2.5
1685 (C=O) cm-1, 1668 (C=O) cm-1; H NMR (CDCl3, 500 MHz): δ
Hz, 1H), 7.59-7.57 (m, 2H), 7.51-7.43 (m, 4H), 7.11 (s, 1H); 13
C
1
8.20-8.18 (m, 1H), 8.14-8.12 (m, 1H), 7.81-7.79 (m, 2H), 7.74 (t, J
= 6.5 Hz, 1H), 7.48-7.45 (m, 2H), 7.43-7.40 (m, 1H), 7.08 (s, 1H);
13C NMR (CDCl3, 125 MHz): δ 184.8, 183.9, 146.7, 135.7, 135.0,
134.4, 134.04, 133.99, 132.3, 132.0, 130.0, 129.7, 129.5, 127.5,
127.1, 126.1; HRMS (ESI) for C16H10ClO2 [M+H]+: calcd. 269.0369,
found 269.0375.
NMR (CDCl3, 125 MHz): δ 183.9, 183.1, 166.1 (d, J = 256.3 Hz),
148.3, 135.1 (d, J = 1.3 Hz), 134.7 (d, J =7.5 Hz), 133.2, 130.4 (d, J
= 8.8 Hz), 130.2, 129.5, 129.0 (d, J = 3.8 Hz), 128.5, 121.0 (d, J
=22.5 Hz), 112.7 (d, J = 22.5 Hz); HRMS (ESI) for C16H10FO2
[M+H]+: calcd. 253.0665, found 253.0674.
4.3.15
Purification
6-fluoro-2-(p-tolyl)naphthalene-1,4-dione
by column chromatography
(2o).
(petroleum
4.3.9 2-(3-bromophenyl)naphthalene-1,4-dione (2i). Purification
by column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (20.6 mg, 33%); m.p. 138-140 ºC; IR (neat): ν =
ether/EtOAc, 10/1) as a pale yellow solid (21.8 mg, 41%); m.p.
1
78-80 ºC; IR (neat): ν = 1666 (C=O) cm-1, 1600 (C=C) cm-1; H
1
1687 (C=O) cm-1, 1665 (C=O) cm-1; H NMR (CDCl3, 500 MHz): δ
NMR (CDCl3, 500 MHz): δ 8.22(dd, J1 = 8.5 Hz, J2 = 5.5 Hz, 1H),
7.75 (dd, J1 = 8.0 Hz, J2 = 2.5 Hz, 1H), 7.48 (d, J = 8.0 Hz, 2H),
7.45-7.41 (m, 1H), 7.28 (d, J = 8.0 Hz, 2H), 7.08 (s, 1H), 2.42 (s,
3H); 13C NMR (CDCl3, 125 MHz): δ 184.0, 183.3, 166.1 (d, J =
256.3 Hz), 148.3, 140.7, 134.7 (d, J = 8.8 Hz), 134.4 (d, J = 1.3
Hz), 130.4, 130.3 (d, J = 3.8 Hz), 129.4, 129.3, 121.0 (d, J = 22.5
Hz), 112.7, 112.5, 21.4; HRMS (ESI) for C17H12FO2 [M+H]+: calcd.
267.0821, found 267.0829.
8.20-8.18 (m, 1H), 8.14-8.12 (m, 1H), 7.81-7.80 (m, 2H), 7.74 (m,
1H), 7.63-7.61 (m, 1H), 7.52-7.50 (m, 1H), 7.36 (t, J = 7.5 Hz, 1H),
7.08 (s, 1H); 13C NMR (CDCl3, 125 MHz): δ 184.8, 183.9, 146.7,
135.7, 135.3, 134.1, 134.0, 133.0, 132.31, 132.29, 132.1, 130.0,
128.0, 127.1, 126.1, 122.5; HRMS (ESI) for C16H10BrO2 [M+H]+:
calcd. 312.9864, found 312.9864.
4.3.10
Purification
2-(4-fluorophenyl)naphthalene-1,4-dione
by column chromatography
(2j)23.
(petroleum
4.3.16
Purification
6-chloro-2-phenylnaphthalene-1,4-dione
by column chromatography
(2p).
(petroleum
ether/EtOAc, 10/1) as a pale yellow solid (30.2 mg, 60%); m.p.
140-141 ºC (lit.23 m.p. 140.5-141.5 ºC); IR (neat): ν = 1667 (C=O)
cm-1, 1580 (C=C) cm-1; 1H NMR (CDCl3, 500 MHz): δ 8.19-8.17 (m,
1H), 8.12-8.11 (m, 1H), 7.79-7.77 (m, 2H), 7.61-7.57 (m, 2H),
7.19-7.15 (m, 2H), 7.06 (s, 1H); 13C NMR (CDCl3, 125 MHz): δ
184.9, 184.3, 163.9 (d, J = 250.0 Hz), 146.9, 135.0, 133.9, 132.3,
132.0, 131.5, 131.4, 129.4 (d, J = 3.7 Hz), 126.5 (d, J = 13.3 Hz),
115.7, 115.5.
ether/EtOAc, 10/1) as a pale yellow solid (23.0 mg, 43%); m.p.
1
133-135 ºC; IR (neat): ν = 1671 (C=O) cm-1, 1649 (C=O) cm-1; H
NMR (CDCl3, 500 MHz): δ 8.14 (d, J = 8.5 Hz, 1H), 8.08 (d, J = 2
Hz, 1H), 7.73 (dd, J1= 8.5 Hz, J2 = 2.5 Hz, 1H), 7.58-7.56 (m, 2H),
7.51-7.48 (m, 3H), 7.09 (s, 1H); 13C NMR (CDCl3, 125 MHz): δ
183.9, 183.4, 148.3, 140.9, 134.9, 133.9, 133.2, 133.1, 130.6,
130.2, 129.4, 128.8, 128.5, 126.0; HRMS (ESI) for C16H10ClO2
[M+H]+: calcd. 269.0369, found 269.0361.
4.3.11 [1,2'-binaphthalene]-1',4'-dione (2k). Purification by
column chromatography (petroleum ether/EtOAc, 10/1) as a
pale yellow solid (33.5 mg, 59%); m.p. 39-41 ºC; IR (neat): ν =
4.3.17
Purification
7-methyl-2-phenylnaphthalene-1,4-dione
by column chromatography
(2q)22.
(petroleum
1
1657 (C=O) cm-1, 1592 (C=C) cm-1; H NMR (CDCl3, 500 MHz): δ
ether/EtOAc, 10/1) as a pale yellow solid (34.7 mg, 70%); m.p.
101-102 ºC (lit.22 m.p. 101-102 ºC); IR (neat): ν = 1667 (C=O) cm-
1, 1598 (C=C) cm-1; 1H NMR (CDCl3, 500 MHz): δ 8.01 (d, J = 8 Hz,
1H), 7.97 (s, 1H), 7.58-7.55 (m, 3H), 7.49-7.47 (m, 3H), 7.04 (s,
1H), 2.52 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ 185.0, 184.6,
147.9, 145.0, 135.3, 134.5, 133.5, 132.4, 129.88, 129.87, 129.4,
128.4, 127.3, 126.1, 21.9.
8.22-8.20 (m, 2H), 7.98 (d, J = 8.0 Hz, 1H), 7.93 (d, J = 8.0 Hz,
1H), 7.84-7.81 (m, 2H), 7.69 (d, J = 8.5 Hz, 1H), 7.58-7.52 (m,
2H), 7.50-7.44 (m, 2H), 7.15 (s, 1H); 13C NMR (125 MHz, CDCl3):
δ 185.0, 184.3, 149.5, 137.9, 133.96, 133.92, 133.5, 132.4, 132.3,
131.8, 131.4, 129.9, 128.5, 127.3, 127.2, 126.6, 126.19, 126.16,
125.4, 125.1; HRMS (ESI) for C20H13O2 [M+H]+: calcd. 285.0916,
found 285.0910.
4.3.18
Purification
7-methyl-2-(p-tolyl)naphthalene-1,4-dione
by column chromatography
(2r)24.
(petroleum
4.3.12
6-methoxy-2-phenylnaphthalene-1,4-dione
(2l).
Purification
by column chromatography (petroleum
ether/EtOAc, 10/1) as a pale yellow solid (35.6 mg, 68%); m.p.
113-115 ºC (lit.24 m.p. 115 ºC); IR (neat): ν = 1667 (C=O) cm-1,
1600 (C=C) cm-1; 1H NMR (CDCl3, 500 MHz): δ 8.01 (d, J = 8.0 Hz,
1H), 7.98 (s, 1H), 7.57 (dd, J1 = 8 .0 Hz, J2 = 1.0 Hz, 1H), 7.50-7.48
(m, 2H), 7.29 (d, J = 8.0 Hz, 2H), 7.03 (s, 1H), 2.53 (s, 3H), 2.43 (s,
3H); 13C NMR (CDCl3, 125 MHz): δ 185.1, 184.9, 147.9, 144.9,
140.3, 134.7, 134.5, 132.5, 130.7, 130.0, 129.4, 129.2, 127.4,
126.1, 21.9, 21.4.
ether/EtOAc, 10/1) as a pale yellow solid (38.5 mg, 73%); m.p.
177-179 ºC; IR (neat): ν = 1663 (C=O) cm-1, 1587 (C=C) cm-1; H
1
NMR (CDCl3, 500 MHz): δ 8.15 (d, J = 8.5 Hz, 1H), 7.60-7.56 (m,
3H), 7.49-7.48 (m, 3H), 7.26 (dd, J1 = 9 Hz, J2= 3.0 Hz, 1H), 7.05
(s, 1H), 3.99 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ 185.3, 183.4,
164.2, 148.4, 134.9, 134.2, 133.6, 130.0, 129.6, 129.5, 128.4,
126.1, 120.7, 109.1, 56.0; HRMS (ESI) for C17H13O3 [M+H]+: calcd.
265.0865, found 265.0875.
4.3.19 2-(2-chlorophenyl)-7-methylnaphthalene-1,4-dione (2s).
4.3.13
2-(4-chlorophenyl)-6-methoxynaphthalene-1,4-dione
Purification
by
column
chromatography
(petroleum
(2m). Purification by column chromatography (petroleum
ether/EtOAc, 10/1) as a pale yellow solid (27.0 mg, 48%); m.p.
1
ether/EtOAc, 10/1) as a pale yellow solid (44.8 mg, 75%); m.p.
113-115 ºC; IR (neat): ν = 1652 (C=O) cm-1, 1617 (C=C) cm-1; H
1
178-180 ºC; IR (neat): ν = 1665 (C=O) cm-1, 1596 (C=C) cm-1; H
NMR (CDCl3, 500 MHz): δ 8.04 (d, J = 8.0 Hz, 1H), 7.96 (dd, J1 =
1.0 Hz, J2 = 0.5 Hz, 1H), 7.60-7.58 (m, 1H), 7.51-7.49 (m, 1H),
7.43-7.35 (m, 2H), 7.31-7.29 (m, 1H), 6.96 (s, 1H), 2.53 (s, 3H);
NMR (CDCl3, 500 MHz): δ 8.12 (d, J = 8.5 Hz, 1H), 7.54-7.52 (m,
3H), 7.46-7.44 (m, 2H), 7.24 (dd, J1 = 8.0 Hz, J2 = 3.0 Hz, 1H), 7.02

6
Tetrahedron
ACCEPTED MANUSCRIPT
13C NMR (CDCl , 125 MHz): δ 184.7, 183.4, 148.0, 145.2, 137.4,
2011, 51, 2090. (d) Aithal, B. K.; Kumar, M. R. S.; Rao, B. N.;
3
Udupa, N.; Rao, B. S. S. Cell Biol. Int. 2009, 33, 1039. (e) Paulsen,
M. T.; Ljungman, M. Toxicol. Appl. Pharmacol. 2005, 209, 1. (f)
Nikolovska-Coleska, Z.; Xu, L.; Hu, Z.; Tomita, Y.; Li, P.; Roller, P.
P.; Wang, R.; Fang, X.; Guo, R.; Zhang, M.; Lippman, M. Z.; Yang,
D.; Wang, S. J. Med. Chem. 2004, 47, 2430. (g) Fotso, S.; Maskey,
R. P.; Grün-Wollny, I.; Schulz, K. P.; Munk, M.; Laatsch, H.
Antibiot. 2003, 56, 931. (h) Viault, G.; Grée, D.; Das, S.; Yadav, J.
S.; Grée, R. Eur. J. Org. Chem. 2011, 1233.
134.6, 133.3, 133.2, 132.0, 130.6, 130.5, 129.9, 129.8, 127.4,
126.8, 126.4, 21.9; HRMS (ESI) for C17H12ClO2 [M+H]+: calcd.
283.0526, found 283.0521.
4.3.20 2-(tert-butyl)naphthalene-1,4-dione (2t)25. Purification by
column chromatography (petroleum ether/EtOAc, 6/1) as a
yellow solid (12.4 mg, 29%); m.p. 76-78 ºC (lit.25 m.p. 76−77 ºC);
IR (neat): ν = 1679 (C=O) cm-1, 1592 (C=C) cm-1; H NMR (CDCl3,
1
3. (a) Skrzyńska, A.; Romaniszyn, M.; Pomikło, D.; Albrecht, Ł. J. Org.
Chem. 2018, 83, 5019, and references cited therein. (b) Wu, K.-L.;
Mercado, E. V.; Pettus, T. R. R. J. Am. Chem. Soc. 2011, 133, 6114.
(c) Tran, H. N. A.; Bongarzone, S.; Carloni, P.; Legname, G.;
Bolognesi, M. L. Bioorg. Med. Chem. Lett. 2010, 20, 1866. (d) Ryu,
D. H.; Zhou, G.; Corey, E. J. J. Am. Chem. Soc. 2004, 126, 4800. (e)
Liu, Y.; Sun, J.-W. J. Org. Chem. 2012, 77, 1191. (f) Hegedus, L. S.;
Mulhern, T. A.; Mori, A. J. Org. Chem. 1985, 50, 4282. (g) Zhang,
X.; Chen, Y.-H.; Tan, B. Tetrahedron Lett. 2018, 59, 473. (h)
500 MHz): δ 8.11-8.09 (m, 1H), 8.05-8.03 (m, 1H), 7.75-7.69 (m,
2H), 6.85 (s, 1H), 1.38 (s, 9H); 13C NMR (CDCl3, 125 MHz): δ
185.9, 184.9, 158.4, 133.9, 133.8, 133.6, 133.3, 131.6, 126.9,
125.6, 35.7, 29.4.
4.3.21
Purification
2-methyl-3-phenylnaphthalene-1,4-dione
by column chromatography
(2u)10a
(petroleum
.
ether/EtOAc, 10/1) as a pale yellow solid (21.3 mg, 43%); m.p.
111-112 ºC (lit.10a m.p. 111-112 ºC); IR (neat): ν = 1655 (C=O) cm-
Albrecht, Ł.; Gomez, C. V.; Jacobsen, C. B.; Jøergensen, K. A. Ó rg.
1, 1592 (C=C) cm-1; H NMR (CDCl3, 500 MHz): δ 8.17-8.15 (m,
1
Lett. 2013, 15, 3010. (i) Blom, J.; Johansen, T. K.; Jensen, F.;
Jrgensen, K. A. Chem. Commun. 2016, 52, 7153. (j) Martín-
Santos, C.; Jarava-Barrera, C.; del Pozo, S.; Parra, A.; Díaz-
Tendero, S.; Mas-Balleste, R.; Cabrera, S.; Aleman, J. Angew.
Chem., Int. Ed. 2014, 53, 8184. (k) Maddox, S. M.; Dawson, G. A.;
Rochester, N. C.; Ayonon, A. B.; Moore, C. E.; Rheingold, A. L.;
Gustafson, J. A. ACS Catal. 2018, 8, 5443.
1H), 8.14-8.12 (m, 1H), 7.76-7.74 (m, 2H), 7.50-7.42 (m, 3H),
7.26-7.24 (m, 2H), 2.12 (s, 3H); 13C NMR (CDCl3, 125 MHz): δ
185.7, 184.2, 146.2, 144.1, 133.7, 133.6, 133.5, 132.2, 132.1,
129.3, 128.5, 128.1, 126.6, 126.2, 14.6.
4.4 Mechanistic Studies
4. (a) Wang, D.; Ge, B.; Ju, A.; Zhou, Y.; Xu, C.; Ding, Y. J. Organomet.
Chem. 2015, 780, 30-33. (b) Molina, M. T.; Navarro, C.; Moreno
A.; Csákÿ, A. G. Org. Lett. 2009, 11, 4938-4941.
4.4.1
Reaction of 3 under the Standard Reaction Conditions
5. (a) Khodade, V. S.; Dharmaraja, A. T.; Chakrapani, H. Bioorg. Med.
Chem. Lett. 2012, 22, 3766. (b) Dharmaraja, A. T.; Dash, T. K.;
Kokimalla, B.; Chakrapani, H. Med.Chem.Comm. 2012, 3, 219. (c)
Ullah, I.; Kkahera, R. A.; Hussain, M.; Villinger, A.; Langer, P.
Tetrahedron Lett. 2009, 50, 4651. (d) Hadden, M. K.; Hill, S. A.;
Davenport, J.; Matts, R. L.; Blagg, B. S. J. Bioorg. Med. Chem.
2009, 17, 634. (e) Dawood, K. M. Tetrahedron 2007, 63, 9642. (f)
Wallace, D. J.; Chen, C. Tetrahedron Lett. 2002, 43, 6987. (g)
Demchuk, O. M.; Yoruk, B.; Blackburn, T.; Snieckus, V. Synlett
2006, 2908. (h) Echavarren, A. M.; de Frutos, Ó.; Tamayo, N.;
Noheda, P.; Calle, P. J. Org. Chem. 1997, 62, 4524. (i) Tamayo, N.;
Echvarren, A. M.; Paredes, M. C. J. Org. Chem. 1991, 56, 6488. (j)
Stagliano, K. W.; Malinakova, H. C. Tetrahedron Lett. 1997, 38,
6617. (k) Stagliano, K. W.; Malinakova, H. C. J. Org. Chem. 1999,
64, 8034-8040. RSC Adv. 2012, 2, 12739. (m) Echavarren, A. M.;
de Frutos, Ó; Tamayo, N.; Noheda, P.; Calle, P. J. Org. Chem. 1997,
62, 4524.
3 was synthesized according to the literature procedure.14a
To a 25-mL flask, 3 (0.2 mmol), CuI ( 3.8 mg, 10 mol % based on
3), Cu(OTf)2 (7.2 mg, 10 mol % based on 3), and DMSO (2 mL)
were added. The solution was then stirred at 130 ºC for 8 h. GC
analysis showed that no desired product 2a was detected while
the stating material was recovered.
4.4.2
Effect of Radical Scavenger TEMPO on the Formation
of 2a
Procedure: To a 25 mL Schlenk flask, 1a (0.2 mmol), CuI ( 3.8
mg, 10 mol % based on 1a), Cu(OTf)2 (7.2 mg, 10 mol % based
on 1a), TEMPO (0.10 mmol, 0.2 mmol or 0.4 mmol), internal
standard anisole (0.1 mmol), and DMSO (2 mL) were added. The
solution was then stirred at 130 ºC for 8 h. After completion of
the reaction as indicated by TLC, the mixture was sent for GC
analysis (TEMPO: 0.5 equiv, 2a: 80%; TEMPO = 1.0 equiv, 2a:
71% ; TEMPO = 2.0 equiv, 2a: 65%).
6. (a) Pictet, A.; Hubert, A. Ber. Dtsch. Chem. Ges. 1896, 29, 1182. (b)
Morgan, T.; Walls, L. P. J. Chem. Soc. 1931, 2447. (c) Chinnagolla,
R. K.; Jeganmohan, M. Chem. Commun. 2014, 50, 2442.
7. (a) Zhang, S.; Song, F.; Zhao, D.; You, J. Chem. Commun. 2013, 49,
4558. (b) She, Z.; Shi, Y.; Huang, Y.; Cheng, Y.; Song, F.; You, J.
Chem. Commun. 2014, 50, 13914. (c) Itahara, T. J. Org. Chem.
1985, 50, 5546.
Acknowledgments
We are grateful to the Natural Science Foundation of China
(No. 21172197 and 21372201) for financial support.
8. (a) Komeyama, K.; Kashihara, T.; Takaki, K. Tetrahedron Lett.
2013, 54, 1084. (b) Wang, J.; Wang, S.; Wang, G.; Zhang, J.; Yu,
X.-Q. Chem. Commun. 2012, 48, 11796. (c) Ilangovan, A.; Polu, A.;
Satish, G. Org. Chem. Front. 2015, 2, 1616. (d) Deb, A.; Agasti, S.;
Saboo, T.; Maiti, D. Adv. Synth. Catal. 2014, 356, 705. (e) Patil P.;
Nimonkar, A.; Akamanchi, K. G. J. Org. Chem. 2014, 79, 2331. (f)
Wang, D.; Ge, B.; Li, L.; Shan, J.; Ding, Y. J. Org. Chem. 2014, 79,
8607. (g) Fujiwara, Y.; Domingo, V.; Seiple, I. B.; Giznatassio, R.;
Del, B. M.; Baran, P. S. J. Am. Chem. Soc. 2011, 133, 3292.
9. (a) Dötz, K. H. Angew. Chem. Int. Ed. Engl. 1975, 14, 644. (b) Dötz,
K. H.; Stendel, J., Jr. Chem. Rev. 2009, 109, 3227. (c) Dötz, K. H.
Angew. Chem. Int. Ed. Engl. 1984, 23, 587. (d) Harrity, P. A.; Kerr,
W. J. Tetrahedron 1993, 49, 5565, and references cited therein.
(e) Wu, C.; Berbasov, D. O.; Wulff, W. D. J. Org. Chem. 2010, 75,
4441. (f) Hutchinson, E. J.; Kerr, W. J.; Magennis, E. J. Chem.
Commun. 2002, 2262. (g) Waters, M. L.; Bos, M. E.; Wulff, W. D.
J. Am. Chem. Soc. 1999, 121, 6403.
Supplementary Material
Supplementary data (charts for mechanistic studies as well
as copies of 1H & 13C NMR spectra of the compounds) associated
with this article can be found in the online version, at http://.
References and notes
1. (a) For selected reviews, see: (a) Gould, S. T. Chem. Rev. 1997, 97,
2499. (b) Liu, J. K. Chem. Rev. 2006, 106, 2209. (c) Babula, P.;
Adam, V.; Havel, L.; Kizek, R. Ceska Slov. Farm. 2007, 56, 114. (d)
Bishop, K. J. M.; Klajn, R.; Grzybowski, B. A. Angew. Chem. Int. Ed.
2006, 45, 5348. (e) Verma, R. P. Anti Cancer Agents Med. Chem.
2006, 6, 489.
2. (a) Inbaraj, J. J.; Chignell, C. F. Chem. Res. Toxicol. 2004, 17, 55. (b)
Kot, M.; Karcz, W.; Zaborska, W. Bioorg. Chem. 2010, 38, 132. (c)
Seshadrip, P.; Rajaram, A.; Rajaram, R. Free Radical Biol. Med.
10. (a) Liebeskind, L. S.; Baysdon, S. L.; South, M. S. J. Am. Chem. Soc.
1980, 102, 7397. (b) Liebeskind, L. S.; Baysdon, S. L.; South, M. S.;
Iyer, S.; Leeds, J. P. Tetrahedron 1985, 41, 5839.

7
11. (a) Wang, Z.-Q.; Zhang, W.-W.; Gong, L.-B.; Tang, R.-Y.; Yang, X.-
ACCEPTED MANUSCRIPT
H.; Liu, Y.; Li, J.-H. Angew. Chem. Int. Ed. 2011, 50, 8968.
12. Mal, D.; Ghosh, K.; Jana, S. Org. Lett. 2015, 17, 5800.
13. Perri, S. T.; Foland, L. D.; Decker, O. H. W.; Moore, H. W. J. Org.
Chem. 1986, 51, 3067. (b) Bradley, J. C.; Durst, T.; Williams, A. J. T
J. Org. Chem. 1992, 57, 6575.
14. (a) Zhang, W.; Zhang, J.; Liu, Y.; Xu, Z. Synlett 2013, 24, 2709. (b)
Zhang, J.; Wu, D.; Chen, X.; Liu, Y.; Xu, Z. J. Org. Chem. 2014, 79,
4799. (c) Zhang, J.; Wang, H.; Ren, S.; Zhang, W.; Liu, Y. Org. Lett.
2015, 17, 2920. (d) Zhang, J.; Zhang, H.; Shi, D.; Jin, H.; Liu, Y. Eur.
J. Org. Chem. 2016, 5545. (e) Bao, H.; Xu, Z.; Wu, D.; Zhang, H.;
Jin, H.; Liu, Y. J. Org. Chem. 2017, 82, 109. (f) Zhang, J.; Shi, D.;
Zhang, H.; Xu, Z.; Bao, H.; Jin, H.; Liu, Y. Tetrahedron 2017, 73,
154. (g) Ren, S.; Zhang, J.; Wang, H.; Zhang, W.; Liu, Y.; Liu, M.
Eur. J. Org. Chem. 2015, 5381. (h) Zhou, B.; Zheng, L.; Jin, H.; Wu,
Q.; Li, T.; Liu, Y. ChemistrySelect 2018, 3, 7354. (i) Bao, H.; Zhou,
B.; Jin, H.; Liu, Y. J. Org. Chem. 2019, 84, 3579. (j) Bao, H.; Zhou,
B.; Jin, H.; Liu, Y. Org. Biomol. Chem. 2019, 17, 5021.
15. Min, H.; Palani, T.; Park, K.; Kwang, J.; Lee, S. J. Org. Chem. 2014,
79, 6279. (b) Xu, C.-F.; Xu, M.; Jia, Y.-X.; Li, C.-Y. Org. Lett. 2011,
13, 1556.
16. Sibbald, P. A. Org. Lett. 2009, 11, 1147. (b) Albéniz, A. C.; Espinet,
P.; López-Fernández, R.; Sen, A. J. Am. Chem. Soc. 2002, 124,
11278.
17. Gao, A.; Yang, F.; Li, J.; Wu, Y. Tetrahedron 2012, 68, 4950.
18. Chan, C.-K.; Tsai, Y.-L.; Chang, M.-Y. Org. Lett. 2017, 19, 1870.
19. Zhu, L. P.; Yu, H. M.; Guo, Q. P.; Chen, Q.; Wang, R. Org. Lett.
2015, 17, 1978.
20. Xu, Z.; Chen, H.; Wang, Z.; Ying, A.; Zhang, L. J. Am. Chem. Soc.
2016, 138, 5515.
21. Chernyak, N.; Gorelsky, S. I.; Gevorgyan, V. Angew. Chem. Int. Ed.
2011, 50, 2342.
22. Irvine, S.; Kerr, W. J.; McPherson, A. R.; Pearson, C. M.
Tetrahedron 2007, 64, 926.
23. Shcherban, A. I. Izv. Vyssh. Uchebn. Zaved., Khim.Khim.T 1979, 22,
290-293.
24. Hopff, H.; Thalmann, P. Chimia 1959, 13, 101.
25. Periasamy, M.; Bhatt, M. V. Synthesis 1977, 330.