Palladium-Catalyzed (3+3) Annulation of Allenylethylene Carbonates with Nitrile Oxides

Article abstract of DOI:10.1021/acs.orglett.1c01921

In this paper, we designed and synthesized a new type of cyclic carbonates, allenylethylene carbonates (AECs). With AECs as reactive precursors, we developed palladium-catalyzed (3+3) annulation of AECs with nitrile oxides. Various AECs worked well in this reaction under mild reaction conditions. A variety of 5,6-dihydro-1,4,2-dioxazine derivatives with allenyl quaternary stereocenters can be accessed in a facile manner in high yields (≤98%).

Full text of DOI:10.1021/acs.orglett.1c01921

pubs.acs.org/OrgLett
Letter
Palladium-Catalyzed (3+3) Annulation of Allenylethylene
Carbonates with Nitrile Oxides
Ting Pan, Xing Gao, Sen Yang, Lan Wang, Yimin Hu, Min Liu, Wei Wang, Yongjun Wu, Bing Zheng,
and Hongchao Guo*
Cite This: Org. Lett. 2021, 23, 5750−5754
Read Online
ACCESS
Metrics & More
Article Recommendations
*
sı Supporting Information
ABSTRACT: In this paper, we designed and synthesized a new
type of cyclic carbonates, allenylethylene carbonates (AECs). With
AECs as reactive precursors, we developed palladium-catalyzed
(
3+3) annulation of AECs with nitrile oxides. Various AECs
worked well in this reaction under mild reaction conditions. A
variety of 5,6-dihydro-1,4,2-dioxazine derivatives with allenyl quaternary stereocenters can be accessed in a facile manner in high
yields (≤98%).
llenes make up an important class of compounds that not
only have versatile reactivities but also are widespread in
Scheme 1. Palladium-Catalyzed Decarboxylative
Annulations
1
A
bioactive natural product and synthetic compounds, receiving
2
special attention in bioactivity investigation. Therefore, their
synthesis has attracted a great deal of attention, and developing
new synthetic methods for allene compounds is highly
desirable.
Cyclic and acyclic carbonates have been extensively applied
in palladium catalysis for cycloaddition and allylic substitution
3
reactions through decarboxylative catalytic transformations.
Among those cyclic carbonates, vinylethylene carbonates
3k
(VECs) have been intensively studied in the past decade.
Their reactivities have been well exploited, leading to the
4
5
development of various (3+n) and (5+n) annulation
reactions (Scheme 1a) and allylic substitution reactions.
However, the potential of VECs in palladium catalysis has
nearly been exhausted. In this context, some new variants of
6
VECs have been reported. Most recently, the Zi group and
7
the Guo group designed vinyl methylene cyclic carbonates
(
VMCCs) to act as reactive precursors to Pd-oxyallyl species
independently for annulation reactions and developed [3+2]
and [5+2] annulations of VMCCs with electron-deficient
alkenes. Encouraged by our interest in the development of new
8
Pd-catalyzed annulation reactions, we considered the design
of novel cyclic carbonates from different perspectives. Because
of structural peculiarities, unique bonding properties, and
versatile reactivities of allene compounds, we installed an allene
motif onto cyclic carbonates and synthesized allenylethylene
carbonates (AECs) (Scheme 1c). With AECs as reactive
precursors for palladium catalysis, we herein present a Pd-
catalyzed (3+3) annulation reaction of AECs with nitrile
oxides, as shown in Scheme 1c.
syntheses. The conversion rate of every step was high, but
allenyl cyclic carbonates could easily isomerize to propargyl
Received: June 9, 2021
Published: July 21, 2021
Initially, we synthesized a series of AECs through two
different synthetic procedures (Scheme 2; see the Supporting
9
Information for details). Various AECs were smoothly
prepared. However, the yields were generally low in these
©
2021 American Chemical Society
https://doi.org/10.1021/acs.orglett.1c01921
5
750
Org. Lett. 2021, 23, 5750−5754

Organic Letters
pubs.acs.org/OrgLett
Letter
Scheme 2. Synthesis of Allenylethylene Carbonates (AECs)
Table 1. Optimization of Reaction Conditions for (3+3)
Annulation of AEC 1a with Nitrile Oxide 2a
a
t
yield
b
entry
[Pd]
ligand
none
PPh3
XantPhos
DpePhos
dppe
solvent
(h)
(%)
1
2
3
4
5
6
7
8
none
Pd dba ·CHCl
Pd dba ·CHCl
Pd dba ·CHCl
Pd dba ·CHCl
Pd dba ·CHCl
Pd dba ·CHCl
Pd (dba)3
Pd(dba)2
CH Cl2
48
48
16
48
48
68
68
13
24
13
13
36
28
48
48
48
48
48
10
10
0
trace
78
46
trace
29
26
87
82
66
88
72
13
82
92
93
87
91
2
CH Cl2
2
3
3
3
3
3
3
3
2
CH Cl2
2
3
2
cyclic carbonates in the separation step, leading to low isolated
yields. With various AECs in hand, we then chose AEC 1a and
stable nitrile oxide 2a as model reaction partners in
dichloromethane at room temperature to investigate the
optimal reaction conditions (Table 1). In the absence of a
palladium catalyst and ligand, no (3+3) annulation product
was observed (entry 1), indicating that the thermal [3+2]
cycloaddition of allene with nitrile oxide did not occur. With
Pd dba ·CHCl (5 mol %)/PPh (20 mol %) as the catalyst,
CH Cl2
2
3
2
CH Cl2
2
3
2
dppbz
dppf
CH Cl2
2
3
2
CH Cl2
2
3
2
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
XantPhos
CH Cl2
2
2
9
CH Cl2
2
10
11
12
13
14
15
16
17
18
Pd(PPh3)4
Pd(dmdba)2
[Pd(η -cinnamyl)Cl]
CH Cl2
2
CH Cl2
2
3
2
3
3
3
2
CH Cl2
2
3
the trace amount of the product was observed (entry 2).
Encouraged by this result, we next examined various phosphine
ligands in the presence of Pd dba ·CHCl . The use of
[Pd(η -C H )Cl]
CH Cl2
3
5
2
2
Pd(dmdba)2
Pd(dmdba)2
Pd(dmdba)2
Pd(dmdba)2
Pd(dmdba)2
Pd(dmdba)2
Pd(dmdba)2
DCE
CHCl3
toluene
THF
PhCF3
toluene
toluene
2
3
3
XantPhos and Dpephos as ligands led to product 3aa in 78%
and 46% yields, respectively (entries 3 and 4, respectively). A
common dppe ligand was almost ineffective in the reaction
c
(
entry 5). When dppbz and dppf were used, the reaction was
19
d
98
90
sluggish, furnishing desired product 3aa in 29% and 26%
yields, respectively (entries 6 and 7, respectively). With the
XantPhos as the ligand, we then evaluated several palladium
20
a
Unless noted otherwise, the reaction of 1a (0.15 mmol), 2a (0.1
mmol), [Pd] (10 mol %), and a ligand (20 mol % for Ph P, 10 mol %
for diphosphines) was performed in 1 mL of solvent at 25 °C.
Abbreviations: DCE, 1,2-dichloroethane; dba, dibenzylidene acetone;
3
catalysts (entries 8−13). Among them, Pd(dmdba) displayed
2
a good catalytic activity, resulting in the formation of the
b
dmdba, 3,5,3′,5′-dimethoxydibenzylidene acetone. Isolated yield.
corresponding product in the highest 88% yield (entry 11).
c
d
3
With 5 mol % Pd (dmdba) and 10 mol % XantPhos. With 2.5 mol
2
Interestingly, the use of [Pd(η -cinnamyl)Cl] in this reaction
2
3
% Pd (dmdba) and 5 mol % XantPhos.
2
gave product 3aa in 72% yield (entry 12), although [Pd(η -
C H )Cl] was less effective in providing 3aa in 13% yield
3
5
2
(
entry 13). The solvent screening revealed that toluene is an
allenyl-substituted dioxazines (3ba−3la) in good to excellent
yields (82−98%) (entries 1−12). The AEC with biphenyl
moieties also performed the reaction well, leading to the
formation of the corresponding product 3ma in 71% yield
(entry 13). In addition, this annulation reaction can be applied
to the AEC substrate containing a 2-naphthyl group, and the
corresponding product 3na was obtained in 78% yield (entry
14). It is worth noting that methyl- and ethyl-substituted AECs
displayed good reactivity, affording the corresponding product
in 98% and 83% yields, respectively (entries 15 and 16,
respectively). The cyclohexyl AEC was relatively sluggish, and
its reaction required a higher catalyst loading (10 mol % Pd
catalyst), giving the annulation product in 58% yield (entry
17). In particular, the installation of a heterocycle in the
allenylethylene carbonate was also workable (entry 18).
appropriate solvent, and the yield of the desired product was
increased to 93% (entries 14−18 and entry 17, respectively).
In particular, when the catalyst loading was decreased to 5 mol
%
(
%
, the yield of desired product 3aa was increased to 98%
entry 19). Further decreasing the catalyst loading to 2.5 mol
led to a little decrease in the yield (entry 20). On the basis of
the results presented above, the optimal reaction conditions for
the (3+3) annulation were ultimately identified as follows:
Pd(dmdba) (5 mol %) as a catalyst and XantPhos (10 mol %)
2
as a ligand in toluene at room temperature.
Having established the optimal conditions, we tested a
variety of AECs to explore the reaction scope. The results are
summarized in Table 2. Generally, the reaction proceeded
smoothly to give the corresponding products in high yields
(
entries 1−14). The substituted AECs having electron-
We next investigated the scope of nitrile oxides 2, as shown
in Table 3. Stable nitrile oxide 2b displayed good reactivity,
and we performed (3+3) annulation with AEC 1a to produce
the corresponding product 3ab in 81% yield (entry 1). The
withdrawing (F, Cl, and Br) and electron-donating (Me and
OMe) groups on the phenyl ring of the AEC at the para, meta,
or ortho position were well tolerated, producing a number of
5
751
https://doi.org/10.1021/acs.orglett.1c01921
Org. Lett. 2021, 23, 5750−5754

Organic Letters
pubs.acs.org/OrgLett
Letter
Table 2. Scope of AECs for Pd-Catalyzed (3+3)
Annulation
3ad in 92% yield (entry 3). When the reaction was carried out
with 2,4,5-trimethyl-substituted nitrile oxide 2e, the corre-
sponding product 3ae was formed in 67% yield (entry 4).
Unstable nitrile oxides 2f and 2g generated in situ from the
corresponding oxime halides in the presence of a base also
worked in this reaction, providing the desired products 3af and
a
3
ag in moderate 41% and 28% yields, respectively (entries 5
and 6, respectively). This indicated that oxime halides and the
base in the reaction system seem to be unfavorable for the
annulation.
b
Subsequently, the asymmetric variant of the current
annulation reaction of AEC 1a and nitrile oxide 2a was
investigated. Various chiral ligands were screened under the
optimized reaction conditions. Unfortunately, we did not
obtain satisfactory results in terms of enantioselectivity. In
particular, in the presence of Pd dba ·CHCl (5 mol %) and
entry
R
t (h)
3
yield (%)
1
2
3
4
5
6
7
8
9
Ph (1a)
2-FC H (1b)
10
13
13
13
13
12
13
12
14
13
13
13
13
14
5
3aa
3ba
3ca
3da
3ea
3fa
3ga
3ha
3ia
3ja
3ka
3la
3ma
3na
3oa
3pa
3qa
3ra
98
98
88
90
82
98
83
94
98
93
91
98
71
78
98
83
58
98
6
4
3-FC H (1c)
6
4
4-FC H (1d)
6
4
2
3
3
3-ClC H (1e)
6
4
ferrocene chiral phosphine ligand L1 (20 mol %), cyclic
product 3aa was formed in 53% ee with a 16% yield (Scheme
4-ClC H (1f)
6
4
3-BrC H (1g)
6
4
3
). The absolute configuration of chiral product 3aa had not
4-BrC H (1h)
6
4
been assigned.
4-MeC H (1i)
6
4
10
11
12
13
14
15
16
17
18
2-OMeC H (1j)
6
4
Scheme 3. Asymmetric Variant of (3+3) Annulation
3-OMeC H (1k)
6
4
4-OMeC H (1l)
6
4
4-PhC H (1m)
6
4
2-naphthyl (1n)
Me (1o)
Et (1p)
6
36
8
c
cyclohexyl (1q)
3-thienyl (1r)
a
Unless noted otherwise, the reaction mixture of 1 (0.15 mmol), 2a
0.10 mmol), Pd(dmdba) (5 mol %), and XantPhos (10 mol %) was
(
As shown in Scheme 4, to demonstrate the efficiency and the
extensibility of this catalytic process, a scale-up reaction of
2
b
c
stirred in 1 mL of toluene at 25 °C. Isolated yield. With 10 mol %
Pd(dmdba) and 20 mol % XantPhos.
2
Scheme 4. Scale-up Reaction and Transformation of the
Product
Table 3. Scope of Nitrile Oxides for Pd-Catalyzed (3+3)
Annulation of AECs
a
d
entry
R
t (h)
3
yield (%)
1
2
3
2,6-Cl C H (2b)
5
14
4
17
5
3ab
3ac
3ad
3ae
3af
81
68
92
67
41
28
2
6
3
2,6-Br C H (2c)
2
6
3
b
2,6-(OMe) C H (2d)
2 6 3
4
2,4,5-Me C H (2e)
3
6
2
c
5
c
4-MeC H (2f)
6 4
6
2-naphthyl (2g)
74
3ag
a
Unless noted otherwise, the reaction mixture of 1a (0.15 mmol), 2
0.10 mmol), Pd(dmdba) (5 mol %), and XantPhos (10 mol %) was
(
2
b
stirred in 1 mL of toluene at 25 °C. The reaction was performed at
4
c
0 °C. The reaction mixture of the corresponding N-hydroxyformi-
mimidol chloride (0.15 mmol), 1a (0.1 mmol), NaOH (0.15 mmol),
Pd(dmdba) (5 mol %), and XantPhos (10 mol %) was stirred in 1
2
d
mL of toluene at 40 °C. Isolated yield.
AEC 1a and nitrile oxide 2a was conducted under the
optimized reaction conditions, furnishing annulation product
3aa in 79% yield (253 mg). The potential synthetic utility of
this protocol was then displayed through palladium-catalyzed
hydrocarboxylation of product 3aa with benzoic acid, giving
the corresponding allyl ester 4 in 40% yield. In the presence of
structure of product 3ab was unambiguously confirmed by
single-crystal X-ray diffraction analysis. In contrast, 2,6-Br2-
phenyl-substituted nitrile oxide 2c has a relatively weak
reactivity, resulting in the desired (3+3) annulation product
3ac in 68% yield (entry 2). Nitrile oxide 2d having a 2,6-
H and 10% Pd/C, reduction product 5 was obtained in 85%
2
OMe -phenyl group was reactive, affording desired product
yield.
2
5
752
https://doi.org/10.1021/acs.orglett.1c01921
Org. Lett. 2021, 23, 5750−5754

Organic Letters
pubs.acs.org/OrgLett
Letter
A plausible mechanism is proposed as shown in Scheme 5.
Authors
In the presence of a Pd catalyst, AEC 1 performs a ring-
Ting Pan − Department of Chemistry and Innovation Center
of Pesticide Research, China Agricultural University, Beijing
Scheme 5. A Proposed Mechanism
100193, P. R. China
Xing Gao − Department of Chemistry and Innovation Center
of Pesticide Research, China Agricultural University, Beijing
100193, P. R. China; orcid.org/0000-0001-6254-2583
Sen Yang − Department of Chemistry and Innovation Center
of Pesticide Research, China Agricultural University, Beijing
100193, P. R. China
Lan Wang − Department of Chemistry and Innovation Center
of Pesticide Research, China Agricultural University, Beijing
100193, P. R. China
Yimin Hu − Department of Chemistry and Innovation Center
of Pesticide Research, China Agricultural University, Beijing
100193, P. R. China; orcid.org/0000-0003-3701-8418
Min Liu − Department of Chemistry and Innovation Center of
Pesticide Research, China Agricultural University, Beijing
100193, P. R. China
Wei Wang − College of Public Health, Zhengzhou University,
Zhengzhou 450001, P. R. China
Yongjun Wu − College of Public Health, Zhengzhou
University, Zhengzhou 450001, P. R. China
Bing Zheng − Department of Chemistry and Innovation
Center of Pesticide Research, China Agricultural University,
Beijing 100193, P. R. China
opening reaction to afford zwitterionic intermediate A, which
attacks nitrile oxides 2 to give intermediate B. Subsequent
intramolecular annulation led to a (3+3) annulation product 3.
In conclusion, we have developed a palladium-catalyzed
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c01921
(3+3) annulation of AECs with nitrile oxides, offering a useful
Notes
tool for the synthesis of 3,6-disubstituted 5-hydro-1,4,2-
dioxazines. A broad range of AECs and nitrile oxides were
compatible in this procedure, converting into the correspond-
ing annulation compounds in moderate to excellent yields. A
scale-up reaction and late-stage transformation of product 3aa
were also demonstrated. Further studies of the usability of the
AECs in the synthesis of heterocyclic compounds for pesticide
research are currently underway in our laboratory and will be
reported in due course.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work is supported by the National Natural Science
Foundation of China (21871293 and 22071264).
REFERENCES
■
(
1) For selected reviews, see: (a) Zimmer, R.; Dinesh, C. U.;
Nandanan, E. F.; Khan, A. Chem. Rev. 2000, 100, 3067. (b) Krause,
N.; Hashmi, A. S. K. Modern Allene Chemistry; Wiley-VCH:
Weinheim, Germany, 2004. (c) Ma, S. Chem. Rev. 2005, 105, 2829.
ASSOCIATED CONTENT
sı Supporting Information
■
*
(
d) Alcaide, B.; Almendros, P.; Aragoncillo, C. Chem. Soc. Rev. 2010,
9, 783. (e) Krause, N.; Winter, C. Chem. Rev. 2011, 111, 1994.
f) Yu, S.; Ma, S. Angew. Chem., Int. Ed. 2012, 51, 3074. (g) Xiao, Y.;
Sun, Z.; Guo, H.; Kwon, O. Beilstein J. Org. Chem. 2014, 10, 2089.
h) Guo, H.; Fan, Y. C.; Sun, Z.; Wu, Y.; Kwon, O. Chem. Rev. 2018,
18, 10049. (i) Huang, Y.; Liao, J.; Wang, W.; Liu, H.; Guo, H. Chem.
Commun. 2020, 56, 15235.
2) (a) Kinnel, R.; Duggan, A. J.; Eisner, T.; Meinwald, J.; Miura, I.
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c01921.
3
(
Experimental procedure, characterization data, NMR
spectra, and X-ray crystallographic data (PDF)
(
1
Accession Codes
(
CCDC 2065630 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Tetrahedron Lett. 1977, 18, 3913. (b) Lin, R.; Cao, L.; West, F. G. In
Strategies and Tactics in Organic Synthesis; Harmata, M., Ed.; Academic
Press, 2019; Vol. 14, pp 261−323. (c) Cox, P. J.; Imre, S.; Islimyeli,
S.; Thomson, R. H. Tetrahedron Lett. 1982, 23, 579. (d) Guella, G.;
̈
Chiasera, G.; Mancini, I.; Oztunc,
1
(
̧
A.; Pietra, F. Chem. - Eur. J. 1997, 3,
223. (e) Zemlicka, J. Nucleosides Nucleotides 1997, 16, 1003.
f) Zemlicka, J. Pharmacol. Ther. 2000, 85, 251. (g) Zemlicka, J.
Biochim. Biophys. Acta, Mol. Basis Dis. 2002, 1587, 276.
3) For recent reviews, see: (a) Ilardi, E. A.; Njardarson, J. T. J. Org.
Chem. 2013, 78, 9533. (b) He, J.; Ling, J.; Chiu, P. Chem. Rev. 2014,
14, 8037. (c) Ohno, H. Chem. Rev. 2014, 114, 7784. (d) Zhang, Y.;
Khan, A. Synlett 2015, 26, 853. (e) Feng, J.-J.; Zhang, J. ACS Catal.
016, 6, 6651. (f) Ganesh, V.; Chandrasekaran, S. Synthesis 2016, 48,
AUTHOR INFORMATION
Corresponding Author
■
(
Hongchao Guo − Department of Chemistry and Innovation
Center of Pesticide Research and Department of Nutrition
and Health, China Agricultural University, Beijing 100193,
P. R. China; orcid.org/0000-0002-7356-4283;
Email: hchguo@cau.edu.cn
1
2
4347. (g) Meazza, M.; Guo, H.; Rios, R. Org. Biomol. Chem. 2017, 15,
2479. (h) Fumagalli, G.; Stanton, S.; Bower, J. F. Chem. Rev. 2017,
5
753
https://doi.org/10.1021/acs.orglett.1c01921
Org. Lett. 2021, 23, 5750−5754

Organic Letters
pubs.acs.org/OrgLett
Letter
1
-
17, 9404. (i) Allen, B. D. W.; Lakeland, C. P.; Harrity, J. P. A. Chem.
Eur. J. 2017, 23, 13830. (j) Li, T. R.; Wang, Y. N.; Xiao, W. J.; Lu, L.
Q. Tetrahedron Lett. 2018, 59, 1521. (k) Guo, W.; Gomez, J. E.;
Cristofol, A.; Xie, J.; Kleij, A. W. Angew. Chem., Int. Ed. 2018, 57,
1
3735. (l) Li, Q.-Z.; Liu, Y.; Li, M.-Z.; Zhang, X.; Qi, T.; Li, J.-L. Org.
Biomol. Chem. 2020, 18, 3638.
4) (a) Khan, A.; Zheng, R.; Kan, Y.; Ye, J.; Xing, J.; Zhang, Y. J.
(
Angew. Chem., Int. Ed. 2014, 53, 6439. (b) Khan, A.; Yang, L.; Xu, J.;
Jin, L. Y.; Zhang, Y. J. Angew. Chem., Int. Ed. 2014, 53, 11257.
(
2
2
c) Yang, L.; Khan, A.; Zheng, R.; Jin, L. Y.; Zhang, Y. J. Org. Lett.
015, 17, 6230. (d) Khan, I.; Zhao, C.; Zhang, Y. J. Chem. Commun.
018, 54, 4708. (e) Liu, K.; Khan, I.; Cheng, J.; Hsueh, Y. J.; Zhang,
Y. J. ACS Catal. 2018, 8, 11600. (f) Liu, Q.; Liu, T.-X.; Ru, Y.; Zhu,
X.; Zhang, G. Chem. Commun. 2019, 55, 14498. (g) Liu, Y.; Huang,
Q. W.; Li, Q. Z.; Leng, H. J.; Dai, Q. S.; Zeng, R.; Liu, Y. Q.; Zhang,
X.; Han, B.; Li, J. L. Org. Lett. 2019, 21, 7478. (h) Wang, J. W.; Zhao,
L.; Rong, Q. J.; Lv, C.; Lu, Y.; Pan, X.; Zhao, L.; Hu, L. H. Org. Lett.
2
2
020, 22, 5833. (i) Zhao, C.; Khan, I.; Zhang, Y. J. Chem. Commun.
020, 56, 12431.
(
5) (a) Rong, Z. Q.; Yang, L. C.; Liu, S.; Yu, Z.; Wang, Y. N.; Tan, Z.
Y.; Huang, R. Z.; Lan, Y.; Zhao, Y. J. Am. Chem. Soc. 2017, 139,
5304. (b) Wu, Y.; Yuan, C.; Wang, C.; Mao, B.; Jia, H.; Gao, X.;
Liao, J.; Jiang, F.; Zhou, L.; Wang, Q.; Guo, H. Org. Lett. 2017, 19,
268. (c) Yang, L. C.; Rong, Z. Q.; Wang, Y. N.; Tan, Z. Y.; Wang,
1
6
M.; Zhao, Y. Angew. Chem., Int. Ed. 2017, 56, 2927. (d) Yuan, C.; Wu,
Y.; Wang, D.; Zhang, Z.; Wang, C.; Zhou, L.; Zhang, C.; Song, B.;
Guo, H. Adv. Synth. Catal. 2018, 360, 652. (e) Das, P.; Gondo, S.;
Nagender, P.; Uno, H.; Tokunaga, E.; Shibata, N. Chem. Sci. 2018, 9,
3
276. (f) Singha, S.; Patra, T.; Daniliuc, C. G.; Glorius, F. J. Am.
Chem. Soc. 2018, 140, 3551. (g) Yang, Y.; Yang, W. Chem. Commun.
018, 54, 12182. (h) Zhao, H. W.; Du, J.; Guo, J. M.; Feng, N. N.;
Wang, L. R.; Ding, W. Q.; Song, X. Q. Chem. Commun. 2018, 54,
178. (i) Gao, X.; Xia, M.; Yuan, C.; Zhou, L.; Sun, W.; Li, C.; Wu,
B.; Zhu, D.; Zhang, C.; Zheng, B.; Wang, D.; Guo, H. ACS Catal.
2
9
2
019, 9, 1645. (j) Niu, B.; Wu, X. Y.; Wei, Y.; Shi, M. Org. Lett. 2019,
21, 4859. (k) Wei, Y.; Liu, S.; Li, M. M.; Li, Y.; Lan, Y.; Lu, L. Q.;
Xiao, W. J. J. Am. Chem. Soc. 2019, 141, 133. (l) Zhao, H. W.; Wang,
L. R.; Guo, J. M.; Ding, W. Q.; Song, X. Q.; Wu, H. H.; Tang, Z.; Fan,
X. Z.; Bi, X. F. Adv. Synth. Catal. 2019, 361, 4761. (m) Gao, X.; Zhu,
D.; Chen, Y.; Deng, H.; Jiang, F.; Wang, W.; Wu, Y.; Guo, H. Org.
Lett. 2020, 22, 7158. (n) An, X.-T.; Du, J.-Y.; Jia, Z.-L.; Zhang, Q.; Yu,
K.-Y.; Zhang, Y.-Z.; Zhao, X.-H.; Fang, R.; Fan, C.-A. Chem. - Eur. J.
2
020, 26, 3803. (o) Uno, H.; Punna, N.; Tokunaga, E.; Shiro, M.;
Shibata, N. Angew. Chem., Int. Ed. 2020, 59, 8187. (p) Xia, C.; Wang,
D.-C.; Qu, G.-R.; Guo, H.-M. Org. Chem. Front. 2020, 7, 1474.
(q) Zhang, X.; Li, X.; Li, J.-L.; Wang, Q.-W.; Zou, W.-L.; Liu, Y.-Q.;
Jia, Z.-Q.; Peng, F.; Han, B. Chem. Sci. 2020, 11, 2888. (r) Yang, G.;
Ke, Y.-M.; Zhao, Y. Angew. Chem., Int. Ed. 2021, 60, 12775.
(6) (a) Chai, W.; Zhou, Q.; Ai, W.; Zheng, Y.; Qin, T.; Xu, X.; Zi,
W. J. Am. Chem. Soc. 2021, 143, 3595. (b) Zheng, Y.; Qin, T.; Zi, W. J.
Am. Chem. Soc. 2021, 143, 1038.
(7) (a) Yan, B.; Zuo, L.; Chang, X.; Liu, T.; Cui, M.; Liu, Y.; Sun,
H.; Chen, W.; Guo, W. Org. Lett. 2021, 23, 351. (b) Zuo, L.; Yang, Y.;
Guo, W. Org. Lett. 2021, 23, 2013. (c) Yang, Y.; Zuo, L.; Wei, K.;
Guo, W. Org. Lett. 2021, 23, 3195.
(8) (a) Mao, B.; Xu, Y.; Chen, Y.; Dong, J.; Zhang, J.; Gu, K.; Zheng,
B.; Guo, H. Org. Lett. 2019, 21, 4424. (b) Mao, B.; Zhang, J.; Xu, Y.;
Yan, Z.; Wang, W.; Wu, Y.; Sun, C.; Zheng, B.; Guo, H. Chem.
Commun. 2019, 55, 12841. (c) Mao, B.; Liu, H.; Yan, Z.; Xu, Y.; Xu,
J.; Wang, W.; Wu, Y.; Guo, H. Angew. Chem., Int. Ed. 2020, 59, 11316.
(
9) (a) Buzas, A. K.; Istrate, F. M.; Gagosz, F. Org. Lett. 2007, 9, 985.
b) Lin, M.-H.; Kuo, C.-K.; Huang, Y.-C.; Tsai, Y.-T.; Tsai, C.-H.;
Liang, K.-Y.; Li, Y.-S.; Chuang, T.-H. Tetrahedron 2014, 70, 5513.
(
5
754
https://doi.org/10.1021/acs.orglett.1c01921
Org. Lett. 2021, 23, 5750−5754