Organocatalytic asymmetric [4+2] cyclization of 2-benzothiazolimines with azlactones: Access to chiral benzothiazolopyrimidine derivatives

Article abstract of DOI:10.1039/d0cc00736f

An organocatalytic asymmetric domino Mannich/cyclization reaction between 2-benzothiazolimines with azlactones has been successfully developed. With the bifunctional squaramide catalyst, this formal [4+2] cyclization occurs with good to high yields and excellent stereoselectivities (up to 99% ee, >20?:?1 dr), providing an efficient and mild access to chiral benzothiazolopyrimidines bearing adjacent tertiary and quaternary stereogenic centers.

Full text of DOI:10.1039/d0cc00736f

View Article Online
View Journal
ChemComm
Chemical Communications
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Q. Ni, X. Wang, F.
Xu, X. Y. Chen and X. Song, Chem. Commun., 2020, DOI: 10.1039/D0CC00736F.
Volume 54
This is an Accepted Manuscript, which has been through the
Number
January 2018
Pages 1-112
1
4
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Chemical Communications
rsc.li/chemcomm
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/D0CC00736F
COMMUNICATION
Organocatalytic asymmetric [4+2] cyclization of 2-
benzothiazolimines with azlactones: access to chiral
benzothiazolopyrimidine derivatives†
Received 00th January 20xx,
Accepted 00th January 20xx
Qijian Ni,*a Xuyang Wang a , Fangfang Xu a, Xiaoyun Chen b and Xiaoxiao Song *a
DOI: 10.1039/x0xx00000x
An organocatalytic asymmetric domino Mannich/cyclization
reaction between 2-benzothiazolimines with azlactones has
been successfully developed. With the bifunctional squaramide
catalyst, this formal [4+2] cyclization occurs with good to high
CN
O
Ph
O
SCH3
NO2
N
O
N
N
N
N
N
S
F
S
S
yields and excellent stereoselectivities (up to 99% ee, >20:1 dr)
,
Cl
anticancer agent
adenosine
anthelmintics
providing an efficient and mild access to chiral
benzothiazolopyrimidines bearing adjacent tertiary and
quaternary stereogenic centers.
Ph
S
HN
N
CN
Me
Ph
O
N
N
S
N
N
Cl
S
N
N
S
S
Benzothiazolopyrimidine derivatives are widely present in many
natural products and bioactive compounds.1 The typical structural
core of isothioureas, especially the chiral homobenzotetramisole
(HBTM) has drawn tremendous attention from synthetic chemists
because of their prevalence in asymmetric organocatalytic
transformations as a Lewis base.2 Therefore, various synthetic
approaches to these heterocycles have been developed in recent
years.3 In 2015, the Enders group disclosed an N-heterocyclic
carbene-catalyzed Mannich/lactamization domino reaction of 2-
benzothiazolimines with α-chloroaldehydes for the asymmetric
antitumor agent
nucleoside transporter
(S)-HBTM 2
Figure 1 Representative examples of benzothiazolopyrimidine derivatives.
positions, respectively, allowing for designing a cascade [n+2]
cyclization reaction to build up functionalized lactones or lactams
with the use of organocatalyst. For instance, excellent progress has
been made on asymmetric [3+2] cyclization7 of azlactones with 1,3-
dipole surrogates, such as oxaziridines,8 azomethine imines9 or
azonaphthalenes.10 Meanwhile, considerable attention has been
devoted to the asymmetric catalytic [4+2] cyclizations of azlactones
with electron-deficient alkenes11 or quinone methides.12 In the case
of electrophilic imines, the Mannich reactions with azlactones for
the asymmetric preparation of diverse synthetic amino acids have
been well developed.13 However, methods for organocatalytic
asymmetric cyclization of azlactones with imines to construct
heterocycles were not disclosed until a domino reaction of o-
hydroxy aromatic aldimines and azlactones reported by Feng group
in 2011.14 They realized the asymmetric synthesis of 3, 4-
diaminochroman-2-ones catalyzed by guanidine and bisguanidium
salt. Recently, Wang and co-workers disclosed an asymmetric [2+2]
cyclization/penicillin-penillonic acid rearrangement by phosphoric
acid catalysis affording imidazoline adducts with high diastereo- and
enantioselectivity (Scheme 1b).15 Motivated by the previous work
on [n+2] cyclization with azlactones, we envisaged that 2-
benzothiazolimines might be suitable substrates for an asymmetric
organocatalytic [4+2] cyclization with azlactones by a domino
Mannich/cyclization reaction, thus providing highly enantioenriched
benzothiazolopyrimidines bearing adjacent tertiary and quaternary
stereogenic centers (Scheme 1c). The challenges in this task should
synthesis
of
benzothiazolopyrimidinones
with
excellent
stereoselectivities (Scheme 1a).4 Very recently, Masson et al.
developed an elegant strategy to build benzothiazolopyrimidine by
chiral phosphoric acid-catalyzed [4+2] cyclization of 2-
benzothioazolimines with enecarbamates.5 As one of the most
effective strategies, the asymmetric organocatalytic domino
reaction based on 2-benzothiazolimine are still extremely limited.
Azlactones have recently emerged as a type of versatile
reactants for the synthesis of nitrogen-containing compounds
(Scheme 1) because of their multiple reactive sites.6 This substrate
class possess nucleophilic and electrophilic sites at C4 and C5-
a. College of Chemistry and Materials Science, Key Laboratory of Functionalized
Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based
Materials, Anhui Normal University, Wuhu, Anhui 241002, P. R. China. E-mail:
qijianni@ahnu.edu.cn, xsong@ahnu.edu.cn.
b. School of Environmental and Chemical Engineering, Jiangsu University of Science
and Technology, Zhenjiang, 212003, P. R. China.
† In memory of Prof. Dieter Enders (1946-2019).
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
COMMUNICATION
Journal Name
Entry
Cat.
Solvent
Yield of 3a
dr (3aV)ciew ArtieceleoOfn3liane
include the dearomatization of the benzothiazole ring16 and the
(%)b
(%)d
DOI: 10.1039/D0CC00736F
elusive regioselective control on the ambident N-nucleophiles.
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
D
D
D
D
D
THF
THF
THF
THF
THF
47
48
26
70
40
62
51
62
39
70
38
>20:1
>20:1
>20:1
>20:1
>20:1
>20:1
>20:1
>20:1
>20:1
>20:1
>20:1
99
99
99
99
99
99
99
99
76
97
99
a) Previous work of 2-benzothiazolimine:
Cl
O
NHCbz
CPA
CbzHN
O
R
R
R
R
Ar
N
S
NHC
N
S
N
N
Ar
Ar
Enders's work
Masson's work
N
N
S
THF
b) Asymmetric cyclization with azlactones:
dioxane
ethyl acetate
DCM
PhCl
toluene
N
O
NTs
N
NHTs
NCOPh
OH
guanidine
O
R
N
Me
O
N
CPA
R
N
10
11
R
N
Ph
Me
O
Wang's work
Feng's work
Ph
O
O
a Reaction conditions: 1 (0.2 mmol), 2 (0.24 mmol), D (0.02 mmol), solvent
(2 mL), rt, 12 h. b Yield of isolated 3 after flash column chromatography. c
Determined by 1H NMR. d The ee value was determined by HPLC on a chiral
stationary phase.
c) This work:
O
O
R
N
R
NHCOPh
O
O
5
N
squaramide
Ar
N
N
+
NHCOPh
Ph
S
+
Ar
N
N
N
4
Ar
not observed
R
S
S
4

3
1
With optimized reaction conditions in hand, the substrate
scope of this asymmetric [4+2] cyclization was examined. The
reactions of 2-benzothiazolimines 1 with 2a were first conducted
(Scheme 2). In general, the desired benzothiazolopyrimidines were
obtained with moderate to excellent yields, excellent diastereo- and
enantioselectivities. In contrast to the model substrate (1a), the
presence of an electron-donating substituent on the aryl ring led to
dramatic decreases in the yields of the product 3b. Substrates
bearing electron-withdrawing groups, such as -Br, -Cl, -F and -NO2
at the para-position as well as meta-Cl were compatible with the
reaction, affording to the corresponding cycloadducts 3c-3g in 65-
81% yield and 97-99% ee. Bromo substituent at the ortho position
of phenyl ring hindered the Mannich step and resulted in 3h with a
lower yield and stereoselectivity. The 2-benzothiazolimine with α-
naphthyl group showed lower reactivity and resulted in the desired
Scheme 1 Research background.
To implement this hypothesis, we commenced our studies by
examining the model reaction of 2-benzothiazolimine (1a) with
racemic phenylalanine-derived azlactones (2a). Initially, chiral
thioureas or squaramides were chosen as the bifunctional
organocatalysts in view of their good performance in stereocontrol.
To our delight, this regiospecific reaction delivered the desired
product 3a in 47% yield with excellent diastereoselectivity and
enantioselectivity in the presence of 10 mol% of squaramide A at
room temperature (table 1, entry 1). The [2+2] adduct 4 was not
observed. Then a quick screening of catalysts was conducted and
the quinidine-derived squaramide catalyst D proved to be the best
choice for this domino process, with which an excellent efficiency
and stereoselectivity were realized (entries 2-6). No further
improvements were observed when other solvents, such as dioxane,
EtOAc, DCM, PhCl, or toluene were used (entries 7–11). The best
reaction conditions are shown in entry 4, and gave 3a in 70% yield,
>20:1 dr and 99% ee.
O
Bn
NHCOPh
O
O
D
cat. (10 mol%)
Ar
N
Ph
+
R
N
R
N
N
THF , rt, 12 h
Ar
Bn
S
N
S
1
2a
3
O
O
N
O
Bn
NHCOPh
Bn
NHCOPh
Bn
NHCOPh
N
N
Table 1 Optimization on reaction conditionsa
N
N
N
Me
S
S
S
X
3b
21% yield, >20:1 dr, 92% ee
3a
3c
, X = Br, 74% yield,>20:1 dr, 97% ee
O
Bn
70% yield, >20:1 dr, 99% ee
O
O
3d
3e
, X = Cl, 73% yield,>20:1 dr, 97% ee
, X = F, 65% yield, >20:1 dr, 99% ee
Orgcat. (10 mol%)
solvent, rt, 12 h
NHCOPh
Ph
Ph
N
S
Ph
+
N
N
O
O
Bn
N
O
Bn
Bn
Bn
N
NHCOPh
S
NHCOPh
NHCOPh
N
N
N
1a
2a
3a
N
N
S
S
N
CF3
NO2
S
3f
3h
3g
Br
Cl
CF3
F3C
CF3
81% yield,>20:1 dr, 99% ee
F3C
O
57% yield, >20:1 dr, 83% ee
67% yield, >20:1 dr, 99% ee
H
F3C
O
O
H
N
Bn
HN
O
H
N
O
Bn
NHCOPh
NHCOPh
N
O
HN
HN
S
N
Bn
HN
O
NHCOPh
S
HN
N
N
N
S
N
HN
N
O
S
N
S
3j
57% yield, >20:1 dr,98% ee
3i
3k
N
37% yield, 5:1 dr,71% ee
60% yield, >20:1 dr,97% ee
N
O
O
Bn
NHCOPh
Bn
NHCOPh
O
Bn
NHCOPh
A
B
C
F3
C
CF3
N
N
N
F3
C
CF3
S
Ph
Ph
Br
F3CO
Ph
N
N
N
S
S
O
O
F3C
O
CF3
3l
3m
3n
57% yield, 5:1 dr, 99% ee
H
N
H
O
72% yield, >20:1 dr, 99% ee
HN
O
60% yield, 5:1 dr, 99% ee
HN
NH
HN
NH
CH3
HN
O
O
O
Bn
NHCOPh
Bn
NHCOPh
Bn
Br
N
NHCOPh
O
O
N
N
N
N
Cl
Ph
Ph
MeO
Ph
N
N
N
S
S
S
H3C
N
N
3o
3p
3q
66% yield, 6:1 dr, 93% ee
69% yield, >20:1 dr, 99% ee
66% yield, >20:1 dr, 99% ee
D
E
F
a
Scheme 2 The variation of 2-benzothiazolimine. General reaction conditions: 1
(0.2 mmol), 2a (0.24 mmol), D (10 mol%), THF (2 mL, 0.1 M), and 12 h at rt. b All
yields refer to the isolated yields. c The dr values were determined by 1H NMR
d
spectroscopy to be higher than 20:1 in all cases.
The ee values were
determined by HPLC on a chiral stationary phase.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 3 of 4
ChemComm
Journal Name
COMMUNICATION
O
Bn
product 3i in 37% yield with 71% ee. However, the naphthyl group
in beta position was well tolerated by this reaction, affording the
corresponding 3j in 57% yield and 98% ee under the standard
reaction conditions. It was noteworthy that the introduction of a
heterocyclic thienyl group on benzothiazolimine gave the desired
product 3k in good yield with excellent asymmetric induction.
Additionally, the [4+2] adduct 3l was also obtained in 99% ee with
View Article Online
NHCOPh
O
O
N
Standard conditDionOs I: 10.1039/D0CC00736F
Ph
N
S
N
Ph
+
N
Ph
N
S
Bn
3a
2a
2.4 mmol
1a
2 mmol
56% yield, >20:1 dr, 93% ee
72% yield when benzoxazolimine was used as
a substrate.
Meanwhile, substrates 1 bearing substituents on C5 or C6 positions
of benzothiazole rings were successfully applied in the reaction, and
the cycloadducts 3m-3q were obtained in good yields (57-69%) with
excellent enantioselectivities (93-99% ee).
O
Bn
NHCOPh
N
Ph
N
S
3a
Subsequently, the transformations of 2-benzothiazolimines 1a
with azlactones 2 were carried out under the established reaction
conditions. As shown in Scheme 3, the reaction tolerated a wide
range of azlactones with diverse substituents on the aromatic rings
regardless of their electronic properties and substitution patterns,
and the corresponding products 3r-u were generated in good yields
with excellent diastereo- and enantioselectivities.. Furthermore, we
found that the benzyl group with various substituents had almost
no effect on the stereoselectivity, and the products 3v-x were
isolated in 54-77% yields, ≥10:1 dr and 98-99% ee. In addition, we
also tested azlactones linked methyl group instead of the benzyl
group, which delivered the desired 3y in 67% yield, >20:1 dr and
99% ee at 0 °C for 20 h.
Scheme 4 The large-scale reaction and X-ray structure[χabs = 0.009(14)] of 3a.
On the basis of previous reports and stereochemical
outcome, a possible reaction mechanism was proposed. As
shown in Scheme 5, the bifunctional squaramide catalyst D
that serves as dual-role. The azlactone 2a was deprotonated
by the tertiary amine moiety of catalyst D to provide enolate
species. Meanwhile, 2-benzothiazolimine 1a was activated by
the H-bonding interactions between the nitrogen atoms and the
squaramide. Subsequently, nucleophilic attack of the azlactone
enolate on its Si-face via Mannich reaction leads to two possible
intermediates I and II. Finally, the intramolecular lactamization
of the intermediate II produces the desired product 3a and
regenerates the catalyst D.
O
R
O
O
D
NHCOAr
cat. (10 mol%)
Ph
N
Ar
+
N
N
Ph
N
THF , rt, 12 h
R
S
N
O
Bn
S
NHCOPh
1a
2
3
O
O
N
Standard conditions
N
Ph
N
S
Ph
Ph
+
N
N
O
S
O
O
Bn
O
O
O
Bn
Bn
3a
Bn
2a
1a
NH
NH
Ph
NH
Ph
N
N
N
R'
Br
Ph
cat. D
N
N
N
S
S
cat. D
S
cyclization
H
N
3r
3u
3s
3t
R*
Me
, R'=Me, 57% yield, >20:1 dr, 94% ee
, R'=OMe, 73% yield, >20:1 dr, 93% ee
70% yield, >20:1 dr,99% ee
62% yield, >20:1 dr, 99% ee
Me
O
O
X
chiral
scalfold
N
N
S
Me
N
Ar
N
H
N
H
Mannich step
O
N
O
O
O
H
O
S
O
CH3
NHCOPh
N
Me
NHCOPh
NHCOPh
O
O
N
N
N
N
N
Ph
Ph
Ph
Ph
Bn
II
Ph
Bn
N
O
N
N
S
N
N
Ph
Ph
S
S
S
Ph
Bn
N
3y
I
3v
Ph
3w
3x
, X=F, 54% yield, >20:1 dr, 99% ee
, X=Cl, 65% yield, 10:1 dr, 98% ee
Re face attack
67% yield, >20:1 dr,99% eeb
77% yield, >20:1 dr, 99% ee
Scheme 5 Proposed reaction mechanism.
a
Scheme 3 The variation of azlactones. General reaction conditions: 1a (0.2
mmol), 2 (0.24 mmol), D (10 mol%), THF (2 mL, 0.1 M), and 12 h at rt. All yields
refer to the isolated yields. The dr values were determined by 1H NMR
spectroscopy. The ee values were determined by HPLC on a chiral stationary
phase. b Performed at 0 °C for 20 h.
In summary, we have developed an asymmetric domino
Mannich/cyclization reaction between 2-benzothiazolimines
with azlactones derivatives using
a
quinidine-derived
To demonstrate the practicality of this catalytic system, a
large-scale synthesis of product 3a (2 mmol) was conducted. Under
the optimized condition, the reaction of 1a (2 mmol) with azlactone
2a (2.4 mmol) worked smoothly and the desired adduct 3a was
isolated in 56% yield, >20:1 dr and 93% ee. Moreover, the absolute
configuration of the product 3a was unambiguously determined by
X-ray crystallographic analysis (CCDC 1934497), which revealed a
sterically unfavourable cis-configuration between benzyl and phenyl
groups. The configurations of the other adducts 3b-3t were
assigned by analogy.
squaramide organocatalyst. series of optically active
A
benzothiazolopyrimidines with contiguous quaternary and
tertiary stereogenic centers were constructed in moderate to
good yields with excellent diastereo and enantioselectivities.
Further studies on the extension of this protocol to the
synthetic application and new cyclizations are currently
ongoing in our laboratory and will be reported in due course.
We are grateful for the financial support from the
National Natural Science Foundation of China (21602085),
Anhui Provincial Natural Science Foundation (1908085QB55)
and
theꢀScientificꢀResearchꢀFoundationꢀofꢀtheꢀHigher
EducationꢀInstitutionsꢀofꢀAnhuiꢀProvince (KJ2019A0499).
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
COMMUNICATION
Journal Name
Yang, J. Du and N.-N. Feng, Org. Lett., 2017, 19, 26-29; c) J.-c.
Yu, L.-m. Yu, X.-y. Zhao, L. Gan, W.-w. Zhu, ZV.-iecw. AWrticalenOgn,liRne.
Wang and X. Jiang, Org. Chem. Front.,D2O0I1: 810, .510,3290/D400C-2C004047;36dF)
L. Xie, S. Dong, Q. Zhang, X. Feng and X. Liu, Chem. Commun.,
2019, 55, 87-90.
S. Dong, X. Liu, Y. Zhu, P. He, L. Lin and X. Feng, J. Am. Chem.
Soc., 2013, 135, 10026-10029.
a) X. Liu, Y. Wang, D. Yang, J. Zhang, D. Liu and W. Su, Angew.
Chem. Int. Ed., 2016, 55, 8100-8103; b) Q. Zhang, S. Guo, J.
Yang, K. Yu, X. Feng, L. Lin and X. Liu, Org. Lett., 2017, 19,
5826-5829.
Conflicts of interest
There are no conflicts to declare.
8
9
Notes and references
1
a) S. G. Badne, D. K. Swamy, V. N. Bhosale and S. V. Kuberkar,
J. Heterocyclic Chem., 2011, 48, 849-855; b) S. A. Bahashwan,
Alharbi, A. E., Ramadan, M. A., Fayed, A. A., Bahashwan, A.
A. , Trop. J. Pharm. Res., 2013, 12, 989-995; c) P. P.
Nandekar, K. M. Tumbi, N. Bansal, V. P. Rathod, L. B. 10 C. Ma, J. Y. Zhou, Y. Z. Zhang, G. J. Mei and F. Shi, Angew.
Labhsetwar, N. Soumya, S. Singh and A. T. Sangamwar,
Chem. Int. Ed., 2018, 57, 5398-5402.
Medicinal Chemistry Research, 2013, 22, 3728-3742; d) P. R. 11 a) J. Jiang, J. Qing and L.-Z. Gong, Chem. Eur. J., 2009, 15,
Prasad, J. Chem. Pharm. Res., 2015, 7, 317-322; e) J. R.
LaRochelle, M. Fodor, J. M. Ellegast, X. Liu, V. Vemulapalli, M.
Mohseni, T. Stams, S. J. Buhrlage, K. Stegmaier, M. J.
LaMarche, M. G. Acker and S. C. Blacklow, Bioorg. Med.
Chem., 2017, 25, 6479-6485.
a) V. B. Birman, E. W. Uffman, H. Jiang, X. Li and C. J. Kilbane,
J. Am. Chem. Soc., 2004, 126, 12226-12227; b) V. B. Birman
and X. Li, Org. Lett., 2008, 10, 1115-1118; c) C. Joannesse, C.
P. Johnston, C. Concellón, C. Simal, D. Philp and A. D. Smith,
Angew. Chem. Int. Ed., 2009, 48, 8914-8918; d) Y. Zhang and
V. B. Birman, Adv. Synth. Catal., 2009, 351, 2525-2529; e) C.
Simal, T. Lebl, A. M. Z. Slawin and A. D. Smith, Angew. Chem.
Int. Ed., 2012, 51, 3653-3657; f) E. R. T. Robinson, C. Fallan, C.
Simal, A. M. Z. Slawin and A. D. Smith, Chem. Sci., 2013, 4,
7031-7034; b) S. Dong, X. Liu, X. Chen, F. Mei, Y. Zhang, B.
Gao, L. Lin and X. Feng, J. Am. Chem. Soc., 2010, 132, 10650-
10651; c) J. Hejmanowska, A. Albrecht, J. Pięta and Ł.
Albrecht, Adv. Synth. Catal., 2015, 357, 3843-3848; d) S.-Y.
Zhang, M. Lv, S.-J. Yin, N.-K. Li, J.-Q. Zhang and X.-W. Wang,
Adv. Synth. Catal., 2016, 358, 143-153; e) Y. Wang, J. Pan, R.
Jiang, Y. Wang and Z. Zhou, Adv. Synth. Catal., 2016, 358,
195-200; f) S. Ruan, X. Lin, L. Xie, L. Lin, X. Feng and X. Liu,
Org. Chem. Front., 2018, 5, 32-35; g) X. Li, J. Yan, J. Qin, S.
Lin, W. Chen, R. Zhan and H. Huang, J. Org. Chem., 2019, 84,
8035-8045; h) X.-R. Ren, J.-B. Lin, X.-Q. Hu and P.-F. Xu, Org.
Chem. Front., 2019, 6, 2280-2283; i) Y. Wang, Y. Chen, X. Li,
Y. Mao, W. Chen, R. Zhan and H. Huang, Org. Biomol. Chem.,
2019, 17, 3945-3950.
2
2193-2200; g) D. G. Stark, L. C. Morrill, P.-P. Yeh, A. M. Z. 12 a) H. Hu, Y. Liu, J. Guo, L. Lin, Y. Xu, X. Liu and X. Feng, Chem.
Slawin, T. J. C. O'Riordan and A. D. Smith, Angew. Chem. Int.
Ed., 2013, 52, 11642-11646; h) J. Merad, P. Borkar, F. Caijo,
J.-M. Pons, J.-L. Parrain, O. Chuzel and C. Bressy, Angew.
Chem. Int. Ed., 2017, 56, 16052-16056; i) M. D. Greenhalgh,
S. M. Smith, D. M. Walden, J. E. Taylor, Z. Brice, E. R. T.
Robinson, C. Fallan, D. B. Cordes, A. M. Z. Slawin, H. C.
Richardson, M. A. Grove, P. H.-Y. Cheong and A. D. Smith,
Commun., 2015, 51, 3835-3837; b) Y.-C. Zhang, Q.-N. Zhu, X.
Yang, L.-J. Zhou and F. Shi, J. Org. Chem., 2016, 81, 1681-
1688; c) X.-Y. Yu, J.-R. Chen, Q. Wei, H.-G. Cheng, Z.-C. Liu
and W.-J. Xiao, Chem. Eur. J., 2016, 22, 6774-6778; d) J. Zhou,
M.-L. Wang, X. Gao, G.-F. Jiang and Y.-G. Zhou, Chem.
Commun., 2017, 53, 3531-3534; e) Z.-P. Zhang, K.-X. Xie, C.
Yang, M. Li and X. Li, J. Org. Chem., 2018, 83, 364-373.
Angew. Chem. Int. Ed., 2018, 57, 3200-3206; j) Y. Pan, Z. Luo, 13 a) D. Uraguchi, Y. Ueki and T. Ooi, J. Am. Chem. Soc., 2008,
J. Han, X. Xu, C. Chen, H. Zhao, L. Xu, Q. Fan and J. Xiao, Adv.
Synth. Catal., 2019, 361, 2301-2308.
130, 14088-14089; b) X. Liu, L. Deng, X. Jiang, W. Yan, C. Liu
and R. Wang, Org. Lett., 2010, 12, 876-879; c) W.-Q. Zhang,
L.-F. Cheng, J. Yu and L.-Z. Gong, Angew. Chem. Int. Ed.,
2012, 51, 4085-4088; d) S.-H. Shi, F.-P. Huang, P. Zhu, Z.-W.
Dong and X.-P. Hui, Org. Lett., 2012, 14, 2010-2013; e) E. P.
Ávila, R. M. S. Justo, V. P. Gonçalves, A. A. Pereira, R. Diniz
and G. W. Amarante, J. Org. Chem., 2015, 80, 590-594; f) H.
Zhang, Z. Yang, B. N. Zhao and G. Li, J. Org. Chem., 2018, 83,
644-655.
3
a) J. M. Mellor and H. Rataj, Tetrahedron Lett., 1996, 37,
2619-2622; b) B. Viswambharan, T. Okimura, S. Suzuki and S.
Okamoto, J. Org. Chem., 2011, 76, 6678-6685; c) A. B. Atar,
Y. S. Jeong and Y. T. Jeong, Tetrahedron, 2014, 70, 5207-
5213; d) S. Okamoto, Y. Sakai, S. Watanabe, S. Nishi, A.
Yoneyama, H. Katsumata, Y. Kosaki, R. Sato, M. Shiratori, M.
Shibuno and T. Shishido, Tetrahedron Lett., 2014, 55, 1909-
1912.
14 S. Dong, X. Liu, Y. Zhang, L. Lin and X. Feng, Org. Lett., 2011,
13, 5060-5063.
15 M. Zhang, C. Yu, J. Xie, X. Xun, W. Sun, L. Hong and R. Wang,
Angew. Chem. Int. Ed., 2018, 57, 4921-4925.
16 a) D.-C. Wang, M.-S. Xie, H.-M. Guo, G.-R. Qu, M.-C. Zhang
and S.-L. You, Angew. Chem. Int. Ed., 2016, 55, 14111-14115;
b) Z.-P. Yang, C. Zheng, L. Huang, C. Qian and S.-L. You,
Angew. Chem. Int. Ed., 2017, 56, 1530-1534.
4
5
6
Q. Ni, X. Song, J. Xiong, G. Raabe and D. Enders, Chem.
Commun., 2015, 51, 1263-1266.
L. Jarrige, D. Glavač, G. Levitre, P. Retailleau, G. Bernadat, L.
Neuville and G. Masson, Chem. Sci., 2019, 10, 3765-3769.
a) S. Peddibhotla and J. J. Tepe, J. Am. Chem. Soc., 2004, 126,
12776-12777; b) A. N. R. Alba and R. Rios, Chem. Asian J.,
2011, 6, 720-734; c) W. Sun, G. Zhu, C. Wu, G. Li, L. Hong and
R. Wang, Angew. Chem. Int. Ed., 2013, 52, 8633-8637; d) B.
Qiao, X. Liu, S. Duan, L. Yan and Z. Jiang, Org. Lett., 2014, 16,
672-675; e) P. P. deꢁCastro, A. G. Carpanez and G. W.
Amarante, Chem. Eur. J., 2016, 22, 10294-10318; f) D.
Uraguchi, R. Shibazaki, N. Tanaka, K. Yamada, K. Yoshioka
and T. Ooi, Angew. Chem. Int. Ed., 2018, 57, 4732-4736; g)
M. Zhang, C. Yu, J. Xie, X. Xun, W. Sun, L. Hong and R. Wang,
Angew. Chem. Int. Ed., 2018, 57, 4921-4925; h) X. Zheng, W.-
L. Yang, Y.-Z. Liu, S.-X. Wu and W.-P. Deng, Adv. Synth. Catal.,
2018, 360, 2843-2853; i) J. Kikuchi and M. Terada, Angew.
Chem. Int. Ed., 2019, 58, 8458-8462.
7
a) G. Li, W. Sun, J. Li, F. Jia, L. Hong and R. Wang, Chem.
Commun., 2015, 51, 11280-11282; b) H.-W. Zhao, Y.-Y. Liu,
Y.-D. Zhao, H.-L. Pang, X.-Q. Chen, X.-Q. Song, T. Tian, B. Li, Z.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins