Sulfonium Salts Enable the Direct Sulfenylation of Activated C(sp3)?H Bonds

Article abstract of DOI:10.1002/ejoc.202001569

Herein, the direct α-sulfenylation of a series of β-dicarbonyl, β-ketophosphonate, and β-ketonitrile compounds, mediated by sulfonium salts has been described. Traditionally, sulfonium salts which are synthesized by activation of dialkylsulfoxides serve as oxidizing agents or precursors of sulfur ylide. In this transformation, sulfonium salts as readily prepared and operationally simple sulfenylation reagents firstly achieved alkylsulfenylation of various activated C(sp³)?H bonds with the formation of tetra-substituted carbon center.

Full text of DOI:10.1002/ejoc.202001569

Communications
doi.org/10.1002/ejoc.202001569
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Sulfonium Salts Enable the Direct Sulfenylation of
Activated C(sp3)À H Bonds
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Liang Zhang,*[a] Sakkani Nagaraju,[a] Banoth Paplal,[a] Yunliang Lin,[a] and Shuhua Liu*[a]
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Herein, the direct α-sulfenylation of a series of β-dicarbonyl, β-
ketophosphonate, and β-ketonitrile compounds, mediated by
sulfonium salts has been described. Traditionally, sulfonium
salts which are synthesized by activation of dialkylsulfoxides
serve as oxidizing agents or precursors of sulfur ylide. In this
transformation, sulfonium salts as readily prepared and opera-
tionally simple sulfenylation reagents firstly achieved alkylsulfe-
nylation of various activated C(sp3)À H bonds with the formation
of tetra-substituted carbon center.
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Introduction
Sulfur-containing compounds are privileged structural motifs
found in natural products, pharmaceuticals, agrochemicals, and
materials science.[1] Over the past few decades, considerable
endeavors have been devoted to develop novel and efficient
Scheme 1. Sulfenylation of Carbonyl Compounds.
strategies for the formation of CÀ S bond. Among these
methodologies, direct sulfenylation of CÀ H bond to form CÀ S
bond is a concise and atom-economic approach which has
attracted great attention from organic chemists. A variety of
sulfenylation agents such as thiols,[2] disulfides,[3] arenesulfonyl/
phenylsulfenyl chloride,[4] sulfonyl hydrazides,[5] sulfinic acids,[6]
sodium sulfinates,[7] N-thioimides,[8] and triazole derivatives[9]
have been employed in the formation of CÀ S bonds. Among
them, α-sulfenylation of carbonyl compounds is especially
attractive since these sulfenylated products are versatile
building blocks and synthons in organic transformations.[10]
However, traditional approaches mainly focused on using
electrophilic sulfur reagents such as diaryldisulfides,[3f,h] phenyl-
sulfenyl chloride,[4c,d] N-thioarylphthalimides,[8f–r] and triazole
Sulfonium salts can be readily accessible by the activation
of dialkylsulfoxides with electrophiles, which have traditionally
been used as oxidizing agents or precursors of sulfur ylide. In
this context, we utilized sulfonium salts generated in situ as
sulfenylation reagents to realize the direct alkylsulfenylation of
activated C(sp3)À H bonds in β-dicarbonyl, β-ketophosphonate,
and β-ketonitrile compounds under mild reaction conditions,
providing the corresponding sulfenylated products with tetra-
substituted carbon centers (Scheme 1b).
derivative[9c] to introduce a sulfur atom at α-position of carbonyl Results and Discussion
coumpounds (Scheme 1a). Despite some advantages and
achieving enantioselective α-sulfenylation of carbonyl com-
pounds, the exploitation of sulfenylation reagents which are
easy to prepare or handle, inexpensive, commercially available,
and performed under mild reaction conditions remains an
unsolved problem. Furthermore, compared with aryl-or benzyl-
sulfenylation reagents, alkylsulfenylation reagents are relatively
rare.
To start with, we selected β-ketoester 1a and sulfoxide 2a
(DMSO) as the model substrates to optimize the reaction
conditions, as shown in Table 1. Initially, 1a reacted with
sulfonium salt which was generated in situ by 1.5 equiv. DMSO
activated with 1.5 equiv. oxalyl chloride in CH3CN. Unfortu-
nately, no sulfenylated products were obtained after 24 h
(Table 1, entry 1). Then, the amount of DMSO was increased to
3.0 equiv, and the desired sulfenylation product 4a was gained
in 50% yield after 10 h (Table 1, entry 2). Subsequently, various
electrophilic activators were screened, and a similar yield of 4a
was achieved with acetyl chloride as an activator (Table 1,
entry 3–8). With the suitable activator in hand, we continued to
amplify the amount of DMSO from 4.0 to 10.0 equiv. and
maintained 1:2 ratio of acetyl chloride to DMSO (Table 1,
entry 9–12). The results suggested that reaction time became
[a] L. Zhang, S. Nagaraju, B. Paplal, Y. Lin, S. Liu
School of Pharmaceutical Sciences, Shandong Analysis and Test Center
Qilu University of Technology (Shandong Academy of Sciences)
Jinan 250014, P. R. China
E-mail: zhangliang@qlu.edu.cn
liushh@qlu.edu.cn
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/ejoc.202001569
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Table 1. Optimization of Reaction Conditions.[a]
Table 2. Direct Sulfenylation of Activated C(sp3)À H Bond.[a]
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8
Entry
Solvent
DMSO
(equiv)
Activator
Time
Yield
[%][b]
1[c]
2
3
4
5
6
7
8
9
10
11
12
13[d]
14
15
16
17
18[e]
19[f]
20[g]
21[h]
22[i]
23[j]
24[k]
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
DCM
1.5
3.0
3.0
3.0
3.0
3.0
3.0
3.0
4.0
6.0
8.0
10.0
12.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
(COCl)2
(COCl)2
AcCl
BzCl
TFAA
DCC
Tf2O
TfCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
AcCl
24 h
10 h
12 h
12 h
24 h
24 h
24 h
24 h
n.r.
50
51
44
n.r.
n.r.
20
n.r
55
60
79
79
76
66
54
28
62
42
50
68
74
76
77
79
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8 h
3.5 h
2.5 h
2.0 h
2.0 h
3.0 h
3.0 h
3.0 h
2.0 h
24 h
20 min
3.5 h
2.0 h
25 min
25 min
25 min
toluene
THF
DMSO
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
[a] Unless otherwise noted, all the reactions were carried out with 1a
(0.3 mmol), activator/DMSO=1:2 in 0.5 mL solvent as indicated at room
temperature. [b] Isolated yield. [c] (COCl)2/DMSO=1:1. [d] AcCl/DMSO=
1:3. [e] at 0 C. [f] at 50 C. [g] 1.0 mL of CH3CN was used. [h] 0.3 mL of
CH3CN was used. [i] 2.0 equiv. NaBF4 was added as additive. [j] 2.0 equiv.
NaPF6 was added as additive. [k] 2.0 equiv. NaSbF6 was added as additive.
°
°
[a] Unless otherwise noted, all the reactions were carried out with 1 (0.3
mmol), 2 (2.4~6.0 mmol), 3 (1.2~3.0 mmol) in 0.5 mL CH3CN at room
temperature; for details, see the Supporting Information. [b] NaSbF6 was
added as additive. [c] oxalyl chloride was used as activator.
shorter with an increasing amount of DMSO and acetyl chloride,
and the highest yield of 79% was achieved when 8.0 equiv.
DMSO was used (Table 1, entry 11). Then the ratio of acetyl
chloride to DMSO was increased to 1:3, the desired product 4a
was acquired in a similar yield of 76% (Table 1, entry 13). Next,
various solvents such as DCM, toluene, THF, and DMSO were
investigated, and no further improvement in the yield was
observed (Table 1, entry 14–17). Lowering reaction temperature
resulted in a decrease in the yield of sulfenylated product 4a
and a prolonged reaction time (Table 1, entry 18). However,
only 50% yield of 4a was isolated at elevated reaction
Scheme 2. Gram-scale Synthesis.
°
temperature (50 C) with reduced reaction time (Table 1,
entry 19). Variation of concentration did not improve the yield
of 4a further (Table 1, entry 20–21). According to previous
reports,[11] addition of NaSbF6 could increase the stability and
reactivity of sulfonium ions. Additives such as NaBF4, NaPF6, and
NaSbF6 were added separately to the reaction system which not
only maintained a high yield, but also dramatically accelerated
the rate of this sulfenylation reaction (Table 1, entry 22–24).
To explore the generality of this transformation reaction, α-
sulfenylation of a sequence of β-dicarbonyl, β-ketophospho-
nate, and β-ketonitrile compounds involving activated C(sp3)À H
bond was studied, and obtained corresponding products with
tetra- substituted carbon center. As illustrated in Table 2, the
aliphatic five to seven-membered ring β-ketoesters could be
employed as successful substrates and the afforded sulfeny-
lated products showed satisfactory yields (4a, 4b, 4c). Lactone-
derived β-ketoesters also underwent the α-sulfenylation reac-
tion well, and converted into the corresponding products with
good yield (4d). Similarly, acyclic β-ketoesters bearing electron-
donating groups (À Me, À Bn) and electron-withdrawing groups
(À Cl, À F) at α-position could conduct the direct CÀ H bond
methylthiolation and produce the expected products in moder-
ate to good yield (4e, 4f, 4g, 4h), of which electron-with-
drawing groups (À Cl, À F) and more sterically congested group
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Scheme 3. Mechanistic Investigation.
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(À Bn) at α-potision resulted in lower yields and longer reaction
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time. The reactivity of β-ketoesters derived from heteroaromatic
furan and thiophene was also investigated, and the desired
products were observed in moderate yields (4i, 4j). Meanwhile,
α-sulfenylation of β-ketoesters bearing aromatic ring also
proceeded well under optimized reaction conditions to produce
the products 4k, 4l and 4m. The structure of 4k was confirmed
by single-crystal X-ray diffraction (CCDC 2021811).[12] Subse-
quently, cyclic and acyclic β-diketone compounds also can be
employed as effective substrates to produce the sulfenylated
products 4n and 4o. Notably, β-keto amide, β-keto phospho-
nate and β-ketonitrile compounds were all tolerated in this
sulfenylation transformation (4p, 4q, 4r). This methodology
also successfully incorporated methylthio group into dimeth-
yluracil with promising biological activities (4s). Further inves-
tigation of different types of sulfonium salts revealed that
diethyl sulfoxide, dipropyl sulfoxide, dibutyl sulfoxide, and
dibenzyl sulfoxide-derived sulfonium salts all could be compat-
ible in this sulfenylation transformation and generated the
desired products in good yields (4t, 4u, 4v, 4w). However,
sulfonium salts derived from diaryl sulfoxides and arylalkylsulf-
oxides were not accommodated under the optimized reaction
conditions and afforded α-chlorinated products (see supporting
information for details). To illustrate the synthetic utility of this
transformation, we conducted a gram-scale reaction using 1.7 g
of 1a as starting material to produce the desired product 4a in
73% (1.66 g) yield (Scheme 2).
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Scheme 4. Proposed Reaction Pathway.
sulfoxide is firstly treated with activator acetyl chloride to form
sulfonium salt M1, which could improve its reactivity and the
reaction rate can be accelerated by the addition of NaSbF6.
After enolization of carbonyl compound, electrophile M1 under-
goes electrophilic addition and deprotonation with enol
compounds, leading to the formation of intermediate M2 with
concomitant expulsion of hydrogen chloride. Subsequently,
nucleophilic attack of excess sulfoxide takes place at carbon
center adjacent to cationic sulfur, resulting in the formation of
the desired product and new intermediate M3. Finally, M3 is
transformed into corresponding dialkyl sulfide and aldehyde via
deprotonation and cyclic transition state.
To provide some insight into this sulfenylation process,
several control experiments were conducted to illustrate the
reaction pathway (Scheme 3). When the equivalent ratio of
acetyl chloride to DMSO is 1:1, product 4a was not observed
after 24 h, suggesting excess sulfoxide played an indispensable
role in this transformation (Scheme 3a). Under the standard
reaction conditions, we performed the sulfenylation reaction
with 1a, sulfonium salt 2a’ generated in situ and excess
sulfoxide 2v as substrates, only product 4a was obtained in Conclusions
66% yield, and no product 4v was observed. Similar two
experiments were also conducted, and identical results were
obtained (Scheme 3b). This excluded the existence of disulfo-
nium salts which were synthesized by nucleophilic substitution
of excess sulfoxide to sulfonium salt formed initially, and
illustrated that substrate 1a firstly reacted with sulfonium salts
generated in situ, and then further reacted with excess sulfoxide
to acquire the desired products. Subsequently, we used esters
which contained electron-withdrawing group at α-position as
substrates, such as 1y, 1z, and 1aa which were not easy to
enolize. No sulfenylated products were observed after 24 h
In summary, we have developed a novel strategy which enables
the direct installation of alkylthio group into α-position of a
series of β-dicarbonyl, β-ketophosphonate, and β-ketonitrile
compounds using sulfonium salts generated in situ as sulfur
sources. This work not only provides a simple methodology for
the synthesis of α-sulfenylated carbonyl compounds with tetra-
substituted carbon center but further extends the application
scope of sulfonium salts.
under the standard reaction conditions (Scheme 3c). Further- Acknowledgements
more, an intermolecular competitive reaction between sub-
strates 1l and 1b was conducted, and product 4l was obtained
with a higher yield than 4b at the same reaction time
(Scheme 3d). This observation can be ascribed to substrate 1l
which mainly exists in enol form reacts faster with sulfonium
ions than 1b which exists in keto form, indicating that
substrates transformed from ketone to enol.
We gratefully acknowledge the Natural Science Youth Foundation
of Shandong Province (ZR2020QB005), the Youth Foundation of
Qilu University of Technology (Shandong Academy of Sciences),
We thank Prof. Yao Wang (Shandong University) for assistance
with revision of the article.
Based on the above mechanistic investigation and previous
reports,[11,13] a plausible reaction pathway is shown in Scheme 4,
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Zhang, J. Org. Chem. 2015, 80, 4697–4703; f) X. Zhao, L. Zhang, T. Li, G.
Conflict of Interest
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2
3
4
5
6
7
8
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Liu, H. Wang, K. Lu, Chem. Commun. 2014, 50, 13121–13123; g) W. Zhao,
P. Xie, Z. Bian, A. Zhou, H. Ge, M. Zhang, Y. Ding, L. Zheng, J. Org. Chem.
2015, 80, 9167–9175; h) Y. Yang, S. Zhang, L. Tang, Y. Hu, Z. Zha, Z.
Wang, Green Chem. 2016, 18, 2609–2613; i) F. L. Yang, Y. Gui, B. K. Yu,
Y. X. Jin, S. K. Tian, Adv. Synth. Catal. 2016, 358, 3368–3372.
The authors declare no conflict of interest.
Keywords: CÀ S bonds
·
β-Dicarbonyl compounds
·
[6] For selected examples, see: a) C. Liu, L. Ding, Org. Biomol. Chem. 2015,
13, 2251–2254; b) R. Rahaman, N. Devi, J. R. Bhagawati, P. Barman, RSC
Adv. 2016, 6, 18929–18935.
[7] For selected examples, see: a) L. Jiang, J. Qian, W. Yi, G. Lu, C. Cai, W.
Zhang, Angew. Chem. 2015, 127, 15178–15182; Angew. Chem. Int. Ed.
2015, 54, 14965–14969; b) F. Xiao, H. Xie, S. Liu, G. J. Deng, Adv. Synth.
Catal. 2014, 356, 364–368; c) Y. Lin, G. Lu, G. Wang, W. Yi, J. Org. Chem.
2017, 82, 382–389; d) Y. Ding, W. Wu, W. Zhao, Y. Li, P. Xie, Y. Huang, Y.
Liu, A. Zhou, Org. Biomol. Chem. 2016, 14, 1428–1431.
Sulfenylation · Sulfonium salts · Sulfoxides
[1] For selected examples, see: a) E. Block, Reactions of Organosulfur
Compounds, Academic Press, New York, 1978; b) X. Jiang, Sulfur
Chemistry in Topics in Current Chemistry, Spring Nature, Switzerland,
2019; c) P. Chauhan, S. Mahajan, D. Enders, Chem. Rev. 2014, 114, 8807–
8864; d) M. D. McReynolds, J. M. Dougherty, P. R. Hanson, Chem. Rev.
2004, 104, 2239–2258; e) A. Mishra, C. Q. Ma, P. Bäuerle, Chem. Rev.
2009, 109, 1141–1276; f) K. Takimiya, I. Osaka, T. Mori, M. Nakano, Acc.
Chem. Res. 2014, 47, 1493–1502; g) D. Y. Lin, S. Z. Zhang, E. Block, L. C.
Katz, Nature 2005, 434, 470–477; h) D. A. Boyd, Angew. Chem. 2016, 128,
15712–15729; Angew. Chem. Int. Ed. 2016, 55, 15486–15502; i) N. Z.
Wang, P. Saidhareddy, X. F. Jiang, Nat. Prod. Rep. 2020, 37, 246–275;
j) M. H. Feng, B. Q. Tang, S. H. Liang, X. F. Jiang, Curr. Top. Med. Chem.
2016, 16, 1200–1216; k) H. Liu, X. F. Jiang, Chem. Asian J. 2013, 8, 2546–
2563.
[2] For selected examples, see: a) M. A. Hiebel, S. Berteina-Raboin, Green
Chem. 2015, 17, 937–944; b) R. Rahaman, S. Das, P. Barman, Green Chem.
2018, 20, 141–147; c) C. L. Jarvis, M. T. Richers, M. Breugst, K. N. Houk, D.
Seidel, Org. Lett. 2014, 16, 3556–3559; d) C. Ravi, D. C. Mohan, S.
Adimurthy, Org. Lett. 2014, 16, 2978–2981; e) Y. Siddaraju, K. R. Prabhu,
Org. Lett. 2016, 18, 6090–6093; f) Y. Siddaraju, K. R. Prabhu, J. Org. Chem.
2016, 81, 7838–7846; g) J. Wan, S. Zhong, L. Xie, X. Cao, Y. Liu, L. Wei,
Org. Lett. 2016, 18, 584–587; h) D. Yang, P. Sun, W. Wei, L. Meng, L. He,
B. Fang, W. Jiang, H. Wang, Org. Chem. Front. 2016, 3, 1457–1461; i) P.
Sun, D. Yang, W. Wei, L. Jiang, Y. Wang, T. Dai, H. Wang, Org. Chem.
Front. 2017, 4, 1367–1371; j) S. Song, Y. Zhang, A. Yeerlan, B. Zhu, J. Liu,
N. Jiao, Angew. Chem. 2017, 129, 2527–2531; Angew. Chem. Int. Ed.
2017, 56, 2487–2491; k) Q. H. Teng, Y. Yao, W. X. Wei, H. T. Tang, J. L. Li,
Y. M. Pan, Green Chem. 2019, 21, 6241–6245; l) Y. Jiang, J. X. Zou, L. T.
Huang, X. Peng, J. D. Deng, L. Q. Zhu, Y. H. Yang, Y. Y. Feng, X. Y. Zhang,
Z. Wang, Org. Biomol. Chem. 2018, 16, 1641–1645; m) Q. Chen, X. F.
Wang, C. X. Wen, Y. L. Huang, X. X. Yan, J. K. Zeng, RSC Adv. 2017, 7,
39758–39761; n) Y. Siddaraju, K. R. Prabhu, J. Org. Chem. 2018, 83,
2986–2992; o) Y. Siddaraju, K. R. Prabhu, Org. Biomol. Chem. 2017, 15,
5191–5196; p) X. X. Liu, H. H. Cui, D. S. Yang, S. C. Dai, T. T. Zhang, J. Y.
Sun, W. Wei, H. Wang, RSC Adv. 2016, 6, 51830–51833.
[3] For selected examples, see: a) S. Vásquez-Céspedes, A. Ferry, L. Candish,
F. Glorius, Angew. Chem. 2015, 127, 5864–5868; Angew. Chem. Int. Ed.
2015, 54, 5772–5776; b) W. Ge, Y. Wei, Green Chem. 2012, 14, 2066–
2070; c) N. Devi, R. Rahaman, K. Sarma, P. Barman, Eur. J. Org. Chem.
2016, 2, 384–388; d) N. Devi, R. Rahaman, K. Arma, T. Khan, P. Barman,
Eur. J. Org. Chem. 2017, 11, 1520–1525; e) R. Rahaman, N. Devi, P.
Barman, Tetrahedron Lett. 2015, 56, 4224–4227; f) J. Zhao, F. Yang, Z. Yu,
X. Tang, Y. Wu, C. Ma, Q. Meng, Synlett 2019, 30, 2181–2184; g) A. F.
Vaquer, A. Frongia, F. SeccI, E. Tuveri, RSC Adv. 2015, 5, 96695–96704;
h) Y. W. Liu, S. S. Badsara, Y. C. Liu, C. F. Lee, RSC Adv. 2015, 5, 44299–
44305.
[4] For selected examples, see: a) M. Chen, Z. T. Huang, Q. Y. Zheng, Chem.
Commun. 2012, 48, 11686–11688; b) Q. Wu, D. Zhao, X. Qin, J. Lan, J.
You, Chem. Commun. 2011, 47, 9188–9190; c) M. Jereb, A. Togni, Chem.
Eur. J. 2007, 13, 9384–9392; d) M. Jereb, A. Togni, Org. Lett. 2005, 7,
4041–4043; e) D. Wang, S. Guo, R. Zhang, S. Lin, Z. Ya, RSC Adv. 2016, 6,
54377–54381; f) X. Zhao, X. Y. Lu, A. Q. Wei, X. L. Jia, J. Chen, K. Lu,
Tetrahedron Lett. 2016, 57, 5330–5333.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
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38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
[8] For selected examples, see: a) Y. Dong, Q. Jin, L. Zhou, J. Chen, Org. Lett.
2016, 18, 5708–5711; b) T. Hostier, V. Ferey, G. Ricci, D. G. Pardoa, J.
Cossy, Chem. Commun. 2015, 51, 13898–13901; c) M. Tudge, M. Tamiya,
C. Savarin, G. R. Humphrey, Org. Lett. 2006, 8, 565–568; d) D. Zhu, Y. Gu,
L. Lu, Q. Shen, J. Am. Chem. Soc. 2015, 137, 10547–10553; e) C. J.
Nalbandian, E. M. Miller, S. T. Toenjes, J. L. Gustafson, Chem. Commun.
2017, 53, 1494–1497; f) L. Fang, A. J. Lin, H. W. Hu, C. J. Zhu, Chem. Eur.
J. 2009, 15, 7039–7043; g) A. Lin, L. Fang, X. Zhu, C. Zhu, Y. X. Cheng,
Adv. Synth. Catal. 2011, 353, 545–549; h) S. Shirakawa, T. Tokuda, A.
Kasai, K. Maruoka, Org. Lett. 2013, 15, 3350–3353; i) W. C. Gao, J. Tian,
Y. Z. Shang, X. F. Jiang, Chem. Sci. 2020, 11, 3903–3908; j) J. Q. Zhao,
S. W. Luo, X. M. Zhang, X. Y. Xu, M. Q. Zhou, W. C. Yuan, Tetrahedron
2017, 73, 5444–5450; k) Y. You, Z. J. Wu, Z. H. Wang, X. Y. Xu, X. M.
Zhang, W. C. Yuan, J. Org. Chem. 2015, 80, 8470–8477; l) L. Huang, J. Li,
Y. Zhao, J. Org. Chem. 2015, 80, 8933–8941; m) K. Liao, F. Zhou, J. Yu, W.
Gao, J. Zhou, Chem. Commun. 2015, 51, 16255–16258; n) W. C. Gao, J.
Tian, Y. Z. Shang, X. F. Jiang, Chem. Sci. 2020, 11, 3903–3908; o) L. Cui, Y.
You, X. Mi, S. Luo, Org. Chem. Front. 2018, 5, 2313–2316; p) J. W. Han,
Y. X. Zhang, X. Y. Wu, H. N. C. Wong, Chem. Commun. 2019, 55, 397–400;
q) S. J. S. Roy, S. Mukherjee, Org. Biomol. Chem. 2017,15, 6921–6925;
r) Y. E. T. Yuan, L. Yin, Y. J. Xu, Tetrahedron Lett. 2017, 58, 2521–2524.
[9] For selected examples, see: a) M. Marigo, T. C. Wabnitz, D. Fielenbach,
K. A. Jørgensen, Angew. Chem. 2005, 117, 804–807; Angew. Chem. Int.
Ed. 2005, 44, 794–797; b) M. Marigo, K. A. Jørgensen, Chem. Commun.
2006, 19, 2001–2011; c) S. Sobhani, D. Fielenbach, M. Marigo, T. C.
Wabnitz, K. A. Jørgensen, Chem. Eur. J. 2005, 11, 5689–5694; d) J.
Franzén, M. Marigo, D. Fielenbach, T. C. Wabnitz, A. Kjærsgaard, K. A.
Jørgensen, J. Am. Chem. Soc. 2005, 127, 18296–18304.
[10] For selected examples, see: a) B. M. Trost, Chem. Rev. 1978, 78, 363–382;
b) B. M. Trost, Acc. Chem. Res. 1978, 11, 453–461; c) K. Hiroi, M. Nishida,
A. Nakayama, K. Nakazawa, E. Fujii, S. Sato, Y. Kuroki, Chem. Lett. 1979,
8, 969–972; d) T. Yura, N. Iwasawa, R. Clark, T. Mukaiyama, Chem. Lett.
1986, 15, 1809–1812; e) T. Tanaka, T. Azuma, X. Fang, S. Uchida, C.
Iwata, T. Ishida, Y. In, N. Maezaki, Synlett 2000, 1, 33–36.
[11] a) J. V. Crivello, S. Q. Kong, Macromolecules 2000, 33, 825–832; b) K.
Miyatake, K. Yamamoto, K. Endo, E. Tsuchida, J. Org. Chem. 1998, 63,
7522–7524; c) Y. Kawaoka, K. Koge, A. Sudo, T. Endo, Polym. Chem.
2018, 56, 2096–2102; d) B. Varga, Z. Gonda, B. L. Tóth, A. Kotschy, Z.
Novák, Eur. J. Org. Chem. 2020, 10, 1466–1471.
[12] Deposition Number 2021811 (for 4k) contains the supplementary
crystallographic data for this paper. These data are provided free of
charge by the joint Cambridge Crystallographic Data Centre and
Fachinformationszentrum Karlsruhe Access Structures service
www.ccdc.cam.ac.uk/structures.
[13] a) H. Q. Tong, C. Chen, W. B. Liu, Y. P. Pan, L. H. Duan, Asian J. Org.
Chem. 2019, 8, 479–481; b) M. M. D. Pramanik, N. Rastogi, Chem.
Commun. 2016, 52, 8557–8560; c) P. Dai, K. Luo, X. Yu, W. C. Yang, L.
Wu, W. H. Zhang, Adv. Synth. Catal. 2018, 360, 468–473.
[5] For selected examples, see: a) F. L. Yang, S. K. Tian, Angew. Chem. 2013,
125, 5029–5032; Angew. Chem. Int. Ed. 2013, 52, 4929–4923; b) T. T.
Wang, F. L. Yang, S. K. Tian, Adv. Synth. Catal. 2015, 357, 928–932; c) F. L.
Yang, F. X. Wang, T. T. Wang, Y. J. Wang, S. K. Tian, Chem. Commun.
2014, 50, 2111–2113; d) R. Singh, D. S. Raghuvanshi, K. N. Singh, Org.
Lett. 2013, 15, 4202–4205; e) G. Rong, J. Mao, H. Yan, Y. Zheng, G.
Manuscript received: December 14, 2020
Revised manuscript received: January 20, 2021
Accepted manuscript online: January 20, 2021
Eur. J. Org. Chem. 2021, 1365–1369
www.eurjoc.org
1369
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