A novel synthesis of diversely functionalized 1,2,4-triones through the homo- and cross-coupling reactions of β-keto sulfoxonium ylides

Article abstract of DOI:10.1016/j.tetlet.2020.151912

A novel synthesis of functionalized 1,2,4-triones via an oxidative homo-coupling of β-keto sulfoxonium ylides is presented. Preliminary mechanistic study reveals that the formation of the 1,2,4-trione product involves the in situ generation of an α-keto aldehyde intermediate via Cu(II)-promoted oxidative decomposition of β-keto sulfoxonium ylide followed by its coupling with the second molecule of ylide. Based on this intrinsic mechanism, a formal cross-coupling reaction was designed and successfully realized, from which more diversely functionalized 1,2,4-triones were synthesized with high efficiency. Compared with literature methods, notable features of this novel synthetic protocol include easily accessible and safe substrates, excellent functional group tolerance, convenient procedure, mild reaction conditions, and ready scalability.

Full text of DOI:10.1016/j.tetlet.2020.151912

Tetrahedron Letters xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
A novel synthesis of diversely functionalized 1,2,4-triones through the
homo- and cross-coupling reactions of b-keto sulfoxonium ylides
⇑
⇑
Xi Chen, Muhua Wang, Xinying Zhang , Xuesen Fan
Henan Key Laboratory of Organic Functional Molecules and Drug Innovation, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, Collaborative
Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan
453007, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel synthesis of functionalized 1,2,4-triones via an oxidative homo-coupling of b-keto sulfoxonium
Received 20 February 2020
Revised 29 March 2020
Accepted 1 April 2020
Available online xxxx
ylides is presented. Preliminary mechanistic study reveals that the formation of the 1,2,4-trione product
involves the in situ generation of an a-keto aldehyde intermediate via Cu(II)-promoted oxidative decom-
position of b-keto sulfoxonium ylide followed by its coupling with the second molecule of ylide. Based on
this intrinsic mechanism, a formal cross-coupling reaction was designed and successfully realized, from
which more diversely functionalized 1,2,4-triones were synthesized with high efficiency. Compared with
literature methods, notable features of this novel synthetic protocol include easily accessible and safe
substrates, excellent functional group tolerance, convenient procedure, mild reaction conditions, and
ready scalability.
Keywords:
Synthesis
Functionalized 1,2,4-trione
b-Keto sulfoxonium ylide
Homo- and cross-coupling
Ó 2020 Published by Elsevier Ltd.
Introduction
substrates through relatively simple procedure with improved effi-
ciency and atom-economy are still highly desirable.
Multiple carbonyl compounds like triketones are frequently
found in nature and often possess remarkable pharmacological
activities such as antitumor, antiviral, antimicrobial, antiparasitic,
and neuroprotective (Fig. 1) [1]. In addition, triketone derivatives
are also useful building blocks for the construction of more com-
plex molecular scaffolds [2].
As a class of readily obtainable and easy-to-purify synthetic
intermediates, sulfur/sulfonium/sulfoxonium ylides have been
routinely used in cyclopropanation, epoxidation, aziridination, as
well as OAH/NAH bonds insertion reactions [4]. In recent years,
the scope of their applications in organic synthesis is rapidly
expanding, especially as the surrogates of diazo compounds since
they are moisture/air-stable and considerably safer to handle com-
pared with their diazo counterparts [4–6]. In this regard, we have
established a novel synthesis of diversely substituted benzo[a]car-
Due to their importance, various methods for the preparation of
triketone derivatives have been developed, which mainly include:
(
i) Michael addition of substituted furan with methyl vinyl ketone
2
followed by furan ring opening to give 1,4,7-triketones [2a]; (ii)
Lewis acid-catalyzed Michael addition of 1,3-diketone onto
bazoles and indolo[2,1-a]isoquinolines through C(sp )–H function-
alization of 2-arylindoles by using b-keto sulfoxonium ylides as
coupling partners [7]. In addition, we have also developed a novel
synthesis of chimeras of naphthalenone with bis-substituted b-
keto sulfoxonium ylide via the reaction of benzoyl sulfoxonium
methyl vinyl ketone to give b,d-triketones [3a]; (iii) SmCl
alyzed C-acylation of 1,3-dicarbonyl compounds to give 1,3,3 -
triketone derivatives [3b]; (iv) intramolecular cyclization of 2-
3
-cat-
0
(
1,3-dithiolan-2-ylidene)-1-phenyl-butane-1,3-diones to give cyc-
ylides with a-diazo carbonyl compounds [8]. During our continu-
lic 1,2,4-trione derivatives [3d]; (v) hydrogenation of the aldol con-
densation products of 5-hydroxylmethyl furfural with ketones
under the catalysis of Au/TiO to give 1,4,7-triketones [3e]; (vi)
2
Au(I)-catalyzed oxidation of acyl acetylenes to give vicinal tricar-
bonyls [3f], etc. While these literature methods are generally reli-
able, new synthetic protocols using easily accessible and safe
ing study in this regard, we serendipitously discovered an oxida-
tive homocoupling of b-keto sulfoxonium ylides leading to the
formation of functionalized 1,2,4-triones (Scheme 1 (3)). It is worth
to note that Maulide et al. have reported a Ru-catalyzed cross-ole-
fination of sulfoxonium ylides with diazo compounds (Scheme 1
(1)) [9]. Very recently, Zhou et al. disclosed a Ru-catalyzed
homo-coupling of benzoyl sulfoxonium ylides via CAH activa-
tion/annulations affording functionalized isocoumarins (Scheme 1
(2)) [10]. To the best of our knowledge, there is still no previous
⇑
Corresponding authors.
E-mail addresses: xinyingzhang@htu.cn (X. Zhang), xuesen.fan@htu.cn (X. Fan).
https://doi.org/10.1016/j.tetlet.2020.151912
040-4039/Ó 2020 Published by Elsevier Ltd.
0
Please cite this article as: X. Chen, M. Wang, X. Zhang et al., A novel synthesis of diversely functionalized 1,2,4-triones through the homo- and cross-cou-
pling reactions of b-keto sulfoxonium ylides, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151912

2
X. Chen et al. / Tetrahedron Letters xxx (xxxx) xxx
reaction, 3-(dimethyl(oxo)-k-sulfanylidene)-1,4-diphenyl butane-
,2,4-trione (2a) was obtained in 27% yield (Table 1, entry 1). It
1
occurred to us that this unexpected formation of triketone 2a is
mechanistically and synthetically attractive in that it not only
reveals a different version of homo-coupling of b-keto sulfoxonium
ylides compared with what has been disclosed by Zhou [10]
(Scheme 1 (2)), but also provides a potential synthetic approach
toward functionalized 1,2,4-triketones which are otherwise diffi-
cult to obtain. To improve the reaction efficiency, several parame-
ters possibly affecting this novel transformation were optimized.
Fig. 1. Natural products containing tricarbonyl moiety.
3
First, different solvents including PhCl, THF, CH CN, acetone and
DMF were screened. Among them, DMF was found to be the most
efficient in mediating this reaction (entries 2–6). Further study
showed that using O
obvious improvement in the yield of 2a (entries 7–9). Next, Cu
OAc) O, CuBr , Cu(OTf) and Cu(acac) were tried as possible
ꢀH
catalyst, but they were found to be less effective than Cu(OAc)
entries 10–13). In following optimization study, we were pleased
2
, DCP or TBHP as an oxidant resulted in no
(
2
2
2
2
2
2
(
to find that the yield of 2a could be improved to 67% when the
reaction was carried out at 80 °C (entry 14). On the other hand,
temperature higher than 80 °C did not give more positive result
Scheme 1. Different coupling reactions of benzoyl sulfoxonium ylide.
(
entries 15–16). When the loading of catalyst was reduced to 0.2
equiv, the yield of 2a decreased obviously (entry 17). When the
reaction was tried under nitrogen, a slightly decreased efficiency
was observed compared with that carried out under air (entry 18
vs 14). Finally, a control experiment showed that in the absence
report on the oxidative homo- and cross-coupling of b-keto sulfox-
onium ylides to give functionalized 1,2,4-triones [11]. Herein, we
would like to report our detailed results in this aspect.
2
of Cu(OAc) , the formation of 2a was not detected (entry 19).
With the establishment of the optimum reaction conditions, the
generality of substrate was studied. The results listed in Scheme 2
showed that benzoyl sulfoxonium ylides bearing an electron-
donating group (EDG) such as methyl or methoxy on the para-posi-
tion of the phenyl ring took part in this reaction smoothly to afford
Results and discussion
Our study was initiated by treating benzoyl sulfoxonium ylide
1
2
a with Cu(OAc) in dioxane at 60 °C under air for 24 h. From this
Table 1
Optimization studies for the formation of 2a.a
Entry
Catalyst
Oxidant
Solvent
T (°C)
Yieldb (%)
1
2
3
4
5
6
7
8
9
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
2
2
2
2
2
2
2
2
2
2
dioxane
PhCl
THF
60
60
60
60
60
60
60
60
60
60
60
60
60
80
90
100
80
80
80
27
Trace
17
18
33
51
52
35
30
48
32
Trace
Trace
67
68
65
31
60
CH
3
CN
acetone
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
O
DCP
TBHP
2
10
11
12
13
14
15
16
17
18
19
ꢀH
2
O
CuBr
Cu(OTf)
Cu(acac)
2
2
2
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
2
2
2
2
2
c
d
ND
a
b
c
Reaction conditions: 1a (0.5 mmol), catalyst (0.5 mmol), oxidant (0.5 mmol or 1 atm for O
Isolated yield.
2
), solvent (3 mL), air, 24 h.
0
.1 mmol of Cu(OAc)
2
.
d
Under N
2
.
Please cite this article as: X. Chen, M. Wang, X. Zhang et al., A novel synthesis of diversely functionalized 1,2,4-triones through the homo- and cross-cou-
pling reactions of b-keto sulfoxonium ylides, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151912

X. Chen et al. / Tetrahedron Letters xxx (xxxx) xxx
3
Scheme 4. A control experiment.
stance, the starting materials were consumed in 0.5 h to give 2a in
5% yield, suggesting that 3a should be a key intermediate in the
8
formation of 2a.
After having established a convenient synthesis of 1,2,4-triones
through the homo-coupling of sulfoxonium ylides, we were then
interested in exploring the possibility of realizing a cross-coupling
between different sulfoxonium ylides. If successful, more diversely
functionalized 1,2,4-triones would be obtained. For this purpose,
1
a was treated with 1c under standard reaction conditions. From
this reaction, unfortunately, two cross-coupling products (2u and
u’) were formed along with two homocoupling products (2a
2
and 2c) in yields of 15%, 10%, 10% and 17% (Scheme 5). Obviously,
the selectivity of this cross-coupling is too poor to be useful for
practical synthetic missions. Therefore, an alternative strategy
has to be developed to get the envisioned cross-coupling products
in an efficient manner.
a,b,
a
Scheme 2. Substrate scope for the synthesis of 2 (I)
Reaction conditions: 1
b
(
0.5 mmol), Cu(OAc) (0.5 mmol), DMF (3 mL), 80 °C, air, 24 h. Isolated yield.
2
Bearing in mind that 1a could couple with 3a efficiently
(Scheme 4), we deduced that the desired cross-coupling product
might be efficiently formed through the reaction of b-keto sulfox-
2
b and 2c in good yields. Next, 1 bearing an electron-withdrawing
group (EWG) such as fluoro, chloro, bromo, trifluoromethyl or phe-
nyl on the para-position of the phenyl scaffold were also suitable
for this reaction to give 2d-2h. Next, benzoyl sulfoxonium ylides
bearing an EDG, such as methyl or methoxy, or an EWG such as
chloro or bromo on the meta-site of the phenyl ring were found
to be viable for this reaction to give 2i-2l. When 1 bearing an
ortho-methyl substituted phenyl unit was subjected to standard
conditions, the corresponding reaction proceeded equally well to
give 2m without showing obvious steric effect. In addition, di- or
tri-substituted benzoyl sulfoxonium ylides and 1-naphthyl or 2-
naphthyl substituted substrates underwent the desired coupling
reactions to afford 2n-2q. Moreover, this reaction was found to
be applicable for furanyl and thienyl substituted sulfoxonium
ylides to give 2r-2s. Finally, besides various aromatic substituent,
an alkyl unit substituted sulfoxonium ylide could also undergo
the expected homocoupling to give 2t, albeit the yield was lower.
Based on literature reports [4] and experimental results, a plau-
sible mechanism accounting for the formation of 2a from 1a is pro-
posed in Scheme 3. Initially, complexation of 1a with Cu(II) catalyst
gives intermediate A. Next, decomposition of A takes place to give
a carbene intermediate B with the release of DMSO. Then, B is oxi-
onium ylide (as a nucleophile) with an a-keto aldehyde (as an elec-
trophile). Thus, 4-methoxybenzoyl sulfoxonium ylide (1c) was
treated with 3a in the presence of Cu(OAc)2 in DMF at 80 °C for
0.5 h. From this reaction, the formal cross-coupling product 2u
was obtained in an excellent yield of 87% (Scheme 6). Prompted
by this preliminary result, the generality of this cross-coupling
reaction was explored. First, different b-keto sulfoxonium ylides
1 were tried by using 3a as a model substrate. It turned out that
benzoyl sulfoxonium ylides bearing either an EDG or EWG on the
para-, meta- or ortho-site of the phenyl ring reacted with 3a
smoothly to give products 2u-2y in good to excellent yields. It
was also observed that the reactions of 1-naphthyl, 2-naphthyl,
2-furanyl and 2-thienyl substituted b-keto sulfoxonium ylides with
3a took place with almost equally good efficiency to give 2z-2cc. In
addition, substrates 1 with a primary or secondary alkyl unit could
also take part in this reaction to give 2dd-2gg in moderate yields.
To our delight, b-alkoxycarbonyl and b-phenoxycarbonyl units
substituted sulfoxonium ylides were found to be also suitable for
this reaction to give 2hh-2jj. Next, by using 1a as a model sub-
strate, the suitability of different a-keto aldehydes 3 was studied.
dized by DMSO to give an
likely via the formation of intermediate C with the release of Cu
I). Then, 3a reacts with 1a to give intermediate D. Finally, an
a-keto aldehyde intermediate 3a, most
It turned out that all of them could react with 1a smoothly to give
the desired cross-coupling products 2kk-2pp in yields ranging
from 60% to 84%.
(
in situ dehydrogenative oxidation of D affords 2a.
To showcase the synthetic potential of the functionalized 1,2,4-
triketones obtained above, structural elaborations of 2a were car-
ried out [5b,13,14]. From these transformations, 2-oxo-N,2-
diphenylacetamide (4), 3-chloro-4-hydroxy-1,4-diphenylbut-3-
To confirm the mechanism as described above, the proposed
intermediate 3a was prepared separately [12] and then treated
with 1a under standard conditions (Scheme 4). Under this circum-
Scheme 3. Proposed mechanism accounting for the formation of 2a from 1a.
Scheme 5. Cross-coupling reaction of 1a with 1c.
Please cite this article as: X. Chen, M. Wang, X. Zhang et al., A novel synthesis of diversely functionalized 1,2,4-triones through the homo- and cross-cou-
pling reactions of b-keto sulfoxonium ylides, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151912

4
X. Chen et al. / Tetrahedron Letters xxx (xxxx) xxx
sive copper salt was used as an efficient catalyst and air was used
as a sustainable co-oxidant. With notable features such as easily
accessible and safe substrates, high efficiency, convenient syn-
thetic procedure and good atom-economy, the chemical transfor-
mations described in this paper are expected to find broad
applications in related areas.
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgments
We are grateful to the National Natural Science Foundation of
China (21572047), Program for Innovative Research Team in
Science and Technology in Universities of Henan Province
(
20IRTSTHN005), Key Project of Science and Technology of Henan
Province (192102310412) and 111 Project (D17007) for financial
support.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tetlet.2020.151912.
a,b
a
Scheme 6. Substrate scope for the synthesis of 2 (II)
,
Reaction conditions: 1
b
(
0.5 mmol), 3 (0.5 mmol), Cu(OAc)
2
(0.5 mmol), DMF (3 mL), 80 °C, air, 0.5 h.
Isolated yield.
References
[
1] (a) M. Uwamori, A. Saito, M. Nakada, J. Org. Chem. 77 (2012) 5098–5107;
b) G. Pullella, D.A. Wild, G.L. Nealon, M. Elyashberg, M.J. Piggott, J. Org. Chem.
2 (2017) 7287–7299;
c) S.P.D. Senadeera, L. Lucantoni, S. Duffy, V.M. Avery, A.R. Carroll, J. Nat. Prod.
1 (2018) 1588–1597;
(
8
(
8
(
(
(
d) X.-W. Yang, R.B. Crossman, G. Xu, Chem. Rev. 118 (2018) 3508–3558;
e) J.-W. Wu, B.-L. Li, C. Tang, C.-Q. Ke, N.-L. Zhu, S.-X. Qiu, Y. Ye, J. Nat. Prod. 82
2019) 1917–1922.
[
[
2] (a) S.E. Payer, J.H. Schritterwieser, B. Grischek, R.C. Simon, W. Kroutil, Adv.
Synth. Catal. 358 (2016) 444–451;
(
(
b) G. Brahmachari, N. Nayek, ACS Omega 2 (2017) 5025–5035;
c) Y. Chen, W. Zhang, L. Ren, J. Li, A. Li, Angew. Chem. Int. Ed. 57 (2018) 952–
9
56;
d) S. Mao, Y. Wan, H. Peng, L. Luo, G. Geng, J. Org. Chem. 84 (2019) 5261–
270.
3] (a) M.E. Jung, S.-J. Min, K.N. Houk, D. Ess, J. Org. Chem. 69 (2004) 9085–9089;
Scheme 7. Synthetic applications of 2a.
(
5
(
(
b) Q. Shen, W. Huang, J. Wang, X. Zhou, Org. Lett. 9 (2007) 4491–4494;
c) A.O. Terent’ev, I.A. Yaremenko, V.V. Chernyshev, V.M. Dembitsky, G.I.
Nikkin, J. Org. Chem. 77 (2012) 1833–1842;
(
(
d) H. Luo, L. Pan, X. Xu, Q. Liu, J. Org. Chem. 80 (2015) 8282–8289;
e) S. Li, F. Chen, N. Li, W. Wang, X. Sheng, A. Wang, Y. Cong, X. Wang, T. Zhang,
ChemSusChem 10 (2017) 711–718;
f) A.Y. Dubovtsev, D.V. Dar’in, V.Y. Kukushkin, Org. Lett. 21 (2019) 4116–
119.
4] (a) A.C.B. Burtoloso, R.M.P. Dias, I.A. Leonarczyk, Eur. J. Org. Chem. (2013)
005–5016;
(b) J.D. Neuhaus, R. Oost, J. Merad, N. Maulide, Top. Curr. Chem. 376 (2018)
5–61;
c) X. Wu, S. Sun, J.-T. Yu, J. Cheng, Synlett 30 (2019) 21–29, and references
(
4
Scheme 8. Gram-scale synthesis of 2a.
[
5
ene-1,2-dione (5) and 2-chloro-1-phenyl-2-(3-phenylquinoxa-lin-
-yl)ethen-1-ol (6) were obtained in moderate to good yields
1
(
2
(Scheme 7).
cited therein;
To see whether this newly developed synthesis of functional-
(d) D. Baiser, I. Klose, R. Oost, J. Neuhaus, N. Maulide, Chem. Rev. 119 (2019)
8
701–8780.
5] (a) M. Barday, C. Janot, N.R. Halcovitch, J. Muir, C. Aïssa, Angew. Chem. Int. Ed.
6 (2017) 13117–13121;
(b) J. Vaitla, A. Bayer, K.H. Hopmann, Angew. Chem. Int. Ed. 56 (2017) 4277–
281;
ized 1,2,4-triketone derivatives is suitable for enlarged scale syn-
thetic missions, the preparation of 2a was carried out in 6 mmol
scale. Under this circumstance, 2a was obtained in a yield of 58%
[
5
4
(
Scheme 8).
(
(
c) P. Hu, Y. Zhang, Y. Xu, S. Yang, B. Liu, X. Li, Org. Lett. 20 (2018) 2160–2163;
d) G. Zheng, M. Tian, Y. Xu, X. Chen, X. Li, Org. Chem. Front. 5 (2018) 998–
1
002;
(e) Y. Xu, G. Zheng, X. Yang, X. Li, Chem. Commun. 54 (2018) 670–673;
f) H. Oh, S. Han, A.K. Pandey, S.H. Han, N.K. Mishra, S. Kim, R. Chun, H.S. Kim, J.
Park, I.S. Kim, J. Org. Chem. 83 (2018) 4070–4077;
Conclusion
In conclusion, we have developed a convenient and sustainable
(
(
(
g) X. Wu, H. Xiong, S. Sun, J. Cheng, Org. Lett. 20 (2018) 1396–1399;
h) K.S. Halskov, M.R. Witten, G.L. Hoang, B.Q. Mercado, J.A. Ellman, Org. Lett.
synthesis of diversely substituted 1,2,4-triketones through the
homo-coupling of b-ketosulfoxonium ylides or cross-coupling of
20 (2018) 2464–2467;
(
(
(
i) C.-F. Liu, M. Liu, L. Dong, J. Org. Chem. 84 (2019) 409–416;
j) D. Clare, B.C. Dobson, P.A. Inglesby, C. Aïssa, Angew. Chem. Int. Ed. 58
2019) 16198–16202;
b-ketosulfoxonium ylides with
a-keto aldehydes. To our knowl-
edge, this is the first report on the oxidative homocoupling and
cross-coupling of b-ketosulfoxonium ylides, in which the inexpen-
(k) P. Chen, J. Nan, Y. Hu, Q. Ma, Y. Ma, Org. Lett. 21 (2019) 4812–4815.
Please cite this article as: X. Chen, M. Wang, X. Zhang et al., A novel synthesis of diversely functionalized 1,2,4-triones through the homo- and cross-cou-
pling reactions of b-keto sulfoxonium ylides, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151912

X. Chen et al. / Tetrahedron Letters xxx (xxxx) xxx
5
[
6] (a) Y. Xu, X. Yang, X. Zhou, L. Kong, X. Li, Org. Lett. 19 (2017) 4307–4310;
[10] M.-D. Zhou, Z. Peng, H. Wang, Z.-H. Wang, D.-J. Hao, L. Li, Adv. Synth. Catal. 361
(2019) 5191–5198.
(
(
(
(
b) X. Wu, Y. Xiao, S. Sun, J.-T. Yu, J. Cheng, Org. Lett. 21 (2019) 6653–6657;
c) P. Wang, Y. Xu, J. Sun, X. Li, Org. Lett. 21 (2019) 8459–8463;
d) V. Hanchate, A. Kumar, K.R. Prabhu, Org. Lett. 21 (2019) 8424–8428;
e) P. Zhou, W.-T. Yang, A.U. Rahman, G. Li, B. Jiang, J. Org. Chem. 85 (2020)
[11] Just as our work was ready for submission, a similar study about the homo-
coupling of b-ketosulfoxonium ylides was reported: S. Zhu, K. Shi, H. Zhu, Z. Jia,
X. Xia, D. Wang, L. Zou Org. Lett. 22 (2020) 1504–1509.
[12] B. Qin, X. Liu, J. Shi, K. Zheng, H. Zhao, X. Feng, J. Org. Chem. 72 (2007) 2374–
2378.
3
60–366;
(
f) Y. Yuan, X.-F. Wu, Org. Lett. 21 (2019) 5310–5314.
[
[
[
7] G. Chen, X. Zhang, R. Jia, B. Li, X. Fan, Adv. Synth. Catal. 360 (2018) 3781–3787.
8] X. Chen, M. Wang, X. Zhang, X. Fan, Org. Lett. 21 (2019) 2541–2545.
9] J.D. Neuhaus, A. Bauer, A. Pinto, N.A. Maulide, Angew. Chem. Int. Ed. 57 (2018)
[13] D. Wang, M.D. Schwinden, L. Radesca, B. Patel, D. Kronenthal, M.-H. Huang, W.
A. Nugent, J. Org. Chem. 69 (2004) 1629–1633.
[14] C.-H. Hung, P. Gandeepan, L.-C. Cheng, L.-Y. Chen, M.-J. Cheng, C.-H. Cheng, J.
Am. Chem. Soc. 139 (2017) 17015–17021.
1
6215–16218.
Please cite this article as: X. Chen, M. Wang, X. Zhang et al., A novel synthesis of diversely functionalized 1,2,4-triones through the homo- and cross-cou-
pling reactions of b-keto sulfoxonium ylides, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151912