DTBP-Mediated Cascade Spirocyclization and Dearomatization of Biaryl Ynones: Facile Access to Spiro[5.5]trienones through C(sp3)?H Bond Functionalization

Article abstract of DOI:10.1002/ejoc.202100656

Oxidative radical cascade spirocyclization and dearomatization of biary ynones with a variety of hydrocarbons including toluenes, ethers, ketones, and alkanes has been developed to construct alkyl substituted spiro[5.5]trienones.

Full text of DOI:10.1002/ejoc.202100656

European Journal of Organic Chemistry
Accepted Article
Accepted Article
Title: DTBP-Mediated Cascade Spirocyclization and Dearomatization
of Biaryl Ynones: Facile Access to Spiro[5.5]trienones via
C(sp3)–H Bond Functionalization
Authors: Ming-Ming Zhang, Liu-Yu Shen, Sa Dong, Bing Li, Fei Meng,
Wei-Jie Si, and Wen-Chao Yang
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.202100656
Link to VoR: https://doi.org/10.1002/ejoc.202100656
01/2020

10.1002/ejoc.202100656
European Journal of Organic Chemistry
COMMUNICATION
DTBP-Mediated Cascade Spirocyclization and Dearomatization of
Biaryl Ynones: Facile Access to Spiro[5.5]trienones via C(sp3)–H
Bond Functionalization
Ming-Ming Zhang,a Liu-Yu Shen,a Sa Dong,a Bing Li,a Fei Meng,*,a Wei-Jie Si,*,c and Wen-Chao
Yang,*,a,b
[a]
M.-M. Zhang, L.-Y. Shen, Dr. S. Dong, Dr. B. Li, Dr. F. Meng, and Dr. W.-C. Yang
Guangling College and Institute of Pesticide of School of Horticulture and Plant Protection
Yangzhou University
Yangzhou 225009, P. R. China
E-mail: wenchaoyn@yzu.edu.cn; mengfei@yzu.edu.cn
Joint International Research Laboratory of Agriculture & Agri-Product Safety (Yangzhou University)
Yangzhou University
Yangzhou 225009, P. R. China
College of Chemistry and Chemical Engineering
Anyang Normal University
[b]
[c]
Anyang 455000, P. R. China
siweijiezhibao@163.com
Supporting information for this article is given via a link at the end of the document.
Abstract: Oxidative radical cascade spirocyclization and
dearomatization of biary ynones with a variety of hydrocarbons
including toluenes, ethers, ketones and alkanes has been developed
to construct alkyl substituted spiro[5.5]trienones.
(Scheme 1a and 1d) and radical cascade reactions (Scheme 1b
and 1c) have been limited to form a five-membered ring via 5-exo-
trig radical cyclization. Therefore, there is an incentive to broaden
its application to 6-exo-trig radical cyclization with respect to the
preparation of spirocyclic molecules.
The direct transformation of C(sp3)-H bonds to other valuable
chemical bonds, which obviating the separation of intermediates
or prefunctionalization, has been recognized as an atom- and
step-economical synthetic technique in organic chemistry and
thus offers an ideal channel for the late-stage modification of
complex molecular motifs.1 In the past few years, considerable
advances in C(sp3)-H functionalization with simple ketones,
toluene derivatives, cycloalkanes and acetonitrile have been
made.2 Among the established examples, alternative pathways
involving radical-mediated cascade reactions of alkynes with
C(sp3)-H functionalization has attracted special attention thanks
to its ability to form multiple chemical bonds in one
transformation.3,4 For example, Wang and co-workers reported a
radical cascade cyclization of aryl alkynoates using cheap and
available reagent toluene as the benzyl source. In the presence
of TBHP, domino reaction occurred involving C(sp3)-H bond
functionalization, benzyl radical addition, intramolecular 1,4-aryl
migration and decarboxylation.5 Despite of the enormous efforts
devoted to convert C(sp3)-H bonds into other functional groups,
the development of new cascade reactions of alkynes with C(sp3)-
H bond functionalization for the facile synthesis of valuable
molecules is still desired.
Spirocyclic molecules with a myriad of biological activities
has appeared as pivotal core units that exist in a number of
natural products, pharmaceuticals and pesticide chemicals.6
Radical-involved cascade cyclization of C-C unsaturated bonds
coupled with C(sp3)-H bond functionalization has proven to be an
effective strategy toward spirocyclic compounds (Scheme 1).7
However, increasing the diversity of the available methodology in
this area remains unsolved and attracts considerable interest.
Thus far, the reported methods including dearomatization
Scheme 1 Radical functionalization of C(sp3)-H bonds to construct spiro
compounds and radical cascade reactions of ynones.
Ynone, well recognized as a versatile building block in radical
cascade reactions, has been proved to be an efficient reaction
component to access diverse indenones.8 The established
methods generally underwent
a vinyl radical quenching
mechanism, in which vinyl radical added to 2-position of the
1
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202100656
European Journal of Organic Chemistry
COMMUNICATION
o
benzene ring adjacent to the ketone. Recently, Zhu, Liu and Duan
groups have proven that the introduction of p-methoxyphenyl or
p-nitrobenzene groups at this position provide an efficent
approach toward spirocyclic molecules. Metal-catalyzed 6-exo-
trig radical spirocyclization were involved in the transformations
coupled with a dearomatization process (Scheme 1e).6i,6l,6m With
our continuing interest in green organic synthesis and radical
chemistry,9 we herein report a DTBP (di-tert-butyl peroxide)-
promoted radical spirocyclization of biaryl ynones coupled with
C(sp3)-H functionalization of ketones, toluene derivatives, ethers
and cycloalkanes under catalyst-, solvent- and base-free
conditions (Scheme 1f). With the addition of alkyl radicals to
alkyne group and the subsequent spirocyclization of vinyl radicals,
three new chemical bonds were formed to afford the alkyl
substituted spiro[5.5]trienones as target compounds.
Decreasing the reaction temperature (90 C) led to a lower yield
of 3a (entry 8), and higher temperature (130 oC) did not
substantially increase the yield of 3a (entry 9). Reducing the
amount of oxidant from 5 equivalent to 2 equivalent brought a
distinct decrease in the yield (entry 10). Notably, the
transformation without initiator was carried out with no desired
product obtained, which indicated the necessity of the initiator
(entry 11). Accordingly, the best reaction conditions for the
synthesis of spiro[5.5]trienones 3a were identified as follows: 1a
o
(1 equiv), and DTBP (5 equiv) in acetone 2a (0.5 mL) at 110 C
for 10 h under nitrogen atmosphere.
Table 1. Reaction conditions optimization.[a]
entry
oxidant
TBHP
DTBP
TBPB
DCP
temperature
110 oC
110 oC
110 oC
110 oC
110 oC
110 oC
110 oC
90 oC
yield[b]
68
1
2
3
4
5
6
7
8
9
83
56
35
Oxone
K2S2O8
BPO
17
trace
trace
63
DTBP
DTBP
130 oC
83
10
11
DTBP
--
110 oC
110 oC
51
0
Scheme 2 Substrates Scopes of Biaryl Ynones. a All reactions were carried out
in a Schlenk tube in the presence of 1a (0.15 mmol), 2a (0.5 mL), DTBP (5
equiv) at 110 oC for 10 h under N2; isolated yields.
[a] Reaction conditions: 1a (0.2 mmol), oxidant (5 equiv) at indicated temperature
under N2, 10 h, 0.5 mL of acetone.
[b] Isolated yields.
[c] DTBP (2.0 equiv).
As shown in Scheme 2, the optimized conditions were then
applied for the reaction of other biaryl ynone derivatives with
acetones toward spiro[5.5]trienones. The substrates with various
substitutions on aromatic ring adjacent to the ketone, both
electron-donating and -withdrawing groups, were proved to be
suitable for the reaction, delivering the expected products (3a-3h)
in 46% to 88% yields. Furthermore, substrates with substituents
on alkynes were also tested, affording the target compounds (3i-
3k) in medium to good yields. For example, a p-methoxyphenyl-
substituted 1i could react with 2a smoothly to generate the
corresponding 3i in 54% yield. We also performed the 6-exo-trig
radical spirocyclization on the biaryl ynones derived from the
dearomative aryl ring. Substrate 1n with dimethoxy groups could
react smoothly with 2a to afford the corresponding product 3n in
60% yield. Unfortunately, 1o with trimethoxy groups was not
compatible with this transformation (see 3o). Interestingly,
For the initial proof-of-concept experiments and the
subsequent optimization of the reaction conditions, biaryl ynone
(1a) was chosen as the model substrate to react with acetone 2a
in the presence of oxidants. We first screened a variety of
oxidants for their abilities to induce the formation of acetylmethyl
radical species which was further involved in the following radical
dearomatization of biaryl ynones. A short screening (Table 1)
revealed that TBHP (tert-butyl hydroperoxide), DTBP, DCP
(dicumyl peroxide) and TBPB (tert-butyl peroxybenzoate) were
suitable oxidants, among which DTBP was found to be the
optimum promoter (entry 2) for the cascade reactions. In addition,
inorganic peroxides showed lower reactivity than organic ones
(entries 5-6). Using BPO (benzoyl peroxide) in this reaction
resulted in almost no conversion of the starting material (entry 7).
2
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202100656
European Journal of Organic Chemistry
COMMUNICATION
acetophenone substrate that are not compatible in other systems
could successfully afford 3m in medium yield.
Information). A significant isotopic effect (3a and 3a-d5 4:1) was
determined from intermolecular competition reaction, indicating
that cleavage of C(sp3)−H bond in acetone should be involved in
the rate-determining step (see details in the Supporting
Information).
Next, we turned our attention to investigate this oxidative
cascade spirocyclization of biaryl ynones involving C(sp3)–H
functionalization with other substrates such as toluenes, ethers
and cycloalkanes. As shown in Scheme 3, the arylmethanes with
various substituents, such as di-Me, Me, F, Br and I, reacted well
with biaryl ynones to provide the desired products in considerable
yields (3p-3ab). It has been reported previously that alkoxyalkyl
radicals can be produced from simple ethers upon oxidation, such
as in the presence of a TBHP initiator.3e,5 Thus, the present
system was further investigated with tetrahydrofuran or
tetrahydropyran as alkoxyalkyl radical sources to extend its utility,
which successfully delivered etherified spiro[5.5]trienones (3y
and 3z) in 78% and 80% yields. In addition, cycloalkane
substrates, which was generally tolerable according to the
previous literature reports,7 could be successfully transformed in
this reaction (see: 3aa-3ac).
Based on the results above and previous literature for radical
cascade reactions of acetone and dearomatization of aromatic
rings,3h,4g,7 a possible mechanism that initiated by an acetylmethyl
radical species is depicted in Scheme.4 Initially, t-BuO• (A)
species was generated in situ under heating and participates in
the hydrogen abstraction of toluene to obtain benzyl radical B.
Sequent addition of B to the C-C triple bond of the biaryl ynone
gives the vinyl radical intermediate C. which undergoes an
intramolecular radical ipso-cyclization to deliver the radical
intermediate D. Next, single electron transfer (SET) oxidation
between D and t-butoxyl radical occurs to access oxygenium
intermediate E, which is converted into the final product 3p
through demethylation.10
Scheme 4. Control Experiments and Proposed Mechanism
In conclusion, we have developed an efficient system for the
6-exo-trig radical spirocyclization of biaryl ynones with common
solvent acetone or toluene derivatives through continuous radical
addition, cyclization and dearomatization. The key vinyl radical
intermediates were generated in situ through addition of
acetylmethyl radical to C–C triple bond with the aid of DTBP. The
developed protocol provides a convenient approach to construct
the biologically important spiro[5.5]trienones with diverse
substitution in good to excellent yields. The method features a
broad substrate scope and mild reaction conditions, in which no
metal, organic solvent, base or additive is required. Future studies
examining the application of visible light for mediated electron-
transfer event would be conducted in respect to alternative spiro
molecules formation.
Scheme 3. Substrates Scopes of Radical Precursors. a All reactions were
carried out in a Schlenk tube in the presence of 1a (0.15 mmol), alkyl source
(0.5 mL), DTBP (5 equiv) at 110 oC for 10 h under N2; isolated yields.
Several control experiments were conducted to gain a
deeper insight into the mechanism of this reaction. As shown in
Scheme 4, with the addition of radical scavengers 2,6-di-tert-
butyl-4-methyl-phenol
(BHT)
or
2,2,6,6-tetramethyl-1-
Experimental Section
piperidinyloxy (TEMPO) to the model reaction, no dearomative
product 3a was detected, indicating that free-radical
intermediates were involved in the reaction. Moreover, the key
intermediate B was captured by TEMPO and its corresponding
adduct F was detected by HR-MS analysis. (see Supporting
General Procedures for Radical Cascade Spirocyclization
and Dearomatization of Biaryl Ynones for the Synthesis of 3:
A 15 mL pressure tube was charged with 1-(4'-methoxy-[1,1'-
3
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202100656
European Journal of Organic Chemistry
COMMUNICATION
M. Nagasaka, Z. Lv, Z. Guan, Y. Cao, F. Gong, Z. Zhou, J. Zhu, S.
Samanta, A. D. Chowdhury, A. Lei, J. Am. Chem. Soc. 2021, 143, 3628-
3637.
biphenyl]-2-yl)-3-phenylprop-2-yn-1-one (1a, 0.15 mmol),
acetone (2a, 0.5 mL), DTBP (5.0 equiv, 0.75 mmol), and a
magnetic stir bar. Then the mixtures were allowed to react at
110 ℃ for 10 h under nitrogen conditions. After completion of the
reaction, the mixture was concentrated to yield the crude product,
which was further purified by flash chromatography (silica gel,
petroleum ether/ethyl acetate = 5:1) to give the desired product
3a. In the purification of desired products by flash chromatography,
some residual peaks was observed due to methylated byproducts.
[5]
[6]
T. Miao, D. Xia, Y. Li, P. Li, L. Wang, Chem. Commun. 2016, 52, 3175-
3178.
a) J.-F. Hu, H. Fan, J. Xiong, S.-B. Wu, Chem. Rev. 2011, 111, 5465-
5491; b) W.-T. Wu, L. Zhang, S.-L. You, Chem. Soc. Rev. 2016, 45,
1570-1580; c) J. Feng, W. Chen, Q. Liu, Z. Chen, J. Yang, W. Yang, Pest
Manage Sci. 2020, 76, 4192-4201; d) X.-W. Liang, C. Zheng, S.-L. You,
Chem. Eur. J. 2016, 22, 11918-11933; e) B. Tan, L. Bai, P. Ding, J. Liu,
Y. Wang, X. Luan, Angew. Chem., Int. Ed. 2019, 58, 1474-1478; f) Z.
Zuo, J. Wang, J. Liu, Y. Wang, X. Luan, Angew.Chem., Int. Ed. 2020, 59,
653-657; g) W.-C. Yang, M.-M. Zhang, J.-G. Feng, Adv. Synth. Catal.
2020, 362, 4446-4461; h) R. Pawlowski, P. Skorka, M. Stodulski, Adv.
Synth. Catal. 2020, 362, 4462-4486; i) Y. Zhang, J. Zhang, B. Hu, M. Ji,
S. Ye, G. Zhu, Org. Lett. 2018, 20, 2988-2992; j) X. Gao, Y. Yuan, X. Xie,
Z. Zhang, Chem. Commun. 2020, 56, 14047-14050; k) F.-L. Zeng, X.-L.
Chen, K. Sun, H.-L. Zhu, X.-Y. Yuan, Y. Liu, L.-B. Qu, Y.-F. Zhao, B. Yu,
Org. Chem. Front. 2021, 8, 760-766; l) L. Zhou, Y. Xia, Y.-Z. Wang, J.-D.
Fang, X.-Y. Liu, Tetrahedron 2019, 75, 1267-1274; m) During the
submission of this manuscript, Duan and coworkers reported a similar
copper-catalyzed dearomatization of nitrobenzenes, see: D. Xia, X.-F.
Duan, Org. Lett. 2021, 23, 2548-2552; n) C. W. Li, L. Xue, J. Zhou, Y.
Zhao, G. Han, J. Hou, Y. Song, Y. Liu, Org. Lett. 2020, 22, 3291–3296;
o) H. E. Ho, A. Pagano, J. A. Rossi-Ashton, J. R. Donald, R. G. Epton, J.
C. Churchill, M. J. James, P. O’Brien, R. J. K. Taylor, W. P. Unsworth,
Chem. Sci. 2020, 11, 1353-1360; p) X.-J. Zhou, H.-Y. Liu, Z.-Y. Mo, X.-
L. Ma, Y.-Y. Chen, H.-T. Tang, Y.-M. Pan, Y.-L. Xu, Chem. Asian J. 2020,
15, 1536-1539.
Acknowledgements
We acknowledge financial support from the Natural Science
Foundation of the Jiangsu Higher Education Institutions of China
(No. 19KJB150020), the Basic Research Project (Natural Science
Foundation for Young Scholars) of Jiangsu Province, China
(Grant No. BK20200953) and High Level Introduction of Talent
Research Start-up Foundation of YZU (Grant No. 137011457).
[1]
a) H. M. L. Davies, D. Morton, Chem. Soc. Rev., 2011, 40, 1857-1869;
b) J. Wencel-Delord, T. Droge, F. Liu, F. Glorius, Chem. Soc. Rev. 2011,
40, 4740-4761; c) J. Xie, C. Pan, A. Abdukader, C. Zhu, Chem. Soc. Rev.
2014, 43, 5245-5256; d) C. Liu, D. Liu, A. Lei, Acc. Chem. Res. 2014, 47,
3459-3470; e) B.-J. Li, Z.-J. Shi, Chem. Soc. Rev. 2012, 41, 5588-5598.
a) H. Wang, L.-N. Guo, X.-H. Duan, Chem. Commun., 2013, 49, 10370-
10372; b) T. He, L. Yu, L. Zhang, L. Wang, M. Wang, Org. Lett. 2011, 13,
5016-5019; c) J. Zhao, H. Fang, P. Qian, J. Han, Y. Pan, Org. Lett. 2014,
16, 5342-5345; d) B. Schweitzer-Chaput, J. Demaerel, H. Engler, M.
Klussmann, Angew. Chem., Int. Ed. 2014, 53, 8737-8740; e) X.-W. Lan,
N.-X. Wang, W. Zhang, J.-L. Wen, C.-B. Bai, Y. Xing,Y.-H. Li, Org. Lett.
2015, 17, 4460-4463; f) C. Pan, Z. Yang, D. Gao, J.-T. Yu, Org. Biomol.
Chem. 2018, 16, 6035-6038; g) S. Jiang, X.-J. Tian, S.-Y. Feng, J.-S. Li,
Z.-W. Li, C.-H. Lu, C.-J. Li, W.-D. Liu, Org. Lett. 2021, 23, 692-696; h)
W.-C. Yang, J.-G. Feng, L. Wu, Y.-Q. Zhang, Adv. Synth. Catal. 2019,
361, 1700-1709; i) D. Li, W.-C. Yang, Tetrahedron Lett. 2019, 60, 1792-
1795.
[2]
[7]
a) H. Zhang, Z. Gu, P. Xu, H. Hu, Y. Cheng, C. Zhu, Chem. Commun.
2016, 52, 477-480; b) H. Zhang, C. Zhu, Org. Chem. Front. 2017, 4,
1272-1275; c) M. Hu, L.-Y. Guo, Y. Han, F.-L. Tan, R.-J. Song, J.-H. Li,
Chem. Commun. 2017, 53, 6081-6084; d) J.-K. Qiu, B. Jiang, Y.-L. Zhu,
W.-Z. Hao, D.-C. Wang, J. Sun, P. Wei, S.-J. Tu, G.-G. Li, J. Am. Chem.
Soc. 2015, 137, 8928-8931; e) X.-H. Ouyang, R.-J. Song, B. Liu, J.-H. Li,
Chem. Commun. 2016, 52, 2573-2576; f) W.-T. Wei, R.-J. Song, X.-H.
Ouyang, Y. Li, H.-B. Li, J.-H. Li, Org. Chem. Front. 2014, 1, 484-489; g)
C.-S. Wang, T. Roisnel, P. H. Dixneuf, J. Soulé, Adv. Synth. Catal. 2019,
361, 445-450.
[8] a) Y. Zhang, K. Sun, Q. Lv, X. Chen, L. Qu, B. Yu, Chin. Chem. Lett. 2019,
30, 1361-1368; b) Z. Yan, J. Xie, C. Zhu, Adv. Synth. Catal. 2017, 359,
4153-4157; c) C. Pan, B. Huang, W. Hu, X. Feng, J.-T. Yu, J. Org. Chem.
2016, 81, 2087-2093; d) J. Wen, W. Shi, F. Zhang, D. Liu, S. Tang, H.
Wang, X.-M. Lin, A. Lei, Org. Lett. 2017, 19, 3131-3134.
[3]
a) S.-R. Guo, P. S. Kumar, M. Yang, Adv. Synth. Catal. 2017, 359, 2-25;
b) X.-Q. Chu, D. Ge, Z.-L. Shen, T.-P. Loh ACS Catal. 2018, 8, 258-271;
c) W. Yang, M. Zhang, W. Chen, X. Yang, J. Feng, Chin. J. Org. Chem.
2020, 40, 4060-4070; d) W.-T. Wei, W.-M. Zhu, W.-H. Bao, W.-T. Chen,
Y.-L. Huang, L.-H. Gao, X.-D. Xu, Y.-N. Wang, G.-P. Chen, ACS
Sustainable Chem. Eng. 2018, 6, 5615-5619; e) D. Xia, Y. Li, T. Miao, P.
Li, L. Wang, Green Chem. 2017, 19, 1732-1739; f) W. Wei, L. Wang, H.
Yue, P. Bao, W. Liu, C. Hu, D. Yang, H. Wang, ACS Sustainable Chem.
Eng. 2018, 6, 17252-17257; g) Y.-N. Meng, Q.-Q. Kang, T.-T. Cao, S.-Z.
Song, G.-P. Ge, Q. Li, W.-T. Wei, ACS Sustainable Chem. Eng. 2019, 7,
18738-18743; h) Y. Yu, S. Zhuang, P. Liu, P. Sun, J. Org. Chem. 2016,
81, 11489-11495; i) P. Dai, X. Tan, Q. Luo, X. Yu, S. Zhang, F. Liu, W.-
H. Zhang, Org. Lett. 2019, 21, 5096-5100; j) H. Zhang, C. Pan, N. Jin, Z.
Gu, H. Hu and, C. Zhu, Chem. Commun. 2015, 51, 1320-1322; k) C.-Y.
Huang, J. Li, W. Liu, C.-J. Li, Chem. Sci. 2019, 10, 5018-5024.
[9]
a) W. Yang, S. Yang, P. Li, L. Wang, Chem. Commun. 2015, 51, 7520-
7523; b) W. Yang, B. Li, M. Zhang, S. Wang, Y. Ji, S. Dong, J. Feng, S.
Yuan, Chin. Chem. Lett. 2020, 31, 1313-1316; c) W.-C. Yang, P. Dai, K.
Luo, L. Wu, Adv. Synth. Catal. 2016, 358, 3184-3190; d) W.-C. Yang, K.
Wei, X. Sun, J. Zhu, L. Wu, Org. Lett. 2018, 20, 3144-3147; e) M.-M.
Zhang, Y. Sun, W.-W. Wang, K.-K. Chen, W.-C. Yang, L. Wang, Org.
Biomol. Chem. 2021, 19, 3844-3849; f) W.-C. Yang, C.-Y. Chen, J.-F. Li,
Z.-L. Wang, Chin. J. Catal. 2021, DOI: 10.1016/S1872-2067(21)63814-
7.
[10] J. Li, W.-W. Zhang, X.-J. Wei, F. Liu, W.-J. Hao, S.-L. Wang, G. Li, S.-J.
Tu, B. Jiang, J. Org. Chem. 2017, 82, 6621-6628.
[4] a) R.-M. Hu, D.-Y. Han, N. Li, J. Huang, Y. Feng, D.-Z. Xu, Angew. Chem.,
Int. Ed. 2020, 59, 3876-3880; b) X.-J. Huang, F.-H. Qin, Y. Liu, S.-P. Wu,
Q. Li, W.-T. Wei, Green Chem. 2020, 22, 3952-3955; c) Y.-Y. Liang, J.
Huang, X.-H. Ouyang, J.-H. Qin, R.-J. Song, J.-H. Li, Chem. Commun.
2021, 57, 3684-3687 d) Y.-Z. Yang, Y.-C. Wu, R.-J. Song, J.-H. Li, Chem.
Commun. 2020, 56, 7585-7588; e) J. Cheng, J. Xie, C. Zhu, Chem.
Commun. 2018, 54, 1655-1658; f) W. Zhou, S. Ni, H. Mei, J. Han, Y. Pan,
Org. Lett. 2015, 17, 2424-2427; g) W.-J. Xia, Y. Xin, Z.-W. Zhao, X. Chen,
X.-X. Wang, Y. Li, G. Wang, Y.-M. Li, Org. Chem. Front. 2020, 7, 1997-
2002; h) H. Hu, X. Chen, K. Sun, J. Wang, Y. Liu, H. Liu, L. Fan, B. Yu,
Y. Sun, L. Qu, Y. Zhao, Org. Lett. 2018, 20, 6157-6160; i) W. Chen, Y.
Zhang, P. Li, L. Wang, Org. Chem. Front. 2018, 5, 855-859; j) X. Zhang,
M. Wang, P. Li, L. Wang, Chem. Commun. 2014, 50, 8006-8009; k) Z.-
W. Hou, D.-J. Liu, P. Xiong, X.-L. Lai, J. Song, H.-C. Xu, Angew. Chem.
Int. Ed. 2021, 60, 2943-2947; l) H. Wang, M. He, Y. Li, H. Zhang, D. Yang,
4
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202100656
European Journal of Organic Chemistry
COMMUNICATION
Entry for the Table of Contents
A novel DTBP-promoted metal-free cascade cyclization of biary ynones with a variety of hydrocarbons including toluenes, ethers,
ketones and alkanes has been established, which provides an expeditious approach to access functionalized spiro[5.5]trienones in
acceptable to good yields. The products thus obtained represent key structural motifs of biologically active molecules in pesticide.
5
This article is protected by copyright. All rights reserved.