TBAB-Mediated Radical 5-exo-trig ipso-Cyclization of 2-Arylbenzamide for the Synthesis of Spiro[cyclohexane-1,1′-isoindoline]-2,5-diene-3′,4-dione

Article abstract of DOI:10.1002/ejoc.201900321

A TBAB-mediated radical 5-exo-trig ipso-cyclization of N-aryl-2-arylbenzamide is described herein for the synthesis of spiro[cyclohexane-1,1′-isoindoline]-2,5-diene-3′,4-dione. The transformation proceeds regioselectively and provides the final products w

Full text of DOI:10.1002/ejoc.201900321

A Journal of
Accepted Article
Title: TBAB-mediated radical 5-exo-trig ipso-cyclization of 2-
arylbenzamide for the synthesis of spiro[cyclohexane-1,1'-
isoindoline]-2,5-diene-3',4-dione
Authors: Guanyinsheng Qiu, Zhi-Feng Chen, Wenlin Xie, and Hongwei
Zhou
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900321
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10.1002/ejoc.201900321
European Journal of Organic Chemistry
COMMUNICATION
TBAB-mediated radical 5-exo-trig ipso-cyclization of 2-
arylbenzamide for the synthesis of spiro[cyclohexane-1,1'-
isoindoline]-2,5-diene-3',4-dione
Guanyinsheng Qiu* [a,b], Zhi-Feng Chen[b], Wenlin Xie[c], and Hongwei Zhou*[b]
Dedication ((optional))
Abstract: A TBAB-mediated radical 5-exo-trig ipso-cyclization of N-
based 5-exo-trig ipso-cyclization of 2-arylbenzamide remains
rare in the past decades.[12] The success of the reported
example resorted to the use of 2-(4-methoxylphenyl)benzamide
as the substrate. Serveral years ago, few examples on
aryl-2-arylbenzamide is described herein for the synthesis of
spiro[cyclohexane-1,1'-isoindoline]-2,5-diene-3',4-dione.
transformation proceeds regioselectively and provides the final
products with high efficiency and broad reaction scope.
The
a
electrophilic
methoxylphenyl)benzamide have been reported towards
series of spiro[cyclohexane-1,1'-isoindoline]-2,5-diene-3',4-
5-exo-trig
ipso-cyclization
of
2-(4-
Mechanism studies show the use of TBAB as an additive is pivotal
for the reaction. In the process, para-bromination of N-aryl group, 5-
exo-tri ipso-cyclization of N-aryl-2-arylbenzamide nitrogen radical
and sequential aromatization is involved.
a
diones. [13] According to these findings from Kita and co-workers,
electrophilic 5-exo-trig ipso-cyclization of 2-arylbenzamide was
subject to limitation of substrates. Basically, the para-methoxyl
group in 2-aryl of 2-arylbenzamide was always required for
electrophilic 5-exo-trig ipso-cyclization (Scheme 1b). Inspired by
what mentioned above, this paper would like to discolse our
endeavor on radical 5-exo-trig ipso-cyclization of 2-
arylbenzamide 1 for the synthesis of spiro[cyclohexane-1,1'-
isoindoline]-2,5-diene-3',4-diones 2, an important synthetic
building block for many useful molecules (Scheme 1c) [14]. Our
primary aim in this paper was to expand nitrogen radical-based
oxidative 5-exo-trig ipso-cyclization to 2-arylbenzamides without
the required substituent methoxyl group. Furthermore, we
envisioned that this radical 5-exo-trig ipso-cyclization of 2-
arylbenzamides could worked well under metal-free conditions,
and water in the reaction could be incorporated into carbonyl
group of the products 2.
Introduction
Quaternary carbon center is ubiquitous in many natural products
and useful archirectures.[1] To date, its synthetic methodology
development attracted continuous interests of chemists.[2]
Among them, ipso-cyclization dearomatizative reaction was
recognized as one of powerful strategies to construct cyclic
quaternary carbon center.[3]
2-arylbenzamide was
a
versatile synthons towards N-
heterocyclic compounds.[4] Basically, 6-endo-trig cyclization of 2-
arylbenzamide was well recognized. To the best of our
knowledge, transitional metal-catalyzed[5] or nonmetal reagent-
mediated C-H bond functionalization[6] enabled this 6-endo-trig
cyclization of 2-arylbenzamide to produce various phenanthridin-
6(5H)-one derivatives. Considering high importance of
phenanthridin-6(5H)-one[7] and limitation of the previous
protocols, sequential chemistry was focused intensively on 6-
endo-trig cyclization of 2-arylbenzamide under photocatalysis[8]
and electrocatalysis[9] (Scheme 1a). Distinctively, the
Scheme 1. Proposed route for the synthesis of spiro[cyclohexane-1,1‘-
isoindoline]-2,5-diene-3‘,4-diones.
photo/electron-induced
6-endo-trig cyclization of 2-
arylbenzamide involved an amidy N-radical intermediate[10]. It is
noteworthy that amidy nitrogent radical-based 6-endo-trig
cyclization of 2-arylbenzamide was not unprecedent.[11,12]
Thereotically, an amidyl nitriogen radical-based 5-exo-trig ipso-
cyclization of 2-arylbenzamide seemed plausible. This model of
cyclization could construct a cyclic quaternary carbon center.
However, it is surprising to find that amidy nitrogent radical-
[a]
[b]
Dr. G. Qiu
Department of Chemistry, Fudan University
220 Handan Road, Shanghai 200433 (China)
E-mail: 11110220028@fudan.edu.cn
Dr. G. Qiu, Mr. Z. Chen and Prof. H. Zhou
College of Biological, Chemical Science and Engineering, Jiaxing
University, 118 Jiahang Road, Jiaxing 314001, China
[c] Prof. W. Xie
School of Chemistry and Chemical Engineering, Hunan University of
Results and Discussion
Science and Technology, Hunan 411201, China
In light of our previous results in oxone chemistry,[15] our
preliminary trial was conducted in the presence of 2.0 equiv of
oxone and 3.0 equiv of K2CO3 in H2O (entry 2, Table 1).
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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10.1002/ejoc.201900321
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COMMUNICATION
Presented as the previous result using K2S2O8 (entry 1, Table
1)[12], a combination of oxone/K2CO3 could not realize 5-exo-trig
ipso-cyclization of 2-arylbenzamides.We inferred that the above
noted negative result was ascribed to the electrophilic nature of
amidyl nitrogen radical. To adjust electrophilicity of amidyl
nitrogen radical, 2.0 equiv of tetra-n-butylammonium bromide
(TBAB) was added as an additive. To our delight, the model
reaction of N-(4-fluorophenyl)-2-phenylbenzamide 1a in water
afforded a desired spiro[cyclohexane-1,1‘-isoindoline]-2,5-diene-
3‘,4-dione 2a in a 35% isolated yield (entry 3, Table 1). Oxidative
6-endo-trig cyclization product 3a was not detected. Encouraged
by the above result, we then optimized other result-affecting
factors.
(entries 5-6, Table 1). Pure 1,2-dichloroethane (DCE) without
mixing water just offered a trace ammount of the desired product
2a (entry 7, Table 1). This outcome supported our assumption
that oxygen atom of carbonyl group in product 2 probably came
from water. To increase loading of oxone to 5.0 equiv improve
the reaction yield to 75% (entry 8, Table 1). However, decrease
of TBAB ammount made a negative effect on the reaction (entry
9, Table 1). A control experiment without base K2CO3 implied
that the use of K2CO3 did not make a significant impact on,
providing the desired molecule 2a in a similar yield (entry 10,
Table 1). Further reaction temperature screening seemed that
both increase of temperature and descrease of temperature
were unfavorable for the reactions (entries 11-12, Table 1). As
such, we got the optimized conditions: 2.0 equiv of TBAB, 5.0
equiv of oxone, DCE: H2O (v/v = 1:1) as solvent, and 80 oC.
Table
1
Initial studies on oxidative 6-endo-dig radical cyclization of 2-
[a,b]
alkynylbenzamide for the synthesis of 1-imine-isocoumarins
Scheme 2. Reaction scope oxidative 5-exo-trig radical ipso-cyclization of 2-
phenylbenzamide: Effect of N-protecting group [a]
Yield
of 2a
(%)[a,b]
Oxidant
Entry
Additive
Base
Solvent
(2.0 eq.)
H2O
H2O
H2O
1
2
3
/
K2S2O8
oxone
oxone
K2CO3
K2CO3
K2CO3
nd
nd
35
/
TBAB
DCE:H2O
(v/v, 1:1)
THF:H2O
(v/v, 1:1)
MeCN:H2O
(v/v, 1:1)
DCE
4
5
TBAB
TBAB
oxone
oxone
K2CO3
K2CO3
60
36
6
7
TBAB
TBAB
TBAB
oxone
oxone
oxone
K2CO3
K2CO3
K2CO3
20
trace
75
DCE:H2O
(v/v, 1:1)
DCE:H2O
(v/v, 1:1)
DCE:H2O
(v/v, 1:1)
DCE:H2O
(v/v, 1:1)
DCE:H2O
(v/v, 1:1)
8[c]
9[c,d]
10[c]
TBAB
TBAB
TBAB
TBAB
oxone
oxone
oxone
oxone
K2CO3
42
78
65
49
/
/
/
[a] isolated yield based on 2-phenylbenzamide 1
11[c,e]
12[c,f]
With optimized conditions in hand (entry 10, Table1), we then
explored the reaction scope. The results were presented in
Scheme 2. A series of spiro[cyclohexane-1,1‘-isoindoline]-2,5-
diene-3‘,4-dione 2 was achieved accordingly. As illustrated in
Table 2, the substituents R in N-aryl protecting groups could
replaced with chloro, bromo, ketone, and ester. To our delight,
the corresponding products 2b-2g were achieved in 56-80%
yields.
Interestingly, the result from the reaction of N-phenyl-2-
phenylbenzamide showed a para-bromination happened to N-
phenyl protecting group,[4b,6c] and the reaction gave rise to the
product 2c in 75% yield. Considering synthetic versatility of
bromo group, all the the sequential reactions employed the
[a]
[b]
Isolated yield based on 2-alkynylbenzamide 1a.
Standard conditions: 2-
alknylbenzamide 1a (0.2 mmol), TBAB (2.0 equiv), oxone (2.0 equiv), base (3.0
equiv), solvent (4 mL), 80 oC, overnight. [c] 5.0 equiv oxone was used. [d]1.0 equiv
TBAB was used. [e] Reaction temperature = 100 oC. [f] Reaction temperature = 50 oC.
TBAB = n-tetra-butyl ammonium bromide; oxone = 2KHSO5·KHSO4·K 2SO4
Considering solubility of substrate in solvent, the sequential trials
were carried out in a mixed solvent with various organic solvents.
As illustrated in Table 1, it seemed that the mixed solvent
DCE:H2O was favorable for the reaction efficiency, leading to the
desired product 2a in 60% yield (entry 4, Table 1). Other
solvents MeCN:H2O and THF:H2O provided inferior results
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10.1002/ejoc.201900321
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COMMUNICATION
substrates with N-phenyl protecting group, wishing to introduce
bromo atom in the product 2.
As presented in Scheme 3, a series of bromo-containing
spiro[cyclohexane-1,1’-isoindoline]-2,5-diene-3’,4-dione
2 was
afforded accordingly. From the results, the steric effect and
electron effect of the substituents R1 did not make significant
impact on the outcomes, leading to the corresponding products
2l-2r in 54-77% yields. The reaction of the substrate 1s with the
substituent fluoro at R3 gave rise to the desired product 2s in a
moderate yield, while the reaction of the substrate 1t with the
substituent methyl at R3 provided the expected product 2t in a
55% yield. Interestingly, the methoxyl group at R3 was also
compatible for the reaction, offering a dibrominative product 2u
in 52% yield.
[a] isolated yield based on 2-phenylbenzamide 1
To gain insight into mechanism, two control experiments were
conducted in Scheme 5. To clarify the radical process, the
reaction with TEMPO as an additive was carried out. The
reaction was greatly retarded, resulting in 2a in 19% yield.
However, we did not detect any radical-trapped species.
Additionally, wishing to clarify where the carbonyl oxygen of the
product came, we run the reaction of N-phenyl-2-
phenylbenzamide in the presence of DCE:H2O18 as solvent. As
expected, oxygen-18 atom was detected in the product 2c after
analysing its EI-MS spectrum. This result probably supported
our assumption that water has been incorporated into carbonyl
of the product 2.
Scheme 3. Reaction scope on oxidative 6-exo-trig radical ipso-
cyclization of 2-arylbenzamide.[a]
Scheme 5. Control experiments
In light of forementioned results, a plausible mechanism was
proposed in Scheme 6. In the process, in the presence of TBAB
and oxone 2-arylbenzamide was oxidized into dibrominative 2-
arylbenzamide A. It is believed that the formation of the
intermediate A was pivotal for the reaction. The intermediate A
then ocurred to convert into 2-arylbenzamide nitrogen radical B
and bromo radical. A 5-exo-trig ipso-cyclization happened to the
intermediate B, producing a sprio radical species C. The
following radical migration and oxidation provided a sprio cation
species E, which was trapped by water to obtain an intermediate
F. Oxidation of the intermediate F gave rise to the desired
products 2. For a whole process, the use of TBAB as an additive
was very important. From results on blank experiments using
TBAI and other bromide source as additives and descrease of
TBAB loading, it should be convinced that the use of TBAB
probably changed electrophilicity nature of amidyl nitrogen
radical.[10a, 12]
[a] Isolated yield based on 2-phenylbenzamide 1.
During reaction conditions optimization, it was found that the use
of tetra-n-butylammonium iodide (TBAI) as an additive afforded
a 6-endo-trig cyclization product phenanthridin-6(5H)-one 3 in a
reasonable yield. By reducing the loading of oxone to 2.0 equiv,
the yield of the reaction of N-phenyl-2-phenylbenzamide was
further improved, providing the desired phenanthridin-6(5H)-one
3 in 81% yield (Scheme 4).
Scheme 4. Reaction scope oxidative 5-exo-dig radical cyclization of 2-
trimethylsilylethynylbenzamide. [a]
Scheme 6. Proposed pathway for the designed reaction
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2'-(4-fluorophenyl)spiro[cyclohexa[2,5]diene-1,1'-isoindoline]-
3',4-dione (2a) (White solid, 47.6 mg, 78%)
1H NMR (400 MHz, CDCl3) δ 7.96 (d, J = 7.3 Hz, 1H), 7.64-7.59
(m, 2H), 7.39-7.35 (m, 2H), 7.27 (d, J = 7.6 Hz, 1H), 7.05 (t, J =
8.5 Hz, 2H), 6.72 (d, J = 9.9 Hz, 2H), 6.41 (d, J = 9.9 Hz, 2H);
13C NMR (101 MHz, CDCl3) δ 184.36 (s), 167.67 (s), 161.73 (d,
1JCF = 250 Hz), 160.36 (s), 147.44 (s), 141.01 (s), 133.32 (s),
3
3
132.04 (s), 131.46 (s), 130.53 (d, JCF = 8.2 Hz), 128.04 (d, JCF
4
= 8.6 Hz), 125.18 (s), 122.82 (s), 116.27 (d, JCF = 2.3 Hz),
66.71 (s); HRMS (ESI) calcd for C19H13FNO2+: 306.0925
(M+H+), found: 306.0926
2'-(4-chlorophenyl)spiro[cyclohexa[2,5]diene-1,1'-isoindoline]-
3',4-dione (2b) (White solid, 51.5 mg, 80%)
1H NMR (400 MHz, CDCl3) δ 7.95 (d, J = 7.3 Hz, 1H), 7.66 –
7.54 (m, 2H), 7.39 (d, J = 8.9 Hz, 2H), 7.32 (d, J = 8.9 Hz, 2H),
7.26 (d, J = 7.6 Hz, 1H), 6.73 (d, J = 10.0 Hz, 2H), 6.43 (d, J =
10.0 Hz, 2H); 13C NMR (101 MHz, CDCl3) δ 184.28 (s), 167.52
(s), 147.66 (s), 140.86 (s), 134.96 (s), 133.44 (s), 133.03 (s),
131.41 (s), 130.92 (s), 130.15 (s), 129.46 (s), 126.60 (s), 125.21
(s), 122.80 (s), 66.75 (s); HRMS (ESI) calcd for C19H13ClNO2+:
322.0629 (M+H+), found: 322.0637
Conclusion
We have developed a TBAB-mediated oxidative cyclization of 2-
aryllbenzamide for
a
series of spiro[cyclohexane-1,1'-
2'-(4-bromophenyl)spiro[cyclohexa[2,5]diene-1,1'-isoindoline]-
3',4-dione (2c) (Yellow solid, 57.1 mg, 78%)
isoindoline]-2,5-diene-3',4-diones. The transformation was
regioselective in a fashion of 5-exo-trig ipso-cyclization and
provided the final products with high efficiency and a broad
reaction scope. However, it was surprising to find that N-alkyl
protecting group in 2-arylbenzamide was not compatible for the
reaction. Mechanism studies showed the use of TBAB as an
additive was pivotal for the reaction. The use of TBAB as an
additive not only stabilized the resulting 2-arylbenzamide
nitrogen radical intermediate, but also probably changed
electrophilicity nature of amidyl nitrogen radical.
1H NMR (400 MHz, CDCl3) δ 7.96 (d, J = 7.4 Hz, 1H), 7.66-7.60
(m, 2H), 7.48 (dd, J = 8.7, 1.6 Hz, 2H), 7.38 – 7.31 (m, 2H), 7.26
(d, J = 6.7 Hz, 1H), 6.79 – 6.66 (m, 2H), 6.46-6.42 (m, 2H); 13
C
NMR (101 MHz, CDCl3) δ 184.26 (s), 167.47 (s), 147.69 (s),
140.83 (s), 135.55 (s), 133.46 (s), 132.44 (s), 131.41 (s), 130.92
(s), 130.17 (s), 126.72 (s), 125.23 (s), 122.79 (s), 120.94 (s),
66.72 (s); HRMS (ESI) calcd for C19H13BrNO2+: 366.0124
(M+H+), found: 366.0142
4-(3',4-dioxospiro[cyclohexa[2,5]diene-1,1'-isoindolin]-2'-
yl)benzonitrile (2d) (White solid, 41.2 mg, 66%)
Experimental Section
1H NMR (400 MHz, CDCl3) δ 8.04 – 7.95 (m, 1H), 7.78 (d, J =
8.5 Hz, 2H), 7.71 – 7.56 (m, 4H), 7.27 (d, J = 7.7 Hz, 1H), 6.82 –
6.71 (m, 2H), 6.57 – 6.47 (m, 2H); 13C NMR (101 MHz, CDCl3) δ
183.95 (s), 167.46 (s), 148.05 (s), 141.37 (s), 140.41 (s), 134.06
(s), 133.23 (s), 131.08 (s), 130.99 (s), 130.40 (s), 125.49 (s),
122.92 (s), 122.78 (s), 118.26 (s), 109.61 (s), 66.89 (s); HRMS
(ESI) calcd for C20H13N2O2+: 313.0972 (M+H+), found: 313.0936
General procedure for the synthesis of compound 2: N-aryl-
2-arylbenzamides 1 (0.2 mmol), TBAB (2 equiv), Oxone (5
equiv) were added to a test tube, and then co-solvent DCE:H2O
o
(v/v =1:1, 4 mL) was added. The mixture was stirred at 80 C for
14 h. The reaction was quenched with water and extracted three
times with ethyl acetate. The organic phase is dried over
anhydrous sodium sulfate, evaporation of the solvent and
purification by flash column chromatograph provided the desired
product 2.
2'-(4-(trifluoromethyl)phenyl)spiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2e) (Yellow solid, 39.8 mg, 56%)
1H NMR (400 MHz, CDCl3) δ 8.04 – 7.97 (m, 1H), 7.77 – 7.58 (m,
6H), 7.29-7.25 (m, 1H), 6.82 – 6.72 (m, 2H), 6.56 – 6.45 (m, 2H);
13C NMR (101 MHz, CDCl3) δ 184.15 (s), 167.54 (s), 147.95 (s),
140.64 (s), 133.75 (s), 131.24 (s), 130.97 (s), 130.27 (s), 126.46
(s), 126.42 (s), 125.38 (s), 123.91 (s), 122.79 (s), 66.85 (s);
HRMS (ESI) calcd for C20H13F3NO2+: 356.0893 (M+H+), found:
356.0877
General procedure for the synthesis of compound 3: N-aryl-
2-arylbenzamides 1 (0.2 mmol), TBAI (2 equiv), Oxone (2 equiv),
K2CO3 (3 equiv) were added to a test tube, and then co-solvent
DCE: H2O (v/v =1:1, 4 mL) was added. The mixture was stirred
o
at 100 C for 14 h. The reaction was quenched with water and
extracted three times with ethyl acetate. The organic phase is
dried over anhydrous sodium sulfate, evaporation of the solvent
and purification by flash column chromatograph provided the
desired product 3.
2'-(4-acetylphenyl)spiro[cyclohexa[2,5]diene-1,1'-isoindoline]-
3',4-dione (2f) (White solid, 48.7 mg, 74%)
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10.1002/ejoc.201900321
European Journal of Organic Chemistry
COMMUNICATION
1H NMR (400 MHz, CDCl3) δ 7.82-7.95 (m, 3H), 7.72 – 7.66 (m,
2H), 7.66 – 7.56 (m, 2H), 7.26 (d, J = 8.0 Hz, 1H), 6.78 (d, J =
9.9 Hz, 2H), 6.49 (d, J = 9.9 Hz, 2H), 2.58 (s, 3H); 13C NMR (101
MHz, CDCl3) δ 196.81 (s), 184.18 (s), 167.50 (s), 148.18 (s),
141.32 (s), 140.60 (s), 134.93 (s), 133.74 (s), 131.34 (s), 130.87
(s), 130.25 (s), 129.50 (s), 125.36 (s), 123.19 (s), 122.78 (s),
66.92 (s), 26.57 (s); HRMS (ESI) calcd for C21H16NO3+:
330.1125 (M+H+), found: 330.1129
2'-(4-bromo-3-methylphenyl)spiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2k) (Yellow solid, 38.0 mg, 50%)
1H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 6.9 Hz, 1H), 7.70 –
7.55 (m, 2H), 7.51 (d, J = 8.5 Hz, 1H), 7.36-7.35 (m, 1H), 7.26 (d,
J = 7.0 Hz, 1H), 7.09 (dd, J = 8.5, 2.4 Hz, 1H), 6.72 (d, J = 10.0
Hz, 2H), 6.44 (d, J = 10.0 Hz, 2H), 2.37 (s, 3H); 13C NMR (101
MHz, CDCl3) δ 184.38 (s), 167.56 (s), 147.65 (s), 140.90 (s),
139.23 (s), 135.39 (s), 133.38 (s), 133.08 (s), 131.49 (s), 130.88
(s), 130.14 (s), 128.05 (s), 125.23 (s), 124.30 (s), 123.86 (s),
122.80 (s), 66.73 (s), 23.19 (s); HRMS (ESI) calcd for
C20H15BrNO2+: 380.0281 (M+H+), found: 380.0273
methyl 4-(3',4-dioxospiro[cyclohexa[2,5]diene-1,1'-isoindolin]-2'-
yl)benzoate (2g) (White solid, 43.5 mg, 63%)
1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 8.8 Hz, 2H), 8.01 –
7.95 (m, 1H), 7.69 – 7.55 (m, 4H), 7.28-7.23 (m, 1H), 6.77 (d, J
= 10.1 Hz, 2H), 6.48 (d, J = 10.0 Hz, 2H), 3.90 (s, 3H); 13C NMR
(101 MHz, CDCl3) δ 184.20 (s), 167.49 (s), 166.19 (s), 148.18
(s), 141.15 (s), 140.62 (s), 133.69 (s), 131.38 (s), 130.84 (s),
130.71 (s), 130.23 (s), 128.13 (s), 125.34 (s), 123.18 (s), 122.77
(s), 66.92 (s), 52.23 (s); HRMS (ESI) calcd for C21H16NO4+:
346.1074 (M+H+), found: 346.1084
2'-(4-bromophenyl)-6'-chlorospiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2l) (Yellow solid, 54.5 mg, 68%)
1H NMR (400 MHz, CDCl3) δ 7.89 (dd, J = 8.1 Hz, 1H), 7.60 –
7.53 (m, 1H), 7.49 (d, J = 8.6 Hz, 2H), 7.37 – 7.27 (m, 2H), 7.24
(s, 1H), 6.71 (d, J = 8.6 Hz, 2H), 6.46 (d, J = 8.6 Hz, 2H); 13
C
NMR (101 MHz, CDCl3) δ 183.86 (s), 166.41 (s), 146.74 (s),
142.66 (s), 139.90 (s), 135.12 (s), 132.54 (s), 131.36 (s), 130.85
(s), 129.77 (s), 126.88 (s), 126.40 (s), 123.22 (s), 121.31 (s),
66.21 (s); HRMS (ESI) calcd for C19H12BrClNO2+: 399.9734
(M+H+), found: 399.9730
2'-(2,4-dibromophenyl)spiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2h) (Yellow solid, 40.1 mg, 45%)
1H NMR (400 MHz, CDCl3) δ 8.00 (d, J = 7.2 Hz, 1H), 7.89-7.84
(m, 1H), 7.70 – 7.55 (m, 2H), 7.45 (dd, J = 8.4, 2.1 Hz, 1H), 7.29
(d, J = 7.6 Hz, 1H), 7.13 (dd, J = 8.4, 1.0 Hz, 1H), 7.02-6.92 (m,
1H), 6.82 – 6.71 (m, 1H), 6.45 (dd, J = 10.0, 1.8 Hz, 1H), 6.33
(dd, J = 10.1, 1.8 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 184.27
(s), 166.62 (s), 146.51 (s), 144.77 (s), 141.97 (s), 136.68 (s),
133.75 (s), 133.43 (s), 131.73 (s), 131.50 (s), 131.00 (s), 130.77
(s), 130.17 (s), 125.47 (s), 123.64 (s), 122.91 (s), 67.21 (s);
HRMS (ESI) calcd for C19H12Br2NO2+: 443.9229 (M+H+), found:
443.9229
5'-bromo-2'-(4-bromophenyl)spiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2m) (Yellow solid, 48.1 mg, 54%)
1H NMR (400 MHz, CDCl3) δ 8.08 (s, 1H), 7.74 (dd, J = 8.1, 1.6
Hz, 1H), 7.49 (d, J = 8.7 Hz, 2H), 7.31 (d, J = 8.7 Hz, 2H), 7.14
(d, J = 8.2 Hz, 1H), 6.70 (d, J = 9.9 Hz, 2H), 6.44 (d, J = 9.9 Hz,
2H); 13C NMR (101 MHz, CDCl3) δ 183.94 (s), 165.98 (s), 146.82
(s), 139.64 (s), 136.51 (s), 135.08 (s), 133.26 (s), 132.54 (s),
131.22 (s), 128.29 (s), 126.85 (s), 124.46 (s), 124.38 (s), 121.37
(s), 66.42 (s); HRMS (ESI) calcd for C19H12Br2NO2+: 443.9229
(M+H+), found: 443.9215
2'-(4-bromo-3-fluorophenyl)spiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2i) (White solid, 47.6 mg, 62%)
1H NMR (400 MHz, CDCl3) δ 7.97 (d, J = 7.5 Hz, 1H), 7.68 –
7.56 (m, 2H), 7.55 – 7.43 (m, 2H), 7.26 (d, J = 7.5 Hz, 1H), 7.19
(dd, J = 8.7, 1.5 Hz, 1H), 6.74 (d, J = 10.0 Hz, 2H), 6.49 (d, J =
10.0 Hz, 2H); 13C NMR (101 MHz, CDCl3) δ 184.07 (s), 167.36
(s), 159.28 (d, 1JCF = 247 Hz), 147.72 (s), 140.59 (s), 137.35 (s),
133.73 (d, J = 5.0 Hz), 131.10 (d, J = 3.4 Hz), 130.28 (s), 125.34
(s), 122.79 (s), 120.55 (d, J = 3.6 Hz), 112.93 (s), 112.67 (s),
107.17 (s), 106.96 (s), 66.80 (s); HRMS (ESI) calcd for
C19H12BrFNO2+: 384.0030 (M+H+), found: 384.0036
2'-(4-bromophenyl)-5'-chlorospiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2n) (Brown solid, 61.7 mg, 77%)
1H NMR (400 MHz, CDCl3) δ 7.90 (s, 1H), 7.64 – 7.54 (m, 1H),
7.53 – 7.43 (m, 2H), 7.36 – 7.27 (m, 2H), 7.20 (d, J = 8.2 Hz,
1H), 6.75 – 6.64 (m, 2H), 6.49 – 6.36 (m, 2H); 13C NMR (101
MHz, CDCl3) δ 183.97 (s), 166.12 (s), 146.90 (s), 139.09 (s),
136.65 (s), 135.10 (s), 133.70 (s), 133.04 (s), 132.53 (s), 131.20
(s), 126.88 (s), 125.23 (s), 124.13 (s), 121.37 (s), 66.38 (s);
HRMS (ESI) calcd for C19H12BrClNO2+: 399.9734 (M+H+), found:
399.9718
2'-(4-bromo-2-methylphenyl)spiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2j) (Yellow solid, 63.1 mg, 83%)
1H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 6.7 Hz, 1H), 7.70 –
2'-(4-bromophenyl)-5'-fluorospiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2o) (Yellow solid, 53.8 mg, 70%)
7.53 (m, 2H), 7.47-7.46 (m, 1H), 7.29 (d, J = 7.3 Hz, 2H), 7.02 (d, 1H NMR (400 MHz, CDCl3) δ 7.61 (dd, J = 7.2, 2.3 Hz, 1H), 7.53
J = 8.4 Hz, 1H), 6.82 (dd, J = 10.0, 2.8 Hz, 1H), 6.61 (dd, J =
10.0, 2.8 Hz, 1H), 6.44 (d, J = 10.0 Hz, 1H), 6.32 (d, J = 10.0 Hz,
1H), 2.25 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 184.25 (s),
166.90 (s), 147.20 (s), 144.83 (s), 141.97 (s), 139.37 (s), 134.49
(s), 133.21 (s), 133.07 (s), 131.70 (s), 131.07 (s), 130.60 (s),
130.15 (s), 129.80 (s), 125.30 (s), 122.89 (s), 67.06 (s), 18.87
(s); HRMS (ESI) calcd for C20H15BrNO2+: 380.0281 (M+H+),
found: 380.0283
– 7.45 (m, 2H), 7.35 – 7.28 (m, 3H), 7.24 (dd, J = 8.3, 4.1 Hz,
1H), 6.71 (d, J = 10.1 Hz, 2H), 6.44 (d, J = 10.0 Hz, 2H); 13
C
NMR (101 MHz, CDCl3) δ 184.03 (s), 166.31 (d, J = 3.4 Hz),
1
163.56 (d, JCF = 250 Hz), 147.13 (s), 136.27 (d, J = 2.4 Hz),
135.19 (s), 133.57 (d, J = 9.0 Hz), 132.53 (s), 131.07 (s), 126.86
(s), 124.68 (d, J = 8.7 Hz), 121.33 (s), 121.09 (s), 111.95 (d, J =
24 Hz), 66.30 (s); HRMS (ESI) calcd for C19H12BrFNO2+:
384.0030 (M+H+) found: 384.0022
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10.1002/ejoc.201900321
European Journal of Organic Chemistry
COMMUNICATION
122.68 (s), 120.75 (s), 67.17 (s), 15.95 (s); HRMS (ESI) calcd
for C20H15BrNO2+: 380.0281 (M+H+), found: 380.0295
2'-(4-bromophenyl)-6'-methylspiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2p) (Yellow solid, 41.8mg, 55%)
1H NMR (400 MHz, CDCl3) δ 7.85 (d, J = 7.4 Hz, 1H), 7.55 –
7.45 (m, 3H), 7.39 (d, J = 7.5 Hz, 1H), 7.19 (d, J = 8.3 Hz, 2H),
6.64 (d, J = 9.7 Hz, 2H), 6.48 (d, J = 9.7 Hz, 2H), 2.23 (s, 3H);
13C NMR (101 MHz, CDCl3) δ 184.22 (s), 167.85 (s), 145.31 (s),
138.28 (s), 135.62 (s), 134.51 (s), 134.41 (s), 132.49 (s), 132.24
(s), 131.71 (s), 130.31 (s), 129.15 (s), 122.99 (s), 122.02 (s),
66.00 (s), 16.73 (s); HRMS (ESI) calcd for C20H15BrNO2+:
380.0281 (M+H+), found: 380.0283
2-bromo-2'-(4-bromophenyl)-3-
methoxyspiro[cyclohexa[2,5]diene-1,1'-isoindoline]-3',4-dione
(2u) (Yellow solid, 48 mg, 51%)
1H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 7.3 Hz, 1H), 7.68-7.59
(m, 2H), 7.49 (d, J = 8.6 Hz, 2H), 7.34 (d, J = 8.6 Hz, 2H), 7.25
(d, J = 7.2 Hz, 1H), 6.88 (s, 1H), 5.75 (s, 1H), 3.63 (s, 3H); 13
C
NMR (101 MHz, CDCl3) δ 177.90 (s), 167.53 (s), 151.69 (s),
147.71 (s), 142.83 (s), 134.73 (s), 133.71 (s), 132.50 (s), 131.48
(s), 130.36 (s), 127.15 (s), 125.13 (s), 121.86 (s), 121.28 (s),
114.35 (s), 71.28 (s), 55.75 (s); HRMS (ESI) calcd for
C20H14Br2NO3+: 473.9335 (M+H+), found: 473.9333
2'-(4-bromophenyl)-5'-methylspiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2q) (Yellow solid, 47.1 mg, 62%)
1H NMR (400 MHz, CDCl3) δ 7.75 (s, 1H), 7.52 – 7.39 (m, 3H),
7.34 (d, J = 8.8 Hz, 2H), 7.13 (d, J = 7.9 Hz, 1H), 6.70 (d, J =
10.1 Hz, 2H), 6.42 (d, J = 10.0 Hz, 2H), 2.47 (s, 3H). 13C NMR
(101 MHz, CDCl3) δ 184.36 (s), 167.60 (s), 147.97 (s), 140.67
(s), 137.93 (s), 135.70 (s), 134.49 (s), 132.39 (s), 131.52 (s),
130.71 (s), 126.59 (s), 125.36 (s), 122.49 (s), 120.78 (s), 66.55
(s), 21.41 (s); HRMS (ESI) calcd for C20H15BrNO2+: 380.0281
(M+H+), found: 380.0257
5-phenylphenanthridin-6(5H)-one (3) (White solid, 35.7 mg,
66%)
1H NMR (400 MHz, CDCl3) δ 8.61 – 8.53 (m, 1H), 8.37 – 8.29 (m,
2H), 7.86 – 7.77 (m, 1H), 7.62 (t, J = 7.5 Hz, 3H), 7.54 (t, J = 7.4
Hz, 1H), 7.37 – 7.32 (m, 2H), 7.32 – 7.27 (m, 2H), 6.73 – 6.67
(m, 1H); 13C NMR (101 MHz, CDCl3) δ 161.72 (s), 139.16 (s),
138.28 (s), 134.00 (s), 132.83 (s), 130.20 (s), 129.09 (s), 129.02
(s), 128.78 (s), 128.13 (s), 125.85 (s), 122.98 (s), 122.65 (s),
121.78 (s), 119.03 (s), 117.03 (s)
2'-(4-bromophenyl)-5'-methoxyspiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2r) (Yellow solid, 44.4mg, 56%)
1H NMR (400 MHz, CDCl3) δ 7.48 (d, J = 8.7 Hz, 2H), 7.41 (s,
1H), 7.34 (d, J = 8.7 Hz, 2H), 7.18-7.12 (m, 2H), 6.69 (d, J = 9.9
Hz, 2H), 6.41 (d, J = 9.9 Hz, 2H), 3.88 (s, 3H); 13C NMR (101
MHz, CDCl3) δ 184.35 (s), 167.45 (s), 161.49 (s), 147.93 (s),
135.65 (s), 132.92 (s), 132.42 (s), 132.36 (s), 130.64 (s), 126.61
(s), 123.70 (s), 121.94 (s), 120.89 (s), 107.67 (s), 66.32 (s),
55.94 (s); HRMS (ESI) calcd for C20H15BrNO3+: 396.0230
(M+H+), found: 396.0232
Acknowledgements ((optional))
Financial support from China Postdoctoral Science
Foundation (2018M630396 for G. Qiu), the Natural Science
Foundation of China (Nos: 21502069 and 21772067), and
the Natural Science Foundation of Zhejiang (LY19B020004)
is gratefully acknowledged.
2'-(4-bromophenyl)-3-fluorospiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2s) (Yellow solid, 32.3 mg, 42%)
1H NMR (400 MHz, CDCl3) δ 7.99 (d, J = 7.3 Hz, 1H), 7.69-7.60
(m, 2H), 7.52 (dd, J = 8.5, 1.7 Hz, 2H), 7.32 (d, J = 7.6 Hz, 1H),
7.27 (dd, J = 9.1, 2.1 Hz, 2H), 6.74 (d, J = 9.9 Hz, 1H), 6.44 (dd,
J = 9.8, 7.0 Hz, 1H), 6.29 (dd, J = 11.2, 2.6 Hz, 1H); 13C NMR
(101 MHz, CDCl3) δ 177.27 (d, J = 22 Hz), 167.14 (s), 154.36 (d,
J = 270 Hz), 148.55 (d, J = 2.5 Hz), 140.35 (s), 134.86 (s),
133.65 (s), 132.69 (s), 131.13 (s), 130.51 (s), 129.82 (d, J = 4.1
Hz), 127.60 (s), 125.49 (s), 123.45 (d, J = 14.2 Hz), 122.70 (s),
121.73 (s), 67.79 (s); HRMS (ESI) calcd for C19H12BrFNO2+:
384.0030 (M+H+) found: 384.0034
Keywords: amidyl radical · N-arylbenzamide ·ipso-cyclization ·
5-exo-trig · quaternary carbon
[1] E. A. Peterson, L. E. Overman, PNAS, 2004, 101, 11943
[2] For selected reviews, see: a) B. Wang, Y.-Q. Tu, Acc.
Chem. Res., 2011, 44, 1207; b) Z.-L. Song, C.-A. Fan,
Y.-Q. Tu, Chem. Rev., 2011, 111, 7523; c) C.-X. Zhuo, C.
Zheng, S.-L. You, Acc. Chem. Rev., 2014, 47, 2558 d) L.
Pouysegu, D. Deffieux, S. Quideau, Tetrahedron, 2010
,
66, 2235; e) W. Sun, G. Li, L. Hong, R. Wang, Org.
Biomol. Chem., 2016, 14, 2164; f) Q. Ding, X. Zhou, R.
Fan, Org. Biomol. Chem., 2014, 12, 4807; g) Y. Duan, S.
Jiang, Y. Han, B. Sun, C. Zhang, Chin. J. Org. Chem.,
2016, 36, 1973.
2'-(4-bromophenyl)-3-methylspiro[cyclohexa[2,5]diene-1,1'-
isoindoline]-3',4-dione (2t) (Gray solid, 41.8 mg, 55%)
[3] for reviews, see: a) R. Song, Y. Xie, Chin. J. Chem. 2017
,
1H NMR (400 MHz, CDCl3) δ 7.97 (d, J = 7.0 Hz, 1H), 7.64-7.55
(m, 2H), 7.49 (d, J = 8.9 Hz, 2H), 7.35 (d, J = 8.8 Hz, 2H), 7.27 –
7.19 (m, 1H), 6.70 (dd, J = 9.8, 3.0 Hz, 1H), 6.48 (d, J = 3.0, 1.5
Hz, 1H), 6.44 (d, J = 9.8 Hz, 1H), 1.94 (d, J = 1.4 Hz, 3H); 13C
NMR (101 MHz, CDCl3) δ 185.10 (s), 167.51 (s), 147.51 (s),
142.60 (s), 141.44 (s), 137.98 (s), 135.69 (s), 133.32 (s), 132.38
(s), 131.41 (s), 130.69 (s), 129.92 (s), 126.62 (s), 125.14 (s),
35, 280; b) L. Shi, W. Zhang, S. Chen, L. Lu, R. Fan, J.
Tan, C. Zheng, Current. Org. Chem. 2018, 15, 904; c) E.
Vessally, M. Babazadeh, K. Didehban, A. Hosseinian, L.
Edjlali, Current. Org. Chem. 2018, 22, 286; d) C. R.
Reddy, S. K. Prajapti, K. Warudikar, R. Ranjan, B. B.
Rao, Org. Biomol. Chem. 2017, 15, 3130
[4] a) R. Ferraccioli, D. Carenzi, E. Motti, M. Catellani, J. Am.
Chem. Soc. 2006, 128, 722; b) D. M. Kuznetsov, O.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900321
European Journal of Organic Chemistry
COMMUNICATION
Mukhina, A. G. Kutateladze, Angew. Chem. Int. Ed. 2016
,
[9] Electrocatalysis: a) A. Kehl, V. M. Breising, D. Schollmeyer,
S. R. Waldvogel, Chem. Eur. J. 2018, 24, 17230; b) S.
Zhang, L. Li, R. Zhang, K. Xu, C. Zeng, Org. Lett. 2018, 20,
3443; c) K. Subramanian, S. L. Yedage, B. M. Bhanage,
Adv. Synth. Catal. 2018, 360, 2511
[10] For reviews on amidyl N-radical, see: a) J-R. Chen, X.-Q.
Hu, L.-Q. Lu, W.-J. Xiao, Chem. Soc. Rev. 2016, 45, 2044;
b) J. Luo, W. Wei, Adv. Synth. Catal. 2018, 360, 2076; c) H.
Song, X. Liu, Y. Qin, Acta Chim. Sinica 2017, 75, 1137; d)
M. M. Jackman, Y. Cai, S. Castle, Synthesis, 2017, 49,
1785; e) X. Tao, Q. Zhang, Chem. Soc. Rev. 2016, 45, 11,
3069; f) M. Minozzi, D. Nanni, P. Spagnole, Chem. Eur. J.
2009, 15, 7830; g) S. Z. Zard, Chem. Soc. Rev. 2008, 37,
1603
[11] a) S. A. Glover, A. Goosen, J. Chem. Soc. Perkin Trans. 1,
1978, 653; b) A. R. Forrester, A. S. Ingram, and R. H.
Thomson, J. Chem. Soc. Perkin Trans. 1, 1972, 2847
[12] D. H. Hey, G. H. Jones, M. J. Perkins, J. Chem. Soc.
Perkin Trans. 1, 1978, 118.
[13] electrophilic 5-exo-trig ipso-cyclization of 2-(4-
methoxylphenyl)benzamide, see: a) T. Dohi, N. Takenaga,
K.-I. Fukushima, K. Teruyoshi, S. Motoo, H. Fujioka, Y. Kita,
Chem. Commun. 2010, 46, 7697; b) T. Dohi, E. Mochizuki,
D. Yamashita, K. Miyazaki, Y. Kita, Heterocycles, 2014, 88,
254
55, 6988; Other dual functional synthons, see: c) C. Wu,
Z. Wang, Z. Hu, F. Zeng, X.-Y. Zhang, Z. Cao, Z. Tang,
W.-M. He, and X.-H. Xu, Org. Biomol. Chem. 2018, 16,
3177; d) S. Ye, X. Li, W. Xie, and J. Wu, Eur. J. Org.
Chem. 2019, 10.1002/ejoc.201900396; e) L. –Y. Xie, S.
Peng, F. Liu, J.-Y. Yi, M. Wang, Z. Tang, X. Xu, and W.-M
He, Adv. Synth. Catal. 2018, 360, 4259; f) C. Wu, L.-H. Lu,
A. –Z. Peng, G.-K. Jia, C. Peng, Z. Cao, Z. Tang, W.-M.
He, and X. Xu, Green. Chem. 2018, 20, 3683; g) B. Liu, H.
Fang, X. Li, W. Cai, L. Bao, M. Rudolf, F. Plass, L. Fan, X.
Lu, D. M. Guldi, Chem. Eur. J. 2015, 21, 746; h) Y. Zong,
Y. Lang, M. Yang, X. Li, X. Fan, and J. Wu, Org. Lett.
2019, 21, 1935; i) X. Gong, J. Chen, X. Li, W. Xie, and J.
Wu, Chem. Asian. J. 2018, 13, 2543; j) Y. Zhao, Y. Luo, Y.
Zhu, H. Wang, H. Zhou, H. Tan, and Z. Zhou, Synlett, 2018
,
29, 773; k) Y.-H. Zhao, Y. Li, M. Luo, Z. Tang, and K. Deng,
Synlett, 2016, 27, 2597; l) Y. Zhao, Y. Li, T. Guo, Z. Tang,
W. Xie, and G. Zhao, Tetrahedron Lett. 2016, 57, 2257; m)
C. Ma, J.-Y. Zhou, Y.-Z. Zhang, Y. Jiao, G.-L. Mei, F. Shi,
Chem. Asian. J. 2018, 13, 2549; n) T. Guo, Y. Liu, Y.-H.
Zhao, P.-K. Zhang, S.-L. Han, and H.-M. Liu, Tetrahedron
Lett. 2016, 57, 3920; o) S. Ye, X. Li, W. Xie, and J. Wu,
Asian. J. Org. Chem. 2019, 8, 10.1039/C9QO00272C; p)
W. Xie, H. Zhang, J. He, J. Zhang, Q. Yu, C. Luo, and S. Li,
Bioorg. Med. Chem. Lett. 2017, 27, 530; q) W. Xie, S. Xie, Y.
Zhou, X. Tang, J. Liu, W. Yang, and M. Qiu, Eur. J. Med.
Chem. 2014, 81, 22; r) T. Guo, Y. Liu, Y.-H. Zhao, P.-K.
Zhang, S.-L. Han, and H.-M. Liu, Tetrahedron Lett. 2016, 57,
4629
[14] D. M. Collington, D. H. Hey, C. W. Rees, J. Chem. Soc. C:
1968, 1017
[15] Results from our groups: a) S.-T. Yuan, Y.-H. Wang, J.-B.
Liu, G. Qiu, Adv. Synth. Catal. 2017, 359, 1981; b) S.-T.
Yuan, H. Zhou, L. Gao, J.-B. Liu, G. Qiu, Org. Lett. 2018
,
[5] Examples on transitional metal-catalyzed C-H
functionalization of 2-arylbenzamide: a) J. Karthikeyan,
C.-H. Cheng, Angew. Chem. Int. Ed. 2011, 50, 9880; b) J.
Karthikeyan, R. Haridharan, C.-H. Cheng, Angew. Chem.
Int. Ed. 2012, 51, 12343; (c) R. Saha, G. Sekar, Journal
of Catal. 2018, 366, 176; (d) G.-W. Wang, T.-T. Yuan,
D.-D. Li, Angew. Chem. Int. Ed. 2011, 50, 1380;
[6] Examples on nonmetal-mediated C-H functionalization of
2-arylbenzamide: a) D. Liang, W. Yu, N. Nguyen, J.
Deschamps, G. Imler, Y. Li, A. Mackerell, C. Jiang, F.
Xue, J. Org. Chem. 2017, 82, 3589; b) C. Hu, Z. Zhang,
W. Gao, G. Zhang, T. Liu, Q. Liu, Tetrahedron 2018, 74,
665; c) D. Liang, D. Sersen, C. Yang, J. Deschamps, G.
Imler, C. Jiang, F. Xue, Org. Biomol. Chem. 2017, 15, 4390;
d) S. L. Yedage, B. M. Bhanage, J. Org. Chem. 2017, 82,
5769
20, 562; c) R.-X. Wang, S.-T.Yuan, J.-B. Liu, J. Wu, G.
Qiu, Org. Biomol. Chem. 2018, 16, 4501;d) Y. He, G. Qiu,
Org. Biomol. Chem., 2017, 15, 3485; for a review on
Oxone chemistry: e) H. Hussain, I. R. Green, I. Ahmed,
Chem. Rev., 2013, 113, 3329; for examples on oxone
chemistry, see: f) L.-H. Lu; S.-J. Zhou; M. Sun; J.-L. Chen;
W. Xia; X. Yu; X. Xu; and W.-M. He, ACS Sustaniable
Chem. Eng. 2019, 7, 1574; g) L.Y. Xie, S. Peng, F. Liu,
G.- R. Chen. W. Xia, X. Yu, W.-F. Li, Z. Cao, and W.-M.
He, Org. Chem. Front. 2018, 5, 2604; h) L.-H. Lu, S.-J.
Zhou, W.-B. He, W. Xia, P. Chen, X. Yu, X. Xu, and W.-M.
He, Org. Biomol. Chem. 2018, 16, 9064; (i) T. Guo, X.-N.
Wei, Y. Liu, P.-K. Zhang, Y.-H. Zhao, Org. Chem. Front.
2019, 6, 1414; j)K. Deng, X. Li, H. Huang, Electrochimica
Acta. 2016, 204, 84; k) B. Liu, X. Li, M. Stepień, P. J.
Chmielewski, Chem. Eur. J. 2015, 21, 7790; l) S. Qiu, C.
Wang, S. Xie, X. Huang, L. Chen, Y. Zhao, Z. Zeng,
Chem. Commun. 2018, 54, 11383; m) L.-Y. Xie, S. Peng,
T.-G. Fan, Y.-F. Liu, M. Sun, L.-L. Jiang, X.-X. Wang, Z.
Cao, and W.-M. He, Sci China Chem 2019, 62, 460
[7] for selected examples, see: a) S. Boonya-udtayan, N.
Yotapan, C. Woo, S. Ruchirawat, N. Thasana, Chem. Asian
J. 2010, 5, 2113; b) T. Hirata, I. Takahashi, Y. Suzuki, H.
Hasegawa, O. Kiatagawa, J. Org. Chem. 2016, 81, 318
[8] Photocatalysis: Y. Moon, E. Jang, S. Choi, S. Hong, Org.
Lett. 2018, 20, 240
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Entry for the Table of Contents (Please choose one layout)
Layout 2:
TBAB-mediated radical 5-exo-trig
ipso-cyclization of 2-arylbenzamide for
the synthesis of spiro[cyclohexane-
1,1'-isoindoline]-2,5-diene-3',4-dione
Guanyinsheng Qiu, Zhi-Feng Chen,
Wenlin Xie, and Hongwei Zhou
Radical ipso-cyclization: a TBAB-mediated radical
5-exo-trig ipso-cyclization of N-aryl-2-arylbenzamide
is described in this paper.
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