Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles via Intramolecular Dehydrogenation Photocyclization

Article abstract of DOI:10.1002/cjoc.202100103

A catalyst-, acid- and base-free, environmental-friendly method for synthesis of 2H-benzo[g]furo[2,3-e]indazoles, 2H-benzo[g]thieno[2,3-e]indazoles and 2H-benzo[g]pyrrolo[2,3-e]indazoles via UV light irradiation of 3-phenyl-4-(2-heteroaryl)pyrazoles (aryl

Full text of DOI:10.1002/cjoc.202100103

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles via
Intramolecular Dehydrogenation Photocyclization
Authors: Wei Zhang, Ping Wang, Xi Zhang, Rui Wang, Tao Wang, Zhicun Liu,*
Zunting Zhang*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2021, 39, 10.1002/cjoc.202100103.
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Cite this paper: Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles via
Intramolecular Dehydrogenation Photocyclization
Wei Zhang, Ping Wang, Xi Zhang, Rui Wang, Tao Wang, Zhicun Liu,* Zunting Zhang*
Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Labor-
atory for Resource Development of Endangered Crude Drugs in Northwest of China, School of Chemistry and Chemical Engineering, and
Basic Experimental Teaching Center Shaanxi Normal University, Xi’an 710062, People’s Republic of China.
Keywords
2H-benzo[g]furo[2,3-e]indazoles | 6π-electroncyclization | Photocyclization | Dehydrogenative annulation | Chemo-selectivity
Main observation and conclusion
A catalyst-, acid- and base-free, environmental-friendly method for the synthesis of 2H-benzo[g]furo[2,3-e]indazoles, 2H-benzo[g]
thieno[2,3-e]indazoles and 2H-benzo[g]pyrrolo[2,3-e]indazoles via a UV light irradiation of 3-phenyl-4-(2-heteroaryl)pyrazoles (ar-
yl=furanyl, thiophenyl and N-methylpyrrolyl) in EtOH/H2O at room temperature under argon atmosphere was described. Irradiation of
3-(2-hydroxyphenyl)-4-(2-heteroaryl)pyrazoles showed
a
high chemo-selectivity to obtain dehydrogenation product
2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazols-10-ol. The mechanism of photocyclization was expound that through the process of
6π-electroncyclization, [1,5]-hydrogen shift, pyrazole tautomerism, 1,3-eneamine tautomerism and evolution H2.
Comprehensive Graphic Content
R2
R1
R4
X
H2
HO
R1
R3
R2
R2
R1
N
H2
N
R4
R4
H
major product
X
X
EtOH-H O
95%EtOH
(2:1)
2
N
N
R2
R1
N
=H
R3
R
3=OH
N
H
H
R4
H
2O
X
N
N
H
=
=
=
R4
H,
X=
NMe; R
R2
Me;
OMe, CF
F,
CN, CF
;
3
;
O, S,
H,
H, F,
1
3
by-product
*E-mail: zhangzt@snnu.edu.cn.
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Supporting Information
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
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through the copyediting, typesetting, pagination and proofreading process which may lead to
differences between this version and the Version of Record. Please cite this article as doi:
10.1002/cjoc.202100103
This article is protected by copyright. All rights reserved.

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles via
Intramolecular Dehydrogenation Photocyclization
Authors: Wei Zhang, Ping Wang, Xi Zhang, Rui Wang, Tao Wang, Zhicun Liu,*
Zunting Zhang*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2021, 39, 10.1002/cjoc.202100103.
The final Version of Record (VoR) of it with formal page numbers will soon be
published online in Early View: http://dx.doi.org/10.1002/cjoc.202100103.
ISSN 1001-604X • CN 31-1547/O6
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First author et al.
Report
(aryl=furanyl, thiophenyl and N-methylpyrrolyl). Surprisingly,
Background and Originality Content
dehydration products
3 as a by-product, dehydrogenation
products 2 were obtained (Scheme 2). Given our interest in
development of strategy to synthesis ploybenzne fused
heterocyclic aromatic compounds via photoinduced annulation as
well as the existence of limited literature reports on
intramolecular dehydrogenative annulation.[23] In this paper, we
would like to report the syntheses of 2H-benzo[g]furo/thieno
Indazole derivatives have been recognized as important
pharmacophores in the development of antitumor, antimicrobial,
anti-inflammatory agents, and anti-HIV.[1-4] The structurally diverse
indazole moiety has a variety of biological properties, especially in
benzoindazoles. Biological evaluation of those pharmacophores
was revealed that benzo-indazoles was an effective CK2
inhibitors.[5] Moreover, furo-indazole derivatives were used as
[2,3-e]indazoles
and
2H-benzo[g]furo/thieno/pyrrolo
5-HT2C agonists,[6] which was
a promising treatment of
[2,3-e]indazols-10-ol via the intramolecular dehydrogenation
photocyclization of 3-phenyl-4-(2-hetero-aryl)pyrazoles and
3-(2-hydroxyphenyl)-4-(2-hetero-aryl)pyrazoles in solution of
EtOH/H2O. Irradiation of 3-(2-hydroxyphenyl)-4-(2-hetero-aryl)
CNS-related diseases. Although a number of methods for the
preparation of indazoles were known,[7] only few reports on the
synthesis of dibenzoindazoles was disclosed. For example, treating
perchloro-7H-cyclopropano[a]acenaphthylene with hydrazine
hydrate in DMF at 80 oC, 3,4,5,6,7,8,9-heptachlorophenaleno
[1,9-bc]pyrazole was obtained (Scheme 1a),[8] and it was the first
example of a phenalene fused pyrazole. Also, the mixture of
pyrazoles
to
obtain
2H-benzo[g]furo/thieno/pyrrole
[2,3-e]indazols-10-ol is a high chemical selectivity. Using EtOH/H2O
as solvent, catalyst-, acid- and base-free, transition-metal-free and
intramolecular dehydrogenation photocyclization to synthesis
2H-benzo[g]furo/thieno[2,3-e] indazoles is a friendly environment
strategy. Most of the photoinduced cross-dehydrogenative cou-
pling (CDC) reactions were needed oxidants or transition metals.[24,
o
9-diazofluoren and methyl 2-butynoate were heated at 160 C for
20 min to give 1,3-dipolar cycloaddition products of
2H-dibenzo[e,g]indazoles (Scheme 1b).[9] In our previous work,
25]
Photochemical organic synthesis in the absence of photocata-
2H-phenanthro[9,10-c]pyrazoles
photocyclization dehydration of
was
achieved
3-(2-hydroxyphenyl)-4-
by
the
lysts, oxidant, base and acid has received great attention due to
their economic and synthetic value.[26]
(2-phenyl)-1H-pyrazoles in the EtOH–H2O (1/1, v/v) solution
(Scheme 1c).[10]
Scheme 1 Previous Reports on the Synthesis of Dibenzoindazoles.
Scheme 2 Synthesis of 2H-Benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles and
2H-Benzo[g]furo/thieno/pyrrolo[2,3-e]indazols-10-ol via Intramolecular
Dehydrogenation Photocyclization.
work
Polina's
a)
Cl Cl
Cl
H
Cl
R1
R2
R1
R2
R1
R2
R2
Cl
Cl
Cl
R1
N
R4
R4
R4
R4
N
N2H4 H2O
Cl
Cl
Cl
Cl
v,
h
Ar
v,
h
Ar
X
X
X
X
+
DMF, 80
1 h
,
℃
R3
HO
95%EtOH
=H
EtOH-H2
O
(2:1)
Cl
Cl
N
N
N
N
R3
R3=OH
N
N
N
N
Cl
Cl
Cl
Cl
H
H
H
H
1
2
3
by-product
work
major product
Vasin's
b)
=
=
=
CN, CF R3=H, OH; R4
H,
X=
NMe; R1
OMe, CF
R
Me.
;
3
;
3
O, S,
H,
F,
H, F,
2
O
C
Me
MeOH
160
OMe
Me
OMe
N
N
EtOH, 20
℃
℃
N
Me
N2
N
H
O
work
Our
Results and Discussion
c)
previous
R1
R4
R4
R1
R3
The substrate 2-(4-(fur-2-yl)-1H-pyrazol-3-yl)phenol 1a was
OH
28]
synthesized following the literature report.[27,
The UV
v
Ar
,
R2
h
R2
absorption spectroscopy (SI Figure S3) of starting substrate 1a was
determined.
R3
EtOH-H O
2
(1:1)
F
N
N
N
H
N
H
The solution of 1a (0.25 mmol) in EtOH (50 mL) was irradiated
=
=
=
3
R1
R3
OH, OMe, OBz, i-OPr; R
H,
H,
H,
o
2
with a high-pressure mercury lamp (500 W) at 25 C under argon
=
Me; R
Me, OMe, CF
H,
4
atmosphere for 6 hours to give dehydrogenation product 2a (32%,
Table 1, entry 1) and dehydrated product 3a (12%, Table 1, entry
1). Compared to other polar and nonpolar aprotic solvent, polar
protic solvents MeOH and t-BuOH were screened but no
improvement was observed (entries 2–3). Reaction was almost
not carried out in the use of nonpolar aprotic solvent DCM (entry
4) and solvent ACE gave only 20% dehydrogenation product and
trace amount of dehydrated product (entry 5). Better results were
obtained using EtOH–H2O mixed solvents (entries 6–9). The best
results were given when the solvent was EtOH–H2O (v/v, 2/1)
(entry 8). The concentration of the reaction solution was screened
(entries 10-11). It was important to note that formation of
dehydrogenation product was completely inhibited with the
presence of external oxidant, whereas, formation of dehydration
product was slightly boosted (entries 12–13). Thus, the optimal
condition was determined as below: irradiation of 1a (5.0×10-3
mol/L) in EtOH–H2O (v/v, 2/1) under UV irradiation for 6 h at
ambient temperature under an Ar atmosphere.
Photoinduced organic reactions have been playing significant
roles in synthesis of medicinal drugs, preparation of fine
chemicals, especially in the construction of polycyclic aromatic
compounds.[11] As well-known, cyclization is one of the key steps
for the synthesis of fused heterocyclic compounds, which includes
Scholl reaction,[12] photocyclization[13-14] etc. Synthesis of polycyclic
aromatic hydrocarbons or fused heterocyclic aromatic ring via
photochemical cyclization reaction can be divided into three cate-
gories: oxidation photocyclization,[15] elimination photocyclization
[16]
and transition metal catalyzed photocyclization. Oxidants O2 or
I2,[17] were necessary for the intramolecular oxidation photocy-
clization. Elimination photocyclization usually requires a leaving
group at a certain location, such as halogen and hydroxyl, etc.[18]
There are few examples of transition-metal catalyzed
dehydrogenation photocyclizations for synthesis fused heterocyclic
aromatic hydrocarbons as well.[19, 20]
Based on our previous work,[10, 21, 22] we planned to synthesize
Compared with 1a, the absence of hydroxyl group
4-(furan-2-yl)-3-phenyl-1H-pyrazole 1k was preparation according
to literature reports.[29, 30] (UV spectroscopy in SI Figure S3). By a
2H-benzo[g]aryl[2,3-e]indazoles
3
by the photocyclization
dehydration of 3-(2-hydroxyphenyl)-4-(2-heteroaryl)pyrazoles
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Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
similar optimization process as 1a, irradiation of 1k (0.25 mmol) in
EtOH/H2O (v/v, 95/5) with a high pressure mercury lamp (500 W)
at room temperature under Ar atmosphere 3a as the sole product
was obtained and it’s yield was 61%.
1k-1t
was
electron
withdraw
group
CF3,
F,
2H-benzo[g]furo/thieno[2,3-e]indazoles 3 gave in higher yields
than the substrates bearing an electron donor group (Me, OMe).
For instance, substrates 1o, 1p, 1s, 1t containing a CF3 group, the
yields of 3o, 3p, 3s and 3t were 70%, 76%, 80% and 83% and high-
er than others. For the intramolecular dehydrogenation photocy-
clization, the substrates of 1 tolerated Me, OMe, F, CN, CF3
groups.
Table 1 Optimization of the Photocyclization Reaction Conditions a
O
O
O
v
h
Ar
,
+
HO
HO
Solvent
N
N
N
Scheme 3 Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles and
2H-benzo[g]furo/thieno/pyrrolo [2,3-e] indazols-10-ol. a b c
N
H
N
H
N
H
2a
3a
1a
R1
R2
R1
R2
R1
R2
R2
R1
R4
R4
R4
Yield(%)
2a b
Yield(%)
3a b
v,
v,
Ar
h
Ar
h
Entry
Solvent
Concn(N) Time(h) c
X
X
X
X
+
R3
HO
95%EtOH
=H
EtOH-H O
(2:1)
2
N
N
N
N
R3
12
N
R3=OH
N
1
2
EtOH
MeOH
t-BuOH
DCM
10-3
10-3
10-3
10-3
10-3
10-3
10-3
10-3
10-3
10-2
10-4
10-3
10-3
6
6
32
28
N
N
H
H
H
H
3a, 3l-3t
10
Trace
Trace
Trace
11
1a-1t
2a-2j
3a-3e
MeO
HO
F
MeO
HO
MeO
HO
3
12
12
8
Trace
Trace
20
O
S
S
S
O
4
HO
HO
N
N
N
N
N
5
ACE
N
N
H
N
H
N
N
H
H
H
2a
6h
2b
7h
2d
7h
, 45%,
+
, 42%,
+
, 38%,
+
2c
7h
6
EtOH-H2O(1:2)
EtOH-H2O(1:1)
EtOH-H2O(2:1)
EtOH-H2O(3:1)
EtOH-H2O(2:1)
EtOH-H2O(2:1)
8
35
, 40%,
+
2e
,
43%, 8h
+
14
7
7
36
MeO
MeO
MeO
15
8
6
45
F
O
S
S
O
S
11
9
6
38
N
N
N
N
N
N
H
N
H
N
H
N
H
N
H
9
10
11
12
13
8
21
3c
7h
3e
3a
, 21%,
3d
7h
,
20%,
, 18%, 8h
F
6h
3b
7h
, 15%,
, 16%,
CN
11
5
37
EtOH-H2O(2:1)d
EtOH-H2O(2:1)e
6
/
F
F
MeO
HO
35
29
S
N
6
/
O
O
N
HO
HO
HO
HO
a Irradiation of 1a in various solvents (50 ml) with a high pressure mercury
lamp (500 W) at room temperature. b Isolated yields. Reaction time was
determined by the complete consumption of 1a as indicated by the
thin-layer chromatography (TLC). Adding catalyst amount iodine. e In the
N
N
N
N
N
N
H
N
H
N
H
N
H
N
H
c
2i
,
62%, 8h
2j
, 75%,
8h
2g
2h
8h
, 64%,
9h
2f
7h
, 68%,
,
55%,
d
F
3C
MeO
open air.
O
S
S
S
O
With the optimized condition in hand, a array of 2a-2j and
3a-3e, 3l-3t have been synthesized and shown in Scheme 3.
Photocyclization of 1a-1j and 1k-1t in EtOH–H2O (v/v, 2/1) and
EtOH–H2O (v/v, 95/5) under UV irradiation gave corresponding
dehydrogenation products 2a-2j, 3a, 3l-3t and dehydrated
procucts 3a-3e. And all of the isolated products were
N
N
N
N
N
N
N
H
N
H
N
H
N
H
H
3a
, 61%,
7h
3m
3n
7h
3o
10h
3I
7h
64%,
, 71%,
8h
,
53%,
CF3
, 70%,
CF3
,
F
3C
F
F
S
S
S
S
S
1
characterized by FT-IR, H NMR, 13C NMR and HRMS. Moreover,
N
N
N
N
N
N
H
N
H
N
H
N
N
H
H
the absolute structure of 2i was determined by X-ray diffraction
and the data and molecular structure are displayed in Supporting
Information Table S1 and Figure S1.
3p
12h
, 76%,
3q
3r
,
65%, 8h
8h
3s
, 80%,
3t
, 83%,
, 62%,
10h
12h
In the process of annulation 1a-1j via light irradiation, shown
that a high chemo-selectivity to obtain dehydrogenation product
2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazols-10-ol 2, and dehy-
drated 3 as a byproduct. It was important to note that irradiation
of 1a-1e gave dehydrogenation products 2a-2e as the major iso-
mers (38–45%) along with dehydrated products 3a-3e as the mi-
nor isomers (15–21%). Interestingly, photocyclization of 1f-1j only
yielded dehydrogenation products 2f-2j in 55–75% without ob-
servation of dehydration products. When the heteroaromatic of 2
was 1-N-methylpyrrole and R2 was electron withdraw group such
as CN and F, the irradiation reaction of 3-(2-hydroxy-phenyl)-4-
(2-aryl)pyrazoles have a high chemo- selectivity to obtain dehy-
a Irradiation of 1a-1j (0.25 mmol) in EtOH/H2O (50 ml, 5 mM, v/v, 2/1) with
a high pressure mercury lamp (500 W) at room temperature under Ar
atmosphere for 6-9 h. b Irradiation of 1k-1t (0.25 mmol) in EtOH/H2O (50
ml, 5 mM, v/v, 95/5) with a high pressure mercury lamp (500 W) at room
temperature under Ar atmosphere for 7–12 h. Reaction time was
determined by the complete consumption of substrate as indicated by the
thin-layer chromatography (TLC).
c
Since the dehydrogenation and dehydration cyclization prod-
ucts are derivatives of pyrazoles,[31] both 2 and 3 could exist in
1
tautomeric forms (Scheme 4). In the H NMR (DMSO-d6) of 3s, a
major proton peak at 14.31 ppm accompanied by a minor peak at
14.16 ppm were observed along with some other small peaks in
the aromatic region. However, the peaks at 14.31 ppm and 14.16
ppm were disappeared with the presence of D2O and the spectra
was simplified by the deuterium (2D)-exchange experiments,
which indicated the presence of two tautomeric isomers for
7-(trifluoromethyl)-2H-benzo[g]thieno[2,3-e]indazole. Moreover,
drogenation
product
2H-benzo[g]furo/thieno/pyrrolo
[2,3-e]indazols-10-ol.
Similarly, irradiation of 1k-1t with UV light, dehydrogenation
products 3a, 1l-1t was also afforded. The aromatic heterocyclic of
2 was thiophene gave products in better yields than furan. The
yield of 3l was 64% and 3a, 3n were 61%, 53%. As same as 1a-1j of
dehydrogenation photocyclization, when R1 and R2 of substrates
Chin. J. Chem. 2021, 39, XXX－XXX
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First author et al.
Report
the ratio of two isomers (4.35:1) was determined on the basis of
the integration of two active NH peaks. Similar ratio (5:1) was also
observed for 3p.
min and 3.151 min, and the retention time of gas in the quartz
tube was 2.441 min. It showed that there was generated H2 in the
process of photoinduced 1a. (Scheme 6, Eq. 2, Results are
displayed in Supporting Information Figure S2). It is given an evi-
dence for the proposed mechanism of intramolecular dehydro-
genation photocyclization.
Scheme 4 Tautomeric Isomers of 3s.
CF3
CF3
S
S
Conclusions
HN
N
N
N
H
In summary, an efficient, mild, and transition-metal, acid- and
base-free method for the synthesis of (2H-benzo[g]furo/thieno/
pyrrolo[2,3-e]indazols-10-ol and 2H-benzo[g]furo/thieno[2,3-e]
indazoles) in the EtOH/H2O with a high-pressure mercury lamp at
room temperature under argon atmosphere was developed.
Compared to the annulation 3-(2-hydroxyphenyl)-4-(2-phenyl)
3s'
3s
Scheme 5 Plausible Reaction Mechanism.
H
H
razo e
i
razo e
py
py
l
l
-
s
,
v
O
h
au omer sm
O
T
1 5 H hift
au omer sm
T
t
O
t
i
O
H
-1H-pyrazoles,
2-(6-phenyl-[1,2,4]triazolo[4,3-a]pyrimidin-7-yl)
H
ec roc c za on
El li ti
t
y
N
HN
HN
HN
N
H
N
phenol and 2-(5-(naphthalen-1-yl)pyrimidin-4-yl)phenol to
synthese 2H-phenanthro[9,10-c]Pyrazoles,[10] dibenzo[f,h][1,2,4]
triazolo[3,4-b]quinazolines,[21] and polybenzoquinazolines[22] via
N
N
B
A
1k
1k
H
H
H
-
-
e
neam ne
au omer sm
t
,
,
eneam ne
1 3
i
1 3
i
-
the
photocyclization
dehydration,
irradition
shows
of
high
O
O
O
T
au omer sm
O
T
t
i
,
i
v
h
H2
H
H
3-(2-hydroxyphenyl)-4-(2-aryl)pyrazoles
a
N
N
HN
N
N
H
N
H
N
H
N
H
chemoselectivity to afford dehydrogenation product 2H-benzo[g]
furo/thieno/pyrrolo[2,3-e]indazols-10-ol. The mechanism of
dehydrogenation photocyclization was the process of
6π-electroncyclization, [1,5]-hydrogen shift, pyrazole tautomerism,
1,3-eneamine tautomerism and release H2. A green-friendly
method for synthesis of fused indazoles containing heterocyclic
rings was provided.
a
3
E
C
D
Scheme 6 Mechanism Research Experiments.
S
hv
S
(1)
N
N
Experimental
N
N
Ph
Ph
General Information. Unless otherwise noted, all reagents
were purchased from commercial suppliers and used without
purification. Thin-layer chromatography (TLC) analysis was per-
formed using precoated glass plates. Silica gel was used for column
chromatography. 1H NMR spectra were recorded on 400 or 600
MHz spectrometer. Spectra were referenced internally to the re-
sidual proton resonance in CDCl3 (δ 7.26 ppm) or DMSO-d6 (δ 2.50
ppm). Chemical shifts (δ) were reported as part per million (ppm)
in δ scale downfield from TMS. 13C NMR spectra were recorded on
100 or 150 MHz spectrometer and the spectra were referenced to
CDCl3 (δ 77.16 ppm, the middle peak) or DMSO-d6 (δ 39.5 ppm,
the middle peak). Coupling constants (J) are reported in hertz (Hz).
High-resolution mass spectrometry (HRMS) was recorded with a
HRMS-ESI-Q-TOF. Melting points were measured with a mi-
cro-melting point apparatus and uncorrected. IR spectra were
recorded with a FT-IR spectrophotometer with KBr pellets. Hydro-
gen was detected by GC.
1v
3v
O
O
hv Ar, 5h
,
+
(2)
H2
HO
HO
N
N
N
H
N
H
1a
3a
On the basis of experimental results and previous work, [23, e]
a
plausible mechanism for the formation of 3a is proposed and
presented in Scheme 5. Irradiation of 1k with a high-pressure
mercury lamp give trans-6a,6b-dihydro-1H-benzo[g]furo[2,3-e]
indazole A via an intramolecular 6π-electron cyclization.[32] Fol-
lowed by the thermal suprafacial [1,5]-H shift[33] and the recovery
of the aromatic furan ring lead to the formation of intermediate
trans-3b,6a-dihydro-1H-benzo[g]furo[2,3-e]indazole B. Proceeding
the pyrazole tautomerism, trans-3b,6a-dihydro-2H-benzo
[g]furo[2,3-e]indazole C is produced. By the 1,3-eneamine tau-
tomerization, C is tautomerized trans-2,3-dihydro-1H-benzo[g]
furo[2,3-e]indazole D and by the 1,3-eneamine tautomerization of
D, cis-3b,6a-dihydro-2H-benzo[g]furo[2,3-e]indazole E is generat-
ed. Finally, E releases H2 to obtain 3a via the irradiation. This is
General Procedure
(2-heteroaryl)pyrazoles
A
for the Synthesis of 3-Phenyl-4-
(aryl=furanyl, thiophenyl and
N-methylpyrrolyl) 1a-1j.[27,28,34] Refer to the methods in the rele-
vant literatures: the mixture of o-hydroxyacetophenones (10 mmol)
and DMF-DMA (2 eq, 20 mmol) was dissolved in DMF (60 mL). The
reaction mixture was allowed to stir at 120 °C and refluxed for 2 –
4 h. the resulting mixture was poured into saturated salt solution
and then precipitate the solid. After filtration and evaporation of
the solvent. The rough solid (6 mmol) undergo cyclization reaction
with iodine (2 eq, 1.4 mmol) in trichloromethane solution (50
mmol). The products were purified via column chromatography on
silica gel (ethyl acetate/petroleum ether, 1:60) and obtained
3-iodiochromones in good yields (85–95%) (6) [SI Scheme S1 1)].
The mixture of 3-iodiochromones 6 (3 mmol), arylboronic acid
(3 eq, 9 mmol), Pd(PPh3)4 (5% mmol) and Cs2CO3 (5 eq, 15 mmol)
was dissolved in a mixed solvent composed of dioxane : H2O = 4:1
(20 ml : 5 ml). The reaction mixture was allowed to stir at 85 °C for
6 – 12 h under Ar. Then, the crude reaction mixture was poured
similar
to
our
previous
work
annulation
of
o-Phenylfuranylpyridines via photo-induced hydrogen evolution.
[23, e]
To validate the mechanism described above, a series of
experiments was designed and performed (Scheme 6). Subjection
of 1,3-diphenyl-4-(thiophen-2-yl)-1H-pyrazole 1v to the optimal
condition failed to provide dehydrogenative product 3v (Scheme 6,
Eq. 1), which indicated the presence of active hydrogen on
nitrogen and its tautomerism in the pyrazole ring 1v was critical.
H2 was successfully detected by Gas Chromatography (GC) during
the cyclization of 2-(4-(furan-2-yl)-1H-pyrazol-3-yl)phenol 1a. The
retention time of blank sample and standard H2 sample was 2.471
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Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
into water (30 mL) and extracted with EtOAc (3 × 20 mL). The vola-
tiles were removed under reduced pressure and the residue was
purified on silica gel column chromatography (ethyl acetate / pe-
troleum ether, 1:40) to give 3-heteroarylchromones (7) [SI Scheme
S1 2)].
A mixture of 3-iodiochromones 6 (2 mmol), pyrrole (8eq, 16
mmol), and 80mL CH3CN was placed in a 50-mL quartz tube, and
then the tube was irradiated for 5 h with a high-pressure mercury
lamp (500 W). The tube was cooled to room temperature with tap
water by means of an internal cold finger. The solvent was re-
moved under reduced pressure, and the residue was purified by
column chromatography on silica gel (ethyl acetate / petroleum
ether, 1:30) to give the corresponding product (8) [SI Scheme S1
3)].
30 min and the quartz tube was sealed by parafilm; it was
irradiated in
a BL-GHX-V photo-chemical reactor at room
temperature until reactant was consumed completely as indicated
by thin-layer chromatography (TLC). The solvent was removed
under reduced pressure, and the residue was purified by column
chromatography (ethyl acetate/petroleum ether = 1:30 ~ 1:5) to
get 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazols-10-ol
2 and
2H-benzo[g]furo/thieno/pyrrolo[2,3-e] indazoles 3.
Synthesis of 3s in 1 mmol Scale. 4-(Thiophen-2-yl)-3-(3
-(trifluoromethyl)phenyl)-1H-pyrazole 1s (294 mg, 1 mmol) was
added to EtOH/H2O (v/v=95/5) (200 mL, 5 mM). The solution was
contained in 200 mL quartz tube, degassed (ultrasound) for 30 min,
deaerated by bubbling argon for 30 min three times and the
quartz tube was sealed by parafilm, and irradiated in a BL-GHX-V
photo-chemical reactor at room temperature for 2 h, until 1s was
consumed completely as indicated by thin-layer chromatography
(TLC). The solvent was removed under reduced pressure, and the
residue was purified by column chromatography (ethyl acetate /
The mixture of 3-heteroarylchromones 7, 8 (1.4 mmol) and
hydrazine hydrate (2 eq, 2.8 mmol) was dissolved in EtOH (40 mL).
The reaction mixture was allowed to stir at 80 °C and refluxed for 2
–
4 h. All reactions were monitored by TLC until the
3-heteroarylchromones was fully consumed. After that the mix-
ture was poured into ice water (100 mL) and was adjusted to pH 6
– 7 with 10% HCl. The white formed precipitate was filtered and
purified via column chromatography on silica gel gave product
1a-1j in 70% – 95% [SI Scheme S2].
petroleum
ether,
1:15)
to
get
9-(trifluoromethyl)-
2H-benzo[g]thieno[2,3-e]indazole 3s (75%, 219 mg).
H2 Detection by GC.
Gas Chromatography Conditions
With nitrogen as carrier gas, thermal conductivity detector
(TCD temperature at 150 °C) and stainless steel column (column
length 2 m, column temperature at 40 °C, Tam TDS-01 60~80 mesh)
were used for gas chromatography analysis. Under conditions of
gas velocity of 0.06 Mpa and the flow rate of 70 mL/min, gas was
analyzed at room temperature with injection of 50 μL.
Experiment of Photoinduced dehydrogenative annulation of
1a
Solvent chromatographic ethanol (100 mL) and distilled water
(100 mL) were both degassed for 1 h to remove most of the dis-
solved oxygen by ultrasonic method. Then, sodium sulfite (16 g)
was added and the mixture was refluxed for 1 h under nitrogen
atmosphere for solvent deoxidization. To sample quartz tube, 57
mg (0.25 mmol) 1a and a magneton were added, and 50 mL deox-
idized EtOH/H2O (v/v=2/1) was injected into the quartz tube under
nitrogen atmosphere. The blank quartz tube was treated as the
same condition without 1a. The sample quartz tube and blank
quartz tube were irradiated at λ ≥ 300 nm with a high-pressure
mercury lamp (500 W) for 7 h. Gas in the tubes was detected
though Gas Chromatography.
General
Procedure
B
for
the
Synthesis
of
3-Phenyl-4-(2-furanyl/thiophenyl)pyrazoles 1k-1u.[29, 30] The syn-
thesized 3-phenylpyrazoles (5 mmol) and N-halosuccinimide (1.2
eq, 6 mmol) were dissolved in anhydrous dichloromethane (30
mL), the mixture was stirred at room temperature for 15 min to
give 4-iodo-3-phenyl-1H-pyrazoles. After extraction and evapora-
tion of the solvent, the rough solid (20 mmol) was dissolved in 30
mL THF and cooled to 0 °C under an argon atmosphere. NaH (1.5
eq, 30 mmol) was added slowly at 0 °C and the resulting mixture
was allowed to stir for 30 minutes, or until hydrogen evolution was
complete. SEMCl (1.05 eq, 21 mmol, 3.7 mL) was added slowly and
the reaction allowed to warm to room temperature and stirred for
an additional 12 hours. The reaction was quenched with 5 mL
deionized water, extracted with ether, washed with brine, dried
with MgSO4 and the solvent removed. After workup, the resulting
crude mixture was separated via column chromatography on silica
gel
gave
product
4-iodo-3-phenyl-1-((2-
(trimethylsilyl)ethoxy)methyl)-1H-pyrazole 9 [SI Scheme S3].
The mixture of 4-iodo-3-phenyl-1-((2-(trimethylsilyl)ethoxy)
methyl)-1H-pyrazole 9 (1.4 mmol), arylboronic acid (3 eq, 4.2
mmol), Pd(PPh3)4 (5% mmol) and Cs2CO3 (5 eq, 7 mmol) was
dissolved in a mixed solvent composed of dioxane : H2O = 4 : 1 (20
ml : 5 ml). The reaction mixture was allowed to stir at 85 °C for 6 –
12 h under Ar. Then, the mixture was poured into the water and
extracted with ethyl acetate (30 mL × 3). The combined organic
layers were dried over Na2SO4 and concentrated under reduced
pressure. The residue was dissolved in 95% ethanol (15 mL) and 3
N HCl (2 mL) was added refluxing for 3 hours. To quench, 10%
aqueous (byweight) NaOH (6 mL) solution was added until the
mixture was neutralized as measured with pH paper, and
deionized water (5 mL) and ethyl acetate (30 mL) was added. The
organic layer were removed under reduced pressure, and the res-
idue was purified by column chromatography (ethyl acetate / pe-
troleum ether, 1:25) to get 3-phenyl-4-(2-furanyl/thiophenyl)
pyrazoles 1k-1u [SI Scheme S4].
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2021xxxxx.
Acknowledgement
We are grateful for financial support by the National Natural
Science Foundation of China (No: 21672132).
References
(a) Liu, Z.; Chen, L.; Yu, P.; Zhang, Y.; Fang, B.; Wu, C.; Luo, W.; Chen, X.; Li,
C.; Liang, G. J. Discovery of 3‑(Indol-5-yl)-indazole Derivatives as Novel
Myeloid Differentiation Protein 2/Toll-like Receptor 4 Antagonists for
Treatment of Acute Lung Injury. Med. Chem. 2019, 62, 5453-5469; (b)
Baraldi, P. G.; Balbonic, G.; Pavani, M. G.; Spalluo, G.; Tabrizi, M. A.; Clercq,
E. D.; Balzarini, J.; Bando, T.; Sugiyama, H.; Romagnoli, R. Design, Synthesis,
DNA Binding, and Biological Evaluation of Water-Soluble Hybrid Molecules
Containing Two Pyrazole Analogues of the Alkylating Cyclopropylpyr-
roloindole (CPI) Subunit of the Antitumor Agent CC-1065 and Polypyrrole
Minor Groove Binders. J. Med. Chem. 2001, 44, 2536-2543.
General Procedure
[g]furo/thieno/pyrrolo[2,3-e]indazoles
[g]furo/thieno/pyrrolo[2,3-e]indazols-10-ol.
C for the Synthesis of 2H-Benzo
and
2a-2j,
2H-Benzo
3a-3t.
3-(2-Hydroxyphenyl)-4-(2-heteroaryl) pyrazoles (aryl=furanyl, thi-
ophenyl and N-methylpyrrolyl) 1a-1j (0.25 mmol) was added to
EtOH/H2O (v/v=2/1) (50 mL, 5 mM) and 3-phenyl-4-(2-aryl) pyra-
zoles 1k-1t (0.25 mmol) was added to EtOH/H2O (v/v=95/5) (50
mL, 5 mM). The solution was contained in a 100 mL quartz tube,
degassed (ultrasound) for 30 min, deaerated by bubbling argon for
(a) Luo, G.; Chen, L.; Easton, A.; Newton, A.; Bourin, C.; Shields, E.; Mosure,
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
www.cjc.wiley-vch.de

First author et al.
Report
K.; Soars, M. G.; Knox, R. J.; Matchett, M.; Pieschl, R. L.; Post-Munson, D. J.;
noivanov, V. A.; Shiff, A. I.; Borodkin, G. S., Photochemical Generation,
Photochromism and Photocyclization of 2-Norbornadenyl Substituted
Benzo-1,3-Oxazoles. Molecular. Crystals. and Liquid Crystals. 1997, 297,
233-237.
Reimlinger, H., Über die Reaktion von Diazofluoren mit Acetylen. Chem.
Ber. 1967, 100, 3097-3100.
Waghray, D.; Bagdziunas, G.; Jacobs, J.; Meervelt, L. V.; Grazulevicius, J. V.;
Dehaen, W., Diastereoselective Strategies towards Thia[n]helicenes. Chem.
Eur. J. 2015, 21, 18791-18798.
Barachevsky, V. A.; Valova, T. M.; Venidiktova, O. V.; Melekhina, V. G.;
Mityanov, V. S.; Traven, V. F.; Cheptsov, D. A.; Krayushkin, M. M. Photo-
chemical study of electrocyclization of 4-aryl-5-hetarylimidazolones for
information optical recording. Mend. Commu. 2020, 30, 328.
Paria, S.; Reiser, O., Visible Light Photoredox Catalyzed Cascade Cycliza-
tions of α-Bromochalcones or α-Bromocinnamates with Heteroarenes.
Adv. Synth. Catal. 2014, 356, 557-562.
Tsukamoto, T.; Dong, G., Catalytic Dehydrogenative Cyclization of
o-Teraryls under pH-Neutral and Oxidant-Free Conditions. Angew. Chem.
Int. Ed. 2020, 59, 1–6.
Xue, P.; Du, Z.; Wang, T.; Zhang, Z., Synthesis of Diben-
zo[f,h][1,2,4]triazolo[3,4-b]quinazolines via a Two-Step Route with Water
as the Only By-Product. Synthesis. 2015, 47, 3385–3391.
Wei, W.; Li, C.; Wang, T.; Liu, D.; Zhang, Z., Synthesis of polybenzo-
quinazolines via an intramolecular dehydration of photocyclization. Tet-
rahedron. 2016, 72, 5037-5046.
(a) Shi, J.; Kang, Y.; Wang, T.; Liang, Y.; Zhang, Z., Synthesis of Polycyclic
Heteroaromatic Coumarins via Photoinduced Dehydrogenative Annula-
tion of 4-Phenyl-3-heteroarylcoumarins. J. Org. Chem, 2018, 83,
13940-13948; (b) Zhang, J.; Zhang, X.; Wang, T.; Yao, X.; Wang, P.; Wang,
P.; Jing, S.; Liang, Y.; Zhang, Z., Oxidant and Transition-Metal-Free Pho-
Wang, S.; Herrington, J.; Graef, J.; Newberry, K.; Sivarao, D. V.; Senapati,
A.; Bristow, L. J.; Meanwell, N. A.; Thompson, L. A.; Dzierba, C. Discovery
of Indole- and Indazole-acylsulfonamides as Potent and Selective NaV1.7
Inhibitors for the Treatment of Pain. J. Med. Chem. 2019, 62, 831; (b) Li, X.;
Chu, S.; Feher, V. A.; Khalili, M.; Nie, Z.; Margosiak, S.; Nikulin, V.; Levin, J.;
Sprankle, K. G.; Tedder, M. E.; Almassy, R.; Appelt, K.; Yager, K. M., Struc-
ture-Based Design, Synthesis, and Antimicrobial Activity of Inda-
zole-Derived SAH/MTA Nucleosidase Inhibitors. J. Med. Chem. 2003, 46,
5663-5673.
(a) Liu, Z.; Chen, L.; Yu, P.; Zhang, Y.; Fang, B.; Wu, C.; Luo, W.; Chen, X.; Li,
C.; Liang, G. Discovery of 3-(Indol-5-yl)-indazole Derivatives as Novel My-
eloid Differentiation Protein 2/Toll-like Receptor 4 Antagonists for Treat-
ment of Acute Lung Injury. J. Med. Chem. 2019, 62, 5453; (b)Rosati, O.;
Curini, M.; Marcotullio, M. C.; Macchiarulo, A.; Perfumi, M.; Mattioli, L.;
Rismondo, F.; Cravotto, G., Synthesis, docking studies and an-
ti-inflammatory activity of 4,5,6,7-tetrahydro-2H-indazole derivatives.
Bioorg. Med. Chem. 2007, 15, 3463-3473.
Rodgers, J. D.; Johnson, B. L.; Wang, H.; Greenberg, R. A.; Erick-
son-Viitanen, S.; Klabe, R. M.; Cordova, B. C.; Rayner, M. M.; Lam, G. N.;
Chang, C.-H., Potent cyclic urea HIV protease inhibitors with benzofused
heterocycles as P2/P2′ groups. Bioorg. Med. Chem. Lett. 1996, 6,
2919-2924.
Suzuki, Y.; Oishi, S.; Takei, Y.; Yasue, M.; Misu, R.; Naoe, S.; Hou, Z.; Kure,
T.; Nakanishi, I.; Ohno, H.; Hirasawa, A.; Tsujimoto, G.; Fujii, N., Design and
synthesis of a novel class of CK2 inhibitors: application of copper- and
gold-catalysed cascade reactions for fused nitrogen heterocycles. Org.
Biomol. Chem. 2012, 10, 4907–4915.
Shimada, I.; Maeno, K.; Kazuta, K.-i.; Kubota, H.; Kimizuka, T.; Kimura, Y.;
Hatanaka, K.-i.; Naitou, Y.; Wanibuchi, F.; Sakamoto, S.; Tsukamoto, S.-i.,
Synthesis and structure–activity relationships of a series of substituted
2-(1H-furo[2,3-g]indazol-1-yl)ethylamine derivatives as 5-HT2C receptor
agonists. Bioorg. Med. Chem. 2008, 16, 1966–1982.
(a) Inamoto, K.; Katsuno, M.; Yoshino, T.; Arai, Y.; Hiroya, K.; Sakamoto, T.,
Synthesis of 3-substituted indazoles and benzoisoxazoles via Pd-catalyzed
cyclization reactions: application to the synthesis of nigellicine. Tetrahe-
dron. 2007, 63, 2695-2711; (b) Viña, D.; del Olmo, E.; López-Pérez, J. L.;
San Feliciano, A. Regioselective Synthesis of 1-Alkyl- or
toinduced
Direct
Oxidative
Annulation
of
1-Aryl-2-(furan/thiophen-2-yl)butane-1,3-diones. J. Org. Chem. 2017, 82,
12097-12105; (c) Kang, Y.; Wang, T.; Liang, Y.; Zhang, Y.; Wang, R.; Zhang,
Z., Annulation of 2,3-diphenyl-4H-chromen-4-ones via photo-induced hy-
drogen evolution. RSC. Adv, 2017, 7, 44333-44339; (d) Han, J.; Wang, T.;
Liang, Y.; Li, Y.; Li, C.; Wang, R.; Feng, S.; Zhang, Z., Transition-Metal-Free
Photoinduced Intramolecular Annulation of 2,3-Di(hetero)arylchromen
-4-one. Org. Lett. 2017, 19, 3552−3555; (e) Fan, J.; Zhang, W.; Gao, W.;
Wang, T.; Duan, W.-L.; Liang, Y.; Zhang, Z., Syntheses of Benzofuranoquin-
olines and Analogues via Photoinduced Acceptorless Dehydrogenative
Annulation of o-Phenylfuranylpyridines. Org. Lett. 2019, 21, 9183−9187.
Batra, A.; Singh K. N. Recent Developments in Transition Metal-Free
Cross-Dehydrogenative Coupling Reactions for C–C Bond Formation.
Eur. J. Org. Chem. 2020, 43, 6676–6703.
1-Aryl-1H-indazoles
via
Copper-Catalyzed
Cyclizations
of
2-Haloarylcarbonylic Compounds. Org. Lett. 2007, 9, 525-528; (c) O’Dell, D.
K.; Nicholas, K. M., Synthesis of 1H-Indazoles by Reductive Cyclization of
o-Nitro-ketoximes. Heterocycles. 2004, 63, 373-382.
Demetriadou, K. P.; Koutentis, A. P., 3,4,5,6,7,8,9-Heptachlorophenaleno
[1,9-bc]pyrazole. Molbank. 2009, 2009, M625.
Vasin, V. A.; Popkova, Y. A.; Bezrukova, Y. V.; Razin, V. V.; Somov, N. V.,
Thermal Rearrangements of 3H- and 4H-Pyrazoles Prepared by Reactions
of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate.
Russ. J. Org. Chem. 2018, 54, 1189-1199.
Wang, Q.; Zhang, Z.; Du, Z.; Hua, H.; Chen, S., One-pot synthesis of
2H-phenanthro[9,10-c]pyrazoles from isoflavones by two dehydration
processes. Green. Chem., 2013, 15, 1048-1054.
a) Ravelli, D.; Protti, S.; Fagnoni M., Carbon−Carbon Bond Forming Reac-
tions via Photogenerated Intermediates. Chem. Rev. 2016, 116,
9850−9913; b) Liu W.; Li J.; Querard P.; Li C-J., Transition-Metal-Free C−C,
C−O, and C−N Cross-Couplings Enabled by Light. J. Am. Chem. Soc. 2019,
141, 6755−6764.
Bosque, I.; Chinchilla, R.; Gonzalez-Gomez, J. C.; Guijarro, D.; Alonso,
F. Cross-dehydrogenative coupling involving benzylic and allylic C–H
bonds. Org. Chem. Front. 2020, 7, 1717–1742.
Li, Y.; Zhang, J.; Li, D.; Chen Y., Metal-Free C(sp3)−H Allylation via Aryl
Carboxyl Radicals Enabled by Donor−Acceptor Complex. Org. Lett. 2018,
20, 3296−3299.
Biegasiewicz, K. F.; Gordon, J. S.; Rodriguez, D. A.; Priefer, R., Develop-
ment of a general approach to the synthesis of a library of isoflavonoid
derivatives. Tetrahedron Lett. 2014, 55, 5210–5212.
Xie, F.; Cheng, G.; Hu, Y., Three-Component, One-Pot Reaction for the
Combinatorial Synthesis of 1,3,4-Substituted Pyrazoles. J. Comb. Chem.
2006, 8, 286-288.
Grzybowski, M.; Skonieczny, K.; ButenschÖn, H.; Gryko, D. T., Comparison
of Oxidative Aromatic Coupling and the Scholl Reaction. Angew. Chem. Int.
Ed. 2013, 52, 9900-9930.
Shankaraiah, K.; Chandrasekhar, G.; Siva Nagi Reddy, K.; Sabitha, G., First
examples of 2,6-diarylnicotinaldehydes prepared under conventional and
microwave conditions. Tetrahedron. Lett. 2015, 56, 842-846.
Xiao, T.; Li, L.; Xie, Y.; Mao, Z.-W.; Zhou, L., Synthesis of Gem-Difluorinated
Fused Quinolines via Visible Light-Mediated Cascade Radical Cyclization.
Org. Lett. 2016, 18, 1004-1007.
Nayak, M. K.; Wan, P., Direct and water-mediated excited state intramo-
lecular proton transfer (ESIPT) from phenol OH to carbon atoms of ex-
tended ortho-substituted biaryl systems. Photochem. Photobiol. Sci. 2008,
7, 1544-1554.
Goikhman, R.; Jacques, T. L.; Sames, D., C−H Bonds as Ubiquitous Func-
tionality: A General Approach to Complex Arylated Pyrazoles via Sequen-
tial Regioselective C-Arylation and N-Alkylation Enabled by SEM-Group
Transposition. J. Am. Chem. Soc. 2009, 131, 3042–3048.
(a) Zhang, Z.-T.; Tan, D.-J.; Xue. D., A Concise One-Pot Synthesis of
3,4-Diaryl-1H-pyrazoles from Natural Isoflavones and Hydrazine Hydrate.
Helv. Chim. Acta. 2007, 90, 2096-2108; (b) Shironina, T. M.; Igidov, N. M.;
Koz'minykh, E. N.; Kon'shina, L. O.; Kasatkina, Y. S.; Koz'minykh, V. O.,
Ivakhnenko, E. P.; Makarova, N. I.; Knyazhansky, M. I.; Bren, V. A.; Cher-
www.cjc.wiley-vch.de
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
1,3,4,6-Tetracarbonyl
Compounds:
IV.
Reaction
of
tent dihydrophenanthrenes and their [1,5] H-shift isomers. Chem. Sci.
2018, 9, 3844−3855.
Zhang, J.; Tan, D.-J.; Wang, T.; Jing, S.-S.; Kang, Y.; Zhang, Z.-T., Synthesis,
crystal structure, characterization and antifungal activity of
3,4-diaryl-1H-Pyrazoles derivatives. J. Mol. Struct. 2017, 1149, 235-242.
3,4-Dihydroxy-2,4-hexadiene-1,6-diones with Hydrazine and Arylhydra-
zines. Russ. J. Org. Chem. 2001, 37, 1486-1494; (c) Shestopalov, A. M.;
Emeliyanova, Y. M.; Shestopalov, A. A.; Rodinovskaya, L. A.; Niazimbetova,
Z. I.; Evans, D. H., One-Step Synthesis of Substituted
6-Amino-5-cyanospiro-4-(piperidine-4‘)-2H,4H-dihydropyrazolo[3,4-b]pyra
ns. Org. Lett. 2002, 4, 423-425.
(The following will be filled in by the editorial staff)
Irie, M.; Fukaminato, T.; Matsuda, K.; Kobatake, S., Photochromism of Di-
arylethene Molecules and Crystals: Memories, Switches, and Actuators.
Chem. Rev. 2014, 114, 12174-12277.
Shi, Y.-g.; Mellerup, S. K.; Yuan, K.; Hu, G.-F.; Sauriol, F.; Peng, T.; Wang, N.;
Chen, P.; Wang, S. Stabilising fleeting intermediates of stilbene photocy-
clization with amino-borane functionalisation: the rare isolation of persis-
Manuscript received: XXXX, 2021
Manuscript revised: XXXX, 2021
Manuscript accepted: XXXX, 2021
Accepted manuscript online: XXXX, 2021
Version of record online: XXXX, 2021
Chin. J. Chem. 2021, 39, XXX－XXX
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Entry for the Table of Contents
Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles via Intramolecular Dehydrogenation Photocyclization
Wei Zhang, Ping Wang, Xi Zhang, Rui Wang,Tao Wang, Zhicun Liu,* Zunting Zhang*
Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
R1
R2
R1
R3
R2
R1
R2
R2
R1
R4
R4
R4
R4
v,
h
Ar
v,
h
Ar
X
X
X
X
+
HO
95%EtOH
=H
EtOH-H O
2
(2:1)
N
N
N
N
R3
R3=OH
N
N
N
N
H
H
H
H
by-product
major product
=
=
=
CN, CF R3=H, OH; R4
X=
NMe; R
and
OMe, CF
R
Me.
;
;
3
O, S,
acid-
H,
F,
H, F,
H,
chemo-selectivity.
high
1
3
2
base-free; environmental-friendly method;
catalyst-,
A catalyst-, acid- and base-free, environmental-friendly method for the synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles derivatives via
irradiation of 3-phenyl-4-(2-heteroaryl)pyrazoles in EtOH/H2O with UV light at room temperature under argon atmosphere was described. Irradiation
of 3-(2-hydroxyphenyl)-4-(2-heteroaryl)pyrazoles showed
thieno/pyrrolo[2,3-e]indazols-10-ol.
a high chemo-selectivity to obtain dehydrogenation product 2H-benzo[g]furo/
www.cjc.wiley-vch.de
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
Chin. J. Chem. 2021, 39, XXX－XXX