Iron(III) chloride-promoted cyclization of α,-alkynic tosylhydrazones with diselenides: Synthesis of 4-(arylselanyl)-1: H-pyrazoles

Article abstract of DOI:10.1039/d0ob00048e

A highly efficient iron(iii) chloride-promoted cyclization between α,-alkynic tosylhydrazones and diselenides to form a 4-(arylselanyl)-1H-pyrazole skeleton is studied. This reaction forms C-N and C-Se bonds in one step by utilizing inexpensive iron(iii) chloride instead of expensive transition metal additives. This strategy features easily synthesized substrates, mild reaction conditions and high tolerance to functional groups.

Full text of DOI:10.1039/d0ob00048e

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DOI: 10.1039/D0OB00048E
Organic &
Biomolecular Chemistry
ARTICLE
Iron(Ⅲ) chloride-promoted cyclization of α,β-alkynic
tosylhydrazones with diselenides: Synthesis of 4-(arylselanyl)-
1H-pyrazoles
Hai-Feng Yao,a Fang-Hui Li,a Jian Li,a Shun-Yi Wang*a and Shun-Jun Ji*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
A highly efficient Iron (III) chloride-promoted cyclization between α,β-alkynic tosylhydrazones and diselenides to form a 4-
(arylselanyl)-1H-pyrazole skeleton is studied. This reaction constructs C-N, C-Se in one step utlization of unexpensive Iron
(III) chloride instead of expensive transition metal additives. This strategy features easily synthesized substrates, mild
reaction conditions and shows high tolerance to functional groups..
R2
R2
N
a)
Introduction
NHTs
[Pd], [Cu] etc
base, solvent,
N
R1
R1
Pyrazole-containing compounds are important components
of the family of heteroaromatic molecules, widely introduced
into drug skeletons,1 and also often used as ligands in transition
metal catalyzed cross-coupling reactions.2 The synthesis of
pyrazole skeleton has been thoroughly studied for its significant
importance. It could be obtained by the dehydration
condensation reaction between 1,3-dicarbonyl compounds and
hydrazones.3 However, strict restrictions on the structures of the
substrates limits its application.4 Sakamoto’s group and
N
X
Ts
X = Br, Cl, ONf
R2 = ester, amide, aryl, alkyl
Ts
b)
[Ru(bpy)3]Cl2 6H2O (2 mol%)
NaOH (1.5 equiv)
NHTs
N
N
N
blue LEDs (450-460 nm)
CHCl3, rt
H
R
R
H
c)
d)
N
N2
Ar2
O
N
1) TsNHNH2
2) Base
Ar2
Ar1
H
Ar1
H
Ar1
Ts
Venkateswarlu’s group reported
a
palladium catalyzed
intramolecular C-N bond formation reaction of 2-bromoaryl N-
tosylhydrazones to construct benzopyrazole skeleton with
various substituents successfully (Figure 1, a).5a, 5b The following
study showed that direct C-H activation could also furnish the
same structure.6 Xiao’s group turned β, γ-unsaturated N-
tosylhydrazones into pyrazoline products with the assistance of
photosensitive catalysts (Figure 1, b).7 Further exploration done
and more complex products were achieved.8 The main drawback
of these methods is the use of the expensive transition metal
catalysts. In 2003, Aggarwal found that N-tosylhydrazones were
fantastic diazo precursors, in the [3+2] cycloadditions with
terminal alkynes (Figure 1, c),9 which generated pyrazoles
efficiently. After that, this type of 1,3-dipolar cycloaddition
received more attention.10 In 2015, our group used isocyanides
and N-tosylhydrazones as substrates in the presence of NIS and
CHP to construct pyrazoles via [4+1] cycloaddition (Figure 1,
d).11 Taking I2 as the catalyst and TBHP as the oxidant can
completes the same conversion.12
NIS (4 mol%)
CHP (1.0 equiv)
NHTs
N
N
N
+
C
N
R
NH
R
1,4-dioxane
Ar
Me
Ar
100 o
C
Figure 1. construction of pyrazole/pyrazoline skeleton via N-tosylhydrazones
Furthermore, organoselenium compounds has raised
continuous attention for its applications in synthetic chemistry13
and potential biopharmacological activities.14 Wu’s group
reported a number of multi-component reactions to construct C-
Se bonds that selenium powder participated (Figure 2, a).15
Zhao’s group,16 Zeni’s group17 and our team18 made great
progress, either. KSeCN (Figure 2, b)19, selenosulfonates (Figure
2, c)20 also can be applied as selenolation reagents. Moreover,
diselenides has been found to be excellent synthons for building
C-Se bonds. The main methods for synthesizing selenium-
containing frameworks can be attributed to transition metal
catalysis (Figure 2, d),21 Lewis acid promotion,22 addition of
photosensitive catalyst and so on.23
aKey Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry,
Chemical Engineering and Materials Science & Collaborative Innovation Centre of
Suzhou Nano Science and Technology.Soochow University.
bAnalysis and Testing Center; Soochow University.
Suzhou, 215123, People’s Republic of China. E-mail: shunyi@suda.edu.cn;
shunjun@suda.edu.cn; Fax: (+)86 512 65880307
Electronic Supplementary Information (ESI) available: See DOI: 10.1039/x0xx00000
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Journal Name
a)
was performed under oxygen atmosphere, 3aa was obtained in 80%
DOI: 10.1039/D0OB00048E
yield. Therefore, the optimal conditions were confirmed as
follow: 1a (0.2 mmol, 1 equiv) and 2a (0.4 mmol, 2 equiv), in
the presence of FeCl3 (0.4 mmol, 2 equiv), in DCE (4 mL) at
room temperature for 12 hours.
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Se
I
[Cu]
Se
+
+
N
N
H
H
b)
O
O
X
O
Se
KSeCN
CuI, DMF
!40 o
R1
R2
R2
+
O
Table 1. Optimizations of the reaction conditionsa
C
X = Br, I
c)
PhSe
Ph
Ph
NNHTs
FeCl3
FG
FG
O
S
+
PhSeSePh
Ph
N
solvent
R
+
FG
X
X
Ni
N
H
Ph
27 o
C
H
H
Ph
FG
O
Br
R
1a
2a
3aa
X = S or Se
R2
R2
d)
R3
R3
Entry
1
Solvent
2a/equiv FeCl3/equiv Time/h
Yield%b
86
PhSeSePh, [Rh]/[Ag]
inert atmosphere
N
N
N
SePh
N
DCM
DCE
2
2
2
2
8
8
R1
2
87
R1
3
MeCN
2
2
8
43
e) This work
4
Toluene
MeNO2
C2H5OH
DMF
Dioxane
THF
2
2
8
77
R2
N
NHTs
R2
R3Se
R1
N
5
2
2
8
53
FeCl3
solvent, rt.
R3SeSeR3
+
6
2
2
8
trace
trace
trace
trace
trace
89
N
R1
H
7
2
2
8
R3 = aryl, alkyl
R1 = aryl, alkyl
R2 = aryl
conduct C-N, C-Se
in one step
8
2
2
8
9
2
2
8
Figure 2. Construction of C-Se bond via various selenium-containing reagents.
10
11
12
13
14
15
16
17
18c
19d
20e
DMA
DCE
2
2
8
2
2
12
12
12
12
12
12
12
12
12
12
To the best of our knowledge, few synthetic methods have
been reported for constructing compounds containing both
pyrazole and selenoether skeletons. Herein, we reported the
efficient synthesis of selenopyrazole through FeCl3 promoted
reaction of α,β-alkynic tosylhydrazones and diselenides under
mild conditions (Figure 2, e). The reaction features
chemoselectivity and excellent functional group tolerance.
DCE
2
1
58
DCE
2
0.5
0.2
2
34
DCE
2
22
DCE
1.5
1.0
0.5
2
84
DCE
2
73
DCE
2
69
DCE
2
N.R.
N.R.
80
DCE
2
2
Results and discussion
DCE
2
2
aAll reactions were performed with 1a (0.2 mmol, 1 equiv), 2a (X equiv), FeCl3 (Y
We started our research by the reaction of (1,3-diphenylprop-2-
yn-1-ylidene)-4-methylbenzenesulfonohydrazide (1a) and 1,2- equiv) in solvent (4 mL) at room temperature unless otherwise mentioned. bIsolated
yields. cCuCl2.2H2O (0.4 mmol, 2 equiv) instead of FeCl3 (0.4 mmol, 2 equiv).
diphenyldiselane (2a) at room temperature in the presence of
FeCl3. When the reaction was performed with 1a (0.2 mmol), 2a
(0.4 mmol), FeCl3 (0.4 mmol) at room temperature for 8 hours
in DCM, DCE and toluene, the desired selenopyrazole 3aa was
observed in 86%, 87% and 77% yields, respectively (Table 1,
e
dCu(OAc)2.H2O (0.4 mmol, 2 equiv) instead of FeCl3 (0.4 mmol, 2 equiv). The
reaction was performed under oxygen atmosphere.
1
entries 1, 2 and 4). The structure of 3aa was confirmed by H
NMR, 13C NMR, IR spectroscopy, and X-single crystal
diffraction (Figure 3). When using acetonitrile and nitromethane
as solvents, 3aa was obtained in moderate yields (Table 1, entries
3 and 5). However, the reaction was quite inert when performed
in polar solvents such as ethanol, DMF, 1,4-dioxane, THF and
DMA (Table 1, entries 6-10). We then chosed DCE as the
reaction solvent, and extended the reaction time to 12 hours. The
yield further increased to 89% (Table 1, entry 11). Reduction in
the amount of FeCl3 (Table 1, entries 12-14) or 1,2-
diphenyldiselane (2a) significantly lowered the reaction
efficiency (Table 1, entries 15-17). Finally, we examined the
effect of copper salts as the additives. It should be noted that both
CuCl2.2H2O and Cu(OAc)2.H2O showed no activity for the
reaction (Table 1, entries 18-19). When the reaction of 1a and 2a
Figure 3. single crystal structure of 3aa
With the optimal reaction conditions evaluated, we investigated
the scope of α,β-alkynic tosylhydrazones and the results were
summarized in Table 2. When R1 was a substituted aryl ring,
2 | J. Name., 2012, 00, 1-3
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3 Se
R
Ph
View Article Online
NHTs
whether electron-donating groups or weak electron-withdrawing
groups, the reaction proceeded well with exceptional yields of
desired products 3ba-3ea in 84% to 89% yields. When the para
position of the benzene ring was -NO2, the yield of 3fa was
slightly lower to 68% for the strong electron-withdrawing effect.
When R1 was an alkyl substituents, products could be generated
in a good to excellent yield (Table 2, 3ga-3ja). It should be noted
that the reaction of N'-(4,4-dimethyl-1-phenylpent-2-yn-1-
ylidene)-4-methylbenzenesulfonohydrazide 1h with 2a afforded
the desired product 3ha in up to 96% yields. The reaction of 4-
methyl-N'-(1-phenyl-3-(thiophen-2-yl)prop-2-yn-1-
ylidene)benzenesulfonohydrazide 1k with 2a could also give the
desired product 3ka in 74% yield. Unfortunately, 3-pyridine
substituted sulfonohydrazide 1l failed to generate the
corresponding product 3la. Next, R2 substituents’s influence on
the reaction was explored. The electron effect of R2 seemed to
only have a negligible effect on the efficiency of the reaction.
3ma-3oa were observed in 78% to 86% yields. However, 2-furan
substituted substrate only led to a yield of 33% of the product
3pa.
N
FeCl3
R3SeSeR3
DOI: 10.1039/D0OB00048E
+
N
Ph
Ph
DCE, rt
N
H
Ph
1a
2
3
O2N
Se
Ph
H3CO
Se
Ph
Se
Ph
N
Ph
N
N
Ph
3ad
N
N
Ph
3ab
H
N
H
H
3ac
, 86%
, 54%
, 79%
Se
Ph
Se
Ph
NC
Se
Ph
N
N
Ph
N
N
H
Ph
N
Ph
3ag
H
N
H
3ae
3af
, 34%
52%
, 60%
Reaction conditions: aAll reactions were performed with 1a (0.5 mmol), 2 (1.0
mmol), FeCl3 (1.0 mmol) in DCE (4 mL) at room temperature under air for 12 h
unless otherwise mentioned. bIsolated yields.
In order to explore potential applications in synthetic
organic chemistry, we carried out the reaction of 1a and 2a in
gram-scale under the standard conditions. The reaction
underwent smoothly to give 3aa in 89% yield without the
sacrifice of reaction efficiency (Scheme 1).
Table 2. Substrate scope of α,β-alkynic tosylhydrazones 1a,b
NHTs
R2
PhSe
R1
R2
N
FeCl3
DCE, 27 o
+
PhSeSePh
N
C
N
H
3
R1
NHTs
Ph
Se
Ph
Ph
Ph
3aa, 0.8348 g
1
2a
N
standard conditions
+
PhSeSePh
N
PhSe
Ph
PhSe
Ph
Ph
Ph
PhSe
Ph
Ph
PhSe
Ph
N
H
F
Ph
N
N
N
N
N
N
N
N
1a
2a
(2.5 mmol)
H
H
H3CO
H
H
Cl
Scheme 1. Scale up synthesis of 3aa.
3ba,
3ca,
3da,
3ea,
89%
88%
Ph
89%
84%
PhSe
PhSe
PhSe
PhSe
Ph
N
N
N
N
Several control experiments were carried out to gain a
thorough understanding about the pathway of the reaction. 1.1
Equivalents of phenylseleno chloride was added to the reaction
mixture under standard conditions, instead of original diphenyl
diselenide. 3aa was observed in 85% yield (Scheme 2, a).
Interestingly, none of 3aa was obtained in the absence of FeCl3
(Scheme 2, b). These results indicated that the reaction may not
be driven by only selenium species, synergistic effect of diphenyl
diselenide and FeCl3 are essential for the reaction to generate
products efficiently. When radical scavenger BHT was added to
the system, 3aa could still be produced smoothly. Even when
BHT increased to four equivalents, 3aa could also be isolated in
64% yield (Scheme 2, c). This experiment ruled out the
possibility that the reaction might not undergo a radical pathway.
N
N
H
N
H
N
H
O2N
H
3fa,
3ga,
3ha,
3ia,
68%
77%
96%
91%
PhSe
Ph
PhSe
Ph
PhSe
N
N
N
N
H
N
H
N
H
S
N
3ja,
3ka,
3la,
0%
59%
74%
CH3
CF3
OCH3
PhSe
Ph
O
PhSe
PhSe
PhSe
Ph
N
N
N
N
N
Ph
Ph
N
H
N
H
N
H
H
3ma
3na
3oa
3pa
, 33%
, 78%
, 82%
, 86%
Reaction conditions: aAll reactions were performed with 1 (0.5 mmol), 2a (1.0
mmol), FeCl3 (1.0 mmol) in DCE (4 mL) at room temperature under air for 12 h
unless otherwise mentioned. bIsolated yields.
Subsequently, we investigated reactions of different diselenides
with 1a. Generally, the results of diaryl diselenides were better than
dialkyl diselenides to give the desired products. When diaryl diselenyl
ethers used as substrates, 3ab-3ae were achieved in moderate to good
yields. It should be noted that the reaction of dialkyl diselenyl
diselenides 1,2-dibutyldiselane 2f and 1,2-dioctyldiselane 2g with 1a
led to 3af and 3ag in 34% and 60% yields, respectively.
Table 3. Substrate scope of diselenyl sthers 2a,b
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J. Name., 2013, 00, 1-3 | 3
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KBr optics. 1H NMR and 13C NMR spectra were recorded on a
PhSe
Ph
Ph
a)
View Article Online
NHTs
Ph
1
13
N
FeCl3 (2 equiv)
DOI: 10.1039/D0OB00048E
400 MHz ( H NMR) and 100 MHz ( C NMR) spectrometer
Se
Cl
N
+
Ph
N
1
DCE (4 mL)
27 oC, 12 h
using CDCl3 as solvent and TMS as internal standard. The H
H
Ph
NMR data are reported as the chemical shift in parts per million,
multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; m,
multiplet), coupling constant in hertz, and number of protons.
High resolution mass spectra were obtained using a high
resolution ESI-TOF mass spectrometer and high resolution CI-
TOF mass spectrometer. α,β-alkynic tosylhydrazones,25a, 25b, 25c
and diselenides 26a, 26b were prepared by literature methods.
1a
3aa
, 85%
(0.5 mmol)
1.1 equiv
b)
NHTs
N
Se
Ph
Cl
N.R.
+
+
DCE (4 mL)
27 oC, 12 h
Ph
Ph
1.1 equiv
1a
(0.5 mmol)
c)
PhSe
Ph
Ph
NHTs
N
General procedure for the synthesis of products 3 To a
solution of α,β-alkynic tosylhydrazones 1 (0.5 mmol, 1 equiv),
diselenides 2 (1 mmol, 2 equiv) in DCE (4 mL) was added FeCl3
(1 mmol, 2 equiv). The reaction system was stirred at room
temperature under air for 12 hours. After the reaction completed,
the mixture was diluted with ethyl acetate (30 mL) and washed
with water (10 mL ×2), and dried over anhydrous Na2SO4. The
solvents were removed under reduced pressure and the crude
reaction mixture was purified by silica gel column
BHT (4 equiv)
N
PhSeSePh
N
standard conditions
Ph
H
Ph
1a
2a
3aa
, 64%
(0.5 mmol)
Scheme 2. Investigation of the reaction mechanism
Based on our experimental results and related literatures,24
we proposed a plausible mechanism in Scheme 3. First, diphenyl
diselenide 2a is intramolecularly activated by the synergistic
effect of FeCl3 to give the intermediate I. The electrophilic
selenium atom coordinates with alkyne bond of 1a to form the
intermediate onium ion ⅠI, which subsequently isomerizes
from E-form ⅠI to Z-form III. Electron-rich nitrogen atom of
III undergoes intramolecular cyclizaiton to give the intermediate
IV and release of FeCl3 and selenium anion. De-tosylation of IV
furnishes 3aa.
chromatography with petroleum ether/ethyl acetate (VPE : VEA
3 : 1) as an eluent to give the desired product.
=
3,5-diphenyl-4-(phenylselanyl)-1H-pyrazole (3aa) : White solid.
Yield 89% (166.9 mg). IR ν = 1576, 1477, 955, 739, 690 cm-1.
1H NMR (400 MHz, CDCl3) δ 12.74 (s, 1H), 7.56 (d, J = 7.2 Hz,
4H), 7.28 (t, J = 7.3 Hz, 2H), 7.21 (t, J = 7.4 Hz, 4H), 7.08 (s,
5H). 13C NMR (100 MHz, CDCl3) δ 134.4, 129.4 , 128.7 , 128.5,
128.4, 127.0, 125.8, 97.0 ppm. HRMS m/z: calcd for C21H16N2Se
[M+H]+ 377.0551, found: 377.0551.
3-phenyl-4-(phenylselanyl)-5-(4-propylphenyl)-1H-pyrazole
(3ba) : White solid. Yield 88% (184.0 mg). IR ν = 2955, 2925,
2868, 1577, 1475, 1437, 966, 730, 689 cm-1. 1H NMR (400 MHz,
CDCl3) δ 12.27 (s, 1H), 7.49 (d, J = 7.4 Hz, 2H), 7.44 (d, J = 8.0
Hz, 2H), 7.21 (t, J = 7.3 Hz, 1H), 7.11 (t, J = 7.5 Hz, 2H), 7.04
(d, J = 8.1 Hz, 5H), 6.96 (d, J = 7.9 Hz, 2H), 2.50 (t, J = 7.6 Hz,
2H), 1.57 (h, J = 7.3 Hz, 2H), 0.89 (t, J = 7.3 Hz, 3H). 13C NMR
(100 MHz, CDCl3) δ 143.2, 134.6, 131.2, 129.3, 128.5, 128.4,
128.3, 128.2, 127.7, 125.6, 96.5, 37.9, 24.4 , 14.0 ppm. HRMS
m/z: calcd for C24H22N2Se [M+Na]+ 441.0840 ， found:
441.0815.
5-(4-methoxyphenyl)-3-phenyl-4-(phenylselanyl)-1H-
pyrazole (3ca) : White solid. Yield 89% (180.8 mg). IR ν = 1610,
1575, 1500, 956, 732, 692 cm-1. 1H NMR (400 MHz, CDCl3) δ
11.73 (s, 1H), 7.67 (s, 2H), 7.58 (d, J = 7.6 Hz, 2H), 7.32 (s, 3H), 7.17
– 7.09 (m, 5H), 6.82 (d, J = 8.3 Hz, 2H), 3.78 (s, 3H). 13C NMR (100
MHz, CDCl3) δ 160.2, 134.4, 129.7, 129.4, 128.7, 128.5, 128.4, 128.1,
125.8, 114.0, 55.4 ppm. HRMS m/z: calcd for C22H18N2OSe [M+Na]+
429.0477， found: 429.0477.
FeCl3
NHTs
N
Ph
PhSe
Ph
Ph
1a
PhSeSePh
Ph
Ts
H
NHTs
Ph
N
-Ts
2a
N
N
N
Ph
N
H
Ph
3aa
SePh
Ph
IV
Se Ph
Ph Se
FeCl3
l
TsHN
Se
N
FeCl3, PhSe
Ph
Ph
NHTs
Ph
N
PhSe
FeCl3
Ph
Ph
FeCl3
lI
lII
Ph
Se
PhSe
5-(3-fluorophenyl)-3-phenyl-4-(phenylselanyl)-1H-pyrazole
(3da) : White solid. Yield 84% (165.9 mg). IR ν = 1575, 1461, 1222,
Scheme 3. A plausible reaction mechanism
1
965, 733, 683 cm-1. H NMR (400 MHz, CDCl3) δ 12.81 (s, 1H),
7.56 (d, J = 6.9 Hz, 2H), 7.37 (dd, J = 16.1, 8.8 Hz, 2H), 7.32 – 7.23
(m, 3H), 7.19 – 7.14 (m, 1H), 7.10 (s, 5H), 6.96 (t, J = 8.4 Hz, 1H).
13C NMR (100 MHz, CDCl3) δ 163.8, 161.4, 133.8, 120.0, 129.9,
129.5, 129.1, 128.6, 128.3, 128.1, 126.0, 124.0, 115.7, 115.4, 115.2,
97.6 ppm. HRMS m/z: calcd for C21H15FN2Se [M+H]+ 395.0457,
found: 395.0460.
Experimental
General information
All the solvents for routine isolation of products and
chromatography were reagent grade. Flash chromatography was
performed using silica gel (200-300 mesh) with the indicated
solvents. IR spectra were recorded on a spectrophotometer using
19F NMR (376 MHz, CDCl3) δ = -112.55 ppm (s, 1F).
5-(4-chlorophenyl)-3-phenyl-4-(phenylselanyl)-1H-pyrazole (3ea):
White solid. Yield 84% (181.9 mg). IR ν = 1575, 1475, 956, 831, 731,
1
668 cm-1. H NMR (400 MHz, CDCl3) δ 13.03 (s, 1H), 7.52 (d, J =
4 | J. Name., 2012, 00, 1-3
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7.4 Hz, 2H), 7.45 (d, J = 8.3 Hz, 2H), 7.31 (t, J = 7.3 Hz, 1H), 7.24 (t, 128.5, 123.9, 115.1, 98.4, 55.4 ppm. HRMS mV/zie:w AcraticlcledOnflioner
+
J = 7.5 Hz, 2H), 7.17 – 7.03 (m, 7H). 13C NMR (100 MHz, CDCl3) δ C22H18N2OSe [M+Na] 429.0477, found: 429.0478.
DOI: 10.1039/D0OB00048E
134.8, 134.0, 129.6, 129.5, 129.1, 128.6, 128.3, 128.0, 126.0, 97.4 5-phenyl-4-(phenylselanyl)-3-(p-tolyl)-1H-pyrazole (3na) : White
ppm. HRMS m/z: calcd for C21H15ClN2Se [M+H]+ 411.0162, found: solid. Yield 82% (159.2 mg). IR ν = 2800, 1576, 1475, 956, 735, 690
411.0168.
cm-1. 1H NMR (400 MHz, CDCl3) δ 9.65 (s, 1H), 7.62 (d, J = 7.6 Hz,
5-(4-nitrophenyl)-3-phenyl-4-(phenylselanyl)-1H-pyrazole (3fa): 2H), 7.49 (d, J = 7.8 Hz, 2H), 7.30 – 7.23 (m, 3H), 7.13 – 7.05 (m,
Yellow solid. Yield 68% (142.9 mg). IR ν = 1517, 1420, 1340, 852, 7H), 2.32 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 138.8, 134.5, 129.4,
717, 667 cm-1. 1H NMR (400 MHz, CDCl3) δ 12.06 (s, 1H), 8.06 (d, 129.3, 128.7, 128.4, 128.3, 128.2, 128.0, 125.7, 97.0, 21.5 ppm.
J = 8.8 Hz, 2H), 7.89 (d, J = 8.7 Hz, 2H), 7.55 (d, J = 6.9 Hz, 2H), HRMS m/z: calcd for C22H18N2Se [M+H]+ 391.0708, found:
7.33 (dq, J = 14.3, 7.1 Hz, 3H), 7.17 – 7.07 (m, 5H). 13C NMR (100 391.0704.
MHz, CDCl3) δ 147.6, 138.5, 133.2, 129.6, 129.0 , 128.8, 128.3, 128.2, 5-phenyl-4-(phenylselanyl)-3-(4-(trifluoromethyl)phenyl)-1H-
126.4, 123.6, 98.6 ppm. HRMS m/z: calcd for C21H15N3O2Se [M+H]+ pyrazole (3oa) : White solid. Yield 86% (191.5 mg). IR ν = 1526,
422.0402, found: 422.0397.
1422, 1328, 1121, 958, 733, 691 cm-1. 1H NMR (400 MHz, CDCl3) δ
5-cyclopropyl-3-phenyl-4-(phenylselanyl)-1H-pyrazole
(3ga): 12.28 (s, 1H), 7.77 (d, J = 7.8 Hz, 2H), 7.58 (d, J = 7.0 Hz, 2H), 7.49
White solid. Yield 77% (130.6 mg). IR ν = 3052, 1576, 1474, 971, (d, J = 8.2 Hz, 2H), 7.32 (dt, J = 14.4, 7.0 Hz, 3H), 7.11 (dd, J = 9.0,
737, 691 cm-1. 1 H NMR (400 MHz, CDCl3) δ 10.86 (s, 1H), 7.65 (s, 3.9 Hz, 5H). 13C NMR (100 MHz, CDCl3) δ 133.7, 129.6, 129.4, 128.7,
2H), 7.32 (s, 3H), 7.17 (s, 5H), 2.05 (s, 1H), 0.85 (s, 4H). 13C NMR 128.6, 128.3, 128.2, 126.2, 125.3, 125.2, 98.1 ppm. 19F NMR (376
(100 MHz, CDCl3) δ 150.3, 133.8, 129.3, 128.7, 128.6, 128.3, 128.1, MHz, CDCl3) δ = -62.7 ppm (s, 3F). HRMS m/z: calcd for
125.8, 98.8, 8.1, 7.9 ppm. HRMS m/z: calcd for C18H16N2Se [M+H]+ C22H15F3N2Se [M+H]+ 445.0425, found: 445.0427.
341.0551, found: 341.0547.
3-(furan-2-yl)-5-phenyl-4-(phenylselanyl)-1H-pyrazole (3pa)
:
5-(tert-butyl)-3-phenyl-4-(phenylselanyl)-1H-pyrazole (3ha)
:
Black solid. Yield 33% (60.5 mg). IR ν = 1571, 1476, 959, 737, 691
White solid. Yield 96% (171.1 mg). IR ν = 3189, 3060, 2956, 1530, cm-1. 1H NMR (400 MHz, CDCl3) δ 7.74 (d, J = 4.3 Hz, 2H), 7.39 (d,
1436, 968, 730, 685 cm-1. 1H NMR (400 MHz, CDCl3) δ 11.18 (s, J = 23.6 Hz, 4H), 7.21 – 7.08 (m, 6H), 6.42 (s, 1H). 13C NMR (100
1H), 7.65 (dd, J = 6.5, 2.9 Hz, 2H), 7.33 – 7.28 (m, 3H), 7.18 – 7.07 MHz, CDCl3) δ 142.5, 133.0, 129.5, 128.9, 128.5, 128.3, 126.1, 111.8,
(m, 5H), 1.46 (s, 9H). 13C NMR (100 MHz, CDCl3) δ 135.2, 129.2, 109.9, 95.8 ppm. HRMS m/z: calcd for C19H14N2OSe [M+H]+
128.5, 128.4, 128.3, 127.7, 125.5, 95.5, 33.5, 29.6 ppm. HRMS m/z: 367.0344, found: 367.0334.
calcd for C19H20N2Se [M+H]+ 357.0864, found: 357.0861.
4-(naphthalen-1-ylselanyl)-3,5-diphenyl-1H-pyrazole (3ab)
:
5-cyclohexyl-3-phenyl-4-(phenylselanyl)-1H-pyrazole (3ia)
:
Yellow solid. Yield 86% (183.2 mg). IR ν = 1561, 1466, 959, 763,
1
White solid. Yield 91% (174.0 mg). IR ν = 2919, 1541, 1457, 966, 693 cm-1. H NMR (400 MHz, CDCl3) δ 11.60 (s, 1H), 8.03 – 7.98
1
734, 690 cm-1. H NMR (400 MHz, CDCl3) δ 11.56 (s, 1H), 7.81 – (m, 1H), 7.82 (dd, J = 6.4, 3.0 Hz, 1H), 7.68 – 7.61 (m, 5H), 7.48 (td,
7.68 (m, 2H), 7.30 (s, 3H), 7.17 – 7.06 (m, 5H), 2.92 (t, J = 12.0 Hz, J = 7.7, 6.9, 3.7 Hz, 2H), 7.27 (m, 4H), 7.24 – 7.10 (m, 4H). 13C NMR
1H), 1.86 (d, J = 12.1 Hz, 2H), 1.71 (t, J = 15.7 Hz, 3H), 1.48 (q, J = (100 MHz, CDCl3) δ 134.0, 133.2, 132.1, 128.9, 128.7, 128.6, 128.3,
11.8 Hz, 2H), 1.28 (dd, J = 17.7, 9.9 Hz, 3H). 13C NMR (100 MHz, 126.4, 126.3, 126.2, 125.8, 125.6, 96.4 ppm. HRMS m/z: calcd for
CDCl3) δ 134.3, 129.2, 128.4, 128.2, 128.1, 125.7, 96.9, 36.3, 32.7, C25H18N2Se [M+Na]+ 449.0527, found: 449.0536.
26.5, 26.0 ppm. HRMS m/z: calcd for C21H22N2Se [M+H]+ 383.1021, 4-((4-methoxyphenyl)selanyl)-3,5-diphenyl-1H-pyrazole (3ac)
:
found: 383.1001.
5-butyl-3-phenyl-4-(phenylselanyl)-1H-pyrazole (3ja)
White solid. Yield 54% (110.4 mg). IR ν = 1487, 1459, 957, 768, 693
:
White cm-1. 1H NMR (400 MHz, CDCl3) δ 7.64 (d, J = 6.4 Hz, 4H), 7.34 –
solid. Yield 59% (104.5 mg). IR ν = 2950, 2926, 2858, 1577, 1475, 7.26 (m, 6H), 7.00 (d, J = 8.8 Hz, 2H), 6.62 (d, J = 8.8 Hz, 2H), 3.67
972, 731, 688 cm-1. 1H NMR (400 MHz, CDCl3) δ 11.66 (s, 1H), 7.70 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 158.3, 130.2, 128.8, 128.5,
(dd, J = 6.5, 2.8 Hz, 2H), 7.30 – 7.23 (m, 3H), 7.09 (d, J = 7.4 Hz, 123.9, 115.1, 98.4, 55.4 ppm. HRMS m/z: calcd for C22H18N2OSe
5H), 2.64 – 2.52 (m, 2H), 1.45 (p, J = 7.6 Hz, 2H), 1.17 (q, J = 7.4 Hz, [M+H]+ 407.0657, found: 407.0654.
2H), 0.74 (t, J = 7.3 Hz, 3H). 13C NMR (100 MHz, CDCl3) δ 153.4, 4-((3-nitrophenyl)selanyl)-3,5-diphenyl-1H-pyrazole
(3ad)
:
134.0, 131.9, 129.2, 128.5, 128.4, 128.2, 128.1, 125.7, 98.0, 31.3, 26.0, Yellow solid. Yield 79% (166.9 mg). IR ν = 1731, 1523, 1459, 1343,
22.5, 13.8 ppm. HRMS m/z: calcd for C19H20N2Se [M+H]+ 357.0864, 958, 722, 694 cm-1. 1H NMR (400 MHz, CDCl3) δ 13.20 (s, 1H), 7.93
found: 357.0860.
(s, 1H), 7.86 (d, J = 8.0 Hz, 1H), 7.54 (d, J = 7.3 Hz, 4H), 7.26 (dt, J
3-phenyl-4-(phenylselanyl)-5-(thiophen-3-yl)-1H-pyrazole (3ka) : = 14.6, 7.1 Hz, 7H), 7.14 (t, J = 8.0 Hz, 1H). 13C NMR (100 MHz,
Pale yellow solid. Yield 74% (140.7 mg). IR ν = 1572, 1465, 960, CDCl3) δ 148.7, 136.3, 133.7, 129.8, 129.1, 128.6, 128.3, 122.8, 120.8,
722, 691 cm-1. 1H NMR (400 MHz, CDCl3) δ 7.80 (d, J = 2.1 Hz, 1H), 96.3 ppm. HRMS m/z: calcd for C21H15N3O2Se [M+H]+ 422.0402,
7.62 (d, J = 6.4 Hz, 2H), 7.49 (d, J = 4.9 Hz, 1H), 7.31 (d, J = 7.1 Hz, found: 407.0400.
3H), 7.24 (d, J = 3.8 Hz, 1H), 7.18 – 7.09 (m, 5H). 13C NMR (100 4-((3,5-diphenyl-1H-pyrazol-4-yl)selanyl)benzonitrile (3ae) : Pale
MHz, CDCl3) δ 133.8, 131.9, 130.7, 129.5, 129.0, 128.6, 128.4, 128.1, yellow solid. Yield 55% (109.6 mg). IR ν = 2225, 1585, 1480, 958,
1
127.0, 126.0, 125.7, 124.2, 97.1 ppm. HRMS m/z: calcd for 723, 695 cm-1. H NMR (400 MHz, CDCl3) δ 7.67 – 7.59 (m, 4H),
C19H14N2SSe [M+H]+ 383.0116, found: 383.0123.
3-(3-phenyl-4-(phenylselanyl)-1H-pyrazol-5-yl)pyridine (3la)
This is an unsuccessful case. We didn’t get any data about it for the for C22H15N3Se [M+Na]+ 424.0323, found: 424.0314.
7.41 – 7.31 (m, 8H), 7.20 (d, J = 8.5 Hz, 2H). 13C NMR (100 MHz,
CDCl3) δ 132.6, 129.3, 128.8, 128.2, 128.1 ppm. HRMS m/z: calcd
:
reaction didn’t take place at all.
3-(4-methoxyphenyl)-5-phenyl-4-(phenylselanyl)-1H-pyrazole
4-(butylselanyl)-3,5-diphenyl-1H-pyrazole (3af) : White solid.
Yield 34% (59.9 mg). IR ν = 1489, 1458, 958, 766, 691cm-1. 1H NMR
(3ma) : White solid. Yield 78% (158.7 mg). IR ν = 3200, 1611, 1501, (400 MHz, CDCl3) δ 11.60 (s, 1H), 7.79 (d, J = 5.0 Hz, 4H), 7.38 (d,
1
1435, 957, 743, 693 cm-1. H NMR (400 MHz, CDCl3) δ 12.13 (s, J = 6.2 Hz, 6H), 2.37 (t, J = 7.2 Hz, 2H), 1.26 (m, J = 7.1 Hz, 2H),
1H), 7.59 (d, J = 33.9 Hz, 4H), 7.29 (s, 3H), 7.13 (s, 5H), 6.79 (s, 2H), 1.08 (m, J = 7.3 Hz, 2H), 0.62 (t, J = 7.3 Hz, 3H). 13C NMR (100
3.77 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 158.3, 130.2, 128.8,
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
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Organic & Biomolecular Chemistry
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ARTICLE
Journal Name
D. S. Middleton, C. E. Mowbray, S. D. Newman,VCie.wPAhrtiicllleipOsn,liRne.
MHz, CDCl3) δ 128.5, 128.4, 98.6, 31.6, 29.3 22.5, 13.5 ppm. HRMS
m/z: calcd for C19H20N2Se [M+H]+ 357.0864, found: 357.0883.
4-(octylselanyl)-3,5-diphenyl-1H-pyrazole (3ag) : White solid.
Yield 60% (123.4 mg). IR ν = 2919, 2851, 1489, 1460, 958, 770, 691
cm-1. 1H NMR (400 MHz, CDCl3) δ 10.55 (s, 1H), 7.85 (d, J = 6.9 Hz,
4H), 7.44 (dt, J = 13.9, 7.0 Hz, 6H), 2.39 (t, J = 7.2 Hz, 2H), 1.25 (m,
4H), 1.05 (m, 8H), 0.85 (t, J = 7.2 Hz, 3H). 13C NMR (100 MHz,
CDCl3) δ 131.7, 128.5, 128.4, 98.5, 31.9, 29.7, 29.5, 29.4, 29.2, 29.0,
22.7, 14.2 ppm.
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Conclusions
In summary, we have developed a rather practical method
for the construction of 3,5-diphenyl-4-(phenylselanyl)-1H-
pyrazole and analogues by the means of intramolecular 5-endo-
dig-cyclization of α,β-alkynic tosylhydrazones. The reaction
proceeds smoothly under mild conditions and features high
regioselectivity and chemoselectivity. Nothing else is detected in
the reaction except remaining substrates. Futhermore, it avoids
the use of expensive transition metal catalysts. Through this
strategy, we realize the synthesis of molecules that containing
pyrazole and selenium ether skeletons successfully in one step,
which has been rarely reported in the literatures till now. From
this perspective, the protocol we propose shall establish a solid
foundation for the introduction of analogous compounds into
practical use.
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Conflicts of interest
There are no conflicts to declare.
Acknowledgements
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We gratefully acknowledge the National Natural Science
Foundation of China (21971174, 21772137, 21542015, and
21672157), PAPD, the Project of Scientific and Technologic
Infrastructure of Suzhou (SZS201708), and the Major Basic
Research Project of the Natural Science Foundation of the
Jiangsu Higher Education Institutions (no. 16KJA150002),
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Organic & Biomolecular Chemistry
Page 8 of 8
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DOI: 10.1039/D0OB00048E
Iron(Ⅲ) chloride-promoted cyclization of α,β-alkynic
tosylhydrazones
with
diselenides:
Synthesis
of
4-(arylselanyl)-1H-pyrazoles
Hai-Feng Yao,a Fang-Hui Li,a Jian Li,b Shun-Yi Wang*a and Shun-Jun Ji*a
R2
N
NHTs
N
R3Se
FeCl3
R3SeSeR3
+
R2
DCE, rt.
N
R1
R1
H
R3 = aryl, alkyl
R1 = aryl, alkyl
R2 = aryl
A highly efficient Iron (III) chloride-promoted cyclization between α,β-alkynic tosylhydrazones
and diselenides to form a 4-(arylselanyl)-1H-pyrazole skeleton is studied.