Catalyst free 1,3-dipolar cycloaddition of 3-oxo-1,2-pyrazolidinium ylides to β-trifluoroacetyl vinyl ethyl ether: Synthesis of 6-trifluoroacetyl substituted bicyclic pyrazolidinones

Article abstract of DOI:10.1016/j.jfluchem.2011.03.023

A catalyst free cycloaddition reaction of 3-oxo-1,2-pyrazolidinium ylides with β-trifluoroacetyl vinyl ethyl ether is reported, which proceeded smoothly at ambient temperature and afford the bicyclic pyrazolidinone products in good yield. This is the firs

Full text of DOI:10.1016/j.jfluchem.2011.03.023

Journal of Fluorine Chemistry 132 (2011) 402–408
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Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Catalyst free 1,3-dipolar cycloaddition of 3-oxo-1,2-pyrazolidinium ylides to
b
-trifluoroacetyl vinyl ethyl ether: Synthesis of 6-trifluoroacetyl substituted
bicyclic pyrazolidinones
*
Yong Xin, Jingwei Zhao, Jiwei Gu, Shizheng Zhu
Key Laboratory of Organouorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, PR China
A R T I C L E I N F O
A B S T R A C T
Article history:
A catalyst free cycloaddition reaction of 3-oxo-1,2-pyrazolidinium ylides with
b-trifluoroacetyl vinyl
Received 10 March 2011
Received in revised form 26 March 2011
Accepted 29 March 2011
Available online 5 April 2011
ethyl ether is reported, which proceeded smoothly at ambient temperature and afford the bicyclic
pyrazolidinone products in good yield. This is the first report of synthesis of 6-trifluoroacetyl substituted
bicyclic pyrazolidinones that are potentially anti-microbial and herbicidal.
ß 2011 Elsevier B.V. All rights reserved.
Keywords:
1,3-Dipolar
Cycloaddition
Ylides
Trifluoroacetyl
Pyrazolidinones
1. Introduction
noncatalytic 1,3-dipolar cyclization of azomethine imines with
tert-butyl 2-(trifluoromethyl)prop-2-enoate at room temperature.
1,3-Dipolar cycloadditions are powerful methods for construct-
ing a variety of five-membered heterocycles in a convergent
manner of relatively simple precursors [1]. Among the well-
developed dipoles, azomethine imines represents a series of
powerful building blocks, which are stable, easily handled,
inexpensive and atom economic [2]. The cyclic azomethine imine,
3-oxo-1,2-diazetidinium ylides, was firstly synthesized by Murck-
mann in 1911 [3]. However, the very first time it was recognized as
a 1,3-dipole was 1968 [4], from when the detailed chemical
properties [5], thermic behavior and photochromic properties [6]
were investigated. During the past two decades, it was successfully
employed in the reactions with dipolephiles, such as alkynes [7],
alkenes (including unstaturated aldehydes [8], unsaturated
ketones and esters [9] and others [10]), and so on [11].
Cycloadditions of these dipoles, even with highly electron-
deficient alkynes (e.g., dimethyl acetylenedicarboxylate), are often
conducted at elevated temperatures and, in the case of unsymme-
trical alkynes, generally furnish mixtures of regioisomeric hetero-
cycles. Only during recent years, along with the development of
click chemistry, 3-oxo-1,2-diazetidinium ylides were efficiently
used in the cycloaddition reactions in the presence of Cu (I) catalyst
[7(a), (b), (c)–12]. Especially, Shibata et al. [10(e)] reported a
In the course of our study on the chemical transformation of b-
trifluoroacetyl vinyl ethyl ether 1, we found it a dipolephilic partner
of high activity [13]. Thus, we investigated the 1,3-dipolar
cycloaddition reaction of 1 with cyclic azomethine imines, 3-oxo-
1,2-pyrazolidinium ylides. Herein, we report a convenient synthesis
of trifluoroacetyl bearing bicyclic pyrazolidinones, usingthe catalyst
free cycloaddition reaction of 3-oxo-1,2e-pyrazolidinium ylides
with b-trifluoroacetyl vinyl ethyl ether at room temperature.
2. Results and discussion
Initially, we examined the reaction of 1 with 3-oxo-1,2-
pyrazolidinium ylide 2a at room temperature in dichloromethane
which was generally used as solvent in this type of cycloaddition
reaction. Unfortunately, according to 19F NMR, only imperceptible
product was formed. After stirring for 3 days, the reaction
proceeded only near 50%, and after regular isolation the desired
product 3a was isolated in a yield of 40% as yellow oil. The result
encouraged us to screening the solvents in order to improve the
efficiency of the reaction, and the results are listed in Table 1. The
yields were determined by 19F NMR, using 0.1 mmol trifluor-
omethylbenzene (À63 ppm) as internal standard, while the
chemical shifts of
1 and correspongding product 3a are
À78 ppm and À73 ppm, respectively.
We found DMSO as the best solvent. To the best of our
knowledge, the more polar solvent is, the better the 1,3-dipolar
* Corresponding author. Tel.: +86 21 54925185; fax: +86 21 64166128.
E-mail addresses: zhusz@sioc.ac.cn, zhusz@mail.sioc.ac.cn (S. Zhu).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.03.023

Y. Xin et al. / Journal of Fluorine Chemistry 132 (2011) 402–408
403
Table 1
1,3-Dipolar cycloaddition of 3-oxo-1,2-pyrazolidinium ylide 2a to
b
-trifluoroacetyl vinyl ethyl ether 1: effect of solvents on the yield of the reaction.
Entry
Solvents
Yield (%)b
1
CH2Cl2
CHCl3
CCl4
35
32
20
56
12
12
24
80
12
42
40
77
83
41
15
43
2
3
4
DCE
5
Et2O
6
THF
7
DME
8
DMF
9
EtOAc
Benzene
Toluene
CH3CN
DMSO
Acetone
Methanol
Ethanol
10
11
12
13
14
15
16
aThe reactions were conducted in varies of solvents at room temperature between 0.1 mmol of
b
-trifluoroacetyl vinyl ethyl ether 1 and 0.1 mmol of 3-oxo-1,2-pyrazolidinium
ylide 2a. The solvents were used without pre-purification.
b
Determined by 19F NMR.
Table 2
Reaction scope: 3-oxo-1,2-pyrazolidinium ylides.
Entry
Ar
Time (h)
Product
Yield (%)b
1
2
3
4
5
6
7
8
9
10
Ph (2a)
3
6
3a
3b
3c
3d
3e
3f
85
88
89
80
73
78
88
79
82
44
4-MeOC6H4 (2b)
3-NO2C6H4 (2c)
2-FC6H4 (2d)
3-FC6H4 (2e)
4-FC6H4 (2f)
2,3-2FC6H3 (2g)
4-ClC6H4 (2h)
4-BrC6H4 (2i)
2-furanyl (2j)
5
10
10
10
14
8
3g
3h
3i
8
7
3j
aThe reactions were conducted between 1.0 mmol of 1 and 1.0 mmol of 2a–j in 2 mL of DMSO at room temperature.
b
Isolated yield.
cycloaddition reaction proceeds. However, in our case, comparing
entry 15, 16 with entry 12 in Table 1, solubility of 2a in solvents has
a great impact of the efficiency of the reaction. In addition, the 3-
oxa 2a dissolved better in benzene and toluene (Table 1, entry 10
and 11), which are non-polar solvents; but the reaction was less
efficient in ether (Table 1, entry 5 and 6) and ethyl acetate (Table 1,
entry 9), which are more polar solvents.
Inthesubsequentresearch,withoptimizedconditioninhand, we
examined the scope of substrates 2. It was found that the aromatic
ylides, regardless of electron-donating or electron-withdrawing
Table 3
Reaction scope: 4-methyl-3-oxo-1,2-pyrazolidinium ylides.
.
Entry
Ar
Time (h)
Productb
drc
Yield (%)d
1
2
3
Ph (2k)
8
9
9
3k
3l
3: 5
4: 5
1: 3
79
88
82
4-MeOC6H4 (2l)
3-NO2C6H4 (2m)
3m
aThe reactions were conducted between 1.0 mmol of 1 and 1.0 mmol of 2k–m in 2 mL of DMSO at room temperature.
b
The diasteroisomers were hard to be isolated by flash chromatography and the products were the mixture of diasteroisomers.
The dr was determined by 1H NMR of the products, and the cis- and trans-isomers were not specified.
Isolated yield.
c
d

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Y. Xin et al. / Journal of Fluorine Chemistry 132 (2011) 402–408
Scheme 1. Reaction pathway.
substituents on the phenyl ring, participated in this process
with high efficiency (Table 2). Further more, heterocyclic
aldehyde also worked well, but the yield was much lower
(Table 2, entry 10).
To further explore the scope of the reaction, we prepared 4-
methyl-3-oxo-1,2-pyrazolidinium ylides 2k-m and they were
subjected with 1. To our delight, the reaction also proceeded
smoothly and gave the diastereoisomers in good yields (Table 3).
Formation of cycloadducts 3 is explainable by initial 1,3-dipolar
cycloaddition of alkene 1 to azomethine imines 2 to give the fully
saturated cycloadduct 4, which then undergoes elimination of
By subjecting pyrazolidin-3-one (1.1 equiv.) to various aromat-
ic aldehydes (1.0 equiv.) in methanol (20 mmol in 15 mL metha-
nol) at room temperature, the crude products of desired 3-oxo-1,2-
pyrazolidinium ylides were formed. After removing the solvent
methanol, the crude product was recrystallized in ethanol. Washed
by ethyl acetate and dried under vacuum, the pure product 2 was
obtained in moderate yield.
4.2.2. Characterisation data of 2a–2j
4.2.2.1. Benzylidene-5-oxopyrazolidin-2-ium-1-ide (2a) [7(b)].
ethanol to afford the 2,3-dihydropyrazolo[1,2-a]pyrazolone
(Scheme 1).
3
3. Conclusion
2.2g, 65%
In summary, we here report a first synthesis of 6-trifluor-
oacetyl substituted bicyclic pyrazolidinones through a 1,3-
White solid, mp 194–195 8C (lit. mp 192–194 8C). 1H NMR
(CDCl3, 300 MHz):
d 8.30–8.28 (m, 2H), 7.48–.45 (m, 3H), 7.14 (s,
dipolar cycloaddition of 3-oxo-1,2-pyrazolidinium ylides to
b-
1H), 4.52 (td, 2H, J = 8.1 Hz, 2.1 Hz), 2.79 (m, 2H).
trifluoroacetyl vinyl ethyl ether. The reaction proceeded
efficiently in DMSO at room temperature and afforded the
desired products in moderate to good yield, which are
potentially anti-microbial and herbicidal [14]. A wide range of
3-oxo-1,2-pyrazolidinium ylides could participate in the process
successfully.
4.2.2.2. (4-Methoxybenzylidene)-5-oxopyrazolidin-2-ium-1-ide
(2b) [15a].
4. Experimental
2.8g, 69%
4.1. General Information
White solid, mp 173–175 8C (lit. mp 183–86 8C). 1H NMR
(CDCl3, 300 MHz):
4.56 (t, 2H, J = 8.1 Hz), 3.89 (s, 3H), 2.92 (t, 2H, J = 8.1 Hz).
d 8.29 (d, 2H, J = 8.7 Hz), 7.84 (d, 2H, J = 8.7 Hz),
Melting points are measured on a Temp-Melt apparatus and
are uncorrected. 1H (300 MHz) and 19F NMR (282 MHz) spectra
were recorded on a Bruker AM-300 ultra shield, 300 MHz, high
performance digital FT-NMR spectrometer with Me4Si and CFCl3
as the internal and external standards, respectively. 13C NMR
(100 MHz) spectra were recorded on a Bruker AV-400 ultra
shield plus, 400 MHz, high performance digital FT-NMR spec-
trometer with Me4Si as the internal standard. FT-IR spectra were
4.2.2.3. (3-Nitrobenzylidene)-5-oxopyrazolidin-2-ium-1-ide
(2c) [15b].
obtained with
a Nicolet AV-360 spectrophotometer. Low
2.9g, 66%
resolution mass spectra (LRMS) and high resolution mass
spectra (HRMS) were obtained on a Finnigan GC–MS 4021
and a Finnigan MAT-8430 instrument using the electron impact
ionization technique (70 eV) or Electrospray Ionization. Elemen-
tal analyses were performed by this institute. All solvents and
reagents were used without further purification unless other-
wise stated.
Yellow solid, mp 240 8C (lit. mp 236–38 8C). 1H NMR (DMSO,
d 9.34 (s, 1H), 8.54 (d, 1H, J = 7.8 Hz), 8.34 (dd, 1H,
J = 8.1 Hz, 1.8 Hz), 7.87-7.81 (m, 2H), 4.66 (t, 2H, J = 8.1 Hz), 2.64 (t,
2H, J = 8.1 Hz).
300 MHz):
4.2.2.4. (2-Fluorobenzylidene)-5-oxopyrazolidin-2-ium-1-ide
(2d) [7(b)].
4.2. General procedure and spectra data of 2a–m
4.2.1. General procedure to prepare 3-oxo-1,2-pyrazolidinium ylide
2a–j
Cooled in an ice bath, methacrylate 30 mL was added to the
solution of hydrazine hydrate 60 mL in ethanol 240 mL. After
addition, the mixture was heated to reflux for 8 h. Then the solvent
and the volatile components were removed under reduced pressure.
The thick colorless oil, crude pyrazolidin-3-one, was obtained in 80%
yield.
2.2g, 58%
White solid, mp 233–34 8C (lit. mp 230–2318C). 1H NMR (CDCl3,
300 MHz):
(m, 3H), 4.59 (t, J = 8.1 Hz), 2.85 (t, J = 8.1 Hz). 19F NMR (CDCl3,
282 MHz):
À116.8 (s, 1F).
d 9.23 (t, 1H, J = 7.8 Hz), 7.50–7.43 (m, 2H), 7.31–7.09
d

Y. Xin et al. / Journal of Fluorine Chemistry 132 (2011) 402–408
405
4.2.2.5. (3-Fluorobenzylidene)-5-oxopyrazolidin-2-ium-1-ide (2e).
Yellow solid, mp 239–240 8C (lit. mp not available). 1H NMR
(DMSO, 300 MHz): 8.24 (d, 2H, J = 8.7 Hz), 7.76 (d, 2H, J = 8.7 Hz),
d
7.67 (s, 1H), 4.56 (t, 2H, J = 7.8 Hz), 2.57 (t, 2H, J = 7.8 Hz).
4.2.2.10. (Furan-2-ylmethylene)-5-oxopyrazolidin-2-ium-1-ide (2j)
[15a].
1.8g, 47%
White solid, mp 233–235 8C. 1H NMR (DMSO, 300 MHz):
d 8.33
(d, 1H, J = 10.5 Hz), 7.94 (d, 1H, J = 7.8 Hz), 7.70 (s, 1H), 7.59 (q, 1H,
J = 6.3 Hz), 7.37 (td, 1H, J = 8.7 Hz, 1.5 Hz), 4.60 (t, J = 7.8 Hz), 2.59
(t, 7.8 Hz). 19F NMR (DMSO, 282 MHz):
d
À112.1 (dd, J = 9.3 Hz,
8.2 Hz). EI-MS m/z (%): 192 (M+, 36), 191 (72), 108 (100). Anal.
Calcd. For C10H9FN2O C62.49, H4.72, N14.58; Found C62.51,
H4.81, N14.55. FT-IR (KBr, cmÀ1): 1680, 1654, 1609, 1575, 1540,
1451, 1347, 1331, 1292, 1276, 1248, 948, 787, 687.
1.1g, 34%
Dark yellow solid, mp 215–217 8C (lit. mp not available). 1H
NMR (DMSO, 300 MHz):
d 7.98 (s, 1H), 7.78 (s, 1H), 7.58 (d, 1H,
J = 3.3 Hz), 6.80–6.78 (m, 1H), 4.48 (t, 2H, J = 7.8 Hz), 2.58 (t, 2H,
J = 7.8 Hz).
4.2.2.6. (4-Fluorobenzylidene)-5-oxopyrazolidin-2-ium-1-ide
[9(a)].
(2f)
4.3. General procedure to prepare 4-methyl-3-oxo-1,2-
pyrazolidinium ylide 2k–m
Cooled in an ice bath, methyl methacrylate 60 mL was added to
the solution of hydrazine hydrate 26 mL in ethanol 240 mL. After
addition, the mixture was heated to reflux for 12 h. Then the
solvent and the volatile components were removed under reduced
pressure. The thick colorless oil, crude 4-methyl pyrazolidin-3-one,
was obtained in 77% yield.
By subjecting 4-methyl pyrazolidin-3-one (1.1 equiv.) to
various aromatic aldehydes (1.0 equiv.) in methanol (20 mmol
in 15 mL methanol) at room temperature, the crude products of
desired 4-methyl-3-oxo-1,2-pyrazolidinium ylides were formed.
After removing the solvent methanol, the crude product was
recrystallized in ethanol. Washed by ethyl acetate and dried
under vacuum, the pure product 2 was obtained in good yield.
1.9g, 51%
White solid, mp 223 8C (lit. mp not available). 1H NMR (CDCl3,
300 MHz): 8.35 (s, 1H), 7.25–7.13 (m, 4H), 4.53 (t, 2H, J = 8.1 Hz),
2.83 (t, 2H, J = 8.1 Hz). 19F NMR (CDCl3, 282 MHz):
À104.8 (s, 1F).
d
d
4.2.2.7. (2,3-Difluorobenzylidene)-5-oxopyrazolidin-2-ium-1-ide (2g).
2.3g, 55%
Yellow solid, mp 243–245 8C. 1H NMR (DMSO, 300 MHz):
d 8.81
4.4. Characterisation data of 2k–2m
(td, 1H, J = 6.6 Hz, 1.5 Hz), 7.74 (s, 1H), 7.61 (q, 1H, J = 10.2 Hz), 7.41
(m, 1H), 4.66 (t, 2H, J = 8.1 Hz), 2.60 (t, 2H, J = 8.1 Hz). 19F NMR
4.4.1.1. Benzylidene-4-methyl-5-oxopyrazolidin-2-ium-1-ide (2k)
[4(a)]
(DMSO, 282 MHz):
d
À139.1 to 139.3 (m, 1F), À142.4 to 142.5 (m,
1F). EI-MS m/z (%): 210 (M+, 32), 126 (100). Anal. Calcd. For
C10H8F2N2O: C57.14, H3.84, N13.33; Found C57.10, H3.84,
N13.33. FT-IR (KBr, cmÀ1): 1679, 1652, 1597, 1476, 1463, 1436,
1343, 1296, 1108, 949, 817, 668.
4.2.2.8. (4-Chlorobenzylidene)-5-oxopyrazolidin-2-ium-1-ide
2.8g, 75%
(2h) [9(a)].
White solid, mp 123–124 8C (lit. mp 141–142 8C). 1H NMR
(DMSO, 300 MHz):
d 8.32–8.28 (m, 2H), 7.66 (s, 1H), 7.54-7.51 (m,
3H), 4.75 (dd, J = 9.3 Hz, 13.5 Hz), 4.21 (dd, J = 7.2 Hz, 13.5 Hz),
2.80–2.67 (m, 1H), 1.18 (d, 3H, J = 6.9 Hz).
1.8g, 44%
4.4.1.2. (4-Methoxybenzylidene)-4-methyl-5-oxopyrazolidin-2-ium-
White solid, mp 219–220 8C (lit. mp 214–217 8C). 1H NMR
1-ide (2l) [15b]
(DMSO, 300 MHz):
d 8.32 (d, 2H, J = 8.7 Hz), 7.69 (s, 1H), 7.62 (d,
2H, J = 8.7 Hz), 4.57 (t, 2H, J = 7.5 Hz), 2.57 (t, 2H, J = 7.5 Hz).
4.2.2.9. (4-Bromobenzylidene)-5-oxopyrazolidin-2-ium-1-ide
(2i) [9(a)].
3.4g, 78%
White solid, mp 145 8C (lit. mp not avilable). 1H NMR (DMSO,
300 MHz):
d 8.29 (d, 2H, J = 8.7 Hz), 7.60 (s, 1H), 7.11 (d, 2H,
J = 8.7 Hz), 4.70 (dd, 1H, J = 13.2 Hz, 9.6 Hz), 4.15 (dd, 1H,
J = 13.2 Hz, 6.9 Hz), 3.85 (s, 3H), 2.75–2.67 (m, 1H), 1.17 (d, 3H,
J = 7.2 Hz).
2.7g, 53%

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Y. Xin et al. / Journal of Fluorine Chemistry 132 (2011) 402–408
4.4.1.3. Methyl-2-(3-nitrobenzylidene)-5-oxopyrazolidin-2-ium-1-
4.5.2.3. (3-Nitrophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
ide (2m) [15b]
zolo[1,2-a]pyrazol-1(5H)-one (3c).
3.8g, 81%
Yellow solid. Mp 102–104 8C. 0.303 g, 89%. 1H NMR (CDCl3,
Yellow solid, mp 187–188 8C (lit. mp not avilable). 1H NMR
(DMSO, 300 MHz): d 9.35 (s, 1H), 8.53 (d, 1H, J = 7.5 Hz), 8.33 (d, 1H,
J = 8.7 Hz), 7.85-7.80 (m, 2H), 4.81 (dd, 1H, J = 13.2 Hz, 9.6 Hz), 4.29
(dd, 1H, J = 13.5 Hz, 6.6 Hz), 2.85-2.73 (m, 1H), 1.20(d, 3H, J = 7.2 Hz).
300 MHz):
7.57 (t, 1H, J = 8.4 Hz), 5.43 (s, 1H), 3.64 (t, 1H, J = 6.3 Hz), 3.23–3.02
(m, 2H), 2.91-2.86 (m, 1H). 19F NMR (CDCl3, 282 MHz):
À73.58 (s,
3F). 13C NMR (CDCl3, 100 MHz):
175.5 (q, J = 36.4 Hz), 166.0, 148.4,
d8.36 (t, 1H, J = 2.1 Hz), 8.52 (d, 1H, J = 8.1 Hz), 7.81 (s, 2H),
d
d
140.5, 134.5, 133.0 (q, J = 5.1 Hz), 129.5, 123.6, 123.2, 117.5, 116.1 (q,
J = 288.7 Hz), 72.6, 52.2, 35.3. EI-MS m/z (%): 341 (M+, 6), 219 (52), 55
(100). ESI-MS m/z: 342 [M+H]+. HRMS-EI: calc. mass 341.0623, mass
341.0618, formula C14 H10 N3 O4 F3.FT-IR (neat, cmÀ1): 3069, 2909,
2845, 1747, 1670, 1558, 1531, 1418, 1350, 1193, 1142, 999, 822, 738,
714, 580.
4.5. General procedure and spectra data of 3a–m
4.5.1. General procedure of the 1,3-dipolar cycloaddition of 2 to
trifluoroacetyl vinyl ethyl ether (1)
b-
To a solution of b-trifluoroacetyl vinyl ethyl ether 1 (1.0 mmol,
0.168 g) in 2 mL of DMSO, compound 2 (1.0 mmol) was added. After
stirring for 8 h, monitored by TLC, the reaction completed and a
yellow spot (TLC Rf = 0.3, using hexanes: ethyl acetate, 2: (1) was
generated cleanly. The mixture was poured into brine 50 mL and
stirred for 5 min. The water phase was extracted by ethyl ether
(3 Â 30 mL) till the water phase became colorless. The organic phase
was dried over MgSO4 for 0.5–1 h, filtered, and the filtrate was
evaporated in vacuo. The crude product was purified on silica gel
using hexanes: ethyl acetate (5:1–3:1) as eluent. The product 3 was
obtained as yellow oil or solid.
4.5.2.4. (2-Fluorophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
zolo[1,2-a]pyrazol-1(5H)-one (3d).
Yellow oil. 0.251 g, 80%. 1H NMR (CDCl3, 300 MHz):
1H), 7.37-7.10 (m, 4H), 5.70 (s, 1H), 3.45–3.41 (m, 1H), 3.20 (dd, 1H,
d 7.84 (s,
J = 8.4 Hz, 8.7 Hz), 2.94–2.85 (m, 1H). 19F NMR (CDCl3, 282 MHz):
d
4.5.2. Characterisation data of 3a–m
À72.9 (s, 3F), À118.1(m, 1F). 13C NMR (CDCl3, 100 MHz):
d 175.4 (q,
J = 36.4 Hz), 165.9, 161.1 (d, J = 246.4 Hz), 132.9 (q, J = 4.4 Hz),
130.6 (d, J = 8.0 Hz), 129.1 (d, J = 3.7 Hz), 124.6 (d, J = 3.7 Hz), 123.8
(d, J = 12.4 Hz), 117.2, 116.3 (q, J = 288.8 Hz), 115.9 (d, J = 21.9 Hz),
65.8 (d, J = 2.9 Hz), 50.9, 35.5. ESI-MS: 315 [M+H]+. HRMS-ESI:
[M+H]+ calc. mass 315.0764, mass 315.0751, formula C14 H11 N2
O2 F4. FT-IR (neat, cmÀ1): 3079, 2925, 2851, 1731, 1709, 1670,
1560, 1494, 1411, 1361, 1185, 1142, 818, 759, 727, 708.
4.5.2.1. Phenyl-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyrazolo[1,2-
a]pyrazol-1(5H)-one (3a).
Yellow oil. 0.251 g, 85%. 1H NMR (CDCl3, 300 MHz):
1H), 7.39–7.34 (m, 5H), 5.35 (s, 1H), 3.44–3.37 (m, 1H), 3.15–3.07
(m, 1H), 3.0–2.81 (m, 2H). 19F NMR (CDCl3, 282 MHz):
À73.9 (s,
3F). 13C NMR (CDCl3, 100 MHz):
175.5(q, J = 34.5 Hz), 165.8,
d 7.79 (s,
4.5.2.5. (3-Fluorophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
zolo[1,2-a]pyrazol-1(5H)-one (3e).
d
d
136.8, 132.2 (q, J = 4.4 Hz), 128.9, 128.8, 128.1, 118.8, 116.2 (q,
J = 289.0 Hz), 72.6, 50.9, 35.5. ESI-MS m/z: 319 [M+Na]+. HRMS-EI:
calc. mass 296.0773, mass 296.0771, formula C14 H11 N2 O2 F3.
FT-IR (neat, cmÀ1): 3066, 2095, 1738, 1712, 1675, 1606, 1563,
1509, 1426, 1193, 1144, 905, 841.
Yellow oil. 0.229 g, 73%. 1H NMR (CDCl3, 300 MHz):
d 7.80 (s,
1H), 7.34 (dd, 1H, J = 7.8 Hz, 6.0 Hz), 7.20–7.00 (m, 3H), 5.32 (s, 1H),
3.47 (td, 1H, J = 8.4 Hz, 2.4 Hz), 3.15–3.80 (m, 3H). 19F NMR (CDCl3,
282 MHz):
100 MHz):
d
d
À73.0 (s, 3F), À112.1 (m, 1F). 13C NMR (CDCl3,
4.5.2.2. (4-Methoxyphenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydro-
pyrazolo[1,2-a]pyrazol-1(5H)-one (3b).
175.5 (q, J = 36.4 Hz), 165.9, 163.0 (d, J = 245.0 Hz),
140.0 (d, J = 6.6 Hz), 132.5(q, J = 3.6 Hz), 132.2 (d, J = 8.0 Hz), 123.9
(d, J = 2.9 Hz), 118.2, 116.2 (q, J = 288.7 Hz), 115.8 (d, J = 21.1 Hz),
115.0 (d, J = 21.9 Hz), 72.3, 51.3, 35.4. EI-MS m/z (%): 314 (M+, 9),
261 (78), 219 (42), 189 (53), 133 (43), 55 (100). HRMS-EI: calc.
mass 314.0681, mass 314.0678, formula C14 H10 N2 O2 F4. FT-IR
(neat, cmÀ1): 3085, 2930, 2845, 1736, 1704, 1677, 1664, 1563,
1427, 1358, 1193, 1137, 911, 780, 714.
Yellow solid. Mp: 110–112 8C. 0.287 g, 88%. 1H NMR (CDCl3,
300 MHz):
J = 8.7 Hz), 5.33 (s, 1H), 3.81 (s, 3H), 3.4-3.33 (m, 1H), 3.13-2.81 (m,
3H). 19F NMR (CDCl3, 282 MHz): -72.9 (s, 3F). 13C NMR (CDCl3,
100 MHz): 175.5 (q, J = 36.4 Hz), 165.8. 160.1, 132.0 (q, J = 4.4 Hz),
d 7.79 (s, 1H), 7.28 (d, 2H, J = 8.7 Hz), 6.91 (d, 2H,
4.5.2.6. (4-Fluorophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
d
zolo[1,2-a]pyrazol-1(5H)-one (3f).
d
129.3, 128.7, 118.9, 116.3 (q, J = 288.0 Hz), 114.2, 71.8, 55.3, 50.4,
35.6. ESI-MS: 327[M+H]+. HRMS-ESI: [M+H]+: calc. mass 327.09510,
mass 327.09572, formula C15 H14 F3 N2 O3. FT-IR (neat, cmÀ1):
3089, 2926, 1749, 1659, 1565, 1515, 1368, 1250, 1197, 1138, 1026,
994, 904, 833, 714.

Y. Xin et al. / Journal of Fluorine Chemistry 132 (2011) 402–408
407
Yellow oil. 0.245 g, 78%. 1H NMR (CDCl3, 300 MHz):
d
7.79 (s,
(100). ESI-MS m/z: 375 [M+H]+, 377 [M+2+H]+. HRMS-EI: calc.
mass 373.9878, mass 373.9882, formula C14 H10 N2 O2 F3 Br.FT-
IR (neat, cmÀ1): 3025, 2925, 2835, 1736, 1667, 1560, 1480, 1417,
1355, 1193, 1142, 1009, 996, 879, 818, 708.
1H), 7.37 (dd, 1H, J = 8.4 Hz, 5.7 Hz), 7.06 (t, 1H, J = 8.4 Hz), 5.32 (s,
1H), 3.45 (td, J = 8.4 Hz, 2.7 Hz), 3.14–2.80 (m, 3H). 19F NMR (CDCl3,
282 MHz):
100 MHz):
d
À73.0 (s, 3F), À112.9 (m, 1F). 13C NMR (CDCl3,
d
175.5 (q, J = 36.5 Hz), 165.9, 162.9 (d, 245.8 Hz), 133.2
(d, 2.9 Hz), 132.3 (q, 4.3 Hz), 129.8 (d, 8 Hz), 118.5, 116.2 (q,
288.0 Hz), 115.6 (d, 21.2 Hz), 72.1, 51.2, 35.5. ESI-MS: 315 [M+H]+.
HRMS-EI: calc. mass 314.0678, mass 314.0676, formula C14 H10
N2 O2 F4. FT-IR (neat, cmÀ1): 3078, 2926, 1739, 1712, 1563, 1509,
1426, 1362, 1193, 905, 883, 840, 778, 713.
4.5.2.10. (Furan-2-yl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
zolo[1,2-a]pyrazol-1(5H)-one (3j).
4.5.2.7. (2,3-Difluorophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydro-
pyrazolo[1,2-a]pyrazol-1(5H)-one (3g).
Darkyellowoil. 0.126 g, 44%. 1H NMR (CDCl3, 300 MHz):
1H), 7.42 (s, 1H), 6.35 (d, 2H, J = 8.4 Hz), 5.5 (s, 1H), 3.25–3.17 (m,
1H), 3.08-2.78 (m, 3H). 19F NMR (CDCl3, 282 MHz):
À72.6 (s, 3F).
13C NMR (CDCl3, 100 MHz):
175.4 (q, J = 36.3 Hz), 165.4, 148.7,
d7.79(s,
d
d
143.6, 132.4 (q, J = 4.8 Hz), 116.2 (q, J = 2883.3 Hz), 116.3, 110.7,
110.3, 63.3, 48.7, 35.7. EI-MS m/z (%): 286 (M+, 65), 55 (100). ESI-MS
m/z: 287 [M+H]+. HRMS-EI: calc. mass 286.0565, mass 286.0563,
formula C12 H9 N2 O3 F.FT-IR (neat, cmÀ1): 3126, 2929, 1739, 1709,
1675, 1564, 15187, 1364, 1146, 1015, 913, 198, 745, 708, 618, 594.
Yellow solid. Mp 102–104 8C. 0.292 g, 88%. 1H NMR (CDCl3,
300 MHz):
1H, J = 8.4 Hz, 3.3dHz), 3.22 (q, 1H, J = 8.7 Hz), 3.03–2.84 (m, 2H).
19F NMR (CDCl3, 282 MHz):
À73.2 (s, 3F), -137.7 (s, 1F), À143.5 (s,
1F). 13C NMR (CDCl3, 100 MHz):
175.3 (q, J = 36.5 Hz), 165.9,
d 7.83 (s, 1H), 7.18-7.00 (m, 3H), 5.70 (s, 1H), 3.52 (td,
4.5.2.11. Methyl-5-phenyl-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyr-
d
azolo[1,2-a]pyrazol-1(5H)-one (3k).
d
149.9 (qd, J = 115.2 Hz, 13.1 Hz,), 133.2 (q, J = 4.4 Hz), 126.8 (d,
J = 9.5 Hz), 124.5 (t, J = 5.1 Hz), 123.8, 117.7, 117.5, 116.2 (q,
J = 288.7 Hz), 116.6, 65.8, 51.4, 35.4.EI-MS m/z (%): 332 (M+, 9), 219
(51), 151 (46), 55 (100). HRMS-EI: calc. mass 332.0583, mass
332.0584, formula C14 H9 N2 O2 F5. FT-IR (neat, cmÀ1): 3069,
2920, 2851, 1744, 1664, 1565, 1488, 1425, 1409, 1362, 1277, 1223,
1194, 1144, 1022, 977, 929, 819, 786, 768, 747, 717.
Yellow oil. dr: 3:5. 0.245 g, 79%. 1H NMR (CDCl3, 300 MHz):
d
8.16 (s, 1H), 8.12 (s, 0.6H), 7.70–7.63 (m, 6H), 7.57–7.55 (m, 2H),
5.81 (s, 1H), 5.55 (s, 0.6H), 4.03 (t, 0.6H, J = 8.4 Hz), 3.48-3.35 (m,
2.7H), 3.08 (dd, 0.6H, J = 6.6 Hz, 3.0 Hz), 2.86 (t, 1H, J = 8.1 Hz), 1.60
(d, 2.4H, J = 7.2 Hz), 1.52 (d, 3H, J = 6.9 Hz). 19F NMR (CDCl3,
4.5.2.8. (4-Chlorophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
zolo[1,2-a]pyrazol-1(5H)-one (3h).
282 MHz):
100 MHz):
d
d
À72.7 (s, 3F), À72.8 (s, 1.8F). 13C NMR (CDCl3,
175.5 (q, J = 35.6 Hz), 175.3 (q, J = 35.5 Hz), 169.4,
168.6, 138.3, 134.5, 132.8, 132.0, 129.1, 128.9, 128.8, 128.6, 128.2,
128.0, 119.0, 118.3, 116.4 (q, J = 289.1 Hz), 116.3 (q, J = 288.3 Hz),
73.7, 69.8, 59.7, 55.1, 42.1, 41.5, 13.2, 12.2. EI-MS m/z (%): 310 (M+,
13), 233 (56), 69 (100). HRMS-EI: calc. mass 310.0929, mass
310.0925, formula C15 H13 N2 O2 F3.FT-IR (neat, cmÀ1): 3016,
2981, 1712, 1560, 1542, 1422, 1194, 1145, 903, 699.
Yellow oil. 0.261 g, 79%. 1H NMR (CDCl3, 300 MHz):
d 8.02 (s, 1H),
7.61–7.55 (m, 4H), 5.54 (s, 1H), 3.74–3.68 (m, 1H), 3.39–3.04 (m, 3H).
19F NMR (CDCl3, 282 MHz):
100 MHz):
d
À72.6 (s, 3F). 13C NMR (CDCl3,
d
175.0 (q, J = 35.7 Hz), 165.9, 135.9, 134.7, 132.4 (q,
J = 4.4 Hz), 129.4, 128.9, 118.4, 116.2 (q, J = 288.7 Hz), 72.2, 51.3, 35.5.
EI-MS m/z (%): 330 (M+, 17) 332 (M+2+, 6), 219 (95), 55 (100). ESI-MS
m/z: 331 [M+H+], 333 [M+2+H+]. HRMS-EI: calc. mass. 330.0383,
mass 330.0386, formula C14 H10 N2 O2 F3 Cl.FT-IR (neat, cmÀ1):
3033, 2920, 2840, 1674, 1562, 1425, 1361, 1194, 1142, 905, 733, 715.
4.5.2.12. (4-Methoxyphenyl)-2-methyl-6-(2,2,2-trifluoroacetyl)-2,3-
dihydropyrazolo[1,2-a]pyrazol-1(5H)-one (3l).
4.5.2.9. (4-Bromophenyl)-6-(2,2,2-trifluoroacetyl)-2,3-dihydropyra-
zolo[1,2-a]pyrazol-1(5H)-one (3i).
Yellow oil. dr: 4:5. 0.299 g, 88%. 1H NMR (CDCl3, 300 MHz):
d:
8.02 (s, 0.8H), 7.97 (s, 1H), 7.51 (d, 2H, J = 8.7 Hz), 7.34 (d, 1.6H,
J = 8.7 Hz), 7.09 (d, 4H, J = 8.7 Hz), 5.69 (s, 0.8H), 5.40 (s, 1H), 3.99 (s,
5.4H), 3.93–3.88 (m, 1H), 3.37–3.24 (m, 2.8H), 2.98–2.91 (m, 1H),
2.72–2.68 (m, 0.8H), 1.49 (dd, 3H, J = 7.2 Hz, 2.4 Hz), 1.40 (dd, 3H,
Yellow solid. Mp 92–948C. 0.306 g, 82%. 1H NMR (CDCl3,
J = 7.2 Hz, 2.4 Hz). 19F NMR (CDCl3, 282 MHz):
(s, 3F). 13C NMR (CDCl3, 100 MHz):
175.5 (q, J = 36.3 Hz), 175.3 (q,
d
À72.9 (s, 2.4F), -73.0
300 MHz):
d
7.97 (s, 1H), 7.70 (d, 2H, J = 8.1 Hz), 7.47 (d, 2H,
d
J = 8.1 Hz), 5.48 (s, 1H), 3.66 (td, 1H, J = 8.1 Hz, 3.0 Hz), 3.34–3.01
J = 36.3 Hz), 169.3, 168.5, 160.3, 159.9, 132.6 (q, J = 3.9 Hz), 131.7 (q,
J = 4.7 Hz), 131.2, 130.2, 129.5, 129.2, 119.2, 118.6, 116.3 (q,
J = 289.1 Hz), 116.2 (q, J = 288.3 Hz), 114.4, 114.1, 73.2, 68.9, 60.4,
59.5, 55.2, 54.7, 42.1, 41.5, 13.0, 12.3. EI-MS m/z (%): 340 (M+, 26), 69
(100). HRMS-EI: calc. mass 340.1035, mass 340.1036, formula C16
(m, 3H). 19F NMR (CDCl3, 282 MHz):
(CDCl3, 100 MHz):
d
À73.1 (s, 3F). 13C NMR
d
175.5 (q, J = 36.5 Hz), 165.8, 136.5, 132.5 (q,
J = 4.4 Hz), 131.9, 129.8, 122.8, 118.2, 116.2 (q, J = 288.8 Hz), 72.3,
51.4, 35.5. EI-MS m/z (%): 374 (M+, 4), 376 (M+2+, 4), 219 (70), 55

408
Y. Xin et al. / Journal of Fluorine Chemistry 132 (2011) 402–408
H15 N2 O3 F3.FT-IR (neat, cmÀ1): 3017, 2938, 2841, 1708, 1612,
1563, 1423, 1362, 1148, 1063, 1031, 903, 835, 720.
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(d) L. Pezdirc, U. Groselj, A. Meden, B. Stanovnik, J. Svete, J. Heterocycl. Chem. 45
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Yellow oil. dr: 1:3. 0.291 g, 82%. 1H NMR (CDCl3, 300 MHz):
d
8.62 (s, 0.3H), 8.53 (s, 1H), 8.45–8.43 (m, 1.3H), 8.11 (s, 1.6H), 8.02
(d, J = 6.6 Hz), 7.86–7.81 (m, 1.3H), 5.79 (s, 1H), 5.67 (s, 0.3H), 4.39–
4.31 (m, 0.5H), 4.10–4.05 (m, 0.3H), 3.59–3.10 (m, 3.9H), 1.61 (d,
ˇ
ˇ
ˇ
(j) C. Turk, J. Svete, B. Stanovnik, L. Golic, S. Golic-Grdadolnik, A. Golobic, L.
ˇ
Selic, Helv. Chem. Acta 84 (2001) 146–156;
3H, J = 6.9 Hz), 1.50 (d, 1H, J = 7.2 Hz). 19F NMR (CDCl3, 282 MHz):
d
ˇ
ˇ
(k) C. Turk, L. Golic, L. Selic, S. Svete, B. Stanovnik, ARKIVOC V (2001) 87–97;
À73.2 (s). 13C NMR (CDCl3, 100 MHz):
d 175.4 (q, J = 36.3 Hz), 175.3
(l) For patents see: US728733, US4734504, US4902707 and EP0202047.
ˇ
[8] (a) L. Pezdirc, V. Jovanovski, D. Bevk, R. Jakse, S. Pirc, A. Meden, B. Stanovnik, J.
(q, J = 36.3 Hz), 169.3, 169.0, 148.5, 148.3, 141.1, 139.2, 134.5,
134.4, 133.4, 132.9, 129.7, 129.4, 123.7, 123.4, 123.2, 123.1, 117.7,
117.2, 116.2 (q, J = 288.3 Hz), 116.1 (q, J = 288.3 Hz), 72.9, 71.0,
59.9, 57.1, 42.1, 41.3, 14.1, 11.9. EI-MS m/z (%): 355 (M+, 5), 233
(48), 69 (100). HRMS-EI: calc. mass 355.0780, mass 355.0782,
formula C15 H12 N3 O4 F3.FT-IR (neat, cmÀ1): 3078, 2981, 2937,
2854, 1743, 1668, 1558, 1513, 1429, 1359, 1236, 1163, 927, 711.
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We are grateful to the National Natural Science Foundation of
China (NNSFC No. 21032006) for the financial support on this
research.
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