Preparation and structures of some new 1H-pyrazole derivatives

Article abstract of DOI:10.1007/s11164-012-0758-8

Some new 3,5-diaryl-1H-pyrazoles were prepared from aryl methyl ketones via Claisen condensation with aromatic esters and followed by cyclization with hydrazine monohydrate. Their structures were confirmed by IR, ¹H NMR spectroscopy, mass spect

Full text of DOI:10.1007/s11164-012-0758-8

Res Chem Intermed (2013) 39:2311–2320
DOI 10.1007/s11164-012-0758-8
Preparation and structures of some new 1H-pyrazole
derivatives
•
Dun-Jia Wang Yan-Fang Kang
•
•
Chun-Yang Zheng Xian-Hong Wei
Received: 22 March 2012 / Accepted: 30 July 2012 / Published online: 19 August 2012
Ó Springer Science+Business Media B.V. 2012
Abstract Some new 3,5-diaryl-1H-pyrazoles were prepared from aryl methyl
ketones via Claisen condensation with aromatic esters and followed by cyclization
1
with hydrazine monohydrate. Their structures were confirmed by IR, H NMR
spectroscopy, mass spectrometry and elemental analysis. The X-ray structure for
3(5)-(4-tert-butylphenyl)-5(3)-(4-methoxyphenyl)-1H-pyrazole (2b) was presented.
The results show that compound 2b exists as tautomers I and II, and its molecules
are connected by the N–HÁÁÁN intermolecular hydrogen bonds to form cyclic dimers
consisting of the tautomers I and II.
Keywords 1H-Pyrazole Á Preparation Á Crystal structure Á Hydrogen bonds
Introduction
Pyrazoles are of great interest to the biochemical community due to their wide range
of biological activities, such as analgesic, antimicrobial, anti-inflammatory and
antihypertensive properties [1–3]. Recently, we have synthesized some aromatic
1,3-diketones used as ultraviolet absorbents [4]. As 1,3-diketones are well-known
intermediates in the broadest and most efficient route to 1H-pyrazoles [5–7], we
undertook studies on 1H-pyrazole derivatives as an extension of our previous work.
Currently, we have studied the structures and anti-microbial activity of some
substituted pyrazoles [8, 9]. In this paper, some new 1H-pyrazoles were prepared
and characterized by FTIR, 1H NMR spectroscopy, mass spectrometry and
elemental analysis. The compound 3(5)-(4-tert-butylphenyl)-5(3)-(4-methoxy-
phenyl)-1H-pyrazole (2b) was used to carry out the X-ray structure determination.
D.-J. Wang (&) Á Y.-F. Kang Á C.-Y. Zheng Á X.-H. Wei
Hubei Key Laboratory of Pollutant and Reuse Technology, College of Chemistry
and Environmental Engineering, Hubei Normal University, Huangshi 435002, China
e-mail: dunjiawang@163.com
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D.-J. Wang et al.
Experimental
Materials and methods
All reagents and solvents were purchased from commercial sources, and were used
without further purification. Melting points were determined by X-4 digital melting-
point apparatus and are uncorrected. Elemental analysis (C, H, N) was performed
using a Perkin-Elmer 2400 elemental analyzer. 1H NMR spectra were measured on a
Varian Mercury-Plus 400 NMR–nuclear magnetic resonance instrument in CDCl3
solution with TMS as internal standard. Infrared spectra were recorded on a Nicolet
FTIR 5700 spectrophotometer with KBr pellets. Low-resolution electrospray
ionization mass spectra (ESI–MS) were determined with a Finnigan LCQ Advantage
Max spectrometer.
Preparation of the title compounds
Preparation of the title compounds is shown in Scheme 1. The 1H-pyrazole
derivatives were obtained by the condensation of 1,3-diketone compounds with
hydrazine monohydrate in ethanol. The 1,3-diketone compounds were prepared
from aryl methyl ketones via Claisen condensation with aromatic esters according to
the literature methods [4]. The crude products were recrystallized from dilute
ethanol solution to give 1H-pyrazoles derivatives in yields of 59–80 %.
Preparation of 1,3-diketone compounds
The aryl methyl ketones (0.04 mol) are dissolved in 50 mL toluene and NaNH2
(1.95 g, 0.05 mol) is added. The mixture is stirred at 80 °C for 15 min and the
aromatic esters (0.04 mol) are added. The stirring is prolonged for 6 h. The reaction
mixture is cooled to room temperature and acidified with dilute hydrochloric acid.
O
O
O
O
HN
N
1) NaNH2
2) H
NH2NH2 H2O
+
C2H5OH
R1
R2
R2
OCH3
R1
R1
R2
1a - 5a
1b - 5b
CH3
Cl
1: R1=
R2=
OCH3
C(CH3)3
2: R1=
3: R1=
R2=
R2=
4: R1=
5: R1=
CH3
F
R2=
R2=
F
O
Scheme 1 Synthetic route to compounds 1b–5b
123

Preparation and structures of some new 1H-pyrazole derivatives
2313
The toluene layer is separated and the solvent removed by evaporation. The residual
solid is recrystallized from ethanol to obtain the 1,3-diketone compounds 1a–5a.
1-(4-Methylphenyl)-3-(4-chlorophenyl)-propane-1,3-dione (1a)
Colorless crys-
tals, yield 78 %, mp 136–137 °C; IR (KBr): m 3,469 (w), 3,065 (m), 2,952 (m),
2,860 (w), 1,605 (s), 1,545 (m), 1,509 (s), 1,463 (m), 1,369 (w), 1,231 (s), 1,150 (m),
1
1,100 (s), 1,021 (s), 856 (s), 798 (s) cm-1; H NMR (400 MHz, CDCl3): d 2.35
(s, 3H, CH3), 4.61 (s, 0.16H, keto CH2), 6.78 (s, 1,H, enol CH), 7.06–7.09 (m, 2H),
7.48 (d, 2H, Ar–H, J = 8.4 Hz), 7.90 (d, 2H, Ar–H, J = 8.4 Hz), 7.99–8.02
(m, 2H), 17.03 (br s,1H, enol OH) ppm; ESI–MS: m/z 273.68 [M ? 1]?; Anal.
calcd. for C16H13ClO2: C, 70.46; H, 4.80; found C, 70.93; H, 4.75 %.
1-(4-tert-Butylphenyl)-3-(4-methoxyphenyl)-propane-1,3-dione (2a) Colorless crys-
tals, yield 67 %, mp 82–83 °C; IR (KBr): m 3,477 (w), 3,071 (m), 2,972 (s), 2,836 (m),
1,603 (s), 1,547 (m), 1,508 (s), 1,436 (s), 1,307 (m), 1,258 (m), 1,227 (s), 1,168 (s),
1,023 (s), 845 (s), 797 (s), 707 (m) cm-1; 1H NMR (400 MHz, CDCl3): d 1.37 (s, 9H,
C(CH3)3), 3.89 (s, 3H, OCH3), 4.58 (s, 0.16H, keto CH2), 6.79 (s, 1H, enol CH), 6.98
(d, 2H, Ar–H, J = 8.8 Hz), 7.50 (d, 2H, Ar–H, J = 8.8 Hz), 7.91 (d, 2H, Ar–H,
J = 8.8 Hz), 7.98 (d, 2H, Ar–H, J = 8.8 Hz), 17.10 (br s,1H, enol OH) ppm; ESI–
MS: m/z 311.06 [M ? 1]?; Anal. calcd. for C20H22O3: C, 77.39; H, 7.14; found C,
77.28; H, 7.11 %.
1-(4-Phenylphenyl)-3-phenyl-propane-1,3-dione (3a) White powder, yield 62 %,
mp 109–110 °C (Ref. [10] 111 °C); IR (KBr): m 3,448 (w), 3,055 (w), 2,956 (w),
2,863 (w), 1,596 (s), 1,571 (s), 1,509 (s), 1,483 (s), 1,443 (s), 1,295 (s), 1,226 (s),
1,182 (m), 1,070 (m), 1,004 (m), 852 (s), 755 (s), 685 (s) cm-1; 1H NMR (400 MHz,
CDCl3): d 4.70 (s, 0.19H, keto CH2), 6.91 (s, 1H, enol CH), 7.41–7.56 (m, 6H),
7.64–7.67 (m, 2H), 7.72 (d, 2H, Ar–H, J = 8.4 Hz), 8.00–8.02 (m, 2H), 8.07 (d, 2H,
Ar–H, J = 8.4 Hz), 16.92 (br s,1H, enol OH) ppm; ESI–MS: m/z 300.95 [M ? 1]?;
Anal. calcd. for C21H16O2: C, 83.98; H, 5.37; found C, 84.32; H, 5.29 %.
1-(4-Methylphenyl)-3-(4-fluorophenyl)-propane-1,3-dione (4a) Colorless crystals,
yield 72 %, mp 125–126 °C; IR (KBr): m 3,452 (w), 3,078 (m), 2,961 (m), 2,870
(w), 1,602 (s), 1,540 (m), 1,505 (s), 1,456 (m), 1,365 (w), 1,226 (s), 1,158 (s), 1,104
(m), 1,011 (m), 850 (s), 794 (s) cm-1; 1H NMR (400 MHz, CDCl3): d 2.36 (s, 3H,
CH3), 4.56 (s, 0.14H, keto CH2), 6.78 (s, 1H, enol CH), 7.10–7.13 (m, 2H), 7.50 (d,
2H, Ar–H, J = 8.4 Hz), 7.81 (d, 2H, Ar–H, J = 8.4 Hz), 7.96–7.99 (m, 2H), 17.06
(br s,1H, enol OH) ppm; ESI–MS: m/z 257.11 [M ? 1]?; Anal. calcd. for
C16H13FO2: C, 74.99; H, 5.11; found C, 75.46; H, 5.03 %.
1-(4-Fluorophenyl)-3-(furan-2-yl)-propane-1,3-dione (5a) Pale yellow crystals,
yield 76 %, mp 80–81 °C; IR (KBr): m 3,426 (w), 3,065 (w), 2,978 (w), 1,604 (s),
1,549 (m), 1,505 (s), 1,467 (s), 1,298 (m), 1,225 (s), 1,161 (s), 1,093 (m), 1,014 (s),
842 (m), 789 (s), 753 (s) cm-1; 1H NMR (400 MHz, CDCl3): d 4.46 (s, 0.10H, keto
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D.-J. Wang et al.
CH2), 6.59–6.60 (m, 1H), 6.72 (s, 1H, enol CH), 7.14–7.18 (m, 2H), 7.24 (d, 1H,
J = 3.6 Hz), 7.62 (s, 1H), 7.97–8.00 (m, 2H), 16.20 (br s,1H, enol OH) ppm; ESI–
MS: m/z 232.83 [M ? 1]?; Anal. calcd. for C13H9FO3: C, 67.24; H, 3.91; found C,
67.63; H, 3.85 %.
Preparation of 1H-pyrazole derivatives
Hydrazine monohydrate (0.01 mol) in ethanol is added dropwise to a refluxing
ethanol solution (30 mL) of the corresponding 1,3-diketone (0.01 mol). The solution
is then refluxed for 3 h. After completion of the reaction (detected by thin layer
chromatography, TLC), the solvent is removed by evaporation. The residual solid is
recrystallized from dilute ethanol solution to give the title compounds 1b–5b.
3-(4-Chlorophenyl)-5-(4-methylphenyl)-1H-pyrazole (1b) White solid, yield 71 %,
mp 199–200 °C; IR: (KBr): , (b, s), 3,053 (m), 2957 (m), 2,856 (m), 1,605 (m),
1,506 (s), 1,467 (s), 1,451 (m), 1,373 (w), 1,258 (s), 1,220 (s), 1,159 (s), 1,039 (s),
1
978 (s), 798 (s), 755 (s) cm-1; H NMR (400 MHz, CDCl3): d 2.35 (s, 3H, CH3),
6.81 (s, 1H, pyrazolyl C–H), 7.35–7.40 (m, 2H, Ar–H), 7.50 (d, 2H, Ar–H,
J = 8.4 Hz), 7.63 (d, 2H, Ar–H, J = 8.4 Hz), 7.75–7.7.80 (m, 2H, Ar–H) ppm,
pyrazolyl N–H not found; ESI–MS: m/z 269.7 [M ? 1]?; Anal. calcd. for
C16H13ClN2: C, 71.51; H, 4.88; N, 10.42; found C, 71.86; H, 4.83; N, 10.45 %.
3(5)-(4-tert-Butylphenyl)-5(3)-(4-methoxyphenyl)-1H-pyrazole (2b) Colorless nee-
dles, yield 72 %, mp 185–186 °C; IR: (KBr): 3,205 (b, s), 3,019 (m), 2,956 (s), 2,867
(m), 1,615 (s), 1,504 (s), 1,463 (s), 1,245 (s), 1,175 (s), 1,036 (s), 970 (s), 837 (s), 792
(s), 736 (m) cm-1; 1H NMR (400 MHz, CDCl3): d 1.34 (9H, s, C(CH3)3), 3.83 (3H, s,
CH3O), 6.73 (1H, s, pyrazloyl C–H), 6.91 (2H, d, Ar–H, J = 8.4 Hz), 7.42 (2H, d, Ar–
H, J = 8.0 Hz), 7.64–7.67 (4H, m, Ar–H), 8.20 (1H, bs, N–H) ppm; ESI–MS: m/z
612.7 [2 M]?, 306.2 [M ? 1]?; Anal. calcd. for C20H22N2O: C, 78.40; H, 7.24; N,
9.14; found C, 78.21; H, 7.20; N, 9.26 %.
3-(4-Phenylphenyl)-5-phenyl-1H-pyrazole (3b) White solid, yield 80 %, mp 206–
207 °C; IR: (KBr): 3,220 (b, s), 3,030 (m), 3,001 (m), 1,596 (m), 1,487 (s), 1,459 (s),
1
1,178 (m), 1,053 (m), 968 (s), 840 (s), 801 (s), 761 (s), 691 (s) cm-1; H NMR
(400 MHz, CDCl3): d 6.91 (1H, s, pyrazloyl C–H), 7.35–7.48 (6H, m, Ar–H),
7.60–7.65 (4H, m, Ar–H), 7.76 (2H, d, Ar–H, J = 7.6 Hz), 7.82 (2H, d, Ar–H,
J = 8.0 Hz) ppm, N–H not found; ESI–MS: m/z 297.3 [M ? 1]?; Anal. calcd. for
C21H16N2: C, 85.11; H, 5.44; N, 9.45; found C, 85.36; H, 5.29; N, 9.38 %.
3-(4-Fluorophenyl)-5-(4-methylphenyl)-1H-pyrazole (4b) Colorless needles, yield
67 %, mp 190–191 °C; IR: (KBr): 3,186 (b, s), 3,060 (m), 2,964 (m), 2,868 (m),
1,607 (m), 1,510 (s), 1,471 (s), 1,445 (m), 1,360 (w), 1,258 (m), 1,227 (s), 1,155 (s),
1,043 (s), 981 (s), 804 (s), 746 (s) cm-1; 1H NMR (400 MHz, CDCl3): d 2.36 (s, 3H,
CH3), 6.80 (s, 1H, pyrazolyl C–H), 7.05–7.10 (m, 2H, Ar–H), 7.48 (d, 2H, Ar–H,
J = 8.4 Hz), 7.60 (d, 2H, Ar–H, J = 8.4 Hz), 7.68–7.72 (m, 2H, Ar–H) ppm,
123

Preparation and structures of some new 1H-pyrazole derivatives
2315
pyrazolyl N–H not found; ESI–MS: m/z 253.2 [M ? 1]?; Anal. calcd. for
C16H13FN2: C, 76.17; H, 5.19; N, 11.10; found C, 76.46; H, 5.11; N, 11.35 %.
3-(4-Fluorophenyl)-5-(furan-2-yl)-1H-pyrazole (5b) White solid, yield 59 %, mp
164–165 °C; IR: (KBr): 3,147 (b, s), 3,066 (s), 2,993 (m), 2,871 (m), 1,613 (s),
1,509 (s), 1,462 (m), 1,430 (s), 1,233 (s), 1,168 (s), 1,075 (s), 1,011 (s), 894 (s), 837
(s), 787 (s), 730 (s) cm-1; 1H NMR (400 MHz, CDCl3): d 6.15 (1H, bs, N–H), 6.48
(1H, s, pyrazloyl C–H), 6.68 (1H, d, furfural C–H, J = 2.8 Hz), 7.08–7.12 (2H, m,
Ar–H), 6.72 (1H, s, furfural C–H), 7.43 (1H, s, furfural C–H), 7.70–7.74 (2H, m,
Ar–H) ppm; ESI–MS: m/z 229.1 [M ? 1]?; Anal. calcd. for C13H9FN2O: C, 68.41;
H, 3.97; N, 12.27; found C, 68.16; H, 3.92; N, 12.16 %.
Crystal structure determination
A single crystal of compound 2b suitable for X-ray diffraction analysis was
obtained by slow evaporation from CH2Cl2–EtOH (1:2) solutions. A colorless
crystal having dimensions of 0.20 mm 9 0.10 mm 9 0.10 mm was mounted on the
top of the glass fibers. The data were collected at 298 (2) K on a Bruker Smart 1000
CCD diffractometer using graphite monochromatic Mo Ka radiation (k = 0.71073
˚
A). The intensity data were corrected for Lp factors and empirical. The structure was
solved by direct methods with the SHELXTL-97 program [11]. The final refinement
was made by full-matrix least-squares techniques with anisotropic thermal
parameters for the non-hydrogen atoms on F2. All the H atoms were added
according to the theoretical models. Multi-scan absorption correction was applied
by use of the SADABS program [12]. A summary of crystal data is presented in
Table 1.
Results and discussion
Spectral characterization
1
Compounds 1a–5a and 1b–5b were characterized by elemental analysis, FTIR, H
NMR, and mass spectroscopy. The IR spectra of compounds 1a–5a showed that the
strong absorption bands in the regions of 1,605–1,596 cm-1 and 1,509–1,505 cm-1
belonged to the C=O and enolic C=C stretching vibrations, respectively. The enolic
C–O stretching absorption was observed at 1,225–1,231 cm-1. These bands
confirmed the presence of the keto-enol tautomer of the 1,3-diketone compounds.
The IR spectra of compounds 1b–5b exhibited broad bands around 3,220–3,147
cm-1 due to N–H stretching vibrations, strong absorption bands in the region of
1,618–1,596 cm-1 were assigned to the C=N stretching vibrations, and strong
absorption bands at 1,513–1,487 cm-1 were attributed to the N–H bending
vibrations. Medium bands in the range of 1,075–1,036 cm-1 were due to N–N
stretching vibrations [13, 14].
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D.-J. Wang et al.
Table 1 Crystal data and structure refinements for compound 2b
Structural data
Value
Compound
2b
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C
20H22N2O
306.40
298 (2)
Triclinic
P-1
˚
a (A)
9.876 (6)
13.559 (8)
14.095 (8)
˚
b (A)
˚
c (A)
a (o)
b (o)
c (o)
85.706 (12)
74.174 (11)
73.273 (10)
3
˚
Volume (A )
1,739.1 (18)
4
Z
Density (calc.) (g cm-3
)
1.170
Absorption coefficient (mm-1
)
0.073
F(000)
Crystal size (mm3)
Theta range for data collection (o)
656
0.20 9 0.10 9 0.10
1.50–25.00
h/k/l
-11, 11/-16, 15/-13, 16
19,036
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2r(I)]
R indices (all data)
6,043[R(int) = 0.0580]
6,043/0/425
1.455
R1 = 0.1484 wR2 = 0.3926
R1 = 0.2154 wR2 = 0.4299
0.536 and -0.356
-3
˚
Largest diff. peak and hole (e A
)
1
The H NMR spectra of compounds 1a–5a showed that the single peaks at
d = 16.20–17.10 ppm were due to the enolic OH protons, the single peaks at
d = 6.72-6.91 ppm were assigned to the vinylic protons in enol and the single
peaks at d = 4.46-4.70 ppm were attributed to the keto-CH2 protons. These were
consistent with the results of the IR spectra for the 1,3-diketone compounds. The 1H
NMR spectra of compounds 1b–5b displayed the aromatic protons at
d = 6.68–7.82 ppm, and exhibited a typical proton chemical shift of 3,5-disubsti-
tuted pyrazole (4–H) at d = 6.48–6.91 ppm. On the other hand, the N–H resonance
of the pyrazolyl ring of compounds 2b and 5b appeared as a broad and flat signal at
d = 6.15–6.73 ppm, but that of compounds 1b, 3b, and 4b were not observed in
CDCl3. Apparently, there is a fast tautomerism of the 1H-pyrazoles in CDCl3
solution. This is in accordance with the result in the literature [15].
123

Preparation and structures of some new 1H-pyrazole derivatives
2317
Fig. 1 View of compound 2b (tautomers I and II) with the atom-labeling scheme and 50 % probability
displacement ellipsoids
X-ray crystal structure
The crystal structure of compound 2b contains a dimer formed by one tautomer
I and the other tautomer II [16, 17]. Figure 1 shows labeled displacement ellipsoid
plots of these two tautomers, and the selected bond lengths, bond angles and torsion
angles are summarized in Table 2. The pyrazole moiety in both tautomers is nearly
coplanar from the torsion angles N1–C8–C9–C10, C8–C9–C10–N2, C9–C8–N1–
N2, C9–C10–N2–N1 and C8–N1–N2–C10 in tautomer I, and N3–C28–C29–C30,
C28–C29–C30–N4, C29–C28–N3–N4, C29–C30–N4–N3 and C28–N3–N4–C30 in
tautomer II (Table 2). The dihedral angles formed by two benzene rings (C2–C7)
and (C11–C16) with the pyrazole ring are 26.59° and 28.10° for I, respectively, and
those of two benzene rings (C22–C27) and (C31–C36) with the pyrazole ring are
27.00° and 25.86° for II, respectively. But the two pyrazole rings in tautomers I and
II are close to a planar and their dihedral angle is 4.03°, which leads to a strong
intermolecular hydrogen bond in the dimeric structure.
In the structure of compound 2b, the strong intermolecular hydrogen bonds are
the primary factors in building of crystal network. The hydrogen-bonding geometric
parameters are listed in Table 3. The network is connected by the two kinds of
N–HÁÁÁN hydrogen bonds to form cyclic dimers containing the tautomers I and II
˚
(Fig. 2). The first N–HÁÁÁN interaction is from N1 to N3 [N1ÁÁÁN3 = 2.813 (3) A,
N1–H1ÁÁÁN3 = 132 (3)o], and the second is between N4 and N2 [N4ÁÁÁN2 = 2.837
o
˚
(3) A, N4–H4AÁÁÁN2 = 131 (3) ]. Obviously, compound 2b packs via neutral
123

2318
D.-J. Wang et al.
Table 2 Selected geometric parameters for compound 2b
Parameter
Values
˚
Bond lengths (A)
C(5)–C(8)
1.443(8)
1.347(7)
1.405(8)
1.386(8)
1.334(7)
1.474(8)
1.347(6)
C(25)–C(28)
C(28)–N(3)
C(28)–C(29)
C(29)–C(30)
C(30)–N(4)
C(30)–C(31)
N(3)–(4)
1.462(8)
1.332(7)
1.393(8)
1.388(8)
1.353(7)
1.455(8)
1.330(6)
C(8)–N(1)
C(8)–C(9)
C(9)–C(10)
C(10)–N(2)
C(10)–C(11)
N(1)–N(2)
Angles (°)
N(1)–C(8)–C(9)
N(1)–C(8)–C(5)
C(9)–C(8)–C(5)
C(10)–C(9)–C(8)
N(2)–C(10)–C(9)
N(2)–C(10)–C(11)
C(9)–C(10)–C(11)
C(12)–C(11)–C(10)
C(16)–C(11)–C(10)
C(8)–N(1)–N(2)
C(10)–N(2)–N(1)
Torsion angles (°)
N(1)–C(8)–C(9)–C(10)
C(8)–C(9)–C(10)–N(2)
C(9)–C(8)–N(1)–N(2)
C(9)–C(10)–N(2)–N(1)
C(8)–N(1)–N(2)–C(10)
106.0(5)
120.4(5)
133.6(5)
106.3(5)
109.1(5)
119.8(5)
131.1(5)
122.3(5)
121.5(6)
110.9(5)
107.7(5)
N(3)–C(28)–C(29)
N(3)–C(28)–C(25)
C(29)–C(28)–C(25)
C(30)–C(29)–C(28)
N(4)–C(30)–C(29)
N(4)–C(30)–C(31)
C(29)–C(30)–C(31)
C(32)–C(31)–C(30)
C(36)–C(31)–C(30)
N(4)–N(3)–C(28)
N(3)–N(4)–C(30)
108.0(5)
120.4(5)
131.6(5)
106.5(5)
106.3(5)
120.3(5)
133.4(5)
121.7(5)
121.5(5)
108.8(5)
110.3(5)
0.7(4)
-0.8(6)
-0.3(6)
0.6(6)
N(3)–C(28)–C(29)–C(30)
C(28)–C(29)–C(30)–N(4)
C(29)–C(28)–N(3)–N(4)
C(29)–C(30)–N(4)–N(3)
C(28)–N(3)–N(4)–C(30)
0.6(6)
-0.9(6)
0.0(6)
0.9(6)
-0.2(6)
-0.5(6)
˚
Table 3 Hydrogen-bonding geometry for compound 2b (A, °)
D–HÁÁÁA
D–H
HÁÁÁA
DÁÁÁA
D–HÁÁÁA
N(1)–H(1)ÁÁÁN(3)
N(4)–H(4A)ÁÁÁN(2)
0.86 (3)
0.86 (3)
2.16 (3)
2.20 (3)
2.813 (3)
2.837 (3)
132 (3)
131 (3)
N–HÁÁÁN bonds which are assisted by resonance through the ÁÁÁN=C–C=C–NHÁÁÁ
iminoenamine p–conjugated system [18].
Conclusion
To summarize, we prepared some new 1H-pyrazole derivatives from aryl methyl
ketones via Claisen condensation with aromatic esters, followed by cyclization with
123

Preparation and structures of some new 1H-pyrazole derivatives
2319
Fig. 2 View for the packing of the dimeric structure in compound 2b. Dotted lines indicate
intermolecular N–HÁÁÁN hydrogen bonds
hydrazine monohydrate in ethanol. Their structures were established on the basis of
elemental analysis, FTIR, 1H NMR and mass spectroscopy. And the crystal
structure of compound 2b was confirmed by X-ray crystallographic studies. The
results showed that its crystal structure exists as tautomers I and II, and its
molecules are connected by the N–HÁÁÁN intermolecular hydrogen bonds to form
cyclic dimers consisting the tautomers I and II.
Supplementary materials
CCDC reference number 711754 contains the supplementary crystallographic data
for this article. This data can be obtained free of charge from the Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (Fax: ?44-1223-336033; email:
deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk.).
Acknowledgment This work was supported by the important Foundation of the Educational
Commission of Hubei Province PR China (no. CXY2009B029).
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