organic compounds
5-Cyclohexyl-4-methyl-1H-pyrazol-3(2H)-one monohydrate
aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and bOrganic Chemistry Division, School of Advanced Sciences, VIT University, Vellore 632 014, India
*Correspondence e-mail: hkfun@usm.my
In the title compound, C10H16N2O·H2O, the cyclohexane ring is in a chair conformation and its least-squares plane makes a dihedral angle of 53.68 (5)° with the approximately planar pyrazole ring [maximum deviation = 0.034 (1) Å]. Pairs of intermolecular N—H⋯O hydrogen bonds form inversion dimers between neighbouring pyrazolone molecules, generating R22(8) ring motifs. The pyrazolone and water molecules are further linked by intermolecular N—H⋯O, C—H⋯O and O—H⋯O hydrogen bonds into two-dimensional sheets parallel to the bc plane.
Related literature
For pyrazole derivatives and their microbial activities, see: Ragavan et al. (2009, 2010). For related structures, see: Shahani et al. (2009, 2010a,b,c). For ring conformations, see: Cremer & Pople (1975). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supporting information
https://doi.org/10.1107/S1600536810039164/is2608sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810039164/is2608Isup2.hkl
The compound has been synthesized using the method available in the literature (Ragavan et al., 2010) and recrystallized using the ethanol-chloroform 1:1 mixture. Yield: 77%. m.p.: 205.4–206.2 °C.
All H atoms were located in a difference fourier map and were refined freely [refined distances: N—H = 0.889 (14)–0.923 (14) Å, C—H = 0.93 (12)–1.022 (13) Å and O—H = 0.858 (18)–0.888 (17) Å].
Antibacterial and antifungal activities of the azoles are most widely studied and some of them are used in clinical practice as anti-microbial agents. However, the existence of azole-resistant strains had led to the development of new antimicrobial compounds. In particular, pyrazole derivatives are also extensively studied and used as antimicrobial agents. Pyrazole is an important class of heterocyclic compound and many pyrazole derivatives are reported to have the broad spectrum of biological activities, such as anti-inflammatory, antifungal, herbicidal, anti-tumour, cytotoxic and antiviral activities. Pyrazole derivatives also act as antiangiogenic agents, A3 adenosine receptor antagonists, neuropeptide YY5 receptor antagonists, kinase inhibitor for treatment of type-2 diabetes, hyperlipidemia, obesity, and thrombopiotinmimetics. Recently urea derivatives of pyrazoles have been reported as potent inhibitors of p38 kinase. Since the high
of halogens (particularly chlorine and fluorine) in the aromatic part of the drug molecules play an important role in enhancing their biological activity, we are interested to have 4-fluoro or 4-chloro substitution in the aryls of 1,5-diaryl pyrazoles. As part of our on-going research aiming on the synthesis of new antimicrobial compounds, we have reported the synthesis of novel pyrazole derivatives and their microbial activities (Ragavan et al., 2009, 2010).The Θ = 177.06 (10)° and φ = 164.9 (19)° (Cremer & Pople, 1975), and its least-squares plane is at an angle of 53.68 (5)° with the approximately planar pyrazole ring (C7–C9/N1/N2; maximum deviation of 0.034 (1) Å at atom N2). The bond lengths (Allen et al., 1987) and angles are within normal ranges and comparable to those closely related structures (Shahani et al., 2009, 2010a,b,c)
of the title compound, (Fig. 1), consists of one 5-cyclohexyl-4-methyl-1H-pyrazol-3(2H)-one molecule (C1—C10/N1/N2/O1) and one water molecule. The 3-cyclohexyl-4-methyl-1 H-pyrazol-5-ol undergoes an enol-to-keto during the crystallization process (Fig. 2). The cyclohexane ring is in a chair conformation with puckering parameters of Q = 0.5813 (10) Å,In the crystal packing (Fig. 3), pairs of intermolecular N2—H1N2···O1 hydrogen bonds (Table 1) form dimers with neighbouring molecules, generating R22(8) ring motifs (Bernstein et al., 1995). The molecules are further linked by intermolecular N1—H1N1···O1W, C5—H5A···O1W, O1W—H1W1···O1 and O1W—H1W2 ···O1 hydrogen bonds (Table 1) into two-dimensional sheets parallel to the bc plane.
For pyrazole derivatives and their microbial activities, see: Ragavan et al. (2009, 2010). For related structures, see: Shahani et al. (2009, 2010a,b,c). For ring conformations, see: Cremer & Pople (1975). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom numbering scheme. | |
Fig. 2. Enol-to-keto tautomerism of the title compound during crystallization process. | |
Fig. 3. The crystal packing of the title compound, viewed two-dimensional arrays parallel to the bc plane. Dashed lines indicate hydrogen bonds. |
C10H16N2O·H2O | F(000) = 432 |
Mr = 198.26 | Dx = 1.216 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 9296 reflections |
a = 13.4959 (3) Å | θ = 3.0–34.7° |
b = 6.2497 (1) Å | µ = 0.09 mm−1 |
c = 13.9268 (3) Å | T = 100 K |
β = 112.782 (1)° | Block, colourless |
V = 1083.02 (4) Å3 | 0.46 × 0.27 × 0.23 mm |
Z = 4 |
Bruker SMART APEXII CCD area-detector diffractometer | 4715 independent reflections |
Radiation source: fine-focus sealed tube | 3863 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.033 |
φ and ω scans | θmax = 35.0°, θmin = 1.6° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −20→21 |
Tmin = 0.962, Tmax = 0.981 | k = −10→10 |
26403 measured reflections | l = −21→21 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.117 | All H-atom parameters refined |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0623P)2 + 0.2027P] where P = (Fo2 + 2Fc2)/3 |
4715 reflections | (Δ/σ)max < 0.001 |
199 parameters | Δρmax = 0.55 e Å−3 |
0 restraints | Δρmin = −0.28 e Å−3 |
C10H16N2O·H2O | V = 1083.02 (4) Å3 |
Mr = 198.26 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 13.4959 (3) Å | µ = 0.09 mm−1 |
b = 6.2497 (1) Å | T = 100 K |
c = 13.9268 (3) Å | 0.46 × 0.27 × 0.23 mm |
β = 112.782 (1)° |
Bruker SMART APEXII CCD area-detector diffractometer | 4715 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 3863 reflections with I > 2σ(I) |
Tmin = 0.962, Tmax = 0.981 | Rint = 0.033 |
26403 measured reflections |
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.117 | All H-atom parameters refined |
S = 1.03 | Δρmax = 0.55 e Å−3 |
4715 reflections | Δρmin = −0.28 e Å−3 |
199 parameters |
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.47692 (5) | 0.58283 (9) | 0.36443 (4) | 0.01649 (11) | |
N1 | 0.35298 (5) | 0.86770 (11) | 0.49923 (5) | 0.01570 (12) | |
N2 | 0.43455 (5) | 0.74179 (11) | 0.49437 (5) | 0.01560 (12) | |
C1 | 0.22589 (7) | 1.31323 (13) | 0.36124 (7) | 0.02077 (15) | |
C2 | 0.12483 (7) | 1.45257 (14) | 0.33028 (7) | 0.02375 (16) | |
C3 | 0.07738 (7) | 1.44773 (14) | 0.41354 (7) | 0.02298 (16) | |
C4 | 0.05310 (7) | 1.21880 (14) | 0.43594 (7) | 0.02146 (16) | |
C5 | 0.15219 (7) | 1.07543 (13) | 0.46434 (7) | 0.01902 (14) | |
C6 | 0.19853 (6) | 1.08190 (12) | 0.37959 (6) | 0.01492 (13) | |
C7 | 0.29215 (6) | 0.93410 (11) | 0.40136 (5) | 0.01425 (13) | |
C8 | 0.41832 (6) | 0.71084 (12) | 0.39255 (5) | 0.01420 (13) | |
C9 | 0.32907 (6) | 0.83939 (12) | 0.33169 (5) | 0.01507 (13) | |
C10 | 0.28323 (7) | 0.85575 (15) | 0.21552 (6) | 0.02220 (16) | |
O1W | 0.39076 (5) | 0.38748 (10) | 0.17409 (5) | 0.02017 (12) | |
H1A | 0.2820 (10) | 1.3696 (19) | 0.4284 (10) | 0.026 (3)* | |
H1B | 0.2551 (10) | 1.319 (2) | 0.3063 (11) | 0.030 (3)* | |
H2A | 0.0700 (11) | 1.398 (2) | 0.2637 (11) | 0.029 (3)* | |
H2B | 0.1410 (11) | 1.602 (2) | 0.3181 (11) | 0.033 (3)* | |
H3A | 0.1301 (11) | 1.516 (2) | 0.4797 (10) | 0.028 (3)* | |
H3B | 0.0083 (10) | 1.536 (2) | 0.3909 (10) | 0.027 (3)* | |
H4A | −0.0056 (10) | 1.161 (2) | 0.3741 (11) | 0.029 (3)* | |
H4B | 0.0270 (10) | 1.214 (2) | 0.4932 (10) | 0.028 (3)* | |
H5A | 0.2079 (11) | 1.124 (2) | 0.5307 (11) | 0.032 (3)* | |
H5B | 0.1334 (10) | 0.922 (2) | 0.4749 (10) | 0.025 (3)* | |
H6 | 0.1416 (10) | 1.028 (2) | 0.3127 (9) | 0.020 (3)* | |
H10A | 0.2285 (15) | 0.956 (3) | 0.1918 (15) | 0.066 (5)* | |
H10B | 0.3351 (14) | 0.891 (3) | 0.1877 (13) | 0.053 (5)* | |
H10C | 0.2553 (13) | 0.719 (3) | 0.1795 (14) | 0.060 (5)* | |
H1N1 | 0.3647 (11) | 0.938 (2) | 0.5581 (11) | 0.033 (3)* | |
H1N2 | 0.4682 (11) | 0.646 (2) | 0.5476 (11) | 0.034 (3)* | |
H1W1 | 0.4222 (13) | 0.442 (3) | 0.2377 (13) | 0.046 (4)* | |
H1W2 | 0.4323 (13) | 0.284 (3) | 0.1729 (13) | 0.052 (5)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0200 (3) | 0.0165 (2) | 0.0143 (2) | 0.00467 (19) | 0.00818 (19) | 0.00135 (18) |
N1 | 0.0190 (3) | 0.0166 (3) | 0.0112 (2) | 0.0047 (2) | 0.0057 (2) | 0.0004 (2) |
N2 | 0.0187 (3) | 0.0162 (3) | 0.0116 (3) | 0.0051 (2) | 0.0056 (2) | 0.0017 (2) |
C1 | 0.0210 (3) | 0.0161 (3) | 0.0261 (4) | 0.0025 (3) | 0.0102 (3) | 0.0048 (3) |
C2 | 0.0251 (4) | 0.0165 (3) | 0.0282 (4) | 0.0053 (3) | 0.0088 (3) | 0.0047 (3) |
C3 | 0.0227 (4) | 0.0170 (3) | 0.0272 (4) | 0.0040 (3) | 0.0074 (3) | −0.0051 (3) |
C4 | 0.0197 (3) | 0.0206 (4) | 0.0257 (4) | 0.0018 (3) | 0.0105 (3) | −0.0039 (3) |
C5 | 0.0208 (3) | 0.0179 (3) | 0.0211 (3) | 0.0028 (3) | 0.0113 (3) | 0.0010 (3) |
C6 | 0.0158 (3) | 0.0139 (3) | 0.0145 (3) | 0.0018 (2) | 0.0053 (2) | −0.0002 (2) |
C7 | 0.0166 (3) | 0.0135 (3) | 0.0122 (3) | 0.0015 (2) | 0.0052 (2) | 0.0010 (2) |
C8 | 0.0173 (3) | 0.0138 (3) | 0.0118 (3) | 0.0012 (2) | 0.0060 (2) | 0.0009 (2) |
C9 | 0.0180 (3) | 0.0156 (3) | 0.0112 (3) | 0.0034 (2) | 0.0052 (2) | 0.0015 (2) |
C10 | 0.0275 (4) | 0.0259 (4) | 0.0118 (3) | 0.0087 (3) | 0.0059 (3) | 0.0024 (3) |
O1W | 0.0246 (3) | 0.0216 (3) | 0.0139 (2) | 0.0035 (2) | 0.0071 (2) | 0.0007 (2) |
O1—C8 | 1.2880 (9) | C4—C5 | 1.5290 (11) |
N1—C7 | 1.3555 (9) | C4—H4A | 0.985 (14) |
N1—N2 | 1.3760 (9) | C4—H4B | 0.989 (13) |
N1—H1N1 | 0.889 (14) | C5—C6 | 1.5354 (10) |
N2—C8 | 1.3622 (9) | C5—H5A | 0.986 (14) |
N2—H1N2 | 0.923 (14) | C5—H5B | 1.020 (13) |
C1—C2 | 1.5326 (12) | C6—C7 | 1.4982 (10) |
C1—C6 | 1.5378 (11) | C6—H6 | 1.009 (12) |
C1—H1A | 1.012 (13) | C7—C9 | 1.3836 (10) |
C1—H1B | 0.987 (13) | C8—C9 | 1.4226 (10) |
C2—C3 | 1.5267 (13) | C9—C10 | 1.4953 (11) |
C2—H2A | 0.995 (14) | C10—H10A | 0.93 (2) |
C2—H2B | 0.986 (14) | C10—H10B | 0.948 (17) |
C3—C4 | 1.5267 (13) | C10—H10C | 0.987 (19) |
C3—H3A | 1.013 (14) | O1W—H1W1 | 0.888 (17) |
C3—H3B | 1.022 (13) | O1W—H1W2 | 0.858 (18) |
C7—N1—N2 | 108.07 (6) | H4A—C4—H4B | 106.1 (11) |
C7—N1—H1N1 | 126.7 (9) | C4—C5—C6 | 111.20 (7) |
N2—N1—H1N1 | 118.0 (9) | C4—C5—H5A | 109.6 (8) |
C8—N2—N1 | 108.86 (6) | C6—C5—H5A | 108.8 (8) |
C8—N2—H1N2 | 125.1 (9) | C4—C5—H5B | 110.4 (7) |
N1—N2—H1N2 | 119.0 (8) | C6—C5—H5B | 109.5 (7) |
C2—C1—C6 | 109.64 (7) | H5A—C5—H5B | 107.3 (11) |
C2—C1—H1A | 109.2 (7) | C7—C6—C5 | 113.01 (6) |
C6—C1—H1A | 108.4 (7) | C7—C6—C1 | 112.05 (6) |
C2—C1—H1B | 110.0 (8) | C5—C6—C1 | 110.36 (6) |
C6—C1—H1B | 110.7 (8) | C7—C6—H6 | 105.2 (7) |
H1A—C1—H1B | 108.9 (10) | C5—C6—H6 | 108.0 (7) |
C3—C2—C1 | 111.37 (7) | C1—C6—H6 | 107.9 (7) |
C3—C2—H2A | 108.8 (8) | N1—C7—C9 | 109.38 (6) |
C1—C2—H2A | 109.1 (8) | N1—C7—C6 | 121.81 (6) |
C3—C2—H2B | 109.6 (8) | C9—C7—C6 | 128.78 (7) |
C1—C2—H2B | 110.7 (8) | O1—C8—N2 | 122.31 (7) |
H2A—C2—H2B | 107.2 (11) | O1—C8—C9 | 130.36 (6) |
C2—C3—C4 | 111.10 (7) | N2—C8—C9 | 107.32 (6) |
C2—C3—H3A | 109.2 (7) | C7—C9—C8 | 105.99 (6) |
C4—C3—H3A | 109.7 (8) | C7—C9—C10 | 128.25 (7) |
C2—C3—H3B | 110.8 (7) | C8—C9—C10 | 125.68 (7) |
C4—C3—H3B | 109.0 (8) | C9—C10—H10A | 111.8 (12) |
H3A—C3—H3B | 106.9 (11) | C9—C10—H10B | 113.4 (10) |
C3—C4—C5 | 111.51 (7) | H10A—C10—H10B | 108.0 (15) |
C3—C4—H4A | 109.1 (8) | C9—C10—H10C | 114.0 (11) |
C5—C4—H4A | 109.8 (8) | H10A—C10—H10C | 108.0 (15) |
C3—C4—H4B | 111.4 (8) | H10B—C10—H10C | 101.0 (14) |
C5—C4—H4B | 108.8 (8) | H1W1—O1W—H1W2 | 104.0 (14) |
C7—N1—N2—C8 | −6.34 (8) | C5—C6—C7—C9 | 154.47 (8) |
C6—C1—C2—C3 | 57.93 (10) | C1—C6—C7—C9 | −80.10 (10) |
C1—C2—C3—C4 | −56.21 (10) | N1—N2—C8—O1 | −173.49 (7) |
C2—C3—C4—C5 | 54.34 (10) | N1—N2—C8—C9 | 5.81 (8) |
C3—C4—C5—C6 | −54.98 (9) | N1—C7—C9—C8 | −0.75 (9) |
C4—C5—C6—C7 | −176.77 (7) | C6—C7—C9—C8 | −178.70 (7) |
C4—C5—C6—C1 | 56.89 (9) | N1—C7—C9—C10 | 176.30 (8) |
C2—C1—C6—C7 | 175.19 (7) | C6—C7—C9—C10 | −1.65 (14) |
C2—C1—C6—C5 | −57.94 (9) | O1—C8—C9—C7 | 176.10 (8) |
N2—N1—C7—C9 | 4.32 (9) | N2—C8—C9—C7 | −3.12 (8) |
N2—N1—C7—C6 | −177.56 (6) | O1—C8—C9—C10 | −1.05 (14) |
C5—C6—C7—N1 | −23.26 (10) | N2—C8—C9—C10 | 179.74 (8) |
C1—C6—C7—N1 | 102.18 (8) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N1···O1Wi | 0.889 (14) | 1.866 (14) | 2.7513 (9) | 173.7 (12) |
N2—H1N2···O1ii | 0.924 (14) | 1.842 (13) | 2.7552 (9) | 169.5 (13) |
O1W—H1W1···O1 | 0.889 (17) | 1.851 (17) | 2.7354 (8) | 173.2 (18) |
O1W—H1W2···O1iii | 0.860 (19) | 1.961 (19) | 2.8007 (9) | 165.0 (16) |
C5—H5A···O1Wi | 0.987 (14) | 2.503 (15) | 3.4161 (12) | 153.7 (11) |
Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) −x+1, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C10H16N2O·H2O |
Mr | 198.26 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 100 |
a, b, c (Å) | 13.4959 (3), 6.2497 (1), 13.9268 (3) |
β (°) | 112.782 (1) |
V (Å3) | 1083.02 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.46 × 0.27 × 0.23 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.962, 0.981 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 26403, 4715, 3863 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.807 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.117, 1.03 |
No. of reflections | 4715 |
No. of parameters | 199 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.55, −0.28 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N1···O1Wi | 0.889 (14) | 1.866 (14) | 2.7513 (9) | 173.7 (12) |
N2—H1N2···O1ii | 0.924 (14) | 1.842 (13) | 2.7552 (9) | 169.5 (13) |
O1W—H1W1···O1 | 0.889 (17) | 1.851 (17) | 2.7354 (8) | 173.2 (18) |
O1W—H1W2···O1iii | 0.860 (19) | 1.961 (19) | 2.8007 (9) | 165.0 (16) |
C5—H5A···O1Wi | 0.987 (14) | 2.503 (15) | 3.4161 (12) | 153.7 (11) |
Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) −x+1, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2. |
Footnotes
‡Thomson Reuters ResearcherID: A-3561-2009.
Acknowledgements
HKF and TS thank Universiti Sains Malaysia (USM) for the Research University Grant (grant No. 1001/PFIZIK/811160). TS also thanks USM for the award of a research fellowship. VV is grateful to the DST-India for funding through the Young Scientist Scheme (Fast Track Proposal).
References
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Antibacterial and antifungal activities of the azoles are most widely studied and some of them are used in clinical practice as anti-microbial agents. However, the existence of azole-resistant strains had led to the development of new antimicrobial compounds. In particular, pyrazole derivatives are also extensively studied and used as antimicrobial agents. Pyrazole is an important class of heterocyclic compound and many pyrazole derivatives are reported to have the broad spectrum of biological activities, such as anti-inflammatory, antifungal, herbicidal, anti-tumour, cytotoxic and antiviral activities. Pyrazole derivatives also act as antiangiogenic agents, A3 adenosine receptor antagonists, neuropeptide YY5 receptor antagonists, kinase inhibitor for treatment of type-2 diabetes, hyperlipidemia, obesity, and thrombopiotinmimetics. Recently urea derivatives of pyrazoles have been reported as potent inhibitors of p38 kinase. Since the high electronegativity of halogens (particularly chlorine and fluorine) in the aromatic part of the drug molecules play an important role in enhancing their biological activity, we are interested to have 4-fluoro or 4-chloro substitution in the aryls of 1,5-diaryl pyrazoles. As part of our on-going research aiming on the synthesis of new antimicrobial compounds, we have reported the synthesis of novel pyrazole derivatives and their microbial activities (Ragavan et al., 2009, 2010).
The asymmetric unit of the title compound, (Fig. 1), consists of one 5-cyclohexyl-4-methyl-1H-pyrazol-3(2H)-one molecule (C1—C10/N1/N2/O1) and one water molecule. The 3-cyclohexyl-4-methyl-1 H-pyrazol-5-ol undergoes an enol-to-keto tautomerism during the crystallization process (Fig. 2). The cyclohexane ring is in a chair conformation with puckering parameters of Q = 0.5813 (10) Å, Θ = 177.06 (10)° and φ = 164.9 (19)° (Cremer & Pople, 1975), and its least-squares plane is at an angle of 53.68 (5)° with the approximately planar pyrazole ring (C7–C9/N1/N2; maximum deviation of 0.034 (1) Å at atom N2). The bond lengths (Allen et al., 1987) and angles are within normal ranges and comparable to those closely related structures (Shahani et al., 2009, 2010a,b,c)
In the crystal packing (Fig. 3), pairs of intermolecular N2—H1N2···O1 hydrogen bonds (Table 1) form dimers with neighbouring molecules, generating R22(8) ring motifs (Bernstein et al., 1995). The molecules are further linked by intermolecular N1—H1N1···O1W, C5—H5A···O1W, O1W—H1W1···O1 and O1W—H1W2 ···O1 hydrogen bonds (Table 1) into two-dimensional sheets parallel to the bc plane.