143-146Novel pyrazole chalcone has been synthesized by reaction of phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde and acetophenone by Claisen-Schmidt reaction in ethanol by microwave assisted method. It has been characterized by elemental analysis and spectroscopic (FTIR, 1H NMR and MS) studies. Crystal structure of the compound has been determined using single-crystal X-ray diffraction. Hydrogen-bonded chain is formed by C–H···O bonding enhanced by C–H···π interaction. Adjacent chains are connected through the π∙∙∙π interactions

Banpurkar, Anita R

Perdih, Franc

Wazalwar, Sachin S

English

NOPR

Indian Journal of Chemistry Vol. 59B, January 2020, pp. 143-146       Single-crystal X-ray diffraction study of novel pyrazole chalcone derived from  1-phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde Anita R Banpurkar*a, Sachin S Wazalwara & Franc Perdihb a Department of Applied Chemistry, Rajiv Gandhi College of Engineering, Research and Technology, Chandrapur 442 403, India b Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia E-mail: anitabanpurkar1@gmail.com; sacheein@gmail.com; franc.perdih@fkkt.unilj.si Received 1 August 2018; accepted (revised) 31 July 2019 Novel pyrazole chalcone has been synthesized by reaction of phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde and acetophenone by Claisen-Schmidt reaction in ethanol by microwave assisted method. It has been characterized by elemental analysis and spectroscopic (FTIR, 1H NMR and MS) studies. Crystal structure of the compound has been determined using single-crystal X-ray diffraction. Hydrogen-bonded chain is formed by C–H···O bonding enhanced by C–H···π interaction. Adjacent chains are connected through the π···π interactions. Keywords: Microwave assisted pyrazole carbaldehyde, chalcone, acetophenone, single-crystal study Chalcones represent an important class of molecules. It shows presence of an electron donor and electron acceptor group. Phenyl substituents are electron donors, whereas carbonyl groups act as electron acceptors. The aromatic ketone group and enone group in chalcones makes it more active. Chalcones are useful for the preparation of biologically and industrially important compounds1. They are found abundantly in edible plants of species Leguminosae, Asteraceae, Moraceae, etc.2 Chalcones comprise of a class of compounds with important therapeutic and pharmacological potential. It’s easy preparation and great potential of oral administration3 support the feasibility of chalcone-based compounds as therapeutic agents. Chalcone and its derivatives show diverse medicinal properties including anti-inflammatory4, immunomodulatory5, anticancer6, anti-HIV7, antiproliferative8, and α-glucosidase inhibitory activities9. Some pyrazole derivatives show antiviral activity against Herpes infections10. Chalcones are also used as precursors in the biosynthesis of flavonoids11 and isoflavonoids12.  Experimental Section Material and Method All the starting materials and solvents were purchased from commercial sources and were used without further purification. Microwave oven of SAMSUNG, 800W output with digital timer and clock was used for synthesis. Melting points were determined in open capillaries using Electro thermal melting point apparatus and are uncorrected. Progress of reactions was monitored by TLC. Infrared (IR) spectra (4000–600 cm−1) of the samples were recorded using a Perkin–Elmer Spectrum 100, equipped with a Specac Golden Gate Diamond ATR as a solid sample support. 1H NMR spectra were recorded with a BrukerAvance III 500 NMR spectrometer with TMS as internal reference. MS spectra were recorded with an Agilent 6624 Accurate Mass TOF LC/MS instrument (ESI ionization). Elemental (C, H, N) analyses were obtained using Perkin–Elmer 2400 Series II CHNS/O Elemental Analyzer.  Synthesis of 1-phenyl-3-p-tolyl-1H-pyrazole-4-carbal- dehyde, 3:  A mixture of 4-methylacetophenone 1 (1.34 g,  10.0 mmol), phenylhydrazine (1.08 g, 10.0 mmol), 1 drop of conc. HCl and ethanol as a solvent was taken in a 100 mL conical flask and irradiated in microwave oven for 10-20 s at 450 watt at an interval of 5 second each. The resultant dry solid 2 was dissolved in excess of DMF, followed by addition of 15 mmol of POCl3 with continuous stirring in cold condition at about 8° to 10°C. The reaction mixture was allowed to attain RT and heated at about 80°C for 1 h conventionally. On hydrolysis it gave off white colored solid. The solid obtained was washed with water to remove excess of HCl, filtered, dried and recrystallized using ethanol. The recrystallized INDIAN J. CHEM., SEC B, JANUARY 2020   144compound was kept for crystal growth by slow evaporation of saturated solution of compound in mixture of ethanol and chloroform (1:1 v/v) in a dark chamber at low temperature13. Yield 89%. m.p.100°C. IR: 3125 (Ar-CH), 2838 (C–H in CHO), 1673 (C=O), 1518 (C=N), 1450 cm–1 (C=C); 1H NMR (500 MHz, CDCl3): δ 2.36 (s, 3H, Ar-CH3), 7.23-7.25 (d, 2H, Ar-H), 7.30-7.33 (t, 1H, Ar-H), 7.42-7.45 (t, 2H, Ar-H), 7.62-7.63 (d, 2H, Ar-H), 7.71-7.73 (d, 2H, Ar-H), 8.46 (s, 1H, pyrazole-CH), 9.98 (s, 1H, –CHO).  Synthesis of 1-phenyl-3-(1-phenyl-3-p-tolyl-1H-pyrazole-4-yl)prop-2-en-1-one, 4:  A mixture of phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde (2.62 g, 10 mmol), acetophenone (1.20 g, 10 mmol) and 2–3 drops of saturated NaOH solution was subjected to microwave irradiation in presence of ethanol as a solvent for 1–2 min at 450 watt at an interval of 5 second each. The dark yellow solid so obtained was added to crushed ice followed by acidification using 0.1 M HCl to give pale yellow solid. The product obtained was filtered, dried and recrystallized using ethanol. The recrystallized compound was allowed for crystal growth by slow evaporation of its saturated solution with mixture of ethanol and chloroform (1:1 v/v) in a dark chamber at low temperature. Yield 79%. m.p.140°C. IR: 3117 (CH=CH), 3066 (Ar-CH), 1643 (C=O), 1539(C=N), 1448 (C=C), 831 cm–1 (Ar-CH3); 1H NMR (500 MHz, CDCl3): δ 2.36 (s, 3H, Ar-CH3), 7.18 (s, 2H, Ar-H), 7.23 (d, 2H, Ar-H), 7.30 (s, Ar-H), 7.40-7.44 (m, 4H, Ar-H), 7.48 (d, 1H, CH=CH), 7.72 (d, 2H, Ar-H), 7.81 (d, 1H, CH=CH), 7.89 (d, 2H, Ar-H), 8.27 (s, 1H, pyrazolic CH); MS (ESI+): m/z 365 (MH+); HRMS: Calcd for C25H21N2O: 365.1648. Found: 365.1648. Anal. Calcd for C25H20N2O (364.43 g/mol): C, 82.39; H, 5.53; N, 7.69. Found: C, 81.69; H, 5.31; N, 7.35%.  X-ray crystallographic study Single-crystal X-ray diffraction data was  collected on an Agilent Technologies SuperNova Dual diffractometer with an Atlas detector using monochromated Cu-Kα radiation (λ = 1.54184 Å) at RT. The data was  processed using CrysAlis Pro14. Structure was solved by charge-flipping methods implemented in Superflip15 and refined on F2 using full-matrix least-squares procedures using SHELX201416. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were readily located in a difference Fourier maps and were subsequently treated as riding atoms in geometrically idealized positions, with C–H = 0.93 (aromatic and alkenyl) or 0.96 Å (methyl) with Uiso(H) = kUeq(C), where k = 1.5 for methyl groups, which were permitted to rotate but not to tilt, and 1.2 for all other H atoms. CCDC 1848478 contains the supplementary crystallographic data for this paper. This data is provided free of charge by The Cambridge Crystallographic Data Centre. Crystallographic data is listed in Table I.  Results and Discussion The compound 1-phenyl-3-(1-phenyl-3-p-tolyl-1H-pyrazole-4-yl)prop-2-en-1-one 4 was obtained by microwave assisted Claisen-Schmidt reaction between acetophenone and 1-phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde 3 (Scheme I). The IR spectrum of compounds 3 showed characteristic υ(-CH=O) absorption band in the region 1660–1677 cm−1, and υ(-C=N) band in the region 1513–1522 cm−1. The 1H NMR spectra of compounds 3 in CDCl3 exhibit characteristic singlet at 9.95–9.99 ppm attributed  to –CH=O protons, singlet at 8.46–9.28 ppm is Table I — Crystallographic data for 4 Compd code 4 CCDC number 1848478 Molecular formula C25H20N2O Molecular weight 364.43 Crystal System Monoclinic Space group P21/c a (Å) 12.7305(4) b (Å) 15.5517(5) c (Å) 10.9948(4) α (°) 90 β (°) 110.267(4) γ (°) 90 Z 4 V (Å3) 2041.99(13) Dcalc (g cm–3) 1.185 μ (mm–1) 0.570 F(000) 768 Reflections collected 7919 Independent reflections 3874 Rint 0.0216 Parameters 255 R1, wR2 [I> 2σ(I)]a 0.0463, 0.1300 R1, wR2 (all data)a 0.0575, 0.1442 GOFb 1.036 Δρmin, Δρmax (e Å–3) 0.174, –0.136 aR = ∑||Fo| – |Fc||/∑|Fo|; wR2 = {∑[w(Fo2 – Fc2)2]/∑[w(Fo2)2]}1/2. bS = {∑[(Fo2 – Fc2)2]/(n/p)}1/2 where n is the number of reflections and p is the total number of parameters refined. BANPURKAR et al.: NOVEL PYRAZOLE CHALCONE   145attributed to pyrazolic –CH protons. The IR spectrum of compounds 4 shows characteristic absorption band at 3117 cm−1 representing olefinic stretching and at 1643 cm−1attributed to ketonic C=O group. Absorption band in the region 1539 cm−1 represents pyrazolic N–N bond. The 1H NMR of compound 4 exhibit characteristic singlet at 2.36 ppm attributed to three protons of CH3 in tolyl ring, singlet at 8.27 ppm attributed to pyrazolic CH, doublet at 7.48 ppm and 7.81 ppm, respectively, representing CH=CH of chalcone moiety. Furthermore, the mass spectra and elemental analysis support the structure of  compound 4.  Single crystal structure of compound 4 shows that all the bond lengths are within normal ranges (Figure 1)17. In the compound the pyrazole ring N1/N2/C10–C12 is essentially planar with the maximum deviation from planarity of –0.003 (2) for atom C 11. Also, the pyrazolylphenylpropenone backbone is almost planar with the dihedral angle between pyrazole ring and the phenyl ring C4-C9 of 7.63 (10)°. Similar small dihedral angle of 7.54 (11)° is present also between the pyrazole ring and the phenyl ring C13–C18. On the other hand, the dihedral angle between pyrazole and tolyl ring C19–C24 is much larger being 32.95 (9)°. Supramolecular structure of the studied compound is achieved through a hydrogen-bonded chain formed by C12–H12···O1 bonding between the pyrazole CH moiety as a hydrogen-bond donor and the carbonyl O atom as a hydrogen-bond acceptor forming a C(7) graph set motif18. (Table II, Figure 2). This chain is further enhanced by a C23–H23···π interaction between the tolyl CH moiety and pyrazole ring. Adjacent chains are connected through the π···π interactions between pyrazole ring and phenyl ring C13–C18 with centroid-to-centroid distance of 3.9714 (12) Å, and dihedral angle between the rings of 7.54 (11)° and this 2D motif is further enhanced by  C21–H21·π interactions between the tolyl CH moiety and the phenyl C4–C9 ring. CH3OH3CNHH2NiNHNCH3ii~80°CH3CH3CNNiiiMWH3CNNO i EtOH, HCl, MW, 10-20 sii POCl3/DMF, ~80°C, Reflux 1 hiii Acetophenone, aq. NaOH, MW1234MWO  Scheme I — Synthesis of 1-phenyl-3-(1-phenyl-3-p-tolyl-1H-pyrazole-4-yl)prop-2-en-1-one   Figure 1 — Molecular structures and atom numbering scheme for4. Probability ellipsoids are drawn at the 50% level INDIAN J. CHEM., SEC B, JANUARY 2020   146Conclusion Novel pyrazole chalcone was synthesized by microwave assisted Claisen-Schimdt condensation reaction with good yield. Spectroscopic analysis and single crystal study proves the formation of desired compound. In the crystal structure hydrogen-bonded chain is formed by C12–H12···O1 bonding enhanced by a C23–H23···π interaction. Adjacent chains are connected through the π···π interactions.  Acknowledgments Financial support from the Slovenian Research Agency (ARRS) through project P1-0175 is gratefully acknowledged. The authors thank the EN-FIST Centre of Excellence, Ljubljana, Slovenia, for using Super Nova diffractometer.  References 1 Arshad M N, Al-Dies A M, Abdullah M, Asiri A M, Khalid M, Birinji A S, Khalid A, Ataualpa A A & Braga A C, J Mol Struct, 1141 (2017) 142. 2 Modzelewska A, Pettit C, Achanta G, Davidson N E, Huang P & Khan S R, Bioorg Med Chem, 14 (2006) 3491. 3 Wattenberg L W, Coccia J B & Galbraith A R, Cancer Lett, 83 (1994) 165. 4 Hsieh H K, Lee T H, Wang J P, Wang J J & Lin C N, Pharm Res, 15 (1998) 39. 5 Barfod L, Kemp K, Hansen M & Kharazmi A,  Int Immunopharmacol, 2 (2000) 545. 6 Kumar S K, Hager E, Pettit C, Gurulingappa H, Davidson N E, & Khan S R, J Med Chem, 46 (2003) 2813. 7 Artico M, Santo R D, Costi R, Novellino E, Greco G,  Massa S, Tramontano M E, Marongiu E, Montis A D & Colla P L, J Med Chem, 41 (1998) 3948. 8 Liu X L & Go M L, Bioorg Med Chem, 15 (2007) 7021. 9 Seo W D, Kim J H, Kang J E, Ryu H W, Long M J C, Lee H S, Yang M S & Park K H, Bioorg Med Chem Lett, 15 (2005) 5514. 10 Katade S, Phalgune U, Biswas S, Wakharkar R & Deshpande N, Indian J Chem, 47B (2008) 927. 11 Czemmel S, Heppel S C & Bogs J, Protoplasma, 249 (2012) 109. 12 Shelton D, Stranne M, Mikkelsen L, Pakseresht N, Welham, Hiraka H, Tabata S, Sato S, Paquette S, Wang T L, Martin C & Bailey P, Plant Physiol, 159 (2012) 2. 13 Wazalwar S, Banpurkar A & Perdih F, J Mol Struct, 1150 (2017) 258. 14 CrysAlis PRO, Agilent Technologies, Yarnton, England (2013). 15 Palatinus L & Chapuis G, J Appl Crystallogr, 40 (2007) 786. 16 Sheldrick G M, Acta Cryst, C71 (2015) 3. 17 Allen F H, Kennard O, Watson D G, Brammer L, Orpen A G & Taylor R, J Chem Soc Perkin Trans 2, 12 (1987). 18 Bernstein J, Davis R E, Shimoni L & Chang N L, Angew Chem Int Ed, 34 (1995) 1555.  Figure 2 — (a) Chain formation generated by C12–H12···O1hydrogen bonding (blue dashed lines) and C23–H23···πinteractions (black dashed lines). Hydrogen atoms not involved inthe motif shown have been omitted for clarity. (b) π···πinteractions between pyrazole and phenyl rings (black dashedlines). (c) Packing of hydrogen-bonded chains along c-axis. Table II — Hydrogen bond geometry of 4 D–H·A D–H (Å) H·A (Å) D·A (Å) D–H·A (°) Symmetry code C12–H12·O1  0.93 2.38 3.308(2) 174 x, 3/2 – y, ½ + z C21–H21·Cg2 0.93 3.00 3.775(2) 142 –x, ½ + y, ½ – z C23–H23·Cg1 0.93 2.83 3.593(2) 140 x, 3/2 – y, –½ + z Cg1 and Cg2 are N1/N2/C10–C12 and C4–C9 ring centroids, respectively. 

Single-crystal X-ray diffraction study of novel pyrazole chalcone derived from  1-phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde

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Single-crystal X-ray diffraction study of novel pyrazole chalcone derived from 1-phenyl-3-p-tolyl-1H-pyrazole-4-carbaldehyde

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