Newer chalcone scaffolds with reactive functional groups: Process, spectral and single crystal XRD studies European Journal of Chemistry 14 (2) (2023) 297-302 European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2023 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. https://dx.doi.org/10.5155/eurjchem.14.2.297-302.2405 European Journal of Chemistry View Journal Online View Article Online Newer chalcone scaffolds with reactive functional groups: Process, spectral and single crystal XRD studies Niteen Borane , Amar Ghanshyam Deshmukh , Nidhi Harnesh Oza , Rajamouli Boddula and Paresh Narayan Patel ,* Laboratory of Bio-Organic Chemistry, Tarsadia Institute of Chemical Science, Uka Tarsadia University, Bardoli - 394350, Gujarat, India * Corresponding author at: Laboratory of Bio-Organic Chemistry, Tarsadia Institute of Chemical Science, Uka Tarsadia University, Bardoli - 394350, Gujarat, India. e-mail: pareshn111@yahoo.com (P.N. Patel). 10.5155/eurjchem.14.2.297-302.2405 Received: 25 December 2022 Received in revised form: 25 March 2023 Accepted: 30 March 2023 Published online: 30 June 2023 Printed: 30 June 2023 Chalcones are versatile scaffolds for the synthesis of various heterocyclic systems with commercial utility. This work describes the synthesis of five novel chalcone derivatives. Syntheses were performed by a simple one-pot, straightforward Claisen-Schmidt condensation catalyzed with pyrrolidine and KOH. The chalcones were prepared by condensation of 4-formylbenzonitrile with different aromatic ketones at room temperature. The structures of all compounds have been investigated by FT-IR, NMR, and HR-MS spectroscopy. In addition, one chalcone structure was characterized by single-crystal XRD study. Crystal data for C21H15NO2 (Ch2): monoclinic, space group P21/c (no. 14), a = 6.5694(3) Å, b = 33.2697(15) Å, c = 7.4516(4) Å, β = 97.563(2)°, V = 1614.47(14) Å3, Z = 4, T = 293(2) K, μ(MoKα) = 0.083 mm-1, Dcalc = 1.289 g/cm3, 16000 reflections measured (4.898° ≤ 2Θ ≤ 49.99°), 2822 unique (Rint = 0.0249, Rsigma = 0.0196) which were used in all calculations. The final R1 was 0.0484 (I > 2σ(I)) and wR2 was 0.1257 (all data). The absorption maxima of all novel products were evaluated by UV-visible spectroscopy. These well-established structures of all newly prepared chalcone scaffolds with reactive functional groups (i.e. nitrile and 2-propenone) can be exploited as a crucial intermediate in the synthesis of new heterocyclic scaffolds with fluorescence and other applications. Nitrile Chalcone Pyrrolidine Heterocycle Single-crystal XRD 4-Formylbenzonitrile Cite this: Eur. J. Chem. 2023, 14(2), 297-302 Journal website: www.eurjchem.com 1. Introduction Chalcones are privileged structures and have been widely used as an effective template in medicinal chemistry for potential drug findings [1,2]. It is a simple, versatile scaffold established from many naturally occurring compounds [3]. Several chalcone derivatives have also been synthesized due to their convenient synthesis [4]. Various natural products and their modified compounds with chalcone skeleton (Figure 1) have shown plentiful exciting biological activities with medical potential against various diseases [5,6]. Chemically, they consist of two aromatic rings joined by a three-carbon, α,β- unsaturated carbonyl system. Their diverse structures allow them to cyclize and produce a variety of heterocyclic compounds with various biological activities [7-9]. Many synthetic equivalents, such as aza-chalcone and chalcone derivatives incorporating isoxazole, pyrazole, and indole, have been developed in recent decades [10]. Antioxidant, anticancer, antibacterial, antiprotozoal, antiulcer, antiviral, antihistaminic, anti-HIV, cytotoxic and anti-inflammatory actions have been demonstrated (Figure 1) in natural and synthesized chalcone derivatives [8-11]. In recent years, chalcone and its derivatives have exhibited numerous other properties, such as optical, photochemical, and nonlinear optic properties (Figure 1), and have been used as fluorescent dyes in light-emitting diodes, fluorescent sensors, and as fluorescent probes [12-16]. Due to its π-conjugated system, the optical characteristics of chalcone and its deriva- tives have received substantial attention due to their nonlinear optical and fluorescence nature due to the delocalization of the electronic charge and overlapping π-orbitals [17]. Because of their bioactivity and optoelectronic applications, many researchers have recently provoked the multifunctional behavior of chalcones. The chalcone scaffolds with reactive functional groups can enlarge the importance of the chalcone moiety for its synthetic utility. In this paper, we describe the synthesis of five novel chalcone molecules with a reactive functional group. These molecules were prepared by base-catalyzed Claisen-Schmidt condensation. During this investigation, two different catalysts, pyrrolidine and potassium hydroxide, were studied to develop two different protocols and have comparative studies. The spectral behavior of chalcones is an important key factor in understanding the formation of chalcone. ABSTRACT RESEARCH ARTICLE KEYWORDS https://dx.doi.org/10.5155/eurjchem.14.2.297-302.2405 https://www.eurjchem.com/ https://dx.doi.org/10.5155/eurjchem.14.2.297-302.2405 mailto:pareshn111@yahoo.com http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.14.2.297-302.2405&domain=pdf&date_stamp=2023-06-30 298 Borane et al. / European Journal of Chemistry 14 (2) (2023) 297-302 2023 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.14.2.297-302.2405 Figure 1. Chalcone: A privileged structure in chemical sciences. H O CN Ar O OMe NO2 NO2 NO2 Ar CN O Ar Pyrrolidine/KOH ∗∗ ∗ ∗ ∗ K1 K2 K3 K4 K5 EtOH; RT (Ch1 to Ch5)(A) (K1 to K5) Scheme 1. Synthesis of chalcone from 4-formylbenzonitrile. All newly prepared chalcones were analyzed by UV-vis, FTIR, and NMR spectroscopy. These chalcone derivatives can be used as a key intermediate for the synthesis of new novel heterocyclic scaffolds. 2. Experimental 2.1. Materials and methods All required chemicals were obtained from commercial sources and used without further purification. Solvents were dried over molecular sieves if necessary. 1H NMR spectra were recorded in CDCl3 or DMSO-d6 at room temperature using a Bruker AVANCE III 500 MHz (AV500) multi-nuclei solution NMR spectrometer, TMS was used as internal reference, integration, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, quin = quintet, m = multiplet, br = broad, app = apparent), coupling constants (J, Hz), and assignment. 13C and DEPT-135 NMR spectra were measured on a Bruker AVANCE III 125 MHz (AV125) instrument with complete proton decoupling. Chemical shifts in ppm from the residual solvent were reported as an internal standard. Infrared (IR) spectra were recorded neat by ATR on a Thermo Nicolet iS50 FT-IR spectrometer and are reported in cm-1. HR-MS data were obtained in methanol with Thermo Scientific Orbitrap Elite mass spectrometer. The melting point is measured by the open capillary method using a Sigma melting point apparatus. Single- crystal structural data were recorded on Bruker Kappa APEXII. For thin layer chromatography (TLC) analysis throughout this work, Merck precoated TLC plates (silica gel 60GF254, 0.25 mm) were used. The products were purified by recrystallisation or column chromatography on silica gel 60 (Merck, 230-400 mesh). 2.2. General process for pyrrolidine-catalyzed chalcone synthesis To a stirred solution of 4-formylbenzonitrile (A, 1.62 g, 10 mmol) in ethanol (5 mL), aryl methyl ketone derivatives (K1- K5; 10 mmol) dissolved in ethanol (2-3 mL) were added portion-wise (Scheme 1). The reaction mixture was stirred at room temperature for 20 min, during which time it turned into a homogeneous solution. Then 2 mL of pyrrolidine or 1 mL 0.5 mM KOH was added dropwise and the resulting mixture was stirred at room temperature for 6-8 h and the reaction mixture was neutralized by 0.1-0.2 N HCl where precipitation occurred. The precipitated product of chalcone was then collected by filtration. The crude product was purified by recrystallisation from CHCl3:MeOH (1:1, v/v, 10 mL) to produce the product (80- 85% yield) as yellow to light brown needles (Ch1-Ch5). A single crystal suitable for X-ray diffraction of chalcone was obtained by recrystallization of Ch2 from a saturated solution in DMSO. (E)-4-(3-(naphthalen-2-yl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch1): Color: Yellow solid. M.p.: 158-160 °C. 1H NMR (500 MHz, DMSO-d6, δ, ppm): 8.570-8.569 (d, J = 0.5 Hz, 1H, Ar-H), 8.137- 8.116 (dd, J = 8.5, 8.5 Hz, 1H, Ar-H), 8.040-8.025 (d J = 7.5 Hz, 1H, Ar-H), 7.995-7.978 (d, J = 8.5 Hz, 1H, Ar-H), 7.948-7.931 (d, J = 8.5 Hz, 1H, Ar-H), 7.885-7.853 (d, J = 16, 1H, α-CH), 7.812- 7.794 (m, 2H, Ar-H and β-CH), 7.781 (s, 1H, Ar-H), 7.764-7.747 (dd, J = 6.5, 7.0 Hz, 2H, Ar-H), 7.680-7.648 (m, 1H, Ar-H), 7.632- 7.599 (m, 1H, Ar-H). 13C NMR (125 MHz, DMSO-d6, δ, ppm): 189.49 (1C, C=O), 142.02 (1C, CH), 139.30 (1C, Ar-C), 135.70 (1C, Ar-C), 135.00 (1C, Ar-C), 132.72 (1C, Ar-C), 132.53 (1C, Ar- Borane et al. / European Journal of Chemistry 14 (2) (2023) 297-302 299 2023 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.14.2.297-302.2405 Table 1. Comparative yield for two different processes. Compounds Catalyst and Yield (%) KOH Pyrrolidine Ch1 80 82 Ch2 76 79 Ch3 85 86 Ch4 80 83 Ch5 84 86 C), 130.24 (1C, Ar-C), 129.58 (1C, Ar-C), 128.85 (1C, Ar-C), 127.91 (1C, Ar-C), 128.85 (1C, Ar-C), 127.91 (1C, Ar-C), 127.02 (1C, Ar-C), 125.09 (1C, Ar-C), 124.30 (1C, CH), 118.42 (1C, CN), 113.52 (1C, Ar-C). DEPT-135 (125 MHz, DMSO-d6, δ, ppm): 142.03, 132.72, 130.24, 129.58, 128.85, 128.77, 127.92, 127.02, 125.08, 124.30. HR-MS (EI, m/z) calcd. for C20H14ON: 284.1067; Found: 284.1070. (E)-4-(3-(6-methoxynaphthalen-2-yl)-3-oxoprop-1-en-1-yl) benzonitrile (Ch2): Color: Yellow solid. M.p.: 172-174 °C. 1H NMR (500 MHz, DMSO-d6, δ, ppm): 8.500-8.498 (d J = 1 Hz, 1H, Ar-H), 8.114-8.094 (dd, J = 8.5, 8.5 Hz, 1H, Ar-H), 7.919-7.901 (d, J = 9 Hz, 1H, Ar-H), 7.863-7.858 (d, J = 2.5 Hz, 1H, Ar-H), 7.841-7.832 (d, J = 4.5 Hz, 1H, Ar-H) 7.800-7.790 (m, 2H, Ar-H, α-CH), 7.780-7.769 (m, 1H, β-CH), 7.748-7.731 (dd, J = 6.5, 7 Hz, 2H, Ar-H), 7.265-7.242 (dd, J = 9, 9 Hz, 1H, Ar-H), 7.208-7.203 (d, J = 2.5 Hz, 1H, Ar-H), 3.986 (s, 3H, CH3-O). 13C NMR (125 MHz, DMSO-d6, δ, ppm): 189.01 (1C, C=O), 160.04 (1C, Ar-C), 141.58 (1C, CH), 139.43 (1C, Ar-C), 137.48 (1C, Ar-C), 133.00 (1C, Ar- C), 132.69 (1C, Ar-C), 132.02 (1C, Ar-C), 131.18 (1C, Ar-C), 130.18 (1C, Ar-C), 129.67 (1C, Ar-C), 128.71 (1C, Ar-C), 127.84 (1C, Ar-C), 127.52 (1C, Ar-C), 125.08 (1C, Ar-C), 125.05 (1C, CH), 119.96 (1C, Ar-C), 118.45 (1C, CN), 113.37 (1C, Ar-C), 105.90 (1C, Ar-C), 55.49 (1C, CH3-O). DEPT-135 (125 MHz, DMSO-d6, δ, ppm): 141.59, 132.69, 131.19, 130.18, 128.72, 127.52, 125.07, 125.06, 119.97, 105.89, 55.49. HR-MS (EI, m/z) calcd. for C21H16O2N: 314.1176, Found 314.1176. (E)-4-(3-(2-nitrophenyl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch3): Color: Yellow solid. M.p.: 156-158 °C. 1H NMR (500 MHz, DMSO-d6, δ, ppm): 8.241-8.223 (dd, J = 8, 8 Hz, 1H, Ar-H), 7.979- 7.962 (dd, J = 6.5, 7 Hz, 2H, Ar-H), 7.947-7.915 (m, 1H, α-CH), 7.909-7.892 (dd, J = 6.5, 7 Hz, 2H, Ar-H), 7.853-7.819 (m, 1H, β- CH), 7.768-7.750 (dd, J = 7.5, 8 Hz, 1H, Ar-H), 7.484 (s, 2H, Ar- H). 13C NMR (125 MHz, DMSO-d6, δ, ppm): 192.57 (1C, C=O), 147.07 (1C, Ar-C), 143.85 (1C, CH), 139.01 (1C, Ar-C), 135.53 (1C, Ar-C), 135.03 (1C, Ar-C), 133.22 (1C, Ar-C), 132.17 (1C, Ar- C), 129.93 (1C, Ar-C), 129.60 (1C, Ar-C), 129.12 (1C, Ar-C), 125.11 (1C, CH), 118.98 (1C, CN), 113.18 (1C, Ar-C). DEPT-135 (125 MHz, DMSO-d6, δ, ppm): 143.86, 135.04, 133.23, 132.17, 129.93, 129.60, 129.12, 125.12. (E)-4-(3-(3-nitrophenyl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch4): Color: Yellow solid. M.p.: 126-128 °C. 1H NMR (500 MHz, DMSO-d6, δ, ppm): 8.874-8.867 (t, 1H, Ar-H), 8.636-8.618 (m, 1H, Ar-H), 8.534-8.511 (m, 1H, α-CH), 8.211-8.180 (d, J = 16 Hz, 1H, β-CH), 8.165-8.148 (d, J = 8.5 Hz, 2H, Ar-H), 7.971-7.955 (d, J = 8 Hz, 2H, Ar-H), 7.918-7.902 (d, J = 8 Hz, 1H, Ar-H), 7.892- 7.886 (d, J = 3 Hz, 1H, Ar-H). 13C NMR (125 MHz, DMSO-d6, δ, ppm): 188.02 (1C, C=O), 148.74 (1C, Ar-C), 143.63 (1C, CH), 139.43 (1C, Ar-C), 138.86 (1C, Ar-C), 135.31 (1C, Ar-C), 133.21 (1C, Ar-C), 132.58 (1C, Ar-C), 131.15 (1C, Ar-C), 130.20 (1C, Ar- C), 128.11 (1C, Ar-C), 125.16 (1C, Ar-C), 123.49 (1C, CH), 119.07 (1C, CN), 113.11 (1C, Ar-C). DEPT-135 (125 MHz, DMSO-d6, δ, ppm): 143.63, 135.32, 133.21, 132.59, 131.15, 130.20, 128.11, 125.15, 123.49. (E)-4-(3-(4-nitrophenyl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch5): Color: Yellow solid. M.p.: 170-172 °C. 1H NMR (500 MHz, DMSO-d6, δ, ppm): 8.028-7.977 (t, 3H, Ar-H and α-CH), 7.941- 7.924 (d, J = 8.5 Hz, 2H, Ar-H), 7.887-7.870 (d, J = 8.5 Hz, 2H, Ar- H), 7.640-7.609 (d, J = 16 Hz, 1H, β-CH), 6.645-6.628 (d, J = 8.5 Hz, 2H, Ar-H). 13C NMR (125 MHz, DMSO-d6, δ, ppm): 186.13 (1C, C=O), 154.49 (1C, Ar-C), 140.24 (1C, CH), 139.74 (1C, Ar-C), 133.11 (1C, Ar-C), 131.82 (1C, Ar-C), 129.53 (1C, Ar-C), 126.32 (1C, Ar-C), 125.5 (1C, CH), 119.18 (1C, CN), 113.20 (1C, Ar-C), 112.17 (1C, Ar-C). DEPT-135 (125 MHz, DMSO-d6, δ, ppm): 139.74, 133.12, 131.82, 129.54, 126.30, 113.20. 2.3. Single-crystal XRD data collection Single-crystal XRD analysis including data collection, cell refinement, and data reduction was performed with a Stoe IPDS2 area detector using Stoe IPDS2 software [18] and graphite-monochromated MoKα (λ = 0.71073 Å) at 100(2) K Twin integration. The structure was solved by direct methods using SIR2004 [19] and all non-hydrogen atoms were anisotropically refined by full-matrix least squares on F2 using SHELXL [20]. Cell refinement: APEX2 and SAINT [21,22]; Data reduction: SAINT and XPREP [22,23]; Program(s) used to refine structure: SHELXL [20]; molecular graphics: ORTEP-3 [24] for Windows and Mercury [25] software used to prepare material for publication: SHELXL [20] and PLATON [26]. The integration and scaling were performed to obtain reflection profiles from each of the twin components. A component was used to determine the space group, followed by the determination of the initial structure by the direct method (SHELX) [27] using the crystallographic CRYSTALS program [28]. 3. Results and discussion 3.1. Synthesis of five novel chalcone molecules (Ch1-5) Initially, all molecules were prepared by our earlier developed KOH-catalyzed process [29,30]. Thereafter, to have a comparative investigation, we tried to prepare all five structures with the use of pyrrolidine as the catalyst while remaining all parameters. During this study, pyrrolidine was clearly observed to be an effective alternative to KOH. In both processes, we were able to obtain a greater amount of yield with pyrrolidine than KOH (Table 1). The structure of the synthesized compounds was confirmed by infrared (IR), NMR, HR-MS, UV-vis, and single-crystal XRD spectral analysis. 3.2. FT-IR and HR-MS spectroscopic studies The vibrational stretching frequency of the aromatic chalcones was analyzed by FT-IR spectroscopy. The FTIR spect- rums of all prepared chalcones have shown a characteristic absorption band at 2260-2222 cm-1 corresponding to the CN stretching frequency. The existence of the C=O group was confirmed by IR spectral data, which showed sharp bands in the range of 1625-1660 cm-1 in the presence of conjugated ketones, suggesting the presence of the described compounds. The absorption band at 1627 cm-1 indicates the presence of α,β- unsaturated ketone which confirms the formation of chalcone. 3.3. NMR spectroscopic studies Spectral analysis by 1H NMR and 13C NMR revealed the structure of all these compounds (Ch1-5). The chalcones appeared to be geometrically pure and configured trans (JHa-Hb = 16 Hz) according to 1H NMR spectra. The methoxy proton in Ch2 chalcone was observed at δ 3.986 ppm. In the 13C NMR spectrum, carbonyl carbon was observed at δ 198 ppm and aromatic carbons were observed in the range of δ 150 to120 ppm. 300 Borane et al. / European Journal of Chemistry 14 (2) (2023) 297-302 2023 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.14.2.297-302.2405 Table 2. Crystal data and structure refinement for (E)-4-(3-(6-methoxynaphthalen-2-yl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch2). Empirical formula C21H15NO2 Formula weight (g/mol) 313.34 Temperature (K) 293(2) Crystal system Monoclinic Space group P21/c a, (Å) 6.5694(3) b, (Å) 33.2697(15) c, (Å) 7.4516(4) β (°) 97.563(2) Volume (Å3) 1614.47(14) Z 4 ρcalc (g/cm3) 1.289 μ (mm-1) 0.083 F(000) 656.0 Crystal size (mm3) 0.3 × 0.25 × 0.2 Radiation MoKα (λ = 0.71073) 2Θ range for data collection (°) 4.898 to 49.99 Index ranges -7 ≤ h ≤ 7, -37 ≤ k ≤ 39, -7 ≤ l ≤ 8 Reflections collected 16000 Independent reflections 2822 [Rint = 0.0249, Rsigma = 0.0196] Data/restraints/parameters 2822/0/217 Goodness-of-fit on F2 1.088 Final R indexes [I≥2σ (I)] R1 = 0.0484, wR2 = 0.1141 Final R indexes [all data] R1 = 0.0657, wR2 = 0.1257 Largest diff. peak/hole (e.Å-3) 0.17/-0.17 Table 3. Bond lengths for (E)-4-(3-(6-methoxynaphthalen-2-yl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch2). Figure 2. Molecular structure displacement ellipsoid plot drawn at 40% probability (Ch2). Nitrile (CN) is typically observed in the range between δ 115-125 ppm deshielding due to nitrogen. The DEPT spectrum of all prepared compounds clearly confirms the presence of the corresponding quaternary carbons in the molecules. 3.4. UV-Visible spectroscopy The π → π* transition (bathochromic shift) and the n → π* transition (hypsochromic shift) are the two main absorption maxima in chalcone derivatives [31-33]. The absorption maxima at 370 and 371 nm, respectively, in the UV-Visible spectra of chalcones Ch1 and Ch2, and the UV-Visible spectrum of the chalcone Ch3 to Ch5 and the absorption maxima at 372, 373, and 373 nm, are attributable to the π → π* transition, respectively. The productions of chalcone Ch1 to Ch5 were also confirmed by their absorption maxima seen in their respective UV spectrums. 3.5. Single-crystal XRD study Clearly, the structure of 4-(3-(6-methoxynaphthalen-2-yl)- 3-oxoprop-1-en-1-yl)benzonitrile (Ch2) was well recognized by its single-crystal XRD studies (Figure 2). Crystal data and structure refinement for Ch2 are listed in Table 2. The H atoms were comprised in calculated positions and treated as riding atoms: C–H = 0.93–0.96 Å with Uiso(H) = 1.5 Ueq(C-methyl) and 1.2 Ueq(C) for all other H atoms in the compound [34]. The structure was refined for the molecule as a two-component twin: 180 rotations about the axis a; BASF = 0.063(1). The molecular geometry of the compound is very similar, with bond distances and angles in the expected range (Tables 3 and 4). In a single crystal structure, the polynuclear naphthalene ring and the aromatic phenyl ring with the nitrile group are almost coplanar with the α,β-unsaturated carbonyl moiety. Atom Atom Length (Å) Atom Atom Length (Å) C1 C2 1.355(3) C11 O1 1.426(3) C1 C6 1.409(3) C12 C13 1.485(3) C2 C3 1.411(3) C12 O2 1.220(2) C3 C4 1.361(3) C13 C14 1.311(3) C3 O1 1.363(2) C14 C15 1.461(3) C4 C5 1.412(3) C15 C16 1.387(3) C5 C6 1.421(3) C15 C20 1.386(3) C5 C10 1.412(3) C16 C17 1.377(3) C6 C7 1.406(3) C17 C18 1.384(3) C7 C8 1.371(3) C18 C19 1.374(3) C8 C9 1.418(3) C18 C21 1.439(3) C8 C12 1.479(3) C19 C20 1.374(3) C9 C10 1.356(3) C21 N1 1.136(3) Borane et al. / European Journal of Chemistry 14 (2) (2023) 297-302 301 2023 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.14.2.297-302.2405 Table 4. Bond angles for (E)-4-(3-(6-methoxynaphthalen-2-yl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch2). Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C2 C1 C6 121.19(19) C8 C12 C13 119.26(17) C1 C2 C3 120.44(19) O2 C12 C8 120.68(18) C4 C3 C2 120.08(19) O2 C12 C13 120.05(18) C4 C3 O1 125.59(19) C14 C13 C12 121.62(19) O1 C3 C2 114.33(18) C13 C14 C15 127.7(2) C3 C4 C5 120.63(18) C16 C15 C14 123.05(19) C4 C5 C6 119.22(17) C20 C15 C14 119.26(19) C10 C5 C4 122.88(18) C20 C15 C16 117.7(2) C10 C5 C6 117.89(18) C17 C16 C15 121.4(2) C1 C6 C5 118.39(18) C16 C17 C18 119.8(2) C7 C6 C1 122.41(18) C17 C18 C21 120.8(2) C7 C6 C5 119.19(17) C19 C18 C17 119.5(2) C8 C7 C6 121.96(18) C19 C18 C21 119.7(2) C7 C8 C9 118.35(18) C18 C19 C20 120.3(2) C7 C8 C12 123.01(18) C19 C20 C15 121.3(2) C9 C8 C12 118.62(17) N1 C21 C18 178.4(3) C10 C9 C8 120.97(18) C3 O1 C11 117.73(16) C9 C10 C5 121.61(18) Figure 3. Unit cell diagram of (E)-4-(3-(6-methoxynaphthalen-2-yl)-3-oxoprop-1-en-1-yl)benzonitrile (Ch2). In the packing structure, molecules are placed close to each other on the phenyl ring with the nitrile group, this could be due to the linear structure of the nitrile group attached to the fourth position of the phenyl ring (Figure 2). However, the naphthalene sites with the methoxy group are quite far from each other, which could be because of the nonlinear structure on the methoxy group and the bulky naphthalene ring system. As expected, the bond angles at the fusion of two rings in the naphthalene ring were significantly higher than the expected value of 120° for sp2 hybridization. The molecule is packed with weak intermolecular C–H···O, C–H···C and C–H···N interactions using nitrile nitrogen, oxygen from methoxy and carbonyl groups. In addition, weak π-π stacking interactions are observed between naphthalene and phenyl rings. The molecular packing in the unit cell viewed from the axis a is presented in Figure 3. 4. Conclusions Claisen-Schmidt condensations, catalyzed by pyrrolidine/ potassium hydroxide as a base catalyst, were used to synthesize Ch1 to Ch5 derivatives. The prepared molecules were then characterized by HR-MS, FT-IR, and NMR spectroscopy. Selectively, the structure of Ch2 was established by single crystal X-ray diffraction (XRD) study. The optical properties of the chalcones were examined by using ultraviolet-visible (UV- vis) spectral data. The FT-IR spectrum of all prepared molecules shows a characteristic peak at 1660-1630 cm-1, which corres- ponds to the C=O group of the stretching frequency, which confirms the formation of chalcones. Compounds (Ch1-Ch5) were also confirmed by 1H NMR spectral analysis. The 1H NMR spectra suggested that the chalcones were geometrically pure and configured trans (JHa-Hb = 16 Hz) to prove the formation of derivatives of the chalcones. These well-characterized struc- tures of chalcone scaffolds with reactive functional groups (i.e. nitrile and 2-propenone) can be oppressed as a crucial intermediate in the synthesis of various novel heterocyclic scaffolds with numerous applications. Acknowledgements The authors are also thankful to the Indian Institute of Technology, Gandhinagar for NMR spectral analysis and Aether Industry Ltd. for mass analysis. Supporting information CCDC-1431802 contains the supplementary crystallographic data for this article. These data can be obtained free of charge via www.ccdc.cam.ac.uk/ data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033. Disclosure statement Conflict of interest: The authors declare that they have no conflict of interest. Ethical approval: All ethical guidelines have been adhered. Sample availability: Samples of the compounds are available from the author. http://www.ccdc.cam.ac.uk/%20data_request/cif http://www.ccdc.cam.ac.uk/%20data_request/cif mailto:data_request@ccdc.cam.ac.uk 302 Borane et al. / European Journal of Chemistry 14 (2) (2023) 297-302 2023 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.14.2.297-302.2405 CRediT authorship contribution statement Conceptualization: Paresh Narayan Patel; Methodology: Niteen Borane, Amar Ghanshyam Deshmukh, Nidhi Harnesh Oza; Software: Niteen Borane, Paresh Narayan Patel, Rajamouli Boddula; Validation: Paresh Narayan Patel, Rajamouli Boddula; Investigation: Paresh Narayan Patel, Rajamouli Boddula; Resources: Paresh Narayan Patel, Rajamouli Boddula; Data Curation: Paresh Narayan Patel, Rajamouli Boddula; Writing - Original Draft: Niteen Borane, Paresh Narayan Patel; Writing - Review and Editing: Niteen Borane, Paresh Narayan Patel, Rajamouli Boddula; Visualization: Paresh Narayan Patel, Rajamouli Boddula; Funding acquisition: Paresh Narayan Patel, Rajamouli Boddula; Supervision: Paresh Narayan Patel, Rajamouli Boddula; Project Administration: Paresh Narayan Patel, Rajamouli Boddula. Funding The work was financially supported by the GUJCOST, Government of India (Project No. GUJCOST/2020-21/2012). ORCID and Email Niteen Borane nitinborane95@gmail.com https://orcid.org/0000-0002-5636-428X Amar Ghanshyam Deshmukh amudeshmukh93@gmail.com https://orcid.org/0000-0002-9851-8953 Nidhi Harnesh Oza nidhioza0123@gmail.com https://orcid.org/0000-0002-0402-2448 Rajamouli Boddula rajamouliboddula@gmail.com https://orcid.org/0000-0003-0414-715X Paresh Narayan Patel pareshn111@yahoo.com https://orcid.org/0000-0002-8514-4753 References [1]. Dong, F.; Jian, C.; Zhenghao, F.; Kai, G.; Zuliang, L. Synthesis of chalcones via Claisen–Schmidt condensation reaction catalyzed by acyclic acidic ionic liquids. Catal. Commun. 2008, 9, 1924–1927. [2]. Durairaj, M.; Sivakumar, S.; Gnanendra, S. Chemical synthesis of chalcones by claisen-Schmidt condensation reaction and its characterization. Int. J. Res. Appl. Sci. Eng. Technol. 2018, 6, 2311– 2315. [3]. Bohm, B. A. Introduction to flavonoids; CRC Press: Boca Raton, FL, 1999. [4]. Gao, F.; Huang, G.; Xiao, J. Chalcone hybrids as potential anticancer agents: Current development, mechanism of action, and structure- activity relationship. Med. Res. Rev. 2020, 40, 2049–2084. [5]. Mahapatra, D. K.; Bharti, S. K.; Asati, V. Chalcone derivatives: Anti- inflammatory potential and molecular targets perspectives. Curr. Top. Med. Chem. 2017, 17, 3146–3169. [6]. Rocha, S.; Ribeiro, D.; Fernandes, E.; Freitas, M. A systematic review on anti-diabetic properties of chalcones. Curr. Med. Chem. 2020, 27, 2257–2321. [7]. Xu, S.; Chen, M.; Chen, W.; Hui, J.; Ji, J.; Hu, S.; Zhou, J.; Wang, Y.; Liang, G. Chemopreventive effect of chalcone derivative, L2H17, in colon cancer development. BMC Cancer 2015, 15, 870. [8]. Lin, Y.; Zhang, M.; Lu, Q.; Xie, J.; Wu, J.; Chen, C. A novel chalcone derivative exerts anti-inflammatory and anti-oxidant effects after acute lung injury. Aging (Albany NY) 2019, 11, 7805–7816. [9]. Henry, E. J.; Bird, S. J.; Gowland, P.; Collins, M.; Cassella, J. P. Ferrocenyl chalcone derivatives as possible antimicrobial agents. J. Antibiot. (Tokyo) 2020, 73, 299–308. [10]. de Mello, M. V. P.; Abrahim-Vieira, B. de A.; Domingos, T. F. S.; de Jesus, J. B.; de Sousa, A. C. C.; Rodrigues, C. R.; Souza, A. M. T. de A comprehensive review of chalcone derivatives as antileishmanial agents. Eur. J. Med. Chem. 2018, 150, 920–929. [11]. Cheng, P.; Yang, L.; Huang, X.; Wang, X.; Gong, M. Chalcone hybrids and their antimalarial activity. Arch. Pharm. (Weinheim) 2020, 353, e1900350. [12]. Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Poojary, B. Structural and optical properties of a new chalcone single crystal. J. Cryst. Growth 2012, 354, 182–187. [13]. Anuradha, G.; Vasuki, G.; Khan, I. A.; Kulkarni, M. V. Crystal and Molecular Structure of N-[2-(6-Methoxy-2-oxo-2H-Chromen-4-yl- Benzofuran-3-yl]- Benzamide. Cryst. Struct. Theory Appl. 2012, 01, 107–113. [14]. Xie, Z.; Chen, C.; Xu, S.; Li, J.; Zhang, Y.; Liu, S.; Xu, J.; Chi, Z. White-light emission strategy of a single organic compound with aggregation- induced emission and delayed fluorescence properties. Angew. Chem. Int. Ed Engl. 2015, 54, 7181–7184. [15]. Tandel, S. N.; Deshmukh, A. G.; Rana, B. U.; Patel, P. N. Studies of novel benzofuran based chalcone scaffolds: A dual spectroscopic approach as selective hydrazine sensor. Chem. Phys. Lett. 2023, 817, 140426. [16]. Ali, M. K. M.; Elzupir, A. O.; Ibrahem, M. A.; Suliman, I. I.; Modwi, A.; Idriss, H.; Ibnaouf, K. H. Characterization of optical and morphological properties of chalcone thin films for optoelectronics applications. Optik (Stuttg.) 2017, 145, 529–533. [17]. Dhanaraj, P. V.; Rajesh, N. P.; Vinitha, G.; Bhagavannarayana, G. Crystal structure and characterization of a novel organic optical crystal: 2- Aminopyridinium trichloroacetate. Mater. Res. Bull. 2011, 46, 726– 731. [18]. STOE IPDS diffractometer control software, version 2.87. Stoe & Cie GmbH Darmstadt, Germany. [19]. Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Spagna, R. SIR2004: an improved tool for crystal structure determination and refinement. J. Appl. Crystallogr. 2005, 38, 381–388. [20]. Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Crystallogr. C Struct. Chem. 2015, 71, 3–8. [21]. Bruker (2012). APEX. Bruker AXS Inc., Madison, Wisconsin, USA. [22]. Bruker (2012). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. [23]. Bruker (2012). XPREP. Bruker AXS Inc., Madison, Wisconsin, USA. [24]. Farrugia, L. J. WinGXandORTEP for Windows: an update. J. Appl. Crystallogr. 2012, 45, 849–854. [25]. Macrae, C. F.; Edgington, P. R.; McCabe, P.; Pidcock, E.; Shields, G. P.; Taylor, R.; Towler, M.; van de Streek, J. Mercury: visualization and analysis of crystal structures. J. Appl. Crystallogr. 2006, 39, 453–457. [26]. Spek, A. L. Structure validation in chemical crystallography. Acta Crystallogr. D Biol. Crystallogr. 2009, 65, 148–155. [27]. Sheldrick, G. M. A short history of SHELX. Acta Crystallogr. A 2008, 64, 112–122. [28]. Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.; Watkin, D. J. CRYSTALS version 12: software for guided crystal structure analysis. J. Appl. Crystallogr. 2003, 36, 1487–1487. [29]. Patel, P. N.; Chadha, A. Synthesis, single crystal structure and spectroscopic aspects of Benzo[b]thiophene-3-carbaldehyde based chalcones. J. Chem. Crystallogr. 2016, 46, 245–251. [30]. Rai, S.; Patel, P. N.; Chadha, A. Preparation, characterisation, and crystal structure analysis of (2E,2′E)-3,3′-(1,4-phenylene)bis(1-(2- aminophenyl)prop-2-en-1-one. Crystallogr. Rep. 2016, 61, 1086– 1089. [31]. Patel, P. N.; Chadha, A. A simple metal free highly diastereoselective synthesis of heteroaryl substituted (±) cyclohexanols by a branched domino reaction. Tetrahedron 2018, 74, 204–216. [32]. Tandel, S.; Patel, N. C.; Kanvah, S.; Patel, P. N. An efficient protocol for the synthesis of novel hetero-aryl chalcone: A versatile synthon for several heterocyclic scaffolds and sensors. J. Mol. Struct. 2022, 1269, 133808. [33]. Patel, P. N.; Desai, D. H.; Patel, N. C.; Deshmukh, A. G. Efficient multicomponent processes for synthesis of novel poly-nuclear hetero aryl substituted terpyridine scaffolds: Single crystal XRD study. J. Mol. Struct. 2022, 1250, 131737. [34]. Patel, P. N.; Desai, D. H.; Patel, N. C. Synthesis, spectral, and single crystal XRD studies of novel terpyridine derivatives of benzofuran-2- carbaldehyde and their Cu(II) complex. Russ. J. Coord. Chem. 2021, 47, 909–914. Copyright © 2023 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at http://www.eurjchem.com/index.php/eurjchem/pages/view/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution, or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (http://www.eurjchem.com/index.php/eurjchem/pages/view/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). mailto:nitinborane95@gmail.com https://orcid.org/0000-0002-5636-428X mailto:amudeshmukh93@gmail.com https://orcid.org/0000-0002-9851-8953 mailto:nidhioza0123@gmail.com https://orcid.org/0000-0002-0402-2448 mailto:rajamouliboddula@gmail.com https://orcid.org/0000-0003-0414-715X mailto:pareshn111@yahoo.com https://orcid.org/0000-0002-8514-4753 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms http://creativecommons.org/licenses/by-nc/4.0 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms 1. Introduction 2. Experimental 2.1. Materials and methods 2.2. General process for pyrrolidine-catalyzed chalcone synthesis 2.3. Single-crystal XRD data collection 3. Results and discussion 3.1. Synthesis of five novel chalcone molecules (Ch1-5) 3.2. FT-IR and HR-MS spectroscopic studies 3.3. NMR spectroscopic studies 3.4. UV-Visible spectroscopy 3.5. Single-crystal XRD study 4. Conclusions Acknowledgements Supporting information Disclosure statement CRediT authorship contribution statement Funding ORCID and Email References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: