Abstract
Series of quinolone C3-substituted pyrazolines, isoxazolines, pyridines and pyrimidines were synthesized in good yields by the cyclocondensation reactions of 1, 2-unsaturated ketones and hydrazines, hydroxylamine hydrochloride and dimedone respectively. The quinolone derivatives (3, 5 and 7) were synthesized and further studied for their photophysical properties. High absorption and quantum yield are found for N1-phenyl and C3,4-dimethoxy substituents on phenyl ring (3h). Energy optimization by PM6 methods showed high stability required for selection of suitable candidates to be use as future blue emitters.
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Introduction
Until the 1950s, fluorescence was merely recognized as an ‘odd’ physical or physico-chemical phenomenon. However, during the last 50 years, the interest in the application of fluorescent molecules has steadily, sometimes even dramatically, increased and today fluorescent dyes play important role in many aspects of modern life [1]. The oldest use of fluorescent dyes probably represents the coloration of textile goods. More modern applications, to name a few, include optical brightness, which are practically colorless compounds that absorb in the near UV-region and emit in the far blue to violet part of the VIS spectrum, fluorescent pigments used as safety markings on cloth, fluorescent markers and probes, which are extremely important in analytical and medicinal chemistry. Interest in fluorescent dyes has been intensified mainly on analytical applications in biological sciences. Fluorescent compounds are widely used as markers in biochemical and nucleic acid technology is the subject of intensive investigations [2–4]. Recently, pyrazoloquinolines PQ (1H-pyrazolo [3,4-b] quinolines) are found to be highly fluorescent materials in the blue spectral region [5] as well as promising materials for electroluminescent applications [6, 7]. The substituents effects at different positions on fluorescent were studied on quinoline derivatives [8, 9], except the substituents effect at 3-position. The C3-heterocyclic moiety explains the long wavelength fluorescing state due to twisted intermolecular charge transfer (TICT) state [10]. Hence, we designed heterocyclic moiety at 3-position on quinolone nucleus.
Recently, we have reported the synthesis of highly fluorescent dipyrazolo [3,4-b: 3,4-d] pyridines [11], pyrazolo[3,4-b]-pyrrolo-[2,3-d]-pyridines [12], 2,6-dirayl-4-alkoxy pyridinecarbonitriles [13, 14] and spiro-oxazino-quinolines [15]. These reports and our ongoing interest in this field prompted us to synthesize new carbostyril fluorescent heterocycles. In present communication, we report variety of quinolone C3-substituted dihydropyrazole, isoxazole and pyridine derivatives and studied their fluorescence properties with the semiempirical study.
Results and discussion
The starting compound chalcones (1) are prepared by the known literature methods [16, 17], which on treatment with various hydrazines 2a–c in presence of catalytic amount of acetic acid in alcohol afforded dihydropyrazoles 3 in 60–65% yields. Here, the 1, 3-Micheal addition reactions occurs by attack of NHR on β-enone carbon, followed by SN2 displacement of hydroxyl group by NH2 in presence of acid catalyst (Scheme 1). The ambident nucleophile, hydroxylamine hydrochloride 4 in the presence of sodium acetate in glacial acetic acid, more nucleophilic nitrogen attack on β-carbon of the enone 1 and yields isoxazole 5 in 60–65% yields (Scheme 2). The pyridines 7 obtained by the Dimroth rearrangement reaction of chalcones 1 with dimedone 6 in ammonium acetate in presence of catalytic amount of acetic acid. The reaction proceeds via pyrone intermediate followed by the incorporation of nitrogen with ring opening and closing protocol (Scheme 3). The structure of compound 3, 5 and 7 were confirmed by the spectroscopic analysis. For example, the 1H NMR spectrum of compound 3a showed quartet (J = 6.3 Hz) at δ 3.45 for one protons of C3H group in dihydropyrazole, singlet at δ 3.55 for NCH3, quartet (J = 6.3 Hz) at δ 4.02 for C3H proton and triplet at δ 4.85 for C2H. The multiplet between 7.22 and 7.80 corresponded to four protons of benzene ring of quinolone in 3a. The doublet appeared at δ 7.55 and δ 8.10 with coupling constant 8.3 Hz for aromatic proton of p-Cl-substituted aromatic ring. The mass spectrum of 3a displayed a molecular ion peak m/z at 354, which was constituent with the molecular weight of 3a. The structure of the other compounds 5 and 7 were established on the basis of spectroscopic and analytical data (experimental section). Spectroscopic data for chalcones 1a–d were in agreement with the literature data [16, 17]. All the compounds are thermally stable up to 350°C (DSC scanning), hence useful for optoelectronic devices.
Synthesis of quinolone dihydropyrazole derivatives
Synthesis of quinolone isoxazole derivatives
Synthesis of quinolone pyridine derivatives
Photophysical study
The photophysical properties of compounds 3, 5 and 7 were determined with respect to quinine sulphate which was used as a reference standard for the present study. Compounds 3, 5 and 7 showed absorption and emission in near to visible region (Tables 1, 2 and 3).
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A)
Photophysical properties of dihydropyrazole derivatives (3a–o): Electron acceptor chromophore quinolone and electron donor dihydropyrazole are linked together and showed pseudoaromatacity. Compound 3h and 3i having donor chromophores OCH3 and 3,4-diOCH3 on C5-phenyl ring and N1-phenyl group showed red-shift absorption maximum (UVλ Max /nm) equal to 398, 415 nm, emission maximum (Emλ Max /nm) equal to 478, 512 nm and quantum yields (ΦF) 0.22, 0.24 respectively (Fig. 1). While, compound 3j having acceptor C4–NO2 chromophores on phenyl ring showed large decrease in absorption (UVλ Max /nm) and emission maximum (Emλ Max /nm) to 361 and 431 nm and quantum yield (ΦF) 0.17 (Table 1). The increasing order of absorption and emission maximum for N1-substituted is –CH2CH2OH < H < Ph, as in compounds 3d, 3i and 3n respectively. This indicates that ethyl group at N1 in dihydropyrazole (3k–o) showed hypsochromic shift, while phenyl groups showed bathochromic shift as compared with N1H (3a–e). Compound with donor substituents showed lowest extension coefficient (e.g. 3i = ε = 8,990 cm–1), showed high fluorescence maximum; while the compound with acceptor substituents (e.g. 3j = ε = 10,220 cm–1), showed lower values of absorption, emission and quantum yields. Figure 2, indicates the fluorescence tubes of the compounds 3h and 3i respectively under the fluorescence lamp (Fig. 2).
Fig. 1 
Fluorescence spectra at room temperature of dihydropyrazole (3f–3j)
Fig. 2 
The Fluorescence compounds 3h and 3i respectively under Fluorescence Lamp
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B)
Photophysical properties of isoxazole derivatives (5a–e): The donor chromophores on C5-aryl groups showed bathochromic shift in absorption and emission properties. e.g. compound 5c and 5d having C4–OCH3 and C3, 4–diOCH3 chromophores showed absorption maximum (UVλ Max /nm) to 375, 380 nm, emission maximum (Emλ Max /nm) to 452, 474 nm and quantum yields are 0.21, 0.22 respectively (Table 2). The electron acceptor group on phenyl ring e.g. 5e, showed lower values of absorption and emission maxima.
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C)
Photophysical properties of pyridine derivatives (7a–e): The compound 7d having C3, 4–diOCH3 group, showed absorption maximum (UVλ Max /nm) to 390 nm, emission maximum (Emλ Max /nm) to 478 nm and quantum yield (ϕF) 0.21. While the acceptor chromophores 7e showed absorption and emission maximum to (361 nm and 415 nm) and quantum yield (ϕF) 0.15 (Table 3).
Semiempirical study
The theoretical model obtained by the energy optimization computational programme by PM6 (version 8.331, 2009) [18], showed that fluorescence properties are dependent on the heat of formation and GAP values of the compounds, e.g. compounds 3i and 3h showed higher, while 3j and 3f showed lower photophysical properties. The compounds 3i and 3h showed low GAP values equal to 7.080; 7.083 eV and heat of formation are −51.32 and −15.78 Kcal/mole, hence more thermally stable. While compound 3j and 3f showed GAP values about 7.953, 7.156 eV and heat of formation are −15.40, 14.72 Kcal/moles, showed high GAP vales and low heat of formation, hence less thermally stable. Therefore compound 3j and 3f has low absorption and emission properties. Similar trends were also observed for compound 5 and 7. For example, compound 5d and 5c showed higher absorption and emission values, while compound 5e showed lower absorption and emission maximum (Table 4).
Conclusion
In conclusion, we have described a novel and efficient method for the synthesis of quinoline substituted dihydropyrazole, isoxazole and pyridine derivatives. The electron donor chromophores on phenyl ring of the heterocyclic system showed high red shift absorption, while electron withdrawing chromophores showed blue-shift absorption. The semiempirical studied with the help of PM6 method, showed that compound having low GAP values i.e. high HOMO-LUMO energy and high heat of formation showed high fluorescence maximum. While, compound with high GAP values i.e. low HOMO-LUMO energy and low heat of formation showed lower shift to fluorescence maximum. The predicated hypothesis is found true for the observed values. The efficient blue light emission and physical and chemical stability makes these quinolone derivatives as a promising family of materials which may be useful in photophysical applications. The theoretical results obtained are in agreement with the HOMO, LUMO and heat of formation obtained by the semiempirical PM6 methods.
Experimental
General
Melting points were determined on a Gallenkamp Melting Point Apparatus in open capillary tubes and are uncorrected. The 1H and 13C NMR spectra were recorded on a Varian XL-300 spectrometer (300 MHz, 75 MHz respectively). Chemical shifts are reported in ppm from internal tetramethylsilane standard and are given in δ-units. The solvent for NMR spectra was deuteriochloroform (CDCl3) or DMSO (d 6 ). Infrared spectra were taken on a Shimadzu IR-408, in potassium bromide pellets. The mass spectra were recorded on QP-2010s. UV spectra were recorded on a Shimadzu UV-1601 UV–VIS Spectrophotometer. Fluorescence spectra were recorded using RF-5301 PC Spectrofluorophotometer (150-W Xe lamp), compounds for UV and fluorescence measurements were dissolved in chloroform (CHCl3). UV and fluorescence scan were recorded from 200 to 600 nm. Determination of quantum yields: emission signals were set in relation to known area of the emission signal of quinine sulphate at pH 1. Elemental analyses were performed on a Hosli CH-Analyzer and are within ±0.3 of the theoretical percentages. All reactions were monitored by thin layer chromatography, carried out on 0.2 mm silica gel 60 F254 (Merck) plates using UV light (254 and 366 nm) for detection. Column chromatography was carried out on silica gel (s.d. Fine Chemicals, 60–120 mesh powder). Starting materials were obtained from commercial suppliers and used without further purification. Common reagent-grade chemicals and staring materials are either commercially available and were used without further purification or prepared by standard literature procedures.
General Procedure for the 4, 5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-1-methyl- quinolin-2-(1H)-one (3a–o)
A mixture of chalcone 1 (0.01 mol), hydrazine hydrate or phenyl hydrazine or 2-hydroxyethylhydrazine 2a–c (0.01 mol) in catalytic amount of acetic acid (0.5 mL) in ethanol (10 mL) were refluxed for 3–4 h. (TLC Check, toluene: acetone 8:2). The reaction mixture was cooled to room temperature and poured in ice-cold water (30 mL) and further stirred for 30 min. The obtained precipitated solid was filtered, washed with water, dried and recrystallized from ethanol to afford 3 in 50–65% yields.
3-[5-(4-Chlorophenyl)-4,5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-1-methyl quinolin-2-(1H)-one (3a)
Yield: 2.60 g, (65%), mp. 147–148°C (ethanol, yellow prism); IR (KBr): 3,484, 3,332, 1,677, 1,614, 1,520 cm−1; 1H NMR (CDCl3) δ = 3.45(q, J = 6.3 Hz, 1H, CH), 3.55(s, 3H, NCH3), 4.02(q, J = 6.5 Hz, 1H, CH), 4.85(t, J = 6.5 Hz, 1H, CH), 7.22–7.40(m, 4H, ArH), 7.55(d, 2H, J = 8.3 Hz, ArH), 8.10(d, 2H, J = 8.3 Hz, ArH). MS (70ev): m/z = 354.0[M+1]. Anal. Calcd for C19H16ClN3O2 (353.5): C, 64.50; H, 4.56; N, 11.88. Found: C, 64.80; H, 4.70; N, 11.80%.
3-[5-(4-Bromophenyl)-4,5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-1-methyl quinolin-2-(1H)-one (3b)
Yield 2.22 g, (62%), mp. 180–182°C (ethanol, yellow prism); IR (KBr): 3,558, 3,230, 1,671, 1,598, 1,515 cm−1; 1H NMR (CDCl3) δ = 3.52(q, J = 5.8 Hz, 1H, CH), 3.80(s, 3H, NCH3), 4.22(q, J = 5.6 Hz, 1H, CH), 5.20(t, J = 5.6 Hz, 1H, CH), 6.80–7.22(m, 4H, ArH), 7.65(d, 2H, J = 8.2 Hz, ArH). 8.08(d, 2H, J = 8.2 Hz, ArH). Anal. Calcd. for C19H16BrN3O2 (398.00): C, 57.30; H, 4.05; N, 10.55. Found: C, 57.50; H, 4.07; N, 10.80.
3-[5-(4-Methoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-1-methyl quinolin-2 (1H)-one (3c)
Yield 2.10 g, (56%), mp. 174–178°C (ethanol, yellow prism); IR (KBr): 3,480, 3,122, 1,677, 1,590 cm−1; 1H NMR(CDCl3) δ = 3.65(s, 3H, NCH3), 3.80(q, J = 5.9 Hz, 1H, CH), 4.10(s, 3H, OCH3), 4.30(q, J = 6.1 Hz, 1H, CH), 5.20(t, J = 6.1 Hz, 1H, CH), 6.80–7.22(m, 4H, ArH), 7.62(d, 2H, J = 8.4 Hz, ArH), 8.05(d, 2H, J = 8.4 Hz, ArH). Anal. Calcd for C20H19N3O3 (349.39): C, 68.75; H, 5.48; N, 12.03. Found: C, 68.80; H, 5.70; N, 11.80%.
3-[5-(3,4-Dimethoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-1-methyl quinolin-2-(1H)-one (3d)
Yield: 2.05 g, (65%), mp. 168–170°C (ethanol, yellow prism); IR (KBr): 3,380, 3,120, 1,667, 1,602, 1,508 cm−1; 1H NMR (CDCl3) δ = 3.50(q, J = 6.4 Hz, 1H, CH), 3.60(s, 3H, NCH3), 3.80(s, 6H, 2 × OCH3), 4.06(q, J = 6.2 Hz, 1H, CH), 4.81(t, J = 6.4 Hz, 1H, CH), 6.90–7.22(m, 4H, Ar–H), 7.64(d, 2H, J = 8.0 Hz, Ar–H), 8.12(d, 2H, J = 8.0 Hz, ArH). 13C (75 MHz, CDCl3) δ 28, 44, 56, 60, 62, 108, 110, 112(s), 116, 118, 120, 122, 124, 132, 140, 148, 150, 156, 162, 165. Anal. Calcd for C21H21N3O4(379.42): C, 66.48; H, 5.58; N, 11.07. Found: C, 66.50; H, 5.70; N, 11.08%.
3-[5-(4-Nitrophenyl)-4,5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-1-methyl quinolin-2-(1H)-one (3e)
Yield: 1.80 g, (45%), mp. 171–172°C (ethanol, yellow prism); IR (KBr): 3,440, 3,315, 1,670, 1,610, 1,510 cm−1; 1H NMR (CDCl3) δ = 3.34(q, J = 6.3 Hz, 1H, CH), 3.56(s, 3H, NCH3), 4.08(q, J = 6.5 Hz, 1H, CH), 4.66(t, J = 6.5 Hz, 1H, CH), 6.85–7.35(m, 4H, ArH), 7.45(d, 2H, J = 8.3 Hz, ArH), 8.16(d, 2H, J = 8.3 Hz, ArH). Anal. Calcd for C19H16N4O4 (364.12): C, 62.63; H, 4.43; N, 15.38. Found: C, 62.80; H, 4.63; N, 15.90%.
3-(5-(4-Chlorophenyl)-4,5-dihydro-1-phenyl-1H-pyrazol-3-yl)-4-hydroxy-1-methyl quinolin-2(1H)-one (3f)
Yield: 2.15 g, (50%), mp 212–214°C (ethanol, yellow prism); IR (KBr): 3,441, 3,212, 1,665, 1,590, 1,503, 1,473, 1,423, 1,413 cm−1; 1H NMR (CDCl3) δ = 3.60(s, 3H, NCH3), 3.70(q, J = 6.3 Hz, 1H, CH), 4.20(q, J = 6.1 Hz, 1H, CH), 5.10(t, J = 6.3 Hz, 1H, CH), 6.80–7.15(m, 4H, ArH), 7.20–7.30(m, 5H, ArH), 7.70(d, 2H, J = 8.20 Hz, ArH), 8.08(d, 2H, J = 8 Hz, ArH). MS (70 eV): m/z = 352(M+, 90%), 335(10%), 215(80%), 151(70%), 131(95%), 116(60%), 89(60%), 77(100%). Anal. Calcd for C25H20ClN3O2 (429.5): C, 69.85; H, 4.69; N, 9.77. Found: C, 69.70; H, 4.70; N, 9.55%.
3-(5-(4-Bromophenyl)-4,5-dihydro-1-phenyl-1H-pyrazol-3-yl)-4-hydroxy-1-methyl quinolin-2(1H)-one(3g)
Yield: 2.30 g (58%), mp. 220–222°C. IR (KBr): 3,464, 3,180, 1,666, 1,604, 1,502, 1,430 cm−1; 1H NMR (CDCl3) δ = 3.60(s, 3H, NCH3), 3.70(q, 1H, J = 6.2 Hz, CH), 4.25(q, J = 6.3 Hz, 1H, CH), 5.20(t, J = 6.3 Hz, 1H, CH), 6.80–7.01(m, 4H, ArH), 7.20–7.40(m, 5H, ArH), 7.55(d, 2H, J = 8.2 Hz, ArH), 8.15(d, 2H, J = 8.2 Hz, ArH), 9.10(bs, 1H, OH). Anal. Calcd. for C25H20BrN3O2 (474.0): C, 63.30; H, 4.25; N, 8.86. Found: C, 63.50; H, 4.02; N, 8.90%.
3-(5-(4-Methoxyphenyl)-4,5-dihydro-1-phenyl-1H-pyrazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (3h)
Yield: 2.40 g (60%). mp. 226–228°C (ethanol, yellow prism); IR (KBr): 3,502, 3,190, 1,676, 1,605, 1,540 cm−1; 1H NMR (CDCl3) δ = 3.52(s, 3H, NCH3), 3.55(s, 3H. OCH3), 3.60(q, J = 6.1 Hz, 1H, CH), 4.04(q, J = 6.2 Hz, 1H, CH), 4.82(t, J = 6.2 Hz, 1H, CH), 6.75–6.90(m, 4H, ArH), 7.20–7.30(m, 5H, ArH), 7.60(d, 2H, J = 8.3 Hz, ArH), 8.10(d, 2H, J = 8.3 Hz, ArH). Anal. Calcd for C26H23N3O3 (425.49): C, 73.40; H, 5.45; N, 9.88. Found: C, 73.45; H, 5.70; N, 9.38%.
3-(5-(4-Dimethoxyphenyl)-4,5-dihydro-1-phenyl-1H-pyrazol-3-yl)-4-hydroxy-1-methyl- quinolin-2(1H)-one (3i)
Yield 2.25 g (56%); mp. 248–250°C (ethanol, yellow prism). IR (KBr): 3,488, 3,192, 1,644, 1,607 cm−1; 1H NMR (CDCl3) δ = 3.58(s, 3H, NCH3), 3.62(q, J = 5.6 Hz, 1H, CH), 3.80–3.88(s, 6H, 2 × OCH3), 4.28(q, J = 5.9 Hz, 1H, CH), 5.15(d, J = 5.91 Hz, 1H, CH), 6.95–7.28(m, 4H, ArH), 7.20–7.35(m, 5H, ArH), 7.55(d, 2H, J = 8.1 Hz, ArH). 8.15(d, 2H, J = 8.1 Hz, ArH), 9.15(bs, 1H, OH). 13C (75 MHz, CDCl3) δ = 30, 46, 56 (s), 64 (s), 104, 108, 112(s), 114(s), 118, 119, 120, 122, 125, 130, 132, 136, 140, 144, 148, 149, 151, 160, 162. MS (70 eV): m/z = 455(M+, 90%), 424(10%), 396(10%), 364(15%), 318(98%), 304(20%), 228(40%), 134(50%), 104(60%), 91(95%), 77(100%). Anal. Calcd. for C27H25N3O4 (455.52): C, 71.19; H, 5.53; N, 9.22. Found: C, 71.32; H, 5.44; N, 9.40%.
3-(5-(4-Nitrophenyl)-4,5-dihydro-1-phenyl-1H-pyrazol-3-yl)-4-hydroxy-1-methyl quinolin-2(1H)-one(3j)
Yield: 1.70 g (40%), mp. 212–213°C. IR (KBr): 3,460, 3,182, 1,660, 1,588, 1,510, 1,415 cm−1; 1H NMR (CDCl3) δ = 3.40(s, 3H, NCH3), 3.70(q, 1H, J = 6.2 Hz, CH), 4.12(q, J = 6.3 Hz, 1H, CH), 5.02(t, J = 6.3 Hz, 1H, CH), 6.80–7.10(m, 4H, ArH), 7.25–7.45(m, 5H, ArH), 7.60(d, 2H, J = 8.2 Hz, ArH), 8.22(d, 2H, J = 8.2 Hz, ArH), 9.10(bs, 1H, OH). Anal. Calcd. for C25H20N4O4 (440.15): C, 68.17; H, 4.58; N, 12.72. Found: C, 68.40; H, 4.32; N, 12.90%.
3-(5-(4-Chlorophenyl)-4,5-dihydro-1-(2-hydroxyethyl)-1H-pyrazol-3-yl)-4-hydroxy -1-methylquinolin-2(1H)-one (3k)
Yield 2.15 g (60%); mp. 190–192°C (ethanol, yellow prism); IR (KBr): 3,522, 3,125, 1,674, 1,610, and 1,501 cm−1; 1H NMR (CDCl3) δ = 1.81(t, J = 7.1 Hz, 2H, CH2), 3.5(s, 3H, NCH3), 3.86(t, J = 6.7 Hz, 2H, CH2), 4.01(dd, J = 7.6 & 6.5 Hz, 1H, CH), 4.32(dd, J = 7.6 Hz & 6.5 Hz, 1H, CH pyrazole), 4.80(dd, J = 7.8 & 6.5 Hz, 1H, CH pyrazole), 6.98–7.22(m, 4H, ArH), 7.62(d, 2H, J = 7.8 Hz, ArH). 8.12(d, 2H, J = 7.8 Hz, ArH). Anal. Calcd. for C21H20ClN3O3(397.86): C, 63.40; H, 5.07; N, 10.56. Found: C, 63.50; H, 5.10; N, 10.70%.
3-(5-(4-Bromophenyl)-4,5-dihydro-1-(2-hydroxyethyl)-1H-pyrazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (3l)
Yield: 2.40 g (64%), mp. 186–188°C (ethanol, yellow prism); IR (KBr): 3,512, 3,195, 1,678, 1,605, 1,530 cm−1; 1H NMR (CDCl3) δ = 1.77(t, J = 6.4 Hz, 2H, CH2), 3.45(s, 3H, NCH3), 3.66(t, J = 6.4 Hz, 2H, CH2), 3.92(dd, J = 7.6 & 6.5 Hz, 1H, CH), 4.22(dd, J = 7.6 Hz & 6.5 Hz, 1H, CHpyrazole), 4.62(dd, J = 7.8 & 6.5 Hz, 1H, CHpyrazole), 7.02–7.30(m, 4H, ArH), 7.55(d, 2H, J = 7.8 Hz, ArH). 8.44(d, 2H, J = 7.8 Hz, ArH). Anal. Calcd. for C21H20BrN3O3 (442.32): C, 57.03; H, 4.56; N, 9.50. Found: C, 57.16; H, 4.72; N, 9.62%.
3-(5-(4-Methoxyphenyl)-4,5-dihydro-1-(2-hydroxyethyl)-1H-pyrazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (3m)
Yield 2.02 g (55%), mp. 202–204°C (ethanol, yellow prism); IR (KBr): 3,502, 3,108, 1,675, 1,606, 1,515 cm−1; 1H NMR (CDCl3) δ = 1.80(t, J = 6.4 Hz, 2H, CH2), 3.40(s, 3H, NCH3), 3.52(s, 3H, OCH3), 3.60(t, J = 6.4 Hz, 2H, CH2), 3.97(q, J = 7.6 & 6.5 Hz, 1H, CH), 4.30(q, J = 7.6 Hz & 6.5 Hz, 1H, CH pyrazole), 4.75(t, J = 7.8 & 6.5 Hz, 1H, CH pyrazole), 6.90–7.20(m, 4H, ArH), 7.55(d, 2H, J = 7.8 Hz, ArH). 8.01(d, 2H, J = 7.8 Hz, ArH). Anal. Calcd. for C22H23N3O4 (393.45): C, 67.16; H, 5.89; N, 10.68. Found: C, 67.22; H, 6.05; N, 10.72%.
3-(5-(4-Dimethoxyphenyl)-4,5-dihydro-1-(2-hydroxyethyl)-1H-pyrazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (3n)
Yield 2.12 g (65%). mp. 221–223°C (ethanol, yellow prism); IR (KBr): 3,558, 3,180, 1,680, 1,615, 1,540 cm−1; 1H NMR (CDCl3) δ = 1.74(t, J = 6.71 Hz, 2H, CH2), 3.45(s, 3H, NCH3), 3.50–3.58(s, 6H, 2 × OCH3), 3.86(t, J = 6.74 Hz, 2H, CH2), 4.0(q, J = 7.6 & 6.5 Hz, 1H, CH), 4.32(q, J = 7.6 Hz & 6.5 Hz, 1H, CHpyrazole), 4.81(t, J = 7.8 & 6.5 Hz, 1H, CHpyrazole), 6.98–7.22(m, 4H, ArH), 7.62(d, 2H, J = 7.8 Hz, ArH), 8.12(d, 2H, J = 7.8 Hz, ArH). MS (70e/v): m/z = 424.00 [M+1, 100%], 395(50%), 383(80%), 361(55%), 345(50%), 317(60%), 272(40%), 178(72%), 128(98%). Anal. Calcd. for C23H25N3O5 (423.47): C, 65.24; H, 5.95; N, 9.92. Found: C, 65.30; H, 5.82; N, 10.05%.
3-(5-(4-Nitrophenyl)-4,5-dihydro-1-(2-hydroxyethyl)-1H-pyrazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (3o)
Yield 2.01 g (52%); mp. 194–195°C (ethanol, yellow prism); IR (KBr): 3,512, 3,180, 1,671, 1,608, and 1,512 cm−1; 1H NMR (CDCl3) δ = 1.78(t, J = 7.1 Hz, 2H, CH2), 3.54(s, 3H, NCH3), 3.91(t, J = 6.7 Hz, 2H, CH2), 4.12(dd, J = 7.6 & 6.5 Hz, 1H, CH), 4.38(dd, J = 7.6 Hz & 6.5 Hz, 1H, CH pyrazole), 4.60(dd, J = 7.8 & 6.5 Hz, 1H, CH pyrazole), 6.90–7.15(m, 4H, ArH), 7.55(d, 2H, J = 7.8 Hz, ArH). 8.16(d, 2H, J = 7.8 Hz, ArH). Anal. Calcd. for C21H20N4O5(408.14): C, 61.76; H, 4.94; N, 13.72. Found: C, 61.50; H, 5.11; N, 13.70%.
General Procedure for the isoxazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one-(5a–e)
To a mixture of chalcone 1 (0.01 mol), hydroxylamine hydrochloride 4 (0.69 g, 0.01 mol), sodium acetate (0.73 g, 0.01mole) and catalytic amount of acetic acid (1 mL) in ethanol (15 mL) were refluxed for 8–10 h (TLC Check, toluene: acetone 8:2). The reaction mixture was cooled, concentrated and neutralized with NaOH. The product was isolated and crystallized from ethanol to afford 5 50–65% yields.
3-(5-(4-Chlorophenyl)-isoxazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one-(5a)
Yield 1.85 g (60%). mp. 225–226°C (ethanol, colorless flakes); IR (KBr): 3,431, 3,112, 1,685, 1,612, 1,515 cm−1; 1H NMR (CDCl3) δ = 3.64(s, 3H, NCH3), 7.32–7.50(m, 4H, ArH), 7.63(s, 1H, ArH), 7.96(d, 2H, J = 8.1 Hz, ArH), 8.15(d, 2H, J = 8.1ArH), 11.46(bs, 1H, OH). MS (70 eV): m/z = 353(M+1, 90%), 335(10%), 309(10%), 280(10%), 241(20%), 228(15%), 215(95%), 176(100%), 151(90%), 131(90%), 116(50%), 77(98%), 63(60%), 51(40%). Anal. Calcd for C19H13ClN2O3 (352.5): C, 64.69; H, 3.71; N, 7.94. Found: C, 64.80; H, 3.85; N, 7.80%.
3-[5-(4-Bromophenyl)-isoxazol-3-yl]-4-hydroxy-1-methylquinolin-2-(1H)-one(5b)
Yield: 1.90 g (65%), mp. 196–197°C (ethanol, colorless flakes); IR (KBr): 3,512, 3,234, 1,674, 1,611, 1,524 cm−1; 1H NMR (CDCl3) δ = 3.72(s, 3H, NCH3), 7.15–7.40(m, 4H, ArH), 7.66(s, 1H, ArH), 7.84(d, 2H, J = 8.20 Hz, ArH), 8.22(d, 2H, J = 8.20 Hz, ArH), 11.50(bs, 1H, OH). Anal. Calcd. for C19H13BrN2O3 (397.22): C, 57.45; H, 3.30; N, 7.05. Found: C, 57.62; H, 3.22; N, 7.15%.
3-[5-(4-Methoxyphenyl)-isoxazol-3-yl]-4-hydroxy-1-methylquinolin-2(1H)-one (5c)
Yield 1.75 g (50%), mp. 208–209°C (ethanol, colorless flakes); IR (KBr): 3,512, 3,235, 1,672, 1,602, 1,520 cm−1; 1H NMR (DMSO-d 6) δ = 3.77(s, 3H, NCH3), 4.02(s, 3H, OCH3), 7.20–7.40(m, 4H, ArH), 7.60(s, 1H, ArH), 8.08(d, 2H, J = 8.4 Hz, ArH), 8.22(d, 2H, J = 8.4 Hz, ArH), 11.50(bs, 1H, OH). Anal. Calcd for C20H16N2O4 (348.35): C, 68.96; H, 4.63; N, 8.04. Found: C, 68.80; H, 4.70; N, 7.80%.
3-[5-(3,4-Dimethoxyphenyl)-isoxazol-3-yl]-4-hydroxy-1-methylquinolin-2(1H)-one (5d)
Yield 1.80 g (55%), mp. 215–216°C (ethanol, colorless flakes); IR (KBr): 3,492, 3,231, 1,666, 1,612, 1,521 cm−1; 1H NMR (DMSO-d 6) δ = 3.52(s, 3H, NCH3), 3.60–3.69(s, 6H, 2 × OCH3), 6.25(s, 1H, ArH), 6.61–6.84(m, 4H, ArH), 7.40(d, 6.9 Hz, 1H, ArH), 7.73(d, J = 6.3 Hz, 1H, ArH), 8.09(dd, J = 6.9 & 6.3 Hz, 1H, ArH), 12.68(bs, 1H, OH). MS (70 eV): m/z = 380(M+1, 80%), 319(20%), 304(30%), 288(10%), 243(30%), 227(10%), 215(80%), 201(50%), 180(80%), 165(80%), 116(70%), 77(90%). Anal. Calcd for C21H18N2O5 (378.38): C, 66.66; H, 4.79; N, 7.40. Found: C, 66.80; H, 4.65; N, 7.35%.
3-(5-(4-Nitrophenyl)-isoxazol-3-yl)-4-hydroxy-1-methylquinolin-2(1H)-one-(5e)
Yield 1.55 g (45%). mp. 210–211°C (ethanol, colorless flakes); IR (KBr): 3,413, 3,110, 1,674, 1,602, 1,514 cm−1; 1H NMR (CDCl3) δ = 3.52(s, 3H, NCH3), 7.22–7.44(m, 4H, ArH), 7.60(s, 1H, ArH), 7.80(d, 2H, J = 8.1 Hz, ArH), 8.17(d, 2H, J = 8.1ArH), 11.50(bs, 1H, OH). Anal. Calcd for C19H13N3O5 (363.09): C, 62.81; H, 3.61; N, 11.57. Found: C, 62.70; H, 3.65; N, 11.80%.
General Procedure for the 5, 6, 7, 8-tetrahydro-7, 7-dimethyl-5-oxoquinolin-2-yl)-4 -hydroxy-1-methylquinolin-2(1H)-one (7a–e)
A mixture of chalcone 1 (0.01 mol) and dimedone 6 (0.01 mol) in presence of ammonium acetate (0.01 mol) and ethanol (15 mL) was refluxed for 20–24 h. (TLC, toluene: acetone 8:2). Reaction mixture was cooled at room temperature; the colorless solid precipitated was filtered, washed with cold ethanol, dried and recrystallized from ethanol to afford 9a in 60–70% yields.
3-(4-(4-Chlorophenyl)-5, 6, 7, 8-tetrahydro-7, 7-dimethyl-5-oxoquinolin-2-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (7a)
Yield 2.55 g (68%), mp. 252–253°C (ethanol colorless flakes); IR (KBr): 3,544, 3,234, 1,671, 1,641, 1,508 cm−1; 1H NMR (300 MHz, CDCl3) δ: 2.50(s, 6H, 2 × CH3), 3.20(s, 4H, 2 × CH2), 3.44(s, 3H, NCH3), 7.12–7.40(m, 4H, ArH), 7.81(d, 2H, J = 7.8 Hz, ArH), 8.15(d, 2H, J = 7.8 Hz, ArH), 9.54(s, 1H, ArH), 12.33(bs, 1H, OH). Anal. Calcd for C27H23ClN2O3 (458.0): C, 70.66; H, 5.05; N, 6.10. Found: C, 70.80; H, 5.12; N, 6.17%.
3-(4-(4-Bromophenyl)-5,6,7,8-tetrahydro-7,7-dimethyl-5-oxoquinolin-2-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (7b)
Yield 3.10 g (70%), mp. 256–258°C (ethanol, colorless flakes); IR (KBr): 3,488 (OH), 3,084 (CH), 1,646 (CO), 1,605 (CO), 1,505 (C = N); 1H NMR (CDCl3) δ = 2.42(s, 6H, 2 × CH3), 3.12(s, 4H, 2 × CH2), 3.34(s, 3H, NCH3), 7.25–7.60(m, 4H, ArH), 7.91(d, 2H, J = 8.1 Hz, ArH), 8.20(d, 2H, J = 8.1 Hz, ArH), 9.25(s, 1H, ArH), 12.80(bs, 1H, OH). Anal. Calcd for C27H23BrN2O3 (502.0): C, 64.42; H, 4.61; N, 5.56. Found: C, 64.66; H, 4.71; N, 5.83%.
3-(4-(4-Methoxyphenyl)-5, 6, 7, 8-tetrahydro-7,7-dimethyl-5-oxoquinolin-2-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (7c)
Yield 2.15 g (65%); mp. 268–270°C (ethanol, colorless flakes); IR (KBr): 3,512, 3,221, 1,678, 1,612, 1,544 cm-1; 1H NMR (CDCl3) δ : 1.60(s, 6H, 2 × CH3), 2.10(s, 4H, 2 × CH2), 3.55(s, 3H, NCH3), 3.80(s, 3H, OCH3), 7.20–7.80(m, 4H, ArH), 8.10(d, 2H, J = 8.3 Hz, ArH). 8.25(d, 2H, J = 8.3 Hz, ArH), 9.02(s, 1H, ArH). Anal. Calcd for C28H26N2O4 (454.0): C, 73.99; H, 5.77; N, 6.16; Found: C, 73.80; H, 5.70; N, 6.36%.
3-(4-(3,4-Dimethoxyphenyl)-5,6,7,8-tetrahydro-7,7-dimethyl-5-oxoquinolin-2-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (7d)
Yield 2.80 g (65%),; mp 241–243°C (ethanol, colorless flakes): IR (KBr): 3,466, 3,031, 1,678, 1,656 cm−1; 1H NMR (CDCl3) δ = 3–1.33(s, 6H, 2 × CH3), 2.19–2.33(s, 4H, 2 × CH2), 3.25(s, 3H, NCH3), 3.34–3.42(s, 6H, 2 × OCH3), 7.07–7.73(m, 4H, ArH), 7.98(d, 2H, J = 8.6 Hz, ArH), 8.14(d, 2H, J = 8.6 Hz, ArH), 9.20(s, 1H, ArH), 11.40(bs, 1H, OH). Anal. Calcd for C29H28N2O5 (484.0): C, 71.88; H, 5.82; N, 5.78. Found: C, 72.02; H, 5.91; N, 5.86%.
3-(4-(4-Nitrophenyl)-5, 6, 7, 8-tetrahydro-7, 7-dimethyl-5-oxoquinolin-2-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (7e)
Yield 1.90 g (48%), mp. 252–253°C (ethanol colorless flakes); IR (KBr): 3,520, 3,230, 1,660, 1,635, 1,510 cm−1; 1H NMR (300 MHz, CDCl3) δ : 2.402.45(s, 6H, 2 × CH3), 3.15–3.20(s, 4H, 2 × CH2), 3.52(s, 3H, NCH3), 7.10–7.35(m, 4H, ArH), 7.77(d, 2H, J = 7.8 Hz, ArH), 8.12(d, 2H, J = 7.8 Hz, ArH), 9.86(s, 1H, ArH), 12.60(bs, 1H, OH). Anal. Calcd for C27H23N3O5 (469.16): C, 69.07; H, 4.94; N, 8.95. Found: C, 69.12; H, 5.13; N, 8.72%.
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Authors thanks to CSIR, New Delhi, for the financial assistance and to the Principal, K.T.H. M. College, Nashik - 422 002 for the facilities.
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Toche, R.B., Kazi, M.A., Patil, S.P. et al. Synthesis of Quinolone Substituted Pyrazoles, Isoxazoles and Pyridines as a Potential Blue Luminophors. J Fluoresc 20, 1129–1137 (2010). https://doi.org/10.1007/s10895-010-0654-9
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DOI: https://doi.org/10.1007/s10895-010-0654-9