Introduction of a novel Brønsted acidic ionic liquid for the promotion of the synthesis of quinolines

MOLLIQ-04299; No of Pages 10 Journal of Molecular Liquids xxx (2014) xxx–xxx

Contents lists available at ScienceDirect

Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq

1

Short Communication

4Q1

Farhad Shirini ⁎, Somayeh Akbari-Dadamahaleh, Mohadeseh Rahimi-Mohseni, Omid Goli-Jelodar

5Q3

Department of Chemistry, College of Science, University of Guilan, Rasht 41335, PO Box 1914, Islamic Republic of Iran

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a r t i c l e

7 8 9 10 11 22

Article history: Received 20 January 2014 Received in revised form 17 May 2014 Accepted 3 June 2014 Available online xxxx

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Keywords: Ionic liquid Reusable catalyst Quinolines Friedländer synthesis Solvent-free conditions

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i n f o

a b s t r a c t

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1. Introduction

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Due to the increase in environmental consciousness in chemical research and industry, the challenge for a tolerable calls for clean procedures that avoid the use of harmful organic solvents. Ionic liquid (IL) technology when used in place of classical organic solvents, proposes a new and environmentally safe approach toward modern synthetic chemistry because of the interesting physical and chemical properties of these types of compounds [1–4]. Recently ionic liquids have been successfully employed as dual reagents (solvents + catalysts) for a variety of reactions, but their use as catalyst under solvent-free conditions needs to be given more attention [5]. Ionic liquids have been widely vaunted as greener reagents, suitable for a range of organic reactions and providing possibilities such as, enhanced rate and reactivity, control of product distribution, ease of product recovery and recycling. Quinoline derivatives are famous in medicinal chemistry, they also have wide occurrence in drugs [6,7], natural products [8,9], polymer chemistry and preparation of nano and mesostructures with enhanced electronic and photonic properties [10–12]. The Friedländer annulation is one of the simplest and most straightforward methods for the synthesis of polyfunctional quinolines. This method has attracted considerable attention from the view point of combinatorial chemistry [13–15]. The Friedländer synthesis is an acid or base catalyzed condensation followed by a cyclodehydration between 2-aminoaryl ketones and a second carbonyl compound including a reactive methylene group. Some of

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3,3′-(Butane-1,4-diyl) bis (1-methyl-1H-imidazol-3-ium)·dibromide·disulfuric acid (C4(mim)2-2Br−-2H2SO4) as a new ionic liquid was prepared and efficiently used for the promotion of the one-pot synthesis of quinoline polycyclic compounds via the condensation of 2-aminoaryl ketones and β-ketoesters/ketones. All reactions are performed in the absence of solvent in high to excellent yields during short reaction times. © 2014 Elsevier B.V. All rights reserved.

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Introduction of a novel Brønsted acidic ionic liquid for the promotion of the synthesis of quinolines

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⁎ Corresponding author. Tel./fax: +98 131 3233262. E-mail address: [email protected] (F. Shirini).

the catalysts that employed for this reaction are: ZnCl2[16], phosphoric acid [17], Bi(OTf)3[18], silver phosphotungstate [19], Zr(NO3)4[20], and CAN(Cerium(IV) Ammonium Nitrate) [21], AuCl3[22], AcOH under microwave irradiation [23], sodium fluoride [24], sulfamic acid [25], Y(OTf)3[26],FeCl3 and Mg(ClO4)2[27], HCl [28], and [HBIm][BF4][29]. However, most of the synthetic protocols reported so far suffer from high temperatures (150–200 °C), prolonged reaction times, low yields, difficulties in work-up, use of stoichiometric amounts of the catalysts and often expensive catalysts. Moreover, the synthesis of these heterocyclic compounds has been usually carried out in harmful solvents such as acetonitrile, tetrahydrofuran, dimethylformamide and dimethylsulfoxide, leading to difficult product isolation and recovery procedures. Consequently, a new procedure that addresses these drawbacks is still desirable.

52

2. Experimental

66

2.1. General

67

Merck, Aldrich and Fluka chemicals were used in this study. The purity of the substrates and the completion of the reactions were determined using TLC on silica-gel polygram SILG/UV 254 plates. After completion of the reactions, the products were isolated and characterized by IR, 1HNMR, 13CNMR and melting point.

68 69

2.2. Instrumentation

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70 71 72

A Perkin-Elmer bio-spectrometer was used for running the IR spec- 74 tra. The reaction conversions were measured by GC on a Shimadzu 75

http://dx.doi.org/10.1016/j.molliq.2014.06.005 0167-7322/© 2014 Elsevier B.V. All rights reserved.

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

84

1,4-Dibromobutane (1.770 mL, 15.0 mmol) was added to a solution of 3-methyl imidazole (2.463 g, 30.0 mmol) in dry CH3CN (50 mL) and stirred for 3 days under reflux conditions. After completion of the reaction, the solvent was evaporated under reduced pressure. The white obtained solid was washed with ethylacetate. After drying at 50 °C the 1,4butyl-bis(3-methyl-3H-imidazol-1-ium) dibromide (C4(mim)2-2Br−) was obtained in 94.7% yield (5.37 g).

85 86 87 88 89 90 91 92 93 94

2.4. 3,3′-(Butane-1,4-diyl) bis (1-methyl-1H-imidazol-3-ium)·dibromide· disulfuric acid (C4(mim)2-2Br−-2H2SO4)

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2.5. Catalyst characterization

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2.5.1. IR analysis The corresponding IR spectra of 1,4-butyl-bis(3-methyl-3Himidazol-1-ium) dibromide (C 4(mim)2 -2Br−) and 3,3′-(butane1,4-diyl) bis (1-methyl-1H-imidazol-3-ium)·dibromide·disulfuric acid (C4(mim)2-2Br−-2H2SO4) are presented in Fig. 1. The strong absorptions at 1000, 1100 and 560 cm−1 in the IR of the ionic liquid are assigned to the asymmetric and symmetric stretching and bending of S\O vibrations of sulfate groups. The appearance of these bands which are absent in the IR of imidazole [30] can be indicated that sulfonic groups are successfully introduced in the IL molecule. The broad and

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Fig. 1. IR spectra of (C4(mim)2-2Br−) (top) and (C4(mim)2-2Br−-2H2SO4) (bottom).

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

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117 118 119 120 121 122 123 124 125 126 127 128 129 130

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ð1Þ

The abovementioned studies directed us to accept that the prepared ionic liquid can be either a composition of a dication, 2HSO− 4 and 2HBr, or a dication, 2Br− and 2H2SO4. In order to solve this problem, 20 mL of an aqueous solution of H2SO4 (0.100 M) is titrated with a solution of NaOH (0.100 M). The titration curve is given in Fig. 5. As it can be seen, the obtained curve is very similar to the titration curve of the ionic liquid. On the basis of these results we concluded that the prepared ionic liquid consists of two molecules of H2SO4.

C

104 105

MðacidÞ  VðacidÞ ¼ MðbaseÞ  VðbaseÞ 0:09ðmolarÞ  5 ðmLÞ ¼ 0:10 ðmolarÞ  VðbaseÞ VðbaseÞ ¼ 4:5 mL

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97 98

131 132

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95 96

2.5.3. Titration curve The titration curve for the titration of 5 mL of an aqueous solution of the ionic liquid (0.090 M) with 0.100 M NaOH is given in Fig. 4. This Figure clearly shows that, when 17 mL of the basic solution is added, all the acidic protons are neutralized. On the other hand Eq. (1), shows that for the neutralization of each of the acidic protons 4.5 mL of the basic solution is needed. On the basis of these studies it can be concluded that this ionic liquid has four protic protons.

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99 100

10 mmol H2SO4 98% (0.533 mL) was added dropwise to a solution of C4(mim)2-2Br− (1.891 g, 5 mmol) in dry CH2Cl2 (5 mL) as a solvent over a period of 10 min in an ice bath. After completion of the addition, the reaction mixture was stirred for 1 h at room temperature and for 1 h at 80 °C. The residue was washed with dry CH2Cl2 (2 × 5 mL) and dried under vacuum to give 3,3′-(butane-1,4-diyl) bis (1-methyl-1Himidazol-3-ium)·dibromide·disulfuric acid (C4(mim)2-2Br−-2H2SO4) ionic liquid as a viscous pale orange oil in 96% yield.

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2.3. Preparation of 1,4-butyl-bis(3-methyl-3H-imidazol-1-ium) dibromide (C4(mim)2-2Br−)

2.5.2. 1H NMR and 13C NMR analysis 1 H and 13C NMR spectra of 1,4-butyl-bis(3-methyl-3H-imidazol1-ium) dibromide (C4(mim)2-2Br−) and 3,3′-(butane-1,4-diyl) bis (1-methyl-1H-imidazol-3-ium)·dibromide·disulfuric acid (C4(mim)22Br−-2H2SO4) ionic liquid are presented in Figs. 2 and 3, respectively. The important peaks in the 1H NMR spectrum of the ionic liquid are related to the acidic hydrogens. These peaks are observed in 9.39 and 9.43 ppm. It should be noted that the peaks of the acidic hydrogens are not presented in the 1H NMR of C4(mim)2-Br2. It is very important to mention that at the first step, the main goal of this study was the preparation of 1,4-butyl-bis(3-methyl-3H-imidazol-1-ium) dihydrogen sulfate containing two acidic protons (Scheme 1), while the 1H NMR spectra of the obtained product showed four acidic protons. On the basis of this 1H NMR the titration technique was used to determine the exact number of the acidic protons and consequently the exact structure of the IL.

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82 83

78 79

strong band at 2700–3550 cm−1 arises from the hydroxyl groups in the 112 3,3′-(butane-1,4-diyl) bis (1-methyl-1H-imidazol-3-ium)·dibromide· 113 disulfuric acid (C4(mim)2-2Br−-2H2SO4) ionic liquid. 114

R O

80 81

model GC-16A instrument using a 25 m CBPI-S25 (0.32 mm ID, 0.5 m coating) capillary column. The 1HNMR (400 MHz) and 13CNMR (100 MHz) were run on a Bruker Avance DPX-250 FT-NMR spectrometer (δ in ppm). Microanalyses were done on a Perkin-Elmer 240-B microanalyzer. A Büchi B-545 apparatus in open capillary tubes was used for the determination of melting points.

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F. Shirini et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx

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2.5.4. Halogen test After the abovementioned experiments we decided to do the halogen test. So we added AgNO3 solution to the ionic liquid solution in water. This procedure resulted to a pale yellow solid, which means the formation of AgBr. This result showed that our ionic liquid contains Br − ions. This result shows that after the addition of H2SO4, HBr is not excluded from the reaction solution. On the basis of these results, the structure which is shown in Scheme 2 is selected for the prepared IL.

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2.6. General procedure for the one-pot synthesis of quinolines

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The ionic liquid (0.05 mmol) was added to a mixture of 2-aminoaryl ketones (1 mmol) and β-ketoester/1,3-diketone/cyclic ketone (1.2 mmol) at 50 °C under solvent-free conditions. Upon completion (as indicated by TLC) water (2 mL) was added and the product was separated by filtration. After recrystallization from EtOH the pure product

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(b)

Fig. 2. 1H NMR (a) and 13C NMR (b) spectra of C4(mim)2-2Br−.

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(a)

was obtained in high yields. Then, the water layer was vacuum-dried 162 at 70 °C for 5 h to remove the solvent, and the ionic liquid was reused. 163 The spectral data of the compounds are as follows: 164 1-(2-Methyl-4-phenylquinolin-3-yl)ethanone (a): M. p. 107–108 °C. IR (KBr) ν cm−1: 3058, 2902, 1691, 1265; 1HNMR (CDCl3, 400 MHz) ppm: 1.92 (s, 3H), 2.61 (s, 3H), 7.27–7.30 (m, 2H), 7.31–7.34 (m, 1H), 7.40–7.45 (m, 3H), 7.51 (dd, J = 1 Hz, 8.1 Hz, 1H), 7.61–7.66 (m, 1H), 8.00 (d, J = 8.4 Hz, 1H); 13CNMR(CDCl3, 100 MHz) ppm: 24.2, 32.9, 124.5, 125.6, 126.7, 128.1, 128.3, 129.0, 129.9, 130.0, 134.2, 135.3, 144.0, 146.8, 153.7, 206.3. 2-Methyl-4-phenyl-quinoline-3-carboxylic acid methyl ester (b): M. p. 107–109 °C. IR (KBr) ν cm− 1: 3047, 2942, 1735; 1H NMR (CDCl3, 400 MHz) ppm: 3.27 (s, 3H), 3.52 (s, 3H), 7.28–7.32 (m, 2H), 7.58–7.65 (m, 3H), 7.69–7.74 (m, 2H), 8.04 (t, J = 6.8 Hz, 1H), 8.63 (m, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 22.6, 52.2, 122.7,

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

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R O

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4

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(a)

(b)

180 181 182 183 184 185 186 187 188

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126.1, 127.3, 127.9, 129.0, 129.9, 130.5, 131.8, 133.1, 134.9, 145.0, 146.1, 146.4, 155.1, 171.1. Ethyl 2-methyl-4-phenylquinoline-3-carboxylate (c): M. p. 99–101 °C. IR (KBr) ν cm−1: 3046, 2934, 1716; 1H NMR (CDCl3, 400 MHz) ppm: 0.98 (t, J = 7.6 Hz, 3H), 2.74 (s, 3H), 4.02-4.13 (m, 2H), 7.34-7.42 (m, 6H), 7.54 (d, J = 8.4 Hz, 1H), 7.64 (t, J = 8.4 Hz, 1H), 8.03 (d, J = 8.4 Hz, 1H); 13C NMR(CDCl3, 100 MHz) ppm: 13.8, 22.9, 61.0, 125.1, 126.1, 128.0, 128.4, 128.7, 129.3, 130.0, 135.3, 146.3, 147.8, 153.9, 168.8. (2-Methyl-4-phenylquinoline-3-yl)(phenyl)methanone (d): M. p. 140–143 °C. IR (KBr) ν cm− 1: 3052, 2908, 1680. 1H NMR (CDCl3, 400 MHz) ppm: 2.67 (s, 3H), 7.21 (m, 7H), 7.34 (m, 2H),

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U

177

O

Fig. 3. 1H NMR and 13C NMR spectra of C4(mim)2-2Br−-2H2SO4 ionic liquid.

N

N

N

N

Scheme 1. The expected ionic liquid.

.2 HS SO4-

7.58 (m, 3H), 7.70 (m, 1H), 8.08 (d, J = 8.4 Hz, 1H). 13C NMR (CDCl3, 100 MHz) ppm: 23.9, 124.9, 126.0, 126.4, 127.8, 128.2, 128.3, 128.8, 129.1, 129.6, 129.9, 132.2, 133.3, 134.6, 136.9, 145.3, 147.6, 154.4, 197.5.

189

9-Phenyl-3,4-dihydroacridin-1(2H)-one (e): M. p. 151–153 °C. IR (KBr) ν cm− 1: 3045, 2956, 1695; 1H NMR (CDCl3, 400 MHz) ppm: 2.22 (m, 2H), 2.71 (t, J = 6.5 Hz, 2H), 3.29 (t, J = 6.20 Hz, 2H), 7.14 (m, 2H), 7.45 (m, 5H), 7.77 (m, 1H), 8.21 (d, J = 8.6 Hz, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 22.4, 34.6, 42.7, 123.7, 126.2, 127.4, 127.8, 127.9, 128.0, 128.3, 131.5, 137.5, 148.5, 151.0, 162.0, 197.5.

193

3,3-Dimethyl-9-phenyl-3,4-dihydro-2H-acridin-1-one (f): M. p. 190–191 °C. IR (KBr) ν cm− 1: 3074, 2901, 1670; 1H NMR (CDCl3, 400 MHz) ppm: 1.23 (s, 6H), 2.65 (s, 2H), 3.37 (s, 2H), 7.13–7.21 (m, 2H), 7.34–7.38 (m, 1H), 7.43–7.52 (m, 4H), 7.72– 7.76 (m, 1H), 8.08 (d, J = 8.4 Hz, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 29.1, 29.7, 49.1, 53.8, 123.2, 126.5, 126.9, 127.6, 127.8, 127.9, 128.2, 128.3, 132.3, 137.6, 150.1, 151.2, 161.0, 198.0.

200

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

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F. Shirini et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx

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Titration of 5 mL ionic liquid (0.09 M) with NaOH (0.1 M) 7

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Titration

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Volume of NaOH in mL

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First Derivative

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Titration of 20 mL sulfuric acid (0.1 M) with NaOH (0.1 M)

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1H); 13C NMR (CDCl3, 100 MHz) ppm: 22.5, 22.8, 28.0, 33.1, 126.1, 126.2, 127.4, 127.9, 128.7, 128.8, 129.1, 136.6, 144.8, 150.3, 159.0. 2,3-Dihydro-9-phenyl-1H-cyclopenta[b]quinoline (h): M. p. 129–131 °C. IR (KBr) ν cm−1: 3062, 2915, 1575, 1485; 1H NMR (CDCl3, 400 MHz) ppm: 2.16–2.20 (m, 2H), 2.93 (t, J = 7.4 Hz, 2H),

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9-Phenyl-1,2,3,4-tetrahydroacridine (g): M. p. 138–139 °C. IR (KBr) ν cm−1: 3071, 2952, 1568, 1470, 1451; 1 HNMR (CDCl3 , 400 MHz) ppm: 1.73–1.82 (m, 2H), 1.94–2.00 (m, 2H), 2.61 (t, J = 6.8 Hz, 2H), 3.23 (t, J = 6.8 Hz, 2H), 7.23–7.32 (m, 4H), 7.42–7.56 (m, 3H), 7.64–7.66 (m, 1H), 8.17 (d, J = 8.4 Hz,

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Fig. 4. Titration and its first derivative curves of the ionic liquid with NaOH.

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5

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Volume of NaOH in mL

40 Titration First derivative

Fig. 5. Titration and its first derivative curves of the sulfuric acid with NaOH.

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

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2

N

Br CH3CN

N + Br

H2SO4

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N

N

N

N

N

.2 Br -

N

N

.2 Br - .2 H2SO4

Scheme 2. Synthesis of the ionic liquid from 3-methyl imidazole.

Entry

Catalyst (mmol)

Time (min)

Yield (%)b

t1:5 t1:6 t1:7 t1:8

1 2 3 4

0.01 0.03 0.05 0.07

60 40 25 25

80 86 93 94

t1:9

a

Reaction conditions: 2-aminobenzophenone (1 mmol), acetyl acetone (1.2 mmol), 50 °C under solvent-free conditions. b Isolated yield.

225 226 227 228 229 230

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3.27 (t, J = 7.6 Hz, 2H), 7.37–7.43 (m, 3H), 7.48–7.56 (m, 3H), 7.62– 7.66 (m, 2H), 8.07–8.09 (m, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 24.0, 29.9, 35.3, 124.9, 125.7, 126.4, 128.6, 128.3, 129.3, 133.7, 137.0, 142.5, 148.0, 167.6. 6-Phenyl-7H-indeno[1,2-b]quinolin-7-one (i): 1.1. M. p. 180–182 °C. IR (KBr) ν cm− 1: 3074, 2929, 1621, 1455; (CDCl3, 400 MHz) ppm: 7.44 (t, J = 8.0 Hz, 2H), 7.50–7.59 (m, 4H), 7.60–7.74 (t, J = 8.0 Hz, 3H), 7.81–7.85 (t, J = 8.0 Hz, 1H), 8.32 (s, 2H) 13C NMR (CDCl3 , 100 MHz) ppm: 29.7, 123.0, 124.1, 127.0, 127.7, 128.1, 128.7, 128.9, 129.3, 131.7, 140.0, 133.0, 135.4, 137.7, 163.1. 1-(6-Chloro-2-methyl-4-phenylquinolin-3-yl)ethanone (j): M.p. 159–160 °C. IR (KBr) ν cm− 1: 3056, 2938, 1675 cm−1; 1 HNMR(CDCl3, 400 MHz) ppm: 1.94 (s, 3H), 2.68 (s, 3H), 7.31– 7.34 (m, 2H), 7.49–7.56 (m, 4H), 7.60–7.64 (m, 1H), 7.99 (d, J = 9.4 Hz, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 23.5, 31.9, 124.6, 125.8, 128.7, 129.2, 129.7, 130.2, 130.6, 132.4, 134.5, 135.6, 143.1, 145.6, 153.9, 205.0. Methyl 6-chloro-2-methyl-4-phenylquinoline-3-carboxylate (k): M. p. 131–133 °C; IR (KBr) ν cm− 1: m 3063, 2945, 1735; 1H NMR(CDCl3, 400 MHz) ppm: 2.56 (s, 3H), 3.54 (s, 3H), 7.26–7.92

U

217

D

P

t1:10

O

t1:4

(m, 8H); 13C NMR (CDCl3, 100 MHz) ppm: 23.4, 52.62, 125.1, 125.9, 127.9, 128.6, 128.9, 129.1, 130.4, 131.1, 132.5, 134.9, 145.6, 146.1, 154.8, 168.7. Ethyl 6-chloro-2-methyl-4-phenylquinoline-3-carboxylate (l): M. p. 98–100 °C. IR (KBr) ν cm−1: 3042, 2936, 1712; 1HNMR(CDCl3, 400 MHz) ppm: 0.90 (t, J = 7.0 Hz, 3H), 2.73 (s, 3H), 3.88 (q, J = 7.0 Hz, 2H), 7.30–7.47 (m, 6H), 7.51 (dd, J1 = 8.8 Hz, J2 = 2.4, 1H), 7.88 (d, J = 8.8 Hz, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 13.5, 23.8, 59.9, 124.5, 125.8, 127.9, 128.4, 128.2, 128.9, 130.1, 130.8, 132.2, 134.6, 144.9, 145.4, 154.7, 167.8. 6-(Chloro-2-methyl-4-phenylquinolin-3-yl)(phenyl)methanone (m): M. p. 209–211 °C. IR (KBr) ν cm−1: 2925, 2851, 1680, 1240; 1H NMR (CDCl3, 400 MHz) ppm: 2.49 (s, 3H), 7.12 (m, 7H), 7.41 (m, 1H), 7.46 (m, 3H), 7.66 (d, J = 2.40 Hz, 1H), 7.96 (d, J = 8.8 Hz, 1H). 13C NMR (CDCl3, 100 MHz) ppm: 23.8, 124.7, 125.9, 128.1, 128.3, 128.4, 129.0, 129.7, 130.4, 130.8, 132.3, 133.0, 133.5, 133.9, 136.7, 144.6, 146.0, 154.8, 199.9. 7-Chloro-9-phenyl-3,4-dihydro-1-2H-acridinone (n): M. p. 187–189 °C. IR (KBr) ν cm − 1 : 3032, 2967, 2875, 1688, 1549. 1HNMR (CDCl 3, 400 MHz) ppm: 2.24 (q, J = 6.4 Hz, 2H), 2.70 (t, J = 6.4 Hz, 2H), 3.32 (t, J = 6.4 Hz, 2H), 7.15 (t, 2H), 7.41 (s, H), 7.52 (m, 3H), 7.59 (d, J = 8.4 Hz, 1H,), 7.98 (d, J = 8.4 Hz, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 20.9, 34.2, 40.3, 124.2, 126.3, 127.8, 130.0, 132.2, 136.6, 146.7, 149.9, 162.2, 197.0. 7-Chloro-3,3-dimethyl-9-phenyl-3,4-dihydro-2H-acridin-1-one (o): M. p. 207–209 °C. IR (KBr) ν cm− 1: 3071, 2946, 1693; 1HNMR (CDCl3, 400 MHz) ppm: 1.12 (s, 6H), 2.53 (s, 2H), 3.25 (s, 2H), 7.13–7.16 (m, 2H), 7.28 (d, J = 2.4 Hz, 1H), 7.42–7.55 (m, 3H), 7.71 (dd, J1 = 8.8 Hz, J2 = 2.8 Hz, 1H), 8.05 (d, J = 8.8 Hz, 1H); 13 C NMR (CDCl3, 100 MHz) ppm: 28.4, 32.3, 48.4, 54.3, 123.5, 126.8, 127.7, 127.9, 128.1, 128.2, 130.0, 132.3, 132.5, 136.8, 147.2, 150.2, 161.2, 197.5.

F

Table 1 The effect of different amounts of C4(mim)2-2Br−-2H2SO4 on the reaction of 2-amino benzophenone with acetyl acetone.a

R O

t1:1 t1:2 t1:3

Ph

Ph O

O +

CO2Et

Solvent-free, 50 oC

NH2

C4(mim)2-Br2-(H2SO4)2 :

X = H, Cl

N

CO2Et

C4(mim)2-Br2-(H2SO4)2 (0.05 mmol)

N

N

N

N

.2 Br - .2 H2SO4

Scheme 3. Friedländer reaction in the presence of C4(mim)2-2Br−-2H2SO4 as the catalyst.

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268

269 270

F. Shirini et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx

271 273 t2:1 t2:2

1.92–1.96 (m, 2H), 2.58 (t, J = 6.2 Hz, 2H), 3.30 (t, J = 6.2 Hz, 274 2H), 7.21–7.32 (m, 4H), 7.48–7.69 (m, 3H), 7.94 (d, J = 8.6 Hz, 275 1H); 13C NMR (CDCl 3, 100 MHz) ppm: 22.6, 27.7, 35.6, 124.2, 276

7-Chloro-9-phenyl-1,2,3,4-tetrahydroacridine (p): M. p. 160–163 °C. IR (KBr) ν cm− 1: 3060, 2944, 1604, 1572, 1481, 1215, 703; 1 HNMR(CDCl3, 400 MHz) ppm: 1.71–1.83 (m, 2H),

272

7

Table 2 Preparation of quinoline derivatives using C4(mim)2-2Br−-2H2SO4 as the catalyst.a,b Entry

Time (min)

Yield (%)

M. p. (°C)

Ref.

t2:4

a

25

93

106–108

[36]

t2:5

b

35

95

105–106

[37]

t2:6

c

93

98–100

[37]

t2:7

d

25

94

140–142

[38]

t2:8

e

20

91

155–156

[37]

t2:9

f

25

95

189–190

[37]

t2:10

g

15

90

139–142

[37]

t2:11

h

25

93

129–132

[37]

t2:12

i

5

92

179–182

[37]

t2:13

j

15

90

159–160

[37]

Ketone

Product

R O

O

Substrate

F

t2:3

U

N C O

R

R

E

C

T

E

D

P

35

(continued on next page)

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8

F. Shirini et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx

Table 2 (continued) Entry

Time (min)

Yield (%)

M. p. (°C)

Ref.

t2:15

k

30

92

130–131

[37]

t2:16

l

30

93

99–101

[39]

t2:17

m

35

91

207–210

[37]

t2:18

n

15

96

188–190

[37]

t2:19

o

35

96

207–210

[37]

t2:20

p

30

92

159–161

[40]

t2:21

q

25

93

97–99

[37]

t2:22

r

15

98

241–243

t2:23 t2:24

a

Ketone

Product

This work

278 279 280 281 282 283 284 285 286 287 288 289

N

Isolated yield. Products were characterized by their physical constants, comparison with authentic samples, IR and NMR spectroscopy.

U

277

b

C

O

R

R

E

C

T

E

D

P

R O

O

Substrate

F

t2:14

126.9, 128.1, 128.8, 128.9, 129.0, 129.5, 130.4, 131.6, 136.8, 144.9, 145.9, 129.8. 7-Chloro-2,3-dihydro-9-phenyl-1H-cyclopenta[b]quinoline (q): M. p. 97–98 °C. IR (KBr) ν cm−1: 3043, 2941, 1608, 1481; 1H NMR (CDCl3, 400 MHz) ppm: 2.23 (m, 2H), 2.94 (t, J = 7.4 Hz, 2H), 3.24 (t, J = 7.4 Hz, 2H), 7.41–7.32 (m, 2H), 7.41–7.55 (m, 5H), 7.96 (d, J = 8.8 Hz, 1H); 13C NMR (CDCl3, 100 MHz) ppm: 23.3, 31.4, 36.2, 126.5, 128.0, 128.1, 128.6, 128.8, 129.0, 130.2, 131.3, 134.7, 136.0, 141.9, 146.9, 168.5. 8-Chloro-10-phenyl-11H-indeno[1,2-b]quinolin-11-one (r): M. p. 240–243 °C. IR (KBr) ν cm−1: 3045, 2917, 1717, 1611.51, 1572, 1442; 1H NMR (CDCl3, 400 MHz) ppm: 7.43–7.46 (m, 2H), 7.51–7.55 (td, J1 = 7.60 Hz, J2 = 0.80 Hz, 1H), 7.60–7.634 (m, 3H), 7.66–7.67

(d, J = 2.00 Hz, 1H), 7.69–7.70 (d, J = 2.40 Hz, 1H), 7.72–7.75 (m, 1H), 8.10–8.15 (t, J = 9.80 Hz, 2H) 13C NMR (CDCl3, 100 MHz) ppm: 121.7, 123.3, 124.0, 127.4, 128.4, 128.7, 129.3, 129.4, 131.3, 131.8, 132.4, 133.1, 135.5, 137.5, 143.1, 147.1, 148.8, 162.2, 189.9.

290 291 292 293

3. Results and discussion

294

Very recently and in continuation of our ongoing research program on the development of new catalysts and methods for organic transformations [31,32], we have reported the preparation of 1,3-disulfonic acid imidazolium hydrogen sulfate and its application in the promotion of some of the organic reactions [33–35]. Herein and in continuation of these studies we wish to report the preparation of 3,3′-(butane-1,4diyl) bis (1-methyl-1H-imidazol-3-ium)·dibromide·disulfuric acid

295

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

296 297 298 299 300 301

F. Shirini et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx

Recovery of the catalyst

After optimization of the reaction conditions, the optimized condition was applied for both cyclic and acyclic carbonyl compounds. The results are tabulated in Table 2. As we can see, using this method β-ketoesters, such as methyl acetoacetate and ethyl acetoacetate are converted to their quinoline products in high yields (Table 2, entries 2, 3, 11, 12). In addition, cyclic ketones such as cyclopentanone and cyclohexanone (Table 2, entries 7, 8, 16, 17) and various cyclic and acyclic 1,3-diketones such as acetyl acetone, 1-phenylbutane-1,3-dione, cyclohexanedione, dimedone and 1,3-indandion (Table 2, entries 5, 6, 9, 14, 15, 18) are reacted efficiently with o-aminobenzophenones to give the corresponding substituted quinolines in good to excellent yields during acceptable reaction times. The reusability of the ionic liquid catalyst was assessed by conducting the reaction of 2-aminobenzophenone and ethyl acetoacetate over six successive cycles without any pretreatment of the ionic liquid (Fig. 6). In order to show the merit of the catalyst, we have compared the results obtained from the reaction of 5-chloro-2-amino benzophenone and acetylacetone in the presence of C4(mim)2-2Br−-2H2SO4 with some of the other catalysts used for the similar reaction (Table 3). This comparison clearly shows that, using this method, the requested product is obtained in shorter reaction times and under relatively milder reaction conditions. The plausible pathways of the reaction are shown in Scheme 4. On the basis of these mechanisms and in the first step, the carbonyl group is activated by C4(mim)2-2Br−-2H2SO4 for a crossed-aldol reaction, creating an amino ketone (I and/or II). This intermediate subsequently condenses with itself, and produces the ring with concomitant formation of the C_N (a) or C_C (b) bond.

Time (min) and Yield (%)

100 80 60 Time (min)

40

Yield (%)

20 0

1

2

3

4

5

6

F

Run

O

Fig. 6. Reusability of the ionic liquid.

t3:1 t3:2

Table 3 Preparation of 1-(6-chloro-2-methyl-4-phenylquinolin-3-yl)ethanone in the presence of different catalysts.

P

309 310

D

307 308

E

305 306

T

303 304

R O

311

(C4(mim)2-2Br−-2H2SO4) ionic liquid and its applicability as a new, efficient and recyclable catalyst in the acceleration of the Friedländer reaction. After preparation and identification of C4(mim)2-2Br−-2H2SO4 and in order to show the efficiency of this reagent the reaction of 2-aminobenzophenone with ethyl acetoacetate was investigated in the presence of this IL as the catalyst. These investigations clarified that the best results can be obtained when the reaction was performed in the absence of solvent at 50 °C using 0.05 mmol of the catalyst (Table 1, Scheme 3).

302

9

Entry

Catalyst

Conditions

t3:4 t3:5 t3:6 t3:7 t3:8 t3:9

1 2 3 4 5 6

[Hbim]BF4 Y(OTf)3 TBBDA Amberlyst-15 Zr(NO3)4 C4(mim)2-2Br−-2H2SO4

100 °C/solvent-free CH3CN, r.t. H2O/reflux EtOH/reflux H2O/reflux 50 °C/solvent-free

Time (min)

Yield (%)

Ref.

198 360 300 120 360 15

93 81 94 90 86 90

[29] [41] [42] [43] [44] This work

N C O

R

R

E

C

t3:3

U

(a)

(b)

Scheme 4. Proposed pathways of the reaction.

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339

F. Shirini et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx

350

Acknowledgments

351 Q6 352

We are thankful to the University of Guilan Research Council for the partial support of this work.

353

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354 355 356 357 358 359 360 361 362 363 364 365 366 367 368

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O

341 342

[16] [17] [18] [19] [20] [21] [22] [23] [24] [25]

R O

4. Conclusion

P

340

D

10

Please cite this article as: F. Shirini, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.06.005

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