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ZnO nanoparticle-catalyzed efficient onepot three-component synthesis of 3,4,5trisubstituted furan-2(5H)-ones Sunil U. Tekale, Sushma S. Kauthale, Vijay P. Pagore, Vivekanand B. Jadhav & Rajendra P. Pawar Journal of the Iranian Chemical Society ISSN 1735-207X Volume 10 Number 6 J IRAN CHEM SOC (2013) 10:1271-1277 DOI 10.1007/s13738-013-0266-9

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Author's personal copy J IRAN CHEM SOC (2013) 10:1271–1277 DOI 10.1007/s13738-013-0266-9

ORIGINAL PAPER

ZnO nanoparticle-catalyzed efficient one-pot three-component synthesis of 3,4,5-trisubstituted furan-2(5H)-ones Sunil U. Tekale • Sushma S. Kauthale • Vijay P. Pagore • Vivekanand B. Jadhav Rajendra P. Pawar



Received: 15 January 2013 / Accepted: 15 April 2013 / Published online: 30 April 2013 Ó Iranian Chemical Society 2013

Abstract An efficient and high-yielding protocol using nano-ZnO (50–100 nm) as an efficient heterogeneous catalyst for one-pot three-component synthesis of pharmacologically significant furanone derivatives by the condensation of aromatic aldehyde, amine and dimethylacetylenedicarboxylate has been developed. Since the catalyst is heterogeneous, it can be easily separated and recycled several times without much loss of its catalytic activity. Use of aqueous medium, recyclable nanocatalyst, operational simplicity, non-chromatographic purification technique, excellent yield and short reaction time makes this approach an attractive protocol for the synthesis of 3,4,5-trisubstituted furan-2(5H)-ones. Keywords Aldehyde  Amine  DMAD  Furan-2(5H)-ones  Nano-ZnO

Introduction Furanones are the five-membered heterocyclic compounds possessing lactone ring in their structures. These heterocycles are the core structures of many bioactive natural products as well as synthetic drugs such as rubrolide, sarcophine, benfurodil hemisuccinate, etc. [1, 2]. 5H-Furan-2-one derivatives exhibit many pharmacological and biological

S. U. Tekale  V. P. Pagore  V. B. Jadhav Department of Chemistry, Shri Muktanand College, Gangapur (MS), Maharashtra 431 109, India S. S. Kauthale  R. P. Pawar (&) Department of Chemistry, Deogiri College, Station Road, Aurangabad, Maharashtra 431 005, India e-mail: [email protected]

activities including antifungal, antibacterial, anti-oxidants, anti-inflammatory, anti-microbial and anti-cancer agents [3– 7]. They are mutagenic in nature [8]. Chen et al. [9] reported the LasR receptor inhibition on biofilm formation of Pseudomonas aeruginosa species. Consequently, furanones constitute the biologically important targets in medicinal chemistry. Currently, one-pot multicomponent reactions (MCRs) are becoming more popular over routine multistep organic synthesis in terms of efficiency and practicability, as they facilitate the construction of pharmacologically and medicinally active targets in a single step leading to diverse molecular complexity [10]. These reactions allow the formation of new bonds in one pot avoiding the number of steps; afford clean reaction profile, high yield and are atom economic. Thus MCRs are emerging as efficient and powerful tools in modern synthetic organic chemistry for academia and industry. With the growing environmental hazards and emerging green approaches, organic synthesis in aqueous medium is preferred rather than the common organic solvents. Water is abundant, easily available, low cost, non-toxic and green reaction medium. It has high cohesive energy density and high dielectric constant compared to organic solvents. It has special effects on reactions due to inter- and intramolecular non-covalent interactions leading to novel solvation processes. Water is being utilized for many organic reactions. Organic synthesis in aqueous medium is preferred from commercial as well as economic point of view [11]. Heterogeneous catalysts are superior to homogeneous ones in terms of easy separation, recycling ability in successive runs and minimization of metal traces in the products. Consequently, performing multicomponent reactions in aqueous medium using reusable heterogeneous

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catalysts is largely used in organic synthesis. These also provide a number of active sites per unit area as compared to their homogeneous counter parts. Reactions on solid supports can be applied to increase reactivity. The surface area of a catalyst increases with decreasing particle size. Recently, nano-catalysts have become viable alternatives to the conventional materials due to their high surface area, greater reactivity, easy recovery and reusability. Nano-particles of transition metal oxides have attracted significant attention as efficient catalysts in many organic reactions due to their high surface-to-volume ratio and low co-ordinating sites. Zinc oxide is a versatile wide band gap (3.37 eV) semiconductor material; basically recruited for its potential applications in solar cells, gas sensing materials, optoelectronics, biomedical devices, etc. [12–14]. Owing to its low toxicity, low cost, low corrosion, large surface area, high pores volume and eco-friendly nature [15], nano-ZnO is being extensively employed as a promising Lewis acid reusable heterogeneous catalyst for diverse range of one-pot multicomponent organic transformations [16–19]. As per literature survey, only a few synthetic protocols are documented for the synthesis of furanones. 3,4-Bisstannyl-2(5H) furanones were synthesized by Sweeney et al. [20] using Stille reaction. Bassetti [21] reported rhodium-catalyzed ring-closing metathesis from acrylic esters using first-generation Grubbs’ catalyst as an effective promoter. Fukuta [22] carried out rhodium-catalyzed hydroformylation of propargyl alcohols into 2(5H)-furanones under high pressure in which substituted cyclohexenes were also obtained. 3-Substituted-2,5-dihydro-2,5dimethoxyfurans can be hydrolyzed to 3-substituted-furan2(5H)-ones [23]. Furanones were obtained as the unexpected products during the palladium-catalyzed synthesis of 2(2H)-pyranone from (Z)-2-en-4-ynoic acids [24]. A multistep approach was employed by Ahn [25] for the synthesis of 3,4-diaryl-2(5H)-furanone derivatives with potent cytotoxic activities from acetophenone precursors. A two-step synthesis was documented in literature for the synthesis of 5-(substituted-phenyl)-3-(substituted-arylidene)-2(3H)-furanones [26]. Y.V.D. Nageswar et al. [27] firstly synthesized 3,4,5-trisubstituted furan-2(5H)-ones by the three-component reaction between aldehyde, amine and diethylacetylenedicarboxylate using b-cyclodextrin supramolecule. Nagarapu et al. [28] documented a similar organic transformation using SnCl2 2H2O as the catalyst. Scheme 1 ZnO nanoparticle catalyzed one pot three component synthesis of trisubstituted furan-2(5H)-ones

Experimental All the chemicals were purchased from Aldrich or SD Fine Chemicals and used without further purification. Melting points were recorded in capillaries open at one end and were uncorrected. 1H NMR spectra were recorded using DMSO-d6 solvent on 400 MHz Varian Spectrophotometer with TMS as an internal standard and chemical shifts (d) are expressed in ppm. IR spectra of samples were recorded on Bruker Vector 22 FTIR spectrophotometer using KBr discs. Mass spectra were analyzed on Shimadzu mass analyzer with EI 70 eV. TEM images were recorded on the Transmission Electron Microscope instrument (TECNAI G2 20 U-TWIN, FEI, Netherlands). EDX analysis of the catalyst was carried out using scanning electron microscope (JEOL JSM6360A) instrument 6360 (LA). General procedure for the ZnO nanoparticle-catalyzed synthesis of 3,4,5-trisubstituted furan-2(5H)-ones: A solution of aromatic amine (2 mmol), dimethylacetylenedicaboxylate (2 mmol) and ZnO (5 mol%) nanoparticles in Ethanol:H2O (1:1) (2 mL) was magnetically stirred at room temperature for 15 min. To it aromatic aldehyde (2 mmol) was added and the contents were heated with stirring at 90 °C for 2.5 h. The progress of reaction was monitored by TLC in 70 % EA:hexane. After completion of the reaction; the reaction mass was concentrated under reduced pressure. To this crude hot ethanol (10 mL) was O

CHO

COOMe

R1

NH2 Nano ZnO (5 mol%) R2

COOMe

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Some of these protocols although one pot, suffer from several aspects such as the use of expensive reagents, inconvenient handling, reusability of catalyst, poor yields, longer reaction time, sophisticated purification techniques, etc. Considering the widespread utility of furanone derivatives and availability of few literature protocols for the synthesis of furanones and their limitations, in the present work we have successfully developed a synthetic route with the minimized drawbacks. Herein, we wish to report a simple, convenient, rapid (2.5 h) and high-yielding method using ZnO nanoparticle as an efficient, non-toxic and commercially available reusable heterogeneous catalyst for the synthesis of 3,4,5-trisubstituted furan-2(5H)-ones by the condensation of aromatic aldehyde, amine and DMAD in ethanol:H2O (1:1) at 90 °C (Scheme 1).

EtOH : H2O (1:1) o

90 C, 2.5 h

OMe

R1

NH

O O

R2

Author's personal copy J IRAN CHEM SOC (2013) 10:1271–1277

added and filtered off to separate the catalyst. The filtrate was further concentrated and purified by recrystallization from ethanol. Using this procedure a series of furanones was synthesized (Table 1). The spectral data of representative compounds is represented below. Methyl 2,5-dihydro-5-oxo-2-phenyl-4-(phenylamino)furan3-carboxylate (entry 1, Table 1) Faint yellow solid; MP (°C) 159–162; 1H NMR (400 MHz, DMSO-d6) d ppm 3.6 (s, 3H), 6.12 (s, 1H), 7.05–7.6 (m, 10H), 11.78 (brs, 1H, NH); IR (KBr) cm-1 3,211.48, 2,956.87, 2,370.51, 1,697.06, 1,640.00, 1,498.69, 1,232.51, 1,080.14; ESMS: 310 (M?1)?.

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to-volume ratio and affords high catalytic activity which helps to enhance the rate of reaction along with reduction in the reaction time. EDX Energy-dispersive X-ray spectroscopy (EDS or EDX) is a sophisticated instrumental analytical technique applicable for the elemental analysis and chemical characterization of materials. The chemical composition of crystalline ZnO was studied using EDX in the energy range of 0–20 kV on using scanning electron microscope (JEOL JSM6360A) instrument 6360 (LA). The EDX analysis (Fig. 2) indicates highly pure nature of the catalyst. XRD

Methyl4-(p-tolylamino)-2,5-dihydro-5-oxo-2-phenylfuran3-carboxylate (entry 2, Table 1) Off-white solid; MP (°C) 284–287; 1H NMR (400 MHz, DMSO-d6) d ppm 2.18 (s, 3H), 3.56 (s, 3H), 5.98 (s, 1H), 7.05-(d, 2H, J = 7.05 Hz), 7.1–7.3 (m, 5H), 7.4 (d, 2H, J = 7.30 Hz), 11.8 (br, s, 1H, NH); IR (KBr) cm-1 3,228.84, 2,924.09, 2,854.65, 2,366.66, 1,658.78, 1,597.06, 1,494.83, 1,234.44, 1,089.78; ESMS: 324.01 (M?1)?.

XRD studies of nano-ZnO showed a characteristic pattern as shown in Fig. 3. The presence of diffraction peaks at 2h values of 32.08, 34.74, 36.64, 48.04, 57.04, 63.22, 68.28 and 69.24 correspond to (100), (002), (101), (102), (110), (103), (200) and (201) planes, respectively. The strongest peak at 2h = 36.64 belongs to the (101) plane of the ZnO. No impurity peaks were detected. The XRD pattern indicates the face centered cubic structure of zinc oxide nanoparticles.

Methyl 4-(4-fluorophenylamino)-2,5-dihydro-5-oxo-2phenylfuran-3-carboxylate (entry 4, Table 1) Results and discussion Faint yellow solid; MP (°C) 293–295; 1H NMR (400 MHz, DMSO-d6) d ppm 3.58 (s, 3H), 6.07 (s, 1H), 7.15–7.45 (m, 9H), 11.8 (br, s, 1H, NH); IR (KBr) cm-1 3,228.84, 2,951.09, 2,360.87, 1,708, 1,676.14, 1,512.19, 1,234.44, 999.13; ESMS: 327.99 (M?1)?. Methyl 2-(4-chlorophenyl)-2,5-dihydro-5-oxo-4(phenylamino)furan-3-carboxylate (entry 5, Table 1) Off-white solid; MP (°C) 149–152; 1H NMR (400 MHz, DMSO-d6) d ppm 3.56 (s, 3H), 6.05 (s, 1H), 7.10–7.58 (m, 9H), 11.90 (br, s, 1H, NH); IR (KBr) cm-1 3,265.49, 2,956.87, 2,368.59, 1,707.00, 16.8.63, 1,213.23, 1,128.36; ESMS: 344.03 (M?1)?. Catalyst characterization: TEM The size and morphology of nano-ZnO were studied using transmission electron microscope (TEM). From the TEM images (Fig. 1), particle size of the nano-crystalline ZnO was found to be in the range of 50–100 nm. On account of this small particle size, the catalyst exhibits high surface-

Initially to optimize the reaction conditions, various solvents and catalysts were screened for three-component model condensation of aniline (1 mmol), dimethylacetylenedicarboxylate (1 mmol) and benzaldehyde (1 mmol). The effect of various alcoholic solvents such as ethanol (EtOH), methanol (MeOH), isopropyl alcohol (IPA), polyethylene glycol (PEG), etc. and catalysts like L-proline, TBAF was investigated. The results are summarized in (Table 2). It was observed that neither the use of fluorinated reagent (entry 8) nor alcohol, i.e., 2,2,2-trifluoroethyl alcohol (entry 1) could give good results within 5–8 h. Nano-CuO was unable to increase the yield (entry 9). The combination of zinc oxide nanoparticle (5 mol%) and ethanol gave better yields (83 %) in 5 h (entry 6). The use of EtOH:H2O (1:1) solvent system was more effective than the mere use of ethanol in terms of reduced reaction time and higher yields. Thus, better results were obtained using 5 mol% ZnO and ethanol:H2O solvent system within 3 h. Furthermore, increasing the catalyst concentration from 5 to 10, 15 and 20 mol% could increase the yields to 94, 95 and 95 % indicating that 5 mol% of the nano-ZnO sufficient enough to afford the corresponding furan-2 (5H)-ones

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Author's personal copy 1274 Table 1 ZnO nanoparticlecatalyzed one-pot threecomponent synthesis of trisubstituted furan-2(5H)-ones

J IRAN CHEM SOC (2013) 10:1271–1277

Entry

Aldehyde (R1)

Amine (R2)

Product O

1

H

MP(°C)b

94

159–162

95

284–287

88

239–242

84

293–295

89

149–152

87

273–275

85

240–243

84

181–183

88

>300

84

>300

85

271–273

83

>300

OMe NH

O

H

Yield (%)a

O

(F1) O

2

H

4-Me

OMe NH

O O

Me

(F2) MeO

3

4-OMe

O

H

OMe NH

O O

(F3) O

4

H

4-F

OMe NH

O O

F

(F4) Cl

5

4-Cl

O

H

OMe NH

O O

(F5) O

6

2-Cl

H

Cl

OMe NH

O O

(F6) O

7

3-OCH3

H

OMe

H3CO

NH

O O

(F7) Me

8

4-Me

O

H

OMe NH

O O

(F8) 9

H

O

4-CHMe2

OMe NH

O O

(F9) O

10

H

OMe

2-F

NH

O O

F

(F10) Cl

11

2,4-Cl2

2-F

O

Cl

b

Melting points were compared with the literature values in Ref. [28]

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NH

O O

a

Yields of reactions performed on aldehyde (2 mmol), amine (2 mmol), DMAD (2 mmol) in 1:1 EtOH:H2O (2 mL) using 5 mol % nano-ZnO at 90 °C for 2.5 h

OMe

F

(F11) MeO

12

2,4(OMe)2

H

O

OMe NH

OMe O O

(F12)

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Fig. 1 TEM images of the nano-crystalline ZnO Table 2 Effect of various reaction conditions on the one-pot threecomponent synthesis of furanones

Fig. 2 EDX analysis of nano-ZnO

Entry

Reaction conditionsa

Yield (%)b

1

ZnO (5 mol%), TFE, 70 °C, 5 h

30

2

ZnO(5 mol%), MeOH, 60 °C, 5 h

67

3

ZnO (5 mol%), IPA, 85 °C, 5 h

38

4

ZnO (5 mol%), Ethylene glycol, 80 °C, 5 h

26

5

ZnO (5 mol%), PEG, 80 °C, 8 h

12

ZnO (5 mol%), EtOH, 80 °C, 5 h

83

L-Proline

(5 mol%), EtOH, 80 °C, 7 h TBAF (5 mol%), THF, 70 °C, 8 h

28 09

9

Nano-CuO (5 mol%), EtOH, 80 °C, 5 h

32

10

b-Cyclodextrin (mol%), H2O, 60–70 °C, 12–16 h

78–88 [27]

11

SnCl2, EtOH, reflux, 6.5–7.0 h

85–90 [28]

12

ZnO, EtOH:H2O (1:1), 90 °C, 2.5 h

94 (present work)

6 7 8

1000

Intensity (a.u.)

ZnO

a

Reactions were tried on benzaldehyde (1 mmol), aniline (1 mmol), DMAD (1 mmol) in 1 mL solvent

800

b

600

Table 3 Recycle study of nano-ZnO catalyst

Isolated yields

Run Yield (%)a

400

1

2

3

4

94

91

87

84

a

Reactions were carried on benzaldehyde (1 mmol), aniline (1 mmol), DMAD (1 mmol) using 5 mol% nano-ZnO catalyst in 1:1 EtOH:H2O (1 mL) at 90 °C for 2.5 h

200

0 20

30

40

50

60

70

80

2 Theta (degree)

Fig. 3 XRD of nano-ZnO

in higher yields. Nano-ZnO seems to be more efficient than the other screened catalysts. The catalyst recovered after the reaction gives good recycle results (Table 3).

To explore the scope and feasibility of these optimized conditions a series of furanones was obtained from different substituted amines, aldehydes and DMAD in the presence of 5 mol% nano-ZnO at 90 °C (Table 1). Studies reveal that almost all aldehydes and amines reacted cleanly to afford the corresponding products in excellent yields. Substituents on neither the aldehyde nor amine had prominent effect on yield of reaction. This is one of the

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H

ZnO

N NH2

R

COOMe

O

2

R2

H

COOMe

R1

DMAD O OMe N+

H

ZnO

H

R2

COOMe O ZnO

O

OMe

R1

O

NH

O O

OMe N+

H R2

H

R2

O+H O

OMe

ZnO

Fig. 4 Proposed mechanism for ZnO nanoparticle-catalyzed synthesis of trisubstituted furan-2(5H)-ones

important advantages of the present ZnO nanoparticlecatalyzed synthesis of furanones. The plausible mechanism for the ZnO nanoparticlecatalyzed synthesis of furan-2(5H)-ones from aldehydes, amines and DMAD is depicted in Fig. 4. Initially, ZnO promotes the formation of enamine from amine and DMAD. ZnO polarizes the carbonyl group of aldehyde to form polarized adduct which reacts with the enamine followed by cyclization with the elimination of methanol molecule to afford the corresponding furan-2(5H)-ones.

Conclusion In summary, we have successfully developed an efficient protocol for the one-pot three-component synthesis of 3,4,5-trisubstituted furan-2(5H)-ones from aldehydes, amines and DMAD using nano-crystalline ZnO as a reusable heterogeneous catalyst. The catalyst being heterogeneous can be recycled several times with consistent catalytic activity which makes this an economically useful method. It is superior in terms of short reaction time, low catalyst concentration and higher yield as compared with the previous literature protocols. Experimental simplicity, clean reaction profile, use of reusable, economical and cheap heterogeneous nano-ZnO catalyst are the important advantages of this method. Compatibility with various functional groups, non-chromatographic purification technique, short reaction times and excellent yields make this protocol as an attractive process.

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Acknowledgments The authors are thankful to the Principal, Deogiri College Aurangabad, for providing laboratory facilities and constant encouragement during the work. We thank the Department of Physics, Pune University, for providing the Sophisticated Analytical and Instrument (SAIF) Facilities.

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