Synthesis of Pyrazole by Using Polyvinylsulfonic Acid (PVSA) as a

0 downloads 0 Views 2MB Size Report
of the pyrazole derivatives. Keywords: Pyrazole, catalysis, hydrazine, polyvinylsulfonic acid (PVSA), 1,3-diketone; recycle. INTRODUCTION. Pyrazole ring has ...
Send Orders for Reprints to [email protected] Current Catalysis, 2016, 5, 00-00

1

Synthesis of Pyrazole by Using Polyvinylsulfonic Acid (PVSA) as a Novel Bronsted Acid Catalyst Sunil S. Ekbotea, Sandip T. Gadgea, and Bhalchandra M. Bhanagea,* a

Department of Chemistry, Institute of Chemical Technology, N. Parekh Marg, Matunga, Mumbai-400019. India Abstract: Background: Pyrazoles are useful intermediates in pharmaceutical, agrochemical, photographic and other fields. Pyrazole nucleus has been reported to possess a wide spectrum of biological properties such as anti-inflammatory, anti-depressant, anti-bacterial, anti-tumor, anti-microbial, anti-viral, anti-fungal and anti-filarial agent. The aims of this paper to introduce readers the polyvinylsulfonic acid (PVSA) as a new catalytic system for the synthesis of pyrazoles. The PVSA was found to be an inexpensive, stable, easy to handle and biodegradable catalyst.

Bhalchandra M. Bhanage

Methods: The catalyst is well characterized using various techniques such as IR, XRD and DSC. All products were characterised using melting point, GC-MS, 1H and 13C NMR techniques. Results: The various acidic catalysts were compared with PVSA under optimized reaction condition and it was found that PVSA giving better yield of desired product. Different reaction parameters such as solvent, temperature, time, and substrate were studied to achieve optimal catalyst performance using PVSA as a catalytic system. Conclusion: We have described PVSA as a novel Bronsted acid catalyst for the synthesis of pyrazoles. The catalyst was isolated by simple filtration process and recycled up to four cycles providing the excellent yield of the pyrazole derivatives.

Keywords: Pyrazole, catalysis, hydrazine, polyvinylsulfonic acid (PVSA), 1,3-diketone; recycle. INTRODUCTION Pyrazole ring has received more attention in the recent years, because they have proven it to be extremely useful intermediate for the synthesis of new biological active compounds. Literature reports reveal that many synthetic pyrazole derivatives are used in pharmaceutical, agrochemical, photographic and other fields. Pyrazole nucleus has been reported to possess a wide spectrum of biological properties such as anti-inflammatory, [1] anti-depressant, [2] anti-bacterial, [3] antitumor, [4] anti-microbial, [5] anti-viral, [6] antifungal and anti-filarial agent [7, 8].

*Address correspondence to this author at the Department of Chemistry Institute of Chemical Technology, Matunga, Mumbai – 400 019, India; Tel: +91-22-3361-2601; Fax: +91-22-3361-1020; E-mails: [email protected]; [email protected]

2211-5447/16 $58.00+.00

Several methodologies using various starting materials and catalysts have been reported for synthesis of pyrazole [9-19]. However, most of these methods utilizes a circuitous route, expensive starting materials, longer reaction time, specific or selective catalysts and often may require mixed solvent systems. The direct condensation of 1,3diketone and hydrazine in presence of acidic catalyst is one of the simplest and most simple procedure for the synthesis of pyrazoles. A variety of catalysts such as H2SO4, [20] polystyrene supported sulfonic acid, [21] layered zirconium sulfophenylphosphonate, [22] Sc(OTf)3, [23] Y-zeolite, [24] and silica supported sulfuric acid, [25, 26] have been reported for this transformation. Polyvinylsulfonic acid (PVSA) is known since several decades, however the catalyst activities of PVSA were not explored. It is a strong aliphatic polymeric sulfonic acid and having high solubility in water and lower aliphatic alcohols. Compared to

©2016 Bentham Science Publishers

2 Current Catalysis, 2016, Vol. 5, No. 1

Ekboteet al.

H C

mined with the help of GC–MS analysis (Shimadzu QP-2010).

CH2

SO2 O H2N

NH2

O

OH

EXPERIMENTAL

n

N

H2O

N H

Preparation and Characterization of Polyvinylsulfonic Acid (PVSA)

Scheme (1). PVSA catalyzed synthesis of pyrazole.

Breslow‘s method was used to prepare PVSA [27, 28]. A precursor of PVSA such as sodium salt of polyvinylsulfonic acid (Na-PVSA) was characterized by DSC, XRD, and FT-IR techniques.

1a

2a

3a

the conventional Bronsted acid catalyst, PVSA has several advantages such as it is biodegradable, easy to handle, recyclable and tunable acidity etc. PVSA a novel acid catalyst proved for the excellent performance in Michael addition reaction of indoles to α,β-unsaturated ketones and was first time reported for this reaction [27]. Similarly, PVSA proved to be excellent in the synthesis of bis(indolyl)methanes [28]. In continuation of investigations for the applications of PVSA in organic synthesis, [27, 28] we investigated synthesis of pyrazole via condensation of 1,3-diketones and hydrazine in presence of PVSA as biodegradable and recyclable catalyst and ethanol as solvent (Scheme 1). MATERIALS AND METHOD The monomer sodium vinylsulfonate (40% w/w) required for the polymer preparation was obtained from M/s Dharamasi Morarjee Chemical Compay, India. Potassium persulfate and sodium bisulfate was procured from M/s S. D. fine chemicals India. Hydrazines and 2,4-ketones or 1,3diketones were procured from M/s Aldrich chemicals. X-ray diffractograms of Na-PVSA was recorded with Siemens D-5000 XRD diffractometer. Perkin-Elmer pyres 6 DSC instrument was used for recording of DSC of Na-PVSA. IR spectra were recorded using Perkin-Elmer FT-IR spectrometer (100 Spectrochem Series). Viscosity measurement was carried out using Ubbelohde Viscometer. The reaction analysis is performed by HPLC (Jasco, Column C-8) with UV detector. 1H NMR spectra were recorded on Varian-400 NMR spectrometer using TMS as internal standard. The yield of products has been determined by GC (PerkinElmer Clarus 400) (Column RTX@17 30m x 0.25mm x 0.25µm) (Condition: 80°C hold for 2 min, increase@10°C/min then hold for 20 min at 240°C). Purity of all the compounds was deter-

Preparation of Sodium Salt of Polyvinylsulfonic Acid (Na PVSA) 150 g of 40% sodium vinylsulfonate was taken in to 250 mL amber colored glass bottle and acidified with dilute sulfuric acid to pH 4.5. At 5 oC, 0.6 g potassium persulfate followed by 0.24 g of sodium bisulfite were added to the reaction mixture. Reaction mass was maintained at 5 oC for 24 h under stirring. The contents of bottle and 20 mL of water washing were transferred to a beaker. A viscous polymer was obtained by adding 250 mL of methanol. The re-precipitation of the product was done by dissolving the polymer in to 250 mL water followed by addition of 750 mL of methanol. The polymer treated with methanol which gives a gummy precipitate (56.1 g) after drying at 75 oC in vaccuo. The re-precipitated of Na-PVSA was done by dissolving it in to 210 mL of water followed by addition of 100 mL methanol. The oily product was appeared and separated. The oily mass was then dissolved in 80 mL water and was reprecipitated with addition of 40 mL of methanol. Separated oil mass was again treated with 200 mL methanol. 34 g of Na-PVSA product was obtained after drying at 75 oC under vacuum. The specific viscosity was found out to be 1.72 with average molecular weight of ~55,000, which is relevant to the reported one. Preparation of PVSA 32 g of Na-PVSA was dissolved in 500 mL of distilled water. Through a cation exchange column containing 250 mL activated cation exchange resin (Indion 225, capacity = 1.8 meq/mL) the solution was passed. The washing of column was done by distilled water till the eluent showed absence of

Synthesis of Pyrazole by Using Polyvinylsulfonic Acid (PVSA)

acidic pH. 16 g of PVSA was obtained by concentrating the acidic fraction under vacuum at 80 oC. By 16 mL distilled water, clear solution was obtained under stirring. This solution contains ~50 % w/w PVSA in water. Acidimetric titration was done to measure PVSA concentration in solution. For entire experimental study This solution was used. The pH of the 0.01N solution was found to be 2.83. Typical Procedure for Preparation of Pyrazole Phenylhydrazine (140 mg, 1.3 mmol), 2,4pentanedione (100 mg, 1 mmol) were added to 2 mL of absolute ethanol containing 21.6 mg (0.1 mmol) of PVSA ( 50% w/w) in 10 mL glass tube with screw cap. The reaction mass was stirred for 30 minutes at 35oC. The progress of the reaction was monitored by TLC and G.C. After period of 30 minutes, reaction mass was dissolved in 10 mL of ethyl acetate followed by addition of 5 ml water. Ethyl acetate layer was separated and washed with dilute solution of sodium bicarbonate, followed by water wash. Ethyl acetate layer was dried over anhydrous sodium sulfate, evaporated under vacuum to give crude product. The crude product obtained was analyzed by G.C. and further purified by short silica gel column with solvent mixture containing of 20% ethyl acetate and 80% petroleum ether. Recovery and Recyclability of PVSA Catalyst Filtrate and water washings from the reaction mixture was combined. It passed through an activated cation exchange resin column (indion 225). To the column, washing of distilled water was given till pH was acidic. Fraction obtained was evaporated to dryness under vacuum using rotary evaporator. The content of the flask was used in recycle experiment by dissolving it into appropriate quantity of absolute ethanol. Characterization Data 3,5-dimethyl-1H-pyrazole (3a) m.p. 107-109 oC, lit. m.p. 107-109 oC [29]; 1H NMR (400 MHz, CDCl3): δ 12.34 (br, s, 1H), 5.79 (s, 1H), 2.30 (s, 6H); 13C NMR (100 MHz, CDCl3): δ 144.29, 103.98, 12.22; lit. 1H NMR (400 MHz, CDCl3) [29]: δ 12.37 (br, s, 1H), 5.80 (s, 1H), 2.28 (s, 6H); lit. 13C NMR (100 MHz,

Current Catalysis, 2016, Vol. 5, No. 1

3

CDCl3) [29]: δ 144.29, 103.98, 12.22; GCMS (EI, 70 eV): m/z (%): 96 (100, M+), 81(82), 54(45). 3-methyl-1,5-diphenyl-1H-pyrazole (3b) m.p. 130-131 oC, lit. m.p. 129-131 oC [30]; 1H NMR (400 MHz, CDCl3): δ 7.30-7.18 (m, J = 8 Hz, 10H), 6.31 (s, 1H), 2.40 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 149.6, 143.7, 140.3, 130.9, 129.0, 128.8, 128.5, 128.2, 127.1, 125.3, 107.8, 13.8; lit. 1H NMR (400 MHz, CDCl3) [30]: δ 7.16−7.09 (m, J = 8.0 Hz, 10H), 6.18 (s, 1H), 2.26 (s, 3H); lit. 13C NMR (100 MHz, CDCl3) [30]: δ 149.5, 143.7, 140.2, 130.8, 128.9, 128.7, 128.5, 128.1, 127.1, 125.2, 107.8, 13.7; GCMS (EI, 70 eV): m/z (%): 234(100, M+), 233(82), 218(20), 192(15), 165 (12), 130(10), 116 (12), 77 (26), 51 (13). 3-methyl-5-phenyl-1H-pyrazole (3c) m.p. 121-122 oC, lit. m.p. 121-122 oC [29]; 1H NMR (400 MHz, CDCl3): δ 10.27 (br, s, 1H), 7.73 (d, 2H), 7.42-7.38 (m, 2H), 7.33-7.29 (m, 1H), 6.37 (s, 1H), 2.34 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 150.1, 143.2, 132.7, 128.7,127.8, 125.9, 102.1, 11.7; lit. 1H NMR (400 MHz, CDCl3) [29]: δ 10.28 (br, s, 1H), 7.72 (d, 2H), 7.41-7.37 (m, 2H), 7.33-7.29 (m, 1H), 6.36 (s, 1H), 2.34 (s, 3H); lit. 13C NMR (100 MHz, CDCl3) [29]: δ 150.1, 143.2, 132.7, 128.7, 127.8, 125.9, 102.1, 11.7; GCMS (EI, 70 eV): m/z (%): 158(100, M+), 143 (81), 128(22), 117(10), 89(9), 77(13). 3,5-dimethyl-1-phenyl-1H-pyrazole (3d) 1

H NMR (400 MHz, CDCl3): δ 7.44-7.42 (m, 4H), 7.35-7.32 (m, 1H), 5.99 (s, 1H), 2.30 (s, 3H), 2.28 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 148.9, 139.8, 139.2, 128.8, 127.0, 124.4, 106.7, 13.3, 12.2; lit. 1H NMR (400 MHz, CDCl3) [31]: δ 7.44-7.42 (m, 4H), 7.35-7.32 (m, 1H), 5.99 (s, 1H), 2.30 (s, 3H), 2.28 (s, 3H); lit. 13C NMR (100 MHz, CDCl3) [31]: δ 149.0, 140.0, 139.4, 129.0, 127.3, 124.8, 107.0, 13.6, 12.5; GCMS (EI, 70 eV): m/z (%): 172 (100, M+), 171(72), 154(14), 144(12), 130(42), 118(13), 77(46), 51(20). 3,5-di-tert-butyl-1-phenyl-1H-pyrazole (3e) m.p. 110-112 oC, lit. m.p. 110-112 oC [32]; 1H NMR (400 MHz, CDCl3): δ 7.40 (s, 5H), 6.01 (s, 1H), 1.30 (s, 9H), 1.14 (s, 9H); 13C NMR (100 MHz, CDCl3): δ 160.2, 153.1, 142.5, 128.9. 128.6,

4 Current Catalysis, 2016, Vol. 5, No. 1

128.4, 100.1, 31.8, 31.7, 30.8, 30.6; lit. 1H NMR (400 MHz, CDCl3) [33]: δ 7.39 (s, 5H), 6.00 (s, 1H), 1.32 (s, 9H), 1.15 (s, 9H); lit. 13C NMR (100 MHz, CDCl3) [33]: δ 160.3, 153.0, 142.6, 129.0, 128.7, 128.5, 100.2, 31.9, 31.8, 30.9, 30.6; GCMS (EI, 70 eV): m/z (%): 256 (29, M+), 241(100), 214 (16), 185 (16), 77 (12), 57(13), 41 (9). 3,5-di-tert-butyl-1H-pyrazole (3f) m.p. 189-191 oC, lit. m.p. 190-191 oC [34]; 1H NMR (400 MHz, CDCl3): δ 7.52 (br, s, 1H), 5.90 (s, 1H), 1.32 (s, 18H); 13C NMR (100 MHz, CDCl3): 97.1, 31.9, 30.3; lit. 1H NMR (400 MHz, CDCl3) [35]: δ 5.88 (s, 1H), 1.29 (s, 18H); lit. 13C NMR (100 MHz, CDCl3) [35]: δ 97.2, 31.8, 30.4; GCMS (EI, 70 eV): m/z (%): 180(100, M+), 165(15), 138(12), 96(18), 54 (30).

Ekboteet al.

Various catalysts such as PTSA, ion-exchange resin (Indion 225), sulfamic acid, PVSA, acetic acid, and sulfuric acid was carried for comparing the effectiveness of PVSA (Table 1, entries 1-7). The result indicated that PVSA is better catalyst in comparison to other catalyst (Table 1, entry 4), except sulfuric acid which is highly corrosive and hazardous. The reactions without catalysts were performed at different temperatures (Table 1, entries 6-8). The reaction not proceeded, and the expected products were not obtained. Table 1. Comparison of various catalysts for synthesis of pyrazole.[a]

H C SO2

3,5-diphenyl-1H-pyrazole (3g) m.p. 202-203 oC, lit. m.p. 202-203 oC [29]; 1H NMR (400 MHz, CDCl3): δ 9.88 (br, s, 1H), 7.727.70 (m, 4H), 7.39-7.30 (m, 6H), 6.80 (s, 1H); 13C NMR (100 MHz, CDCl3): δ 147.1, 129.3, 128.6, 127.6, 126.0, 100.1; lit. 1H NMR (400 MHz, CDCl3) [36]: δ 9.96 (br, s, 1H), 7.96 (m, 4H), 7.49 (m, 6H), 7.13 (s, 1H); lit. 13C NMR (100 MHz, CDCl3) [36]: δ 147.0, 129.3, 128.6, 127.6, 126.0, 100.2; GCMS (EI, 70 eV): m/z (%): 220(100, M+), 192(70), 165(15), 133(12), 101(12), 77(42). 1,3,5-triphenyl-1H-pyrazole (3h) m.p. 135-137 oC, lit. m.p. 135-137 oC [37]; 1H NMR (400 MHz, CDCl3): δ 7.96 (d, J = 8.0 Hz, 2H), 7.48 (d, J = 7.2 Hz, 1H), 7.43-7.32 (m, 11H), 6.85 (s, 1H); 13C NMR (100 MHz, CDCl3): δ 152.1, 144.4, 140.1, 133.1, 130.5, 129.0, 128.6, 128.5, 128.1,127.5, 126.0, 125.4, 105.3; lit. 1H NMR (400 MHz, CDCl3) [30]: δ 7.97 (d, J = 8.0 Hz, 2H), 7.46 (d, J = 7.2 Hz, 1H), 7.42−7.32 (m, 11H), 6.86 (s, 1H); lit. 13C NMR (100 MHz, CDCl3) [30]: δ 152.0, 144.5, 140.2, 133.1, 130.6, 1299.0, 128.7, 128.5, 128.4, 128.1, 127.5, 125.9, 125.4, 105.3; GCMS (EI, 70 eV): m/z (%): 296(100, M+), 267(72), 241(42) 192(68), 147(17), 77(44). RESULTS AND DISCUSSIONS In an effect to develop a convenient system for the synthesis of pyrazoles, we focused our attention on the use of 1,3-diketone with hydrazine as substrates in presence of PVSA as catalyst.

CH2

O H2N

NH2

n

OH

N

H2O

1a

Entry

O

N H 2a

Catalyst

3a

Catalyst Loading (mol %)

Temp °C

Yield [%]b

1

PTSA

10

35

72

2

Indion 225

10

35

30

3

Sulfamic acid

10

35

60

4

PVSA

10

35

98

5

Acetic Acid

10

35

69

6

Without catalyst

---

35

---

7

Without catalyst

---

55

---

8

Without catalyst

---

65

---

9

H2SO4

10

35

97

[a]

Reaction conditions: 1,3-diketone (1 mmol), hydrazine (1.3 mmol), temperature (35 °C), ethanol (2 mL), time (30 min); [b]GC yields.

Significant increase in the yield of the product was observed by increasing catalyst loading to 10 mol% (Table 2, entries 1-3). Effect of various solvents such as acetonitrile, methanol, ethanol, dichloromethane, and water were studied (Table 2, entries 3-5). Reaction was performed under sol-

Synthesis of Pyrazole by Using Polyvinylsulfonic Acid (PVSA)

Current Catalysis, 2016, Vol. 5, No. 1

vent free condition to ensure the role of solvent, which gave lower yield of 49% in comparison to the reaction with ethanol (98%) (Table 2, entry 6). Ethanol was selected as solvent, since it is from natural renewable sources, biodegradable, ease of availability, non-hazardous nature (Table 2, entry 2). The temperature also plays important for the effective progress of the PVSA-catalyzed pyrazole synthesis (Table 2, entries 2, 7 and 8). It was observed that at 35 oC, target compound was obtained with 98% yield (Table 2, entry 2). Optimization of the reaction times showed that the reaction was completed within 30 minutes at 35oC (Table 2, entries 2, 9-11).

conditions to afford the corresponding pyrazole derivatives in good to excellent yields (Table 3, entries 1-8). Table 3. Synthesis of pyrazoles derivatives.[a] Entry

Hydrazine H2 N

1

NH 2

1a

1,3-Diketone

H 2O

98

93

H2 N

3

CH2

NH 2

1a

O

H2O

H2N

NH2

n

H N

N H 2a

Solvent

PVSA Loading

4

3a

Temp °C

N H

N

98

3c

N

H2O

1a

Entry

OH

O

O

2b

SO2 O

Yield [%]b

Product

2

Table 2. Optimization of reaction conditions.[a]

H C

5

O

O

98 2a

1b

3d

Time

Yield b (Minutes) [%]

(mol %)

H N

5

1

EtOH

5

35

30

83

2

EtOH

10

35

30

98

3

EtOH

15

35

30

98

4

MDC

10

35

30

03

5

Water

10

35

30

03

6

---

---

35

30

49

7

EtOH

10

25

30

90

O

O

EtOH

10

45

30

98

9

EtOH

10

35

10

89

10

EtOH

10

35

20

93

11

EtOH

10

35

40

97

83

2c

1b

3e

O

6

H2 N

NH 2

1a

O

H2O

N

N H

2c

97

3f

7c

H2 N NH 2

1a

O

H2O N H

2d

N

98

3g

8c

[a]

Reaction conditions: 1,3-diketone (1 mmol), hydrazine (1.3 mmol); [b] GC yields.

To explore the generality and scope of this method, various 1,3-diketones and hydrazines i.e. hydrazine hydrate and phenylhydrazine were reacted with 10 mol % of PVSA, under optimized

N

N

NH 2

O

8

N

N

NH 2

H N

1b

O

O N

NH 2

2d

N

86

3h

[a]

Reaction conditions: 1,3-diketone (1 mmol), hydrazine (1.3 mmol), PVSA (10 mol%), temp. (35 °C), ethanol (2 mL), time (30 min); [b]Isolated yields; [c] temperature was kept 55 °C.

6 Current Catalysis, 2016, Vol. 5, No. 1

Ekboteet al.

By considering the environmental pollution and cost in process chemistry, catalyst recyclability and reusability has great advantage. The effect of reused times of PVSA on catalytic activity is shown in Table 4. PVSA could be reused successfully until the fourth run without significant loss of yield, activity and selectivity.

REFERENCES [1]

[2]

[a]

Table 4. Recycle study of PVSA catalyst.

[3] H C

CH2

SO2 O H2N

NH2

O

OH

[4] n

N

H2O

N H

1a

2a

3a

Entry

Recycle Number

Yield [%]b

1

0

98

2

1

98

3

2

97

4

3

97

5

4

96

[5]

[6] [7] [8]

[a]

Reaction conditions: 1,3-diketone (1 mmol), hydrazine (1.3 mmol), PVSA (10 mol%), temp. (35 oC), ethanol (2 mL), time (30 min); [b] GC yields.

CONCLUSION In summary, we have demonstrated that PVSA is an excellent catalyst in synthesis of pyrazoles by reacting hydrazines and 1,3-diketones. High activity, biodegradability and easy handling make PVSA an ideal catalyst for this transformation. Reaction works under mild conditions, providing high yields of product under short reaction time. Moreover, recyclability and simple experimental technique making it a useful and attractive process for the synthesis of pyrazole derivatives. CONFLICT OF INTEREST

[9]

[10]

[11] [12]

[13]

The authors confirm that this article content has no conflicts of interest. ACKNOWLEDGEMENT The author STG is thankful to CSIR New Delhi for providing the Senior Research Fellowship.

[14]

Gokhan-Kelekci, N.; Yabanoglu, S.; Kupeli, E.; Salgin, U.; Ozgen, O.; Ucar, G.; Yesilada, E.; Kendi, E.; Yesilada, A.; Blgin, A.A., Pyrazole nucleus possess a wide range of biological properties such as anti-inflammatory. Bioorg. Med. Chem., 2007, 15, 5775-5786. Bailey, D.M.; Hansen, P.E.; Hlavac, A.G.; Baizman, E.R.; Pearl, J.; Defelice, A.F.; Feigenson, M.E. Pyrazole compounds possess anti-depressant properties. J. Med. Chem., 1985, 28, 256-260. Mahajan, N.; Havaldar, F.H.; Farnandes, P.S. Microbial/anti-bacterial properties of pyrazole derivative. J. Indian Chem. Soc., 1991, 68, 245-249. Lin, R.; Chiu, G.; Yu, Y.; Connolly, P.J.; Li, S.; Lu, Y.; Adams, M.; Fuentee-Pesquera, A.R.; Emnuel, S.L.; Greenberger, L.M. Anti-tumor activities of pyrazole derivatives. Bioorg. Med. Chem. Lett., 2007, 17, 4557-4561. Farag, A.M.; Mayhoub, A.S.; Barakat, S.E.; Bayomi, A.H. Reported synthesis of new N-phenylpyrazle, derivatives with anti-microbial activities. Bioorg. Med. Chem., 2008, 16, 4569-4578. Larsen, J.S.; Zahran, M.A.; Pedersen, E.B.; Nielsen, C. Reported the antiviaral activities of pyrazole compounds. Monatsh. Chem., 1999, 130, 1167- 1173. Chauhan, P.M.; Singh, S.S.; Chatterjie, R.K. Reported, anti-filarial activities of pyrazole derivatives. Indian J. Chem. B, 1993, 32, 858-861. Barcelo, M.; Ravina, E.; Masaguer, C.F.; Dominuez, E.; Areias, F. M.; Brea, J.; Loza, M. I. Synthesis and biding affinity of new pyrazoles and isoxazoles derivatives as potential atypical anti-psychotic compounds. Bioorg. Med. Chem. Lett., 2007, 17, 48734877. Ahmed, M.S.M.; Kobayashi, K.; Mori, A. Pyrazole and isoxazole derivatives are prepared by palladium catalyzed four-component reaction. Org. Lett., 2005, 7, 4487-4489. Gerstenberger, B.S.; Rauckhorst, M.R.; Starr, J.T. A simple one pot synthesis of diversely functionalized N-arylpyrazoles in the presence of HCl. Org. Lett., 2009, 11, 2097-2100. Deng, X.; Mani, N. Synthesis of substituted pyrazoles from N-mono substituted hydrazones and nitroolefines. Org. Lett., 2006, 8, 3505-3508. Babinski, D.J.; Aguilar, H.R.; Still, R..; Frantz, D.E. Synthesis 0f 3,4,5-trisubstituted pyrazoles from acyclic and cyclic enoltriflates with diazoacetates. J. Org. Chem., 2011, 5915-5923. Rosa, F.A.; Machado, P.; Vargas, P.S.; Bonacorso, H.G.; Zanatta, N.; Martins, M.A.P. Cyclocondensation reaction of unsymmetrical enaminodiketones with tertiary-butylhydrazine hydrochloride to provide 4-substituted 1H-pyrazole-5-carboxylates. Synlett, 2008, 11, 1673-1678. Ma, C.; Li, Y.; Wen, P.; Yan. R..; Ren, Z.; Huang, G. Copper-catalyzed reaction for the synthesis of polysubstitutedpyrazoles from phenylhydrazones and dialkylethylene dicarboxylates. Synlett 2011, 9, 13211323.

Synthesis of Pyrazole by Using Polyvinylsulfonic Acid (PVSA)

[15]

Current Catalysis, 2016, Vol. 5, No. 1

Deng, X.; Mani, N.S. Synthesis of tri and tetrasubstituted pyrazoles by reaction of hydrazones with nitroolefins with strong base like t-BuOK, finally quenching with strong acid like TFA. Org. Lett., 2008, 10, 1307-1310. [16] Deng, X.; Mani, N.S. Reacting N-Arylhydrazones with nitro-olefines in presence of ethylene glycol yielded tri- and tetra-substituted pyrazoles. J. Org. Chem., 2008, 73, 2412-2415. [17] Wiley, R.H.; Hexner, P.E. Synthesis of 3,5dimethylpyrazole by reacting acetylacetone and hydrazine sulfate in aqueous solution of NaOH. Org. Syn., 1963, 4, 351. [18] Heller, S.T.; Natarajan, S.R. Reaction of 1,3diketones (formed in situ from ketone and acid chlorides) converted to pyrazoles by addition of hydrazines catalyzed by acetic acid. Org. Lett., 2006, 8, 2675-2678. [19] Gosselin, F.; Shea, P.D.O.; Webster, R.A.; Reamer, R.A.; Tillyer, R.D.; Grabowski, E.J.J. Synthesis of substituted pyrazoles by condensation of 1,3diketones with arylhydrazines in presence of HCl. Synlett, 2006,19, 3267-3270. [20] Wang, Z.; Quin, H. Solventless condensation of diketones and hydrazines in the presence of a catalytic amount of sulfuric acid at room temperature, afforded pyrazole derivatives. Green Chem., 2004, 6, 90-92. [21] Polshettiwar, V.; Verma, R.S. Room temperature synthesis of pyrazoles and diazepine in aqueous medium catalyzed by PSSA in water. Tetrahedron Lett., 2008, 49, 397-400. [22] Curini, M.; Rosati, O.; Campagna, V.; Montanari, F.; Cravotto, G.; and Boccalini, M. Layered Sulfonyl phosphonates as heterogeneous catalyst in synthesis of pyrazoles and indazoles. Synlett, 2005, 19, 29272930. [23] Xiong, W.; Chen, J.-X.; Liu, M.-C.; Ding, J.-C.; Wu, H.-Y.; Su, W-K. A general and efficient synthesis of pyrazoles catalyzed by Sc(OTf)3 under solvent free conditions. Braz. Chem. Soc., 2009, 20, 367-374. [24] Sreekumar, R.; Padmakumar, R. Simple, efficient, convenient synthesis of pyrroles and pyrazoles using zeolite as catalyst. Synth. Commn., 1998, 28, 16611665. [25] Chen, X.; She, J.; Shang, Z.C.; Wu, J.; Zhang, P. Room temperature synthesis of pyrazoles, diazepines, β-enaminones and β-enaminoesters using silicasupported sulfuric acid as a reusable catalyst under

Received: April 07, 2015

7

solvent free conditions. Synth. Commn., 2009, 39, 947-957. [26] Alinezhad, H.; Tajbaksh, M.; Zare, M. Silica-gel supported sulfuric acid a heterogeneous catalyst in a solvent free synthesis of pyrazoles. J. Mex. Chem. Soc., 2011, 55, 4, 238-241. [27] Ekbote, S.S.; Panda, A.G.; Bhor, M.D.; Bhanage, B. M. PVSA a catalysed Michael addition reaction of indoles to α,β-unsaturated ketones. Catal. Commun., 2009, 10, 1569-1573. [28] Ekbote, S.S.; Deshmukh, K.M.; Qureshi, Z.S.; Bhanage, B.M. Synthesis of bis(indolyl)methane catalyzed by PVSA. Green Chem. Lett. Rev., 2011, 4, 177-183. [29] Lee, B.,; Kang, P.; Lee, K. H.; Cho, J.; Nam, W.; Lee, W. K.; Hur, N. H. Solid-state and solvent-free synthesis of azines, pyrazoles, and pyridazinones using solid hydrazine. Tetrahedron Lett., 2013, 54, 1384-1388. [30] Li, X.; He, L.; Chen, H.; Wu, W.; Jiang, H. Coppercatalysed aerobic C(sp2)-H functionalization for C-N bond formation: Synthesis of pyrazoles and indazoles. J. Org. Chem., 2013, 78, 3636-3646. [31] Schneider,Y.; Prévost, J.; Gobin, M.; Legault,C.Y. Diazirines as potent electrophilic nitrogen sources: Application to the Synthesis of Pyrazoles. Org. Lett., 2014, 16, 596-599. [32] Begtrup, M.; Vedsø, P.; Cabildo, P.; Claramunt, R.M.; Elguero, J.; Meutermans, W. 13C chemical shifts and 1H-13C coupling constants of N-phenyl-, Np-fluorophenyl- and N-o-nitrophenylpyrazoles. Magn. Reson. Chem., 1992, 30, 455-459. [33] Carrillo, J. R.; Cossio, F. P.; Diaz-Ortiz, A.; GomezEscalonilla, M. J.; de la Hoz, A.; Lecea, B.; Moreno, A.; Prieto, P. A complete model for prediction of 1H and 13C–NMR chemical shifts and torsinal angles in phenyl-substituted pyrazoles. Tetrahedron, 2001, 19, 4179-.4187 [34] Zelenin, K. N.; Alekseyev, V. V.; Tygysheva, A. R. 5-Hydroxy-4,5-dihydropyrazoles. Tetrahedron, 1995, 51, 11251-11256. [35] Wyka, J. L.; Omondi, B.; Appavoo, D.;. Guzei, I. A.; Darkwa, James. Solvent-free synthesis of 3,5-di-tertbutylpyrazole and 3,5-di-substitutedbutylpyrazol-1ylethanol. J. Chem. Res., 2012, 8, 474-477. [36] Wiles, C.; Watts, P.; Haswell, S. J. The application of microreactor technology for the synthesis of 1,2azoles. Org. Proc. Res. Dev., 2004, 8, 28-32. [37] Gonda, Z., Novak, Z. Transition-metal-free Narylation of pyrazoles with diaryliodonium salts. Chem. Eur. J., 2015, 21, 16801-16806.

Revised: October 17, 2015

Accepted: January 12, 2016