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Document Type : Original Article

Authors

1 Hamedan University of Technology, Hamedan, 65155, Iran

2 University of Kurdistan, Pasdaran Street, Sanandaj, 66177-15177, Iran

3 Sayyed Jamaleddin Asadabadi University, Hamedan, Iran

Abstract

Zn-[2-boromophenyl-salicylaldimine-methylpyranopyrazole]Cl2 {[Zn-2BSMP]Cl2}, as a Schiff base complex, efficiently catalyzed the pseudo-six-component synthesis of tetrahydrodipyrazolopyridines by the condensation reaction of aryl aldehyde, hydrazine hydrate, ethyl acetoacetate and urea at 80 °C. Urea was used instead of ammonium salts as a source of ammonia by in situ generation of ammonia, in the presence of a little amount of water.

Graphical Abstract

Efficient Pseudo-Six-Component Synthesis of Tetrahydro-pyrazolopyridines Using [Zn-2BSMP]Cl2

Keywords

Main Subjects

Introduction

Pyrazolopyridines as an important biological group of organic compounds show pharmacological activities such as antiviral [1, 2], antimicrobial [3, 4], antileishmanial [5], antitumor [6], hypoglycemic [7], anxiolytic [8], anti-inflammatory [9], antiherpetic [10], antileishmania [11] and antiallergic [12]. Also, they act as protein kinase inhibitors [13, 14]. Pseudo-six-component synthesis of tetrahydrodipyrazolopyridines, by the condensation reaction of aryl aldehyde, hydrazine hydrate, ethyl acetoacetate and ammonium acetate, is an important strategy for the synthesis of the mentioned compounds [13]. Multi-component reactions are important protocol in organic synthesis due to their implementation in one step without the production of by-products. Saving the energy, time, solvent and chemical materials and reducing the production of chemical waste are some other advantages of these reactions [15-20]. The synthesis of tetrahydrodipyrazolopyridines (THPPs) by the condensation reaction of aldehyde, hydrazine hydrate, alkyl acetoacetate and ammonium acetate were reported by different catalysts including triethanolamine–sodium acetate [13], nano-CdZr4(PO4)6 [21], CuFe2O4@HNTs nanocomposite [22], (Fe3O4/KCC-1/IL/HPW) [23], nano-Fe3O4@SiO2-SO3H [24], nano-FeNi3 [25], CuFe2O4@ HNTS [26], nano-ovalbumin [27]. In the mentioned reports ammonium salts were used for the synthesis of THPPs by in situ generation of ammonia in the reaction. But limited methods were reported for the preparation of THPPs which urea used as a source of ammonia in the reaction.

According to the above facts and based on our previous works which have done in the use of Schiff base complex as a catalyst in the synthesis of organic compounds  [28-36], we have applied Zn-[2-boromophenyl-salicylaldimine-methylpyranopyrazole]Cl2  {[Zn-2BSMP]Cl2} as an efficient catalyst for the preparation of 3,5- dimethyl-4-aryl-1,4,7,8-tetrahydrodipyrazolo[3,4-b:4ʹ,3ʹ-e]pyridines (THPPs) by the reaction of aryl aldehyde, ethyl acetoacetate, hydrazine hydrate and urea in water at 80 °C (Scheme 1).

Scheme 1: The preparation of tetrahydro-pyrazolopyridines

Materials and Methods

Procedure for the synthesis of Zn-[2-boromophenyl-salicylaldimine-methylpyranopyrazole]Cl2 ([Zn-2BSMP]Cl2)

A mixture of 6-amino-3-methyl-4-(4-nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile, prepared according to previous literature [37], as an amine (1 mmol, 0.297 g) and ZnCl2 (1 mmol, 0.136 g) was pulverized in a mortar and then added to a 25 mL round-bottomed flask containing 2-hydroxybenzaldehyde (1.5 mmol, 0.183 g) connected to a reflux condenser and stirred at 100 °C for appropriate time. The resulting mixture was then washed several times with ethyl acetate and hexane (9/1) to separate excess salicylaldehyde from the synthesized complex. The accuracy of the preparation of this complex was confirmed by IR analysis and comparison with the previous sample reported in the previous literature [35].

General procedure for the synthesis of tetrahydro-pyrazolopyridines

A mixture of hydrazine hydrate (2 mmol, 0.064 g), ethyl acetoacetate (2 mmol, 0.26 g), aryl aldehyde (1 mmol), urea (3 mmol, 0.18 g) and a few drops of water were added to 25 mL round-bottomed flask connected to a reflux condenser and heated at 80 °C for appropriate times. After completion of the reaction based on TLC test, in order to separate the reaction mixture from the Schiff base complex, the reaction mixture was extracted with warm ethanol (10 mL) and separated from the catalyst by filtration. Lastly, the product was purified by recrystallization from ethanol (90 %).

Selected spectral data of compounds

4-(2-chlorophenyl)-3,5-dimethyl-1,4,7,8-tetrahydrodipyrazolo[3,4-b:4',3'-e]pyridine (8)

White solid; m.p.=230-233 °C; 1H-NMR (250 MHz, DMSO-d6): δ (ppm) 1.90 (s, 6H, 2CH3), 5.09 (s, 1H, CH), 7.17 (t, J = 7.50 Hz, 2H, ArH), 7.30 (d, J = 5.0 Hz, 1H, ArH), 7.50 (d, J = 5.0 Hz, 1H, ArH), 10.70 (s, 3H, 3NH); 13C-NMR (62.5 MHz, DMSO-d6): δ (ppm) 10.8, 31.8, 102.7, 126.8, 127.9, 129.4, 131.0, 132.7, 139.0, 141.1, 161.1. 

3,5-dimethyl-4-p-tolyl-1,4,7,8-tetrahydrodipyrazolo[3,4-b:4',3'-e]pyridine (10)

White solid; m.p.=244-245 °C; IR (KBr, cm-1): 3558, 3308, 2968, 1613, 1509, 1048, 750, 522; 1H-NMR (250 MHz, DMSO-d6): δ (ppm) 2.04 (s, 6H, 2CH3), 2.20 (s, 3H, CH3), 4.75 (s, 1H, CH), 6.98 (s, 4H, ArH), 11.03 (s, 3H, 3NH); 13C-NMR (62.5 MHz, DMSO-d6): δ (ppm) 10.8, 20.9, 32.7, 104.8, 127.8, 128.7, 134.6, 140.1, 140.7, 161.5. 

Results and Discussion

The related amine was prepared according to previous literature by the reaction of 2-bromobenzaldehyde with ethyl acetoacetate, malononitrile and hydrazine hydrate in acidic media [37]. Then, the prepared amine, namely 6-amino-4-(2-bromophenyl)-3-methyl-2,4 dihydropyrano[2,3-c]pyrazole-5-carbonitrile, reacted with 2-hydroxybenzaldehyde and ZnCl2 to give [Zn-2BSMP]Cl2 as a nano-Schiff base complex and catalyst [35]. The steps for the synthesis of catalyst are shown in Scheme 2.

The preparation of [Zn-2BSMP]Cl2 was confirmed by FT-IR spectrum, based on which the broad peak at 3000-3600 cm-1 is related to O-H stretching of hydroxyl group and a peak at 1654 cm-1 is corresponded to stretching mode of C=N bond in the structure of catalyst. The important functional groups in the structure of catalyst were identified by FT-IR analysis. 

Also, the morphology of [Zn-2BSMP]Cl2 as a Schiff base complex and catalyst was investigated by scanning electron microscopy (SEM). SEM analysis of [Zn-2BSMP]Cl2 is depicted in Figure 1. Examination of Scheme 1 proves the presence of nanoscale particles in the synthesized catalyst.

To further investigate the catalyst particle size, the prepared particles of [Zn-2BSMP]Cl2 were studied by transmission electron microscopy (TEM). By checking the image obtained from the TAM analysis in Figure 2, the presence of nano-sized particles in the synthesized catalyst is confirmed.

In the next step, for the optimization of the reaction condition, the reaction of 4-chlorobenzaldehyde, hydrazine hydrate, ethyl acetoacetate and urea was considered as model reaction and different amounts of catalyst, temperature and different solvents, both polar and non-polar were examined on this reaction (Table 1). Different solvents such as ethanol, ethyl acetate, dichloromethane, water and chloroform were examined in this reaction, in which the best result was obtained using 5 mol% of [Zn-2BSMP]Cl2 as a catalyst at 80 °C under solvent-free condition. The model reaction was also tested in the presence of ZnCl2 in comparison with [Zn-2BSMP]Cl2, which did not show the efficiency of [Zn-2BSMP]Cl2 to give the related product (Table 1).

After the optimization of the reaction condition, the optimal conditions were tested on the reaction of different aromatic aldehydes, containing electron donor and electron acceptor groups and halogens on different positions of the aromatic ring, with hydrazine hydrate, ethyl acetoacetate and urea to give 3,5-dimethyl-4-aryl-1,4,7,8-tetrahydrodipyrazolo[3,4-b:4ʹ,3ʹ-e]pyridines (THPPs) with high yields and short reaction times (Table 2). The time and obtained yield from the synthesized products are shown in Table 2.

Table 1: The optimization of the reaction condition

Entry

Catalyst (mol%)

Solvent

Temperature (°C)

Time (min)

Yielda (%)

1

[Zn-2BSMP]Cl2 (5 mol%)

-

80

60

95

2

[Zn-2BSMP]Cl2 (3 mol%)

-

80

60

75

3

[Zn-2BSMP]Cl2 (8 mol%)

-

80

60

95

4

[Zn-2BSMP]Cl2 (5 mol%)

-

60

60

65

5

[Zn-2BSMP]Cl2 (5 mol%)

-

100

60

95

6

[Zn-2BSMP]Cl2 (5 mol%)

Chloroform

Reflux

60

40

7

[Zn-2BSMP]Cl2 (5 mol%)

Ethyl acetate

Reflux

60

85

8

[Zn-2BSMP]Cl2 (5 mol%)

Ethanol

Reflux

60

90

9

[Zn-2BSMP]Cl2 (5 mol%)

Water

80

60

38

10

[Zn-2BSMP]Cl2 (5 mol%)

Dichloromethane

Reflux

60

45

11

-

-

80

60

15

12

ZnCl2 (5 mol%)

-

80

60

61

 

Table 2: The preparation of tetrahydro-pyrazolopyridines

 In the mechanism taken from previously reported literature [38-41], by the nucleophilic attack of hydrazine to the carbonyl groups of ethyl acetoacetate which is activated by the catalyst, 3-methyl-1H-pyrazol-5(4H)-one (I) is prepared after removing of one molecule of water and ethanol. Then, intermediate (II), which is prepared by the tautomerization of (I), reacts with activated aldehyde to give (III). Intermediate (III) as a Michael acceptor reacts with another pyrazolone ring to furnish (IV). Catalytic hydrolysis of urea with water in the reaction mixture generates carbamic acid and ammonia [42, 43]. Nucleophilic attack of ammonia with (IV) prepares (V) converted to (VI) after intra molecular nucleophilic attack and cyclization. Finally, by removing of one molecule of water from (VI), the expected product is prepared (Scheme 3).

Scheme 3: The proposed mechanism for the preparation of tetrahydro-pyrazolopyridines

To study the ability of the catalyst to recover and reuse it for other reactions, the reaction mixture was extracted with warm ethanol and separated from the catalyst by filtration. The recovered catalyst was reused twice in the model reaction, i.e. the reaction of 4-chlorobenzaldehyde, hydrazine hydrate, ethyl acetoacetate and urea, where the reaction times and obtained yields were acceptable. The results of this study are presented in Figure 3.

Figure 3: The reusability of the catalyst

Conclusion

As a result, [Zn-2BSMP]Cl2 was directly used as a Schiff base complex and catalyst without using of any co-catalyst for the pseudo-six-component synthesis of tetrahydro-dipyrazolopyridines by the reaction of aryl aldehyde, hydrazine hydrate, ethyl acetoacetate and urea in the presence of a little amounts of water at 80 °C.

Acknowledgments

The authors thank the Hamedan University of Technology to support in conducting this research.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions

All authors contributed toward data analysis, drafting and revising the paper and agreed to responsible for all the aspects of this work.

 

Conflict of Interest

We have no conflicts of interest to disclose.

 

 

ORCID:

Ahmad Reza Moosavi-Zare

http://orcid.org/0000-0003-0321-9326

Hamid Goudarziafshar

https://orcid.org/0000-0002-5930-6253

HOW TO CITE THIS ARTICLE

Ahmad Reza Moosavi-Zare, Hamid Goudarziafshar, Zahra Jalilian, Fatemeh Hosseinabadi. Efficient Pseudo-Six-Component Synthesis of Tetrahydro-Pyrazolopyridines Using [Zn-2BSMP]Cl2. Chem. Methodol., 2022, 6(8) 571-581

https://doi.org/10.22034/CHEMM.2022.334202.1456

URL: http://www.chemmethod.com/article_150182.html

[1]. Gudmundsson K.S., Johns B.A., Allen S.H., Pyrazolopyridines with potent activity against herpesviruses: Effects of C5 substituents on antiviral activity, Bioorganic & Medicinal Chemistry Letters, 2008, 18:1157 [Crossref], [Google Scholar], [Publisher]
[2]. Shahbazi-Alavi H., Safaei-Ghomi J., Eshteghal F., Zahedi S., Nazemzadeh S.H., Alemi-Tameh F., Tavazo M., Basharnavaz H., Lashkari M.R., Nano-CuCr2O4: an efficient catalyst for a one-pot synthesis of tetrahydrodipyrazolopyridine. Journal of Chemical Research, 2016, 40:361 [Crossref], [Google Scholar], [Publisher]
[3]. Abu-Melha S., Synthesis and antimicrobial activity of some new heterocycles incorporating the pyrazolopyridine moiety, Archiv der Pharmazie, 2013, 346:912 [Crossref], [Google Scholar], [Publisher]
[4]. Panda N., Karmakar S., Jena A.K., Synthesis and antibacterial activity of some novel pyrazolopyridine derivatives, Chemistry of Heterocyclic Compounds, 2011, 46:1500 [Crossref], [Google Scholar], [Publisher]
[5]. de Mello H., Echevarria A., Bernardino A.M., Canto-Cavalheiro M., Leon L.L., Antileishmanial pyrazolopyridine derivatives: synthesis and structure− activity relationship analysis, Journal of Medicinal Chemistry, 2004, 47:5427 [Crossref], [Google Scholar], [Publisher]
[6]. Chu I., Lynch B.M., Synthesis and biological evaluation of xanthine oxidase inhibitors. Pyrazolo [3, 4-d] pyrimidines and pyrazolo [3, 4-b] pyridines, Journal of Medicinal Chemistry, 1975, 18:161 [Crossref], [Google Scholar], [Publisher]
[7]. Hoehn H., Polacek I., Schulze E., Potential antidiabetic agents. Pyrazolo [3, 4-b] pyridines, Journal of Medicinal Chemistry, 1973, 16:1340 [Crossref], [Google Scholar], [Publisher]
[8]. Bare T.M., McLaren C.D., Campbell J.B., Firor J.W., Resch J.F., Walters C.P., Salama A.I., Meiners B.A., Patel J.B., Synthesis and structure-activity relationships of a series of anxioselective pyrazolopyridine ester and amide anxiolytic agents, Journal of Medicinal Chemistry, 1989, 32:2561 [Crossref], [Google Scholar], [Publisher]
[9]. Revesz L., Blum E., Di Padova F.E., Buhl T., Feifel R., Gram H., Hiestand P., Manning U., Neumann U., Rucklin G., Bioorganic & Medicinal Chemistry Letters, 2006, 16:262 [Crossref], [Google Scholar], [Publisher]
[10]. Gudmundsson K.S., Johns B.A., Wang Z., Turner E.M., Allen S.H., Freeman G.A., Boyd Jr. F.L., Sexton C.J., Selleseth D.W., Moniri K.R., Creech K.L., Synthesis of novel substituted 2-phenylpyrazolopyridines with potent activity against herpesviruses, Bioorganic & Medicinal Chemistry, 2005, 13:5346 [Crossref], [Google Scholar], [Publisher]
[11]. de Mello H., Echevarria A., Bernardino A.M., Canto-Cavalheiro M., Leon L.L., Antileishmanial pyrazolopyridine derivatives: synthesis and structure− activity relationship analysis, Journal of Medicinal Chemistry, 2004, 47:5427 [Crossref], [Google Scholar], [Publisher]
[12]. Bettinetti L., Schlotter K., Hubner H., Gmeiner P., Interactive SAR studies: rational discovery of super-potent and highly selective dopamine D3 receptor antagonists and partial agonists, Journal of Medicinal Chemistry, 2002, 45:4594 [Crossref], [Google Scholar], [Publisher]
[13]. Mirjalili B.B.F., Bahabadi N.J., Bamoniri A., Triethanolamine–sodium acetate as a novel deep eutectic solvent for promotion of tetrahydrodipyrazolopyridines synthesis under microwave irradiation, Journal of the Iranian Chemical Society, 2021, 18:2181 [Crossref], [Google Scholar], [Publisher]
[14]. Chioua M., Samadi A., Soriano E., Lozach O., Meijer L., Marco-Contelles J., Synthesis and biological evaluation of 3, 6-diamino-1H-pyrazolo [3, 4-b] pyridine derivatives as protein kinase inhibitors, Bioorganic & Medicinal Chemistry letters, 2009, 19:4566 [Crossref], [Google Scholar], [Publisher]
[15]. Khazaei A., Zolfigol M.A., Karimitabar F., Nikokar I., Moosavi-Zare A.R., N, 2-Dibromo-6-chloro-3, 4-dihydro-2 H-benzo [e][1, 2, 4] thiadiazine-7-sulfonamide 1, 1-dioxide: An efficient and homogeneous catalyst for one-pot synthesis of 4 H-pyran, pyranopyrazole and pyrazolo [1, 2-b] phthalazine derivatives under aqueous media, RSC Advances, 2015, 5:71402 [Crossref], [Google Scholar], [Publisher]
[16]. Moosavi-Zare A.R., Zolfigol M.A., Zarei M., Zare A., Khakyzadeh V., Application of silica-bonded imidazolium-sulfonic acid chloride (SBISAC) as a heterogeneous nanocatalyst for the domino condensation of arylaldehydes with 2-naphthol and dimedone, Journal of Molecular Liquids, 2015, 211:373 [Crossref], [Google Scholar], [Publisher]
[17]. Moosavi-Zare A.R., Asgari Z., Zare A., Zolfigol M.A., Shekouhy M., One pot synthesis of 1, 2, 4, 5-tetrasubstituted-imidazoles catalyzed by trityl chloride in neutral media, RSC advances, 2014, 4:60636 [Crossref], [Google Scholar], [Publisher]
[18]. Moosavi-Zare A.R., Afshar-Hezarkhani H., Design of 2-Carboxy-1-sulfopyridin-1-ium Chloride as an Efficient and Eco-friendly Catalyst for the One-pot Synthesis of Highly Functionalized Tetrahydropyridines, Organic Preparations and Procedures International, 2020, 52:410 [Crossref], [Google Scholar], [Publisher]
[19]. Esmaili S., Moosavi-Zare A.R., Khazaei A., Nano-[Fe3O4@SiO2/N-propyl-1-(thiophen-2-yl) ethanimine][ZnCl2] as a nano magnetite Schiff base complex and heterogeneous catalyst for the synthesis of pyrimido [4, 5-b] quinolones, RSC Advances, 2022, 12:5386 [Crossref], [Google Scholar], [Publisher]
[20]. Moosavi-Zare A.R., Zolfigol M.A., Derakhshan-Panah F., Balalaie S., Synthesis and characterization of 4, 4′-bipyridinium sulfonic acid chloride as a new and efficient catalyst for the preparation of amidoalkyl phenols and bis amidoalkyl phenols, Molecular Catalysis, 2018, 449:142 [Crossref], [Google Scholar], [Publisher]
[21]. Safaei-Ghomi J., Shahbazi-Alavi H., Sadeghzadeh R., Ziarati A., Synthesis of pyrazolopyridines catalyzed by nano-CdZr4 (PO4)6 as a reusable catalyst, Research on Chemical Intermediates, 2016, 42:8143 [Crossref], [Google Scholar], [Publisher]
[22]. Maleki A., Hajizadeh Z., Salehi P., Mesoporous halloysite nanotubes modified by CuFe2O4 spinel ferrite nanoparticles and study of its application as a novel and efficient heterogeneous catalyst in the synthesis of pyrazolopyridine derivatives, Scientific Reports, 2019, 9:5552 [Crossref], [Google Scholar], [Publisher]
[23]. Sadeghzadeh S.M., A heteropolyacid-based ionic liquid immobilized onto magnetic fibrous nano-silica as robust and recyclable heterogeneous catalysts for the synthesis of tetrahydrodipyrazolopyridines in water, RSC advances, 2016, 6:75973 [Crossref], [Google Scholar], [Publisher]
[24]. Safaei-Ghomi J., Shahbazi-Alavi H., A flexible one-pot synthesis of pyrazolopyridines catalyzed by Fe3O4@SiO2-SO3H nanocatalyst under microwave irradiation, Scientia Iranica, 2017, 24:1209 [Crossref], [Google Scholar], [Publisher]
[25]. Safaei-Ghomi J., Sadeghzadeh R., Shahbazi-Alavi H., A pseudo six-component process for the synthesis of tetrahydrodipyrazolo pyridines using an ionic liquid immobilized on a FeNi 3 nanocatalyst, RSC advances, 2016, 6:33676 [Crossref], [Google Scholar], [Publisher]
[26]. Shabalala N.G., Pagadala R., Jonnalagadda S.B., Ultrasonic-accelerated rapid protocol for the improved synthesis of pyrazoles, Ultrasonics Sonochemistry, 2015, 27:423 [Crossref], [Google Scholar], [Publisher]
[27]. Salehi N., Mirjalili B.F., Nano-ovalbumin: a green biocatalyst for biomimetic synthesis of tetrahydrodipyrazolo pyridines in water, Research on Chemical Intermediates, 2018, 44:7065 [Crossref], [Google Scholar], [Publisher]
[28]. Moosavi‐Zare A.R., Goudarziafshar H., Saki K., Synthesis of pyranopyrazoles using nano‐Fe‐[phenylsalicylaldiminemethylpyranopyrazole] Cl2 as a new Schiff base complex and catalyst, Applied Organometallic Chemistry, 2018, 32:e3968 [Crossref], [Google Scholar], [Publisher]
[29]. Moosavi‐Zare A.R., Goudarziafshar H., Jalilian Z., Nano‐Zn [2‐boromophenylsalicylaldiminemethylpyranopyrazole] Cl2 as a novel nanostructured Schiff base complex and catalyst for the synthesis of pyrano [2, 3‐d] pyrimidinedione derivatives, Applied Organometallic Chemistry, 2019, 33:e4584 [Crossref], [Google Scholar], [Publisher]
[30]. Moosavi-Zare A.R., Goudarziafshar H., Delkhosh M.A., Jalilian Z., Nano-Mn-[4-Benzyloxyphenyl-salicylaldimine-methylpyranopyrazole-carbonitrile] Cl2 as a New Schiff Base Complex and Catalyst for the Synthesis of Highly Substituted Tetrahydropyridines, Organic Preparations and Procedures International, 2021, 53:402 [Crossref], [Google Scholar], [Publisher]
[31]. Goudarziafshar H., Moosavi-Zare A.R., Hosseinabadi F., Jalilian Z., Nano-[Mn-PSMP] Cl2 as a new Schiff base complex and catalyst for the synthesis of N, N'-alkylidene bisamides, Research on Chemical Intermediates, 2022, 48:1423 [Crossref], [Google Scholar], [Publisher]
[32]. Moosavi‐Zare A.R., Goudarziafshar H., Nooraei F., Preparation and characterization of nano‐Co‐[4‐chlorophenyl‐salicylaldimine‐methyl pyranopyrazole] Cl2 as a new Schiff base complex and catalyst for the solvent‐free synthesis of 1‐amidoalkyl‐2‐naphthols, Applied Organometallic Chemistry, 2020, 34:e5252 [Crossref], [Google Scholar], [Publisher]
[33]. Moosavi‐Zare A.R., Goudarziafshar H., Dastbaz S., Mn‐[4‐Chlorophenyl‐Salicylaldimine‐Methylpyranopyrazole]Cl2 as a Novel Nanostructured Schiff Base Complex and Catalyst, Journal of the Chinese Chemical Society, 2017, 64:727 [Crossref], [Google Scholar], [Publisher]
[34]. Moosavi‐Zare A.R., Goudarziafshar H., Ghaffari L., Nano–Mn‐[4‐nitrophenyl‐salicylaldimine‐methyl pyranopyrazole] Cl2 as a new nanostructured Schiff base complex and catalyst for the synthesis of hexahydroquinolines, Applied Organometallic Chemistry, 2017, 31:e3845 [Crossref], [Google Scholar], [Publisher]
[35]. Moosavi‐Zare A.R., Goudarziafshar H., Jalilian Z., Nano‐Zn [2‐boromophenylsalicylaldiminemethylpyranopyrazole] Cl2 as a novel nanostructured Schiff base complex and catalyst for the synthesis of pyrano [2, 3‐d] pyrimidinedione derivatives, Applied Organometallic Chemistry, 2019, 33:e4584 [Crossref], [Google Scholar], [Publisher]
[36]. Moosavi-Zare A.R., Goudarziafshar H., Fashi P., Nano-Co-[4-chlorophenyl-salicylaldimine-pyranopyrimidine dione] Cl2 as a new Schiff base complex and catalyst for the one-pot synthesis of some 4H-pyrimido [2, 1-b] benzazoles, Research on Chemical Intermediates, 2020, 46:5567 [Crossref], [Google Scholar], [Publisher]
[37]. Zolfigol M.A., Tavasoli M., Moosavi-Zare A.R., Moosavi P., Kruger H.G., Shiri M., Khakyzadeh V., Synthesis of pyranopyrazoles using isonicotinic acid as a dual and biological organocatalyst, RSC Advances, 2013, 3:25681 [Crossref], [Google Scholar], [Publisher]
[38]. Tamaddon F., Arab D., Urease covalently immobilized on cotton-derived nanocellulose-dialdehyde for urea detection and urea-based multicomponent synthesis of tetrahydro-pyrazolopyridines in water, RSC Advances, 2019, 9:41893 [Crossref], [Google Scholar], [Publisher]
[39]. Tamaddon F., Khorram A., Advanced Catalyst-Free Pseudo-Six-Component Synthesis of Tetrahydrodipyrazolopyridines in Water by Using Ammonium Carbonate as an Ecofriendly Source of Nitrogen, Synlett, 2020, 31:691 [Crossref], [Google Scholar], [Publisher]
[40]. Zhao K., Lei M., Ma L., Hu L., A facile protocol for the synthesis of 4-aryl-1, 4, 7, 8-tetrahydro-3, 5-dimethyldipyrazolo [3, 4-b: 4′, 3′-e] pyridine derivatives by a Hantzsch-type reaction, Monatshefte für Chemie-Chemical Monthly, 2011, 142:1169 [Crossref], [Google Scholar], [Publisher]
[41]. Dabiri M., Salehi P., Koohshari M., Hajizadeh Z., MaGee D.I., An efficient synthesis of tetrahydropyrazolopyridine derivatives by a one-pot tandem multi-component reaction in a green media, Arkivoc, 2014, 4:204 [Crossref], [Google Scholar], [Publisher]
[42]. Beddie C., Webster C.E., Hall M.B., Urea decomposition facilitated by a urease model complex: a theoretical investigation, Dalton Trance, 2005:3542 [Crossref], [Google Scholar], [Publisher]
[43]. Blakeley R.L., Treston A., Andrews R.K., Zerner B.J., Nickel (II)-promoted ethanolysis and hydrolysis of N-(2-pyridylmethyl) urea. A model for urease, Journal of the American Chemical Society, 1982, 104:612 [Crossref], [Google Scholar], [Publisher]