An efficient and simple approach for the synthesis of pyranopyrazoles using imidazole (catalytic) in aqueous medium, and the vibrational spectroscopic studies on 6-amino-4-(4′-methoxyphenyl)-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole using density functional theory

Abstract

a b s t r a c tWe describe a one-pot four component synthesis of pyranopyroles from aryl aldehydes, ethyl acetoacetate, malononitrile and hydrazine hydrate in the presence of catalytic amounts of an organocatalyst imidazole in water as medium. A plausible mechanism for the formation of imidazole catalyzed pyranopyrazoles has been envisaged. This method is rapid, simple, provides products in good yield, and is eco-friendly. In addition, based on the optimized geometry, the frequency and intensity of the vibrational bands of 6-amino-4-(4 -methoxyphenyl)-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole were obtained by the density functional theory (DFT) calculations using 6-31G(d,p) basis set. The vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement.

One-pot, four-component synthesis of pyrano[2,3-c]pyrazoles catalyzed by sodium benzoate in aqueous medium

“…These approaches include one-pot three-component condensation of pyrazolone derivatives, malononitrile, and aromatic aldehydes or pyrazole-aldehydes; 14 three-component cyclocondensation of substituted piperidin-4-ones, pyrazol-5-ones, and malononitrile; 15 four-component reaction of aldehydes, ethyl acetoacetate, malononitrile with hydrazine hydrate; [16][17][18][20][21][22][23][24][25][26][27][28][29][30][31][32] two-component reaction of 3-methyl-2-pyrazolin-5-one with benzylidenemalononitriles; 19 and four-component reaction involving aromatic aldehydes, Meldrum's acid, hydrazine hydrate, and ethyl acetoacetate. 32 Various catalysts and conditions have been used to synthesis pyranopyrazoles, via reactions mentioned above.Some of those catalyst are triethylamie in ethanol or water, 14a,15 p-dodecylbenesulfonic acid (DBSA) in water at 60 °C, 14c hexadecyltrimethylammonium bromide (HTMAB) at 60-80 °C, 14d ammonium acetate in ethanol, 14g triethylbenzylammonium chloride (TEBACl) at 90 °C in water solution, 14i β-cyclodextrin in water, 16 imidazole in aqueous medium, 17 piperidine in ethanol or water, 14h,18 cinchona alkaloid organocatalysts in dichloromethane, 19 per-6-amino-β-cyclodextrin (per-6-ABCD) , 20 Brønsted-acidic ionic liquid under solvent-free conditions, 21 [bmim]OH, 22 L-proline and γ-alumina, 23 32 and cetyltrimethylammonium chloride (CTACl). 33 Other non-catalytic methods were also applied for the synthesis of these compounds.…”

A highly efficient and sustainable synthesis of dihydropyrano[2,3-c]pyrazoles using polystyrene-supported p-toluenesulfonic acid as reusable catalyst

“…diverse biological activities such as antimicrobial, anti-inflammatory, analgesic, antitumor, and molluscidal activities (Abdelrazek, Metz, & Metwally, 2006;El-Tamany, El-Shahed, & Mohamed, 1999;Kuo, Huang, & Nakamura, 1984;Siddekha, Nizam, & Pasha, 2011;Wang et al, 2000;Zaki, Soliman, Hiekal, & Rashad, 2006). Moreover, they also act as potential inhibitors of human chk1 kinase (Foloppe et al, 2006).…”

Green Synthetic Approaches for Biologically Relevant 2-amino-4H-pyrans and 2-amino-4H-pyran-Annulated Heterocycles in Aqueous Media∗

“…Furthermore, these compounds also have been identified as vasodilators, hypotensive, hypoglycemic [97,[100][101][102], and some compounds have been demonstrated an affinity toward A1 and A2a adenosine receptors [103,104]. Scheme 10 illustrates the synthesis of 2-amino-4-substituted pyrano[2,3-c]pyrazole-3-carbonitriles 19 in aqueous media using microwave irradiation [106] or catalysts such as imidazole [107], sodium benzoate [108], CTACl [109], and γ-alumina [110]. Thus, development of environment-friendly and efficacious procedures for the synthesis of pyranopyrazoles in water is of significant interest.…”