Ionic liquid [Et₃NH][HSO₄]catalyslyzed multicomponent synthesis of 6 amino-4-(Substituted phenyl)-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile

A series of 6-amino-4-substituted-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles 5(a-j) as a potent anticancer agent were synthesized via one-pot, four-component condensation reaction of aryl aldehydes, ethyl acetoacetate, malononitrile, and hydrazine hydrate in solvent-free conditions using ionic liquid [Et₃NH][HSO₄] as an efficient, eco-friendly and reusable catalyst. The Multi component coupling reactions (MCRs) indicate a highly appreciated synthetic tool for the establishment of novel and complex molecular scaffold with a minimum number of synthetic steps with the advantage like shorter reaction times, lower costs, high degrees of atom economy etc. From the literature survey it is found that dihydropyrano[2,3-c]pyrazole derivatives posses very important biological activities, including anticancer, antiinflammatory, antimicrobial, inhibitors of human Chk1 kinase, molluscicidal, and insecticidal activities. The solvent used in conventional organic synthesis are suffered by many disadvantage like environmental hazards, toxicity, volatile nature, expensive etc. A new term ‘designer solvents’ referring to Ionic liquids because of their adjustable physical and chemical properties with the change in selected cationic and anionic combination. Ionic liquids have become a promising alternative media for various chemical processes due to their properties including good solvating capability, negligible vapour pressure, non-inflammability, ease of recyclability, controlled miscibility and high thermal stability. Herein we are reporting the use of acidic Bronsted ionic liquid(ABILs) [Et₃NH][HSO₄] triethyl ammonium sulphate for the synthesis of biologically important scaffold 6-amino-4-(substituted phenyl)-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile . Compared to other methods, this new method has advantages, such as excellent yields, a short reaction time, mild reaction conditions and catalyst reusability. The synthesized derivatives 5(a-j) were characterized by FTIR, ¹HNMR, ¹³CNMR and mass spectral data.