Amberlyst A21 Catalyzed Chromatography-Free Method for Multicomponent Synthesis of Dihydropyrano[2,3-c]pyrazoles in Ethanol

Abstract

Amberlyst A21 was found to be an extremely efficient catalyst for synthesis of a series of 6-amino-4-alkyl/ aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-carbonitriles by a four-component reaction of a mixture of ethyl acetoacetate, hydrazine hydrate, aldehyde, and malononitrile in ethanol at room temperature. The catalytic efficiency of Amberlyst A21 was compared with some other resin-bound free and anionic bases in order to ascertain the best catalyst for the said conversion. The catalyst was found to work extremely well also for acyclic/cyclic ketones to give corresponding dihydropyrano[2,3-c]pyrazoles or their spirocyclic variants. Easy recovery of the catalyst and its reusability, room temperature reaction conditions, short reaction time, excellent yields, no chromatographic purification, and evasion of environmentally hazardous solvents in the entire reaction process may make this protocol very useful for academia and industry.

Synthesis of N-hydroxysuccinimide from succinic acid and hydroxylammonium chloride using Amberlyst A21 as reusable solid base catalyst

“…Along with the development in solid base catalysts, more recently, resin-bound catalysts have been becoming more and more important in organic synthesis due to their recyclability, ease of separation and purification, and higher safety feature against potential explosive reagents [12]. Many kinds of ion-exchange resins, namely Amberlyst, Amberlite, and Dowex are now available at low cost, the greater diversity of functionalities, and higher loading capacities [13].…”

DABCO catalyzed rapid one-pot synthesis of 1,4-dihydropyrano [2,3-c] pyrazole derivatives in aqueous media

“…Recently these compounds are synthesized by the condensation of four component reaction catalyzed by piperidine [12], triethylamine [13], L-proline or KF-alumina [14], trichoroaceticacid [15], iodine [16], γ-alumina [17], ionic liquid [18], amberlyst A21 [19], nanosized magnesium oxide [20], Fe 3 O 4 nanoparticles [21] per-6-ABCD [22], silicotungstic acid [23], and isonicotinic acid [24]. Some of the reported methods suffer from one or more limitations such as prolonged reaction time, use of organic solvents, and harsh reaction conditions.…”

Ag/Tio2 Nano Thin Films Catalyzed Efficient Synthesis of 6-Amino-4-Aryl-3-Methyl-1,4-Dihydropyrano[2,3-C] Pyrazole-5-Carbonitriles At Green Conditions

“…Moreover, dihydropyrano [2,3-c]pyrazoles exhibit molluscicidal activity 29 , and has been identified as a screening kit for Chk1 kinase inhibitor 30 . Because of the importance of these compounds, a number of methods have been reported for their synthesis in the presence of various catalysts such as ionic liquids 31,32 , organic bases [33][34][35][36] , amberlyst 37 , glycine 38 , per-6-amino-b-cyclodextrin 39 , and iodine 40 .…”