[18-C-6H3O+]: an in-situ generated macrocyclic complex and an efficient, novel catalyst for synthesis of pyrano[2,3-c]pyrazole derivatives

Abstract

General procedure for the synthesis of pyrano[2,3-c]pyrazoles using crown ether as a catalyst. To a mixture of aromatic aldehyde 1a-p (2 mmol), 2 (2 mmol), 3 (2 mmol), 4a/4b (2 mmol) in water (10 mL) taken in a 50 mL RB flask, crown ether 10 mol% was added. The reaction mixture was subjected to sonication for 10 min at room temperature. The completion of reaction was confirmed using TLC. The solid product was filtered and recrystallized from aqueous ethanol to get the pure products.

Green Synthesis of Pyrazoles: Recent Developments in Aqueous Methods

“…The use of 18-Crown- [6]-ether was made by Mishra et al, in 2020 to develop water mediated multisubstrate synthesis of 14 Template for SYNTHESIS Thieme pyranopyrazoles 12 (Scheme 38) in 89-96% yield in water using ultrasonication within 10 min. Many other solvents such as MeOH, MeCN, DMF, DMSO, DCM have also been attempted in the synthetic protocol however the water was found to be the best among all the solvents under study 83 .…”

“…82 Nizam and co-workers, in 2020, used 18-crown- [6]ether for the four-component synthesis of pyranopyrazoles 12 in 89-96% yield in water using ultrasonication within 10 min (Scheme 38). 83 The use of various solvents, such as MeOH, MeCN, DMF, DMSO, DCM, was examined but water was found to be the best. 83 A two-component synthesis of pyrano[2,3-c]pyrazoles 12 was achieved using the natural waste, water extract of banana peels (WEB) by Chowhan and co-workers, in 2020, starting from arylidenemalononitriles and 3-methyl-1,4-dihydro-5H-pyrazol-5-one (Scheme 39).…”

“…83 The use of various solvents, such as MeOH, MeCN, DMF, DMSO, DCM, was examined but water was found to be the best. 83 A two-component synthesis of pyrano[2,3-c]pyrazoles 12 was achieved using the natural waste, water extract of banana peels (WEB) by Chowhan and co-workers, in 2020, starting from arylidenemalononitriles and 3-methyl-1,4-dihydro-5H-pyrazol-5-one (Scheme 39). 84 The reaction was efficiently performed with various substituted arylidenemalononitriles possessing ortho-, meta-, or para-substituted aryl or hetaryl groups at room temperature and the products were obtained in excellent 91-96% yield.…”

Potassium dihydrogen phosphate‐catalyzed synthesis of benzylpyrazolyl coumarin and pyrano [2,3‐c] pyrazole derivatives via cascade—One‐pot—Multicomponent reaction

“…These compounds have been prepared via the 2‐component [12], 3‐component [13a–c], and 4‐component one‐pot reactions. These methods include the use of crown ether [14], thiamine hydrochloride [15], sodium benzoate [16], heterogeneous catalysts [17a, b], phase transfer catalyst [18], ionic liquids [19a–e], nano‐[CoFe 2 O 4 ] [20], and Baker's yeast [21].…”

Immobilization of Polyoxometalate onto Modified Magnetic Nanoparticles: A New Catalyst for the Synthesis of Dihydropyranopyrazole Derivatives

“…[7][8][9] Though there are different types of catalyst available, yet designing a heterogeneous catalyst has been important for organic reactions because the heterogeneous catalysts have several advantages; (i) recoverability, (ii) reusability, (iii) the use of catalytic amount, (iv) value of the metal leaching into the reaction solution after reuse can be tolerated, (v) not to undergo the structural degradation. [10] So far, many organic acid/base catalysts and their bifunctional systems have been successfully immobilized on various solid supports and have shown impressive catalytic performances in various reactions. [11][12][13][14][15][16][17][18][19][20] Over the past decades, magnetic nanoparticles have been a great topic for research on a wide range of applications, including environmental remediation, [21] targeted drug delivery, [22] and catalysis.…”