Iodine‐Catalyzed One‐Pot Four‐Component Synthesis of Spiro[indoline‐3,4′‐pyrano‐pyrazole] Derivatives

Abstract

in Wiley Online Library (wileyonlinelibrary.com).An efficient, facile, and useful synthetic method was developed for the production of spiro[indoline-3,4 0pyrano-pyrazole] carbonitrile derivatives through a one-pot, four-component reaction involving hydrazine hydrate, diketene, substituted isatins, and malononitrile or ethyl cyanoacetate in the presence of iodine as the efficient catalyst in ethanol at room temperature. Significantly, this remarkable method provides novel spiropyranopyrazole derivatives in good to high yields. The significant aspects of this protocol are facile work-up approach and a greener process because the use of toxic and hazardous solvents are avoided. 6 0 -Amino-5-chloro-3 0 -methyl-2-oxo-1 0 H-spiro[indoline-3,4 0pyrano[2,3-c]pyrazole]-5 0 -carbonitrile (2e).White powder, mp = 295-294°C, 0.28 g, yield: 85%. IR (KBr) (ν max , cm À1 ): 3386 and 3347 (NH 2 ), 3137 (2NH), 2182 (CN), December 2018One-Pot Four-Component Synthesis of Spiro[indoline-3,4 0 -pyrano-pyrazole] Derivatives 2777

Engaging Isatins in Multicomponent Reactions (MCRs) – Easy Access to Structural Diversity

“…This chemical transformation, involving isatin, hydrazine hydrate, ketene, and malononitrile or ethyl cyanoacetate, afforded a library of the desired spirooxindoles (8 examples) with overall very good yields (Scheme 86). [168] The authors postulated that after an initial condensation reaction between hydrazine hydrate and the ketene to provide the pyrazolone intermediate, there then occurs a Michael reaction with the Knoevenagel condensation intermediate, which is followed by enolization and consequent intramolecular cyclization to give the target compounds after imine‐enamine tautomerization (Scheme 86). It seems that iodine is crucial in the last step of the mechanism, in order to activate the nitrile group allowing the oxygen to attack.…”

“…I 2 [114] , [115] , [168] p ‐TSA.H 2 O [116] , [128] , [158] , [176] , [184] H 3 PW 12 O 4 [117] NbCl 5 [170] BF 3 .Et 2 O [67] AgCO 3 [48] …”

Synthesis of pyrano[2,3‐c]pyrazoles: A review

“…In this regard, Rezvanian et al synthesized spiropyranopyrazole derivatives in multicomponent condensation of hydrazine monohydrate 21 , propanedinitrile 23 /ethyl cyanoacetate 77 , diketene 125 , and substituted isatins in ethanol medium using iodine (20%) as catalyst at room temperature. [ 104 ] Different substituted isatins bearing electron‐donating and withdrawing groups were used in the reaction but unsubstituted isatin 40 gave the highest yield of the product 126 (92%) (Scheme 27).…”

An elegant and efficient synthesis of heterocycles integrated with bis‐N‐acyl pyrazoline and bis‐1, 2, 3‐triazole via a green synthetic methodology

“…There are several reports which provide diverse synthetic protocols to synthesize N-substituted pyrazolines and/or triazole derivatives, which suffer from several short comings such as prolonged reaction time, multistep protocols, use of hazardous solvents, and expensive catalysts [31][32][33][34][35][36]. In view of this, we herein report our investigation toward the development of multicomponent reaction by mechanochemical solvent-free approach which overcome most of the demerits of conventional methodology.…”