FACILE MICROWAVE-ASSISTED ONE-POT SOLID PHASE SYNTHESIS OF SPIRO [3H-INDOLE-3,4'-PYRAZOLO[3,4-b] PYRIDINES]

Step-economic, efficient, ZnS nanoparticle-catalyzed synthesis of spirooxindole derivatives in aqueous medium via Knoevenagel condensation followed by Michael addition

“…10 In context of this program, we have previously reported the synthesis of spirooxindole derivatives by a multi-step process catalyzed by Et 3 N in ethanol under refluxing. [11][12][13] Recently two papers 14,15 describing three-component synthesis of spirooxindole derivatives in aqueous medium with surfactants or solvent free, catalyzed by InCl 3 with microwave assistance, appeared in the literature. These methods display an important disadvantage in generating mixtures of pyrans and unsaturated nitriles.…”

4H-Pyrano[2,3-c]pyrazoles: a review

“…60 It was assumed that the formation of the Michael adduct is common in both methods which cyclized regioselectively to pyrano[2,3-c]pyrazol bearing spiro-2-oxindole derivatives. Similarly, Dandia and co-workers ground N-unsubstituted isatin 155 and malononitrile in agate mortar or subjected to microwave irradiation at 640 W to get intermediate 156 (Scheme 52 C) which adsorbed on neutral alumina using methanol and treated with pyrazolone to get pyranopyrazoles 157 61 (Scheme 52 D).…”

Molecular Iodine: A Powerful Catalyst for the Knoevenagel Condensation of Isatins with Malononitrile

“…e most common methods for the synthesis of 2-(2-oxoindolin-3-ylidene)malononitriles are the condensation of isatins with malononitrile in the presence of a catalyst, such as piperidine acetate [5], DBU [6], Al 2 O 3 [7], N(CH 2 CH 2 OH) 3 [8], chitosan [9]. Recently, MW irradiation [10] has also been applied to the condensation. However, most of these procedures have signicant drawbacks such as long reaction times, low yields, harsh reaction conditions, difficult workup, and use of environmentally toxic or expensive reagents or media.…”