Pramod B. Thakur

“On water” catalyst-free, column chromatography-free and atom economical protocol for highly diastereoselective synthesis of novel class of 3-substituted, 3-hydroxy-2-oxindole scaffolds at room temperature

The “on water” highly atom economical and diastereoselective synthesis of a novel class of 3-(thiazolidinedione or oxindole) substituted, 3-hydroxy-2-oxindole scaffolds has been achieved by the reaction of isatin electrophiles with thiazolidinedione or oxindole nucleophiles in a catalyst-free and column chromatography-free protocol at room temperature. The generality of the method has been demonstrated by screening a series of isatin electrophiles as well as thiazolidinedione and oxindole derivatives. The developed method is one of the rare examples of an ideal green protocol for the synthesis of medicinally important 3-hydroxy-2-oxindole scaffolds in which the straightforward synthesis of such a framework was achieved by employing very mild, simple and handy procedures from readily available starting materials.

“On water” highly atom economical and rapid synthesis of a novel class of 3-hydroxy-2-oxindole scaffolds under a catalyst-free and column chromatography-free protocol at room temperature

An “on water” highly atom economical and rapid protocol has been developed for the synthesis of a novel class of 3-(2-pyrazolin-5-one) substituted, 3-hydroxy-2-oxindole scaffolds under catalyst-free and column chromatography-free conditions at rt. The generality of the method has been demonstrated by screening a series of isatin electrophiles as well as 2-pyrazolin-5-one derivatives. The developed method is a good example of green synthesis in which straightforward synthesis of a medicinally important 3-hydroxy-2-oxindole framework is executed by employing very mild, simple and handy procedures from readily available starting materials.

DMF mediated Henry reaction of isatins: an efficient synthesis of 3-hydroxy-2-oxindole

Abstract An efficient Henry reaction has been described for the synthesis of 3-hydroxy-3-(nitroalkyl)-2-oxindole by the reaction of isatins with nitroalkanes in N,N-dimethylformamide (DMF) under anhydrous condition. This method provides high yield of 3-hydroxy-2-oxindoles under mild reaction condition. Moreover, the procedure is environmentally benign in nature, efficient, and applicable to variety of isatins as well as nitroalkanes.

An efficient synthesis of hemiaminal of indoles by using tetrabutylammonium fluoride (TBAF) in water as a reusable reaction media

Abstract The synthesis of hemiaminal of indole is described by the reaction of indole with formaldehyde in the presence of TBAF in water at ambient temperature. The procedure is very efficient, mild, convenient, and environmentally benign with high yield of product. Moreover, the reuse of reaction media makes the procedure an attractive alternative to earlier methods.

DABCO Promoted Regioselective Synthesis of New Diversely Functionalized 3-Hydroxy-2-Oxindole Scaffolds

An efficient and highly regioselective γ-addition of β-keto sulfones on isatins has been achieved in the presence of a catalytic amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) to afford a γ-(3-hydroxy-2-oxindole)-β-keto sulfone structural framework. The scope of the method is tested by screening a series of isatin electrophiles as well as β-keto sulfones. The described method was found to be very handy and provides straightforward access for the diversely functionalized 3-β-keto sulfone substituted-3-hydroxy-2-oxindole structural scaffolds in very good yields from readily available starting materials under metal-free reaction conditions.

An Exploration of Organocatalyst 1,4-Diazabicyclo[2.2.2]octane in the Direct Regioselective and Chemoselective γ-Addition of β-Keto Amide on Isatin to Afford Structurally Diverse Molecular Frameworks

An efficient protocol promoted by 1,4‐diazabicyclo[2.2.2]octane is described for the regioselective and chemoselective γ-addition of β-keto amides on isatins to afford γ-(3-hydroxy-2-oxindole)-β-keto amide structural framework under metal-free conditions. The developed method is mild, generates high yields, and is applicable for a variety of isatin electrophiles as well as β-keto amides. Moreover, the procedure is very handy and environmentally benign in nature, and provides direct access for the synthesis of diverse functionalized 3-β-keto amide-substituted 3-hydroxy-2-oxindole structural scaffolds from readily available starting materials.