Ultrasound‐Assisted Expeditious Catalyst‐Free Green Approach towards Diastereoselective Synthesis of Spiro[indoline‐3,2′‐pyrido[2,1‐b][1,3]oxazine]‐3′,4′‐dicarboxylate Scaffolds

Abstract

An ultrasound assisted efficient, expeditious and environmentally benign new methodology for direct access to broad ranges of structurally interesting and pharmacologically significant spiropyrido[2,1‐b][1,3]oxazino compounds based on three component reactions approach via domino 1,4‐dipolar cycloaddition from easily available starting materials in aq. ethanol medium at room temperature (25–30 °C) has been developed. In comparison to that of conventional methods, simple experimental and workup procedure, excellent yields, good functional group tolerance, cleaner reaction profile, use of green solvent are remarkable features of this sonochemical procedure.Furthermore, using of the ultrasound in this methodology leads to the reduction of the reaction times.

Stereoselective Domino Reactions in the Synthesis of Spiro Compounds

“…Similarly, Mukhopadhyay and co-workers developed a three-component reaction via domino 1,4-dipolar cycloaddition of isatins 492′ with acetylenedicarboxylates 532 and pyridine 531 in aqueous ethanol at room temperature using ultrasound-assisted methodology to obtain spirooxindole-pyrido[2,1- b ][1,3]oxazines 530 in good yields and diastereoselectivities (Scheme 106 ). 114…”