Construction of indolenine-substituted spiro[pyrrolidine-2,3′-oxindoles] from 2-alkenylindolenines and isatin-derived azomethine ylides

Diastereoselective Three-Component 1,3-Dipolar Cycloaddition to Access Functionalized β-Tetrahydrocarboline- and Tetrahydroisoquinoline-Fused Spirooxindoles

A chemselective catalyst-free three-component 1,3-dipolar cycloaddition has been described. The unique polycyclic THPI and THIQs were creatively employed as dipolarophiles, which led to the formation of functionalized β-tetrahydrocarboline- and tetrahydroisoquinoline-fused spirooxindoles in 60-94% of yields with excellent diastereoselectivities (10: 1->99: 1 dr). This reaction not only realizes a concise THPI- or THIQs-based 1,3-dipolar cycloaddition, but also provides a practical strategy for the construction of two distinctive spirooxindole skeletons.

1,3-Dipolar cycloaddition reactions of isatin-derived azomethine ylides for the synthesis of spirooxindole and indole-derived scaffolds: recent developments

The unique therapeutic and biological characteristics of spirooxindole have led to the presentation of numerous reactions for the synthesis of spirooxindoles through 1,3-Dipolar cycloaddition of highly reactive isatin-derived azomethine ylides with activated olefins as the main tool for the formation of spirocyclic oxindoles during the last 4 years. Therefore, there is a need to highlight the recent developments in this area, along with the representative synthetic methods and relevant reaction mechanisms from 2018 to 2021. The representative synthetic methodologies were listed in four sections based on the procedure to form the azomethine ylide species including isatins and amino acids, isatin-derived α-(trifluoromethyl)imine, isatins and benzylamines, and from isatin-derived cyclic imine 1,3-dipoles.

Construction of a spiro[pyrazolone-4,2'-pyridoindole] scaffold via a [3 + 3] cycloaddition of 2-indolylmethanol with a 4-aminopyrazolone-derived azomethine ylide

This work reports a facile [3 + 3] cycloaddition sequence of two important heterocyclic pharmacophores, pyrazolone and 2-indolylmethanol, integrated into a polycyclic hybrid scaffold. In this process, an in situ generated azomethine ylide obtained from 4-aminopyrazolone and benzaldehyde reacts with 2-indolylmethanols to offer spiro[pyrazolone-pyridoindole] scaffolds in high yields with excellent diastereoselectivities. Remarkably, the reaction is carried out at room temperature without any catalyst and base.

Stereoselective synthesis and applications of spirocyclic oxindoles

This review summaries recent synthetic developments towards spirocyclic oxindoles and applications as valuable medicinal and synthetic targets.

Engaging 2-methyl indolenines in a tandem condensation/1,5-hydride transfer/cyclization process: construction of a novel indolenine–tetrahydroquinoline assembly

An efficient BF₃·Et₂O-catalyzed diastereoselective tandem condensation/1,5-hydride transfer/cyclization strategy for the synthesis of a novel indolenine–tetrahydroquinoline assembly was reported.