Highly stereoselective construction of novel dispirooxindole–imidazolidines via self-1,3-dipolar cyclization of ketimines

Abstract

An acid-promoted self-1,3-dipolar cycloaddition of ketimines derived from isatins and benzylamines was successfully developed to assemble unprecedented dispirooxindole-imidazolidine ring systems. Generally, excellent diastereoselectivities (only a single stereoisomer formed) and good yields (up to 94%) were obtained. Consequently, this self-1,3-dipolar cycloaddition protocol offers facile access to a novel dispiroheterocyclic skeleton.

Spiro[4H‐pyran‐3,3′‐oxindoles] Derived from 1,2,3,4‐tetrahydroquinoline—Part 2

“…compounds 2 having an oxindole nucleus but with a spirocyclic ring fused at C‐3, has been considerable, as indicated by a 2014 comprehensive review on “Recent progress on routes to spirooxindole systems derived from isatin” in this journal and a Tetrahedron Report in the same year on “Recent advances in the synthesis of biologically active spirooxindoles”. This interest continues unabated—for example we are aware of seven reports already in 2015 that deal with the conversion of isatins (1 H ‐indole‐2,3‐diones) ( 1 ) into spirooxindoles ( 2 ) (Fig. ), either directly or via a simple derivative of the isatin.…”

Spiro[3H‐pyrazole‐3,3′‐oxindoles] Derived from 1,2,3,4‐Tetrahydroquinoline

“…Interest in spirooxindoles, that is, compounds 2 having an oxindole nucleus but with a spirocyclic ring fused at C‐3, has been considerable, as one may judge from a 2014 comprehensive review on “Recent Progress on Routes to Spirooxindole Systems Derived from Isatin” in this journal and a 2014 Tetrahedron Report on “Recent Advances in the Synthesis of Biologically Active Spirooxindoles.” This interest continues unabated – for example, we are aware of six reports already in 2015 that deal with the conversion of isatins (1 H ‐indole‐2,3‐diones) into spirooxindoles .…”

[3+2]-Cycloaddition of azomethine ylides to 5-methylidene-3-aryl-2-сhalcogen-imidazolones: access to dispiro indolinone-pyrrolidine-imidazolones

“…It should be noted that we were unable to conduct the reaction of 5-methylidene-2-chalcogenimidazolones with azomethine ylides generated from glycine and isatin. Even though there are examples in the literature of the addition of azomethineylides formed from alpha-amino acids and isatin in the presence of various additives [ 21 , 22 ]. In the absence of additives, the Schiff base formed in the course of the reaction is inefficiently attached to double bonds and is of no synthetic value.…”