A Review on the Selective Synthesis of Spiro Heterocycles Through 1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides

Stereoselective synthesis of spirocyclic pyrrolidines/pyrrolizidines/pyrrolothiazolidines using l-proline functionalized manganese ferrite nanorods as a novel heterogeneous catalyst

“…4 For the preparation of ve-membered cyclic amines, in particular pyrrolidines, pyrrolizidines, and dihydropyrroles, cycloaddition of azomethine ylides with alkenes is very effective. [2][3][4][5][6] Azomethine ylides have four p electrons spread over the three-atom C-N-C unit, of which the most common representation has a positive charge located on the nitrogen atom and a negative charge distributed over the two carbon atoms. 7 The cycloaddition of an azomethine ylide with a p-system involves a total of six p electrons [p4s + p2s] and takes place by a thermally allowed, suprafacial process in which two carbon-carbon bonds are formed on the same face of the azomethine ylide and on the same face of the dipolarophile.…”

“…Due to the constrained structure of spiro compounds, the existence of the chiral central spiro carbon and the indole core represents an interesting pharmacophore, and these compounds show a wide range of biological and pharmacological activities. 9 Furthermore, a broad range of natural alkaloids contain well-known spirooxindole moieties, such as formosanine, 4 pteropodine, 5 coerulescine, 6 strychnofoline, 7 rychnophyilline, 4 and alstonisine, 8 with highly pronounced proved pharmacological properties ( Fig. 1 ).…”