Stereoselective [3 + 2] Cycloaddition Reactions of Azomethine Ylides Derived from 5-Methylbenzo[B]thiophene-2,3-dione and Piperidine-2-Carboxylic Acid

A series of spiropyrrolidines have been synthesized in 68-76% yield by 1,3 dipolar cycloaddition reaction of azomethine ylides generated by a decarboxylative route from 5-methylbenzo[b]thiophene and piperidine-2-carboxylic acid with different acetylenic and ethylenic dipolarophiles. The stereochemical course of the cycloaddition has been investigated by spectral data and AM1 quantum chemical method. The novel spiro compounds have been characterized by elemental analyses and spectroscopic techniques.