Diastereoselective Intramolecular Ester Transfer Reaction ofN-Alkenylcar­bamate Derivatives Mediated by Zirconocene-Butene Complex: Preparation of α,γ-Disubstituted γ-Aminobutyric Acid (GABA) Derivatives and 2,4-Di­substituted Pyrrolidine Derivatives

Abstract

Zirconium-mediated diastereoselective alkene-carbonyl coupling reactions of N-alkenylcarbamate derivatives are reported. The present alkene-carbonyl coupling reactions using chiral tert-butyl­ 3-butenylcarbamates having a substituent at the homoallylic position proceeded in a highly diastereoselective manner to give α-methyl-γ-substituted γ-aminobutyric acid (GABA) derivatives. Iodination of the intermediary zirconium species gave the α-iodo­methylated γ-aminobutyrates, which were, in turn, converted to the 5-substituted pyrrolidine-3-carboxylate having cis stereochemistry.