A convergent approach to (R)-Tiagabine by a regio- and stereocontrolled hydroiodination of alkynes

Abstract

The occurrence of unsaturated systems in natural products combined with the mildness and the wide range of applicability of CeCl₃ promoted methodologies suggest several potential future synthetic applications within the field of total synthesis of biologically active molecules. On this concept, the use of CeCl₃·7H₂O–NaI system as an efficient heterogeneous promoter has been highlighted in the iodofunctionalization of carbon–carbon triple bonds. The study has shown that this method would be particularly interesting for the stereoselective formation of trisubstituted (Z)- or (E)-iodoalkenes by simply changing the nature of the solvent. The methodology has been successfully applied to the synthesis of (R)-1-[4,4-bis-(3-methyl-2-thienyl)-3-butenyl]-3-piperidinecarboxylic acid 1, named (R)-Tiagabine, which is a potent and selective γ-aminobutyric acid (GABA) uptake inhibitor with proven anticonvulsant efficacy in humans.