Gold(III)‐Catalysed <i>cis</i>‐to‐<i>trans</i> Cyclopropyl Isomerization

Abstract

Novel chiral gold(III) complexes, based on bisoxazoline (BOX) and 2‐pyridyl‐(–)menthol ligands, were prepared and characterised (X‐ray), and their catalytic properties in cyclopropanation reactions of propargyl esters with alkenes were explored. The BOX‐Au III catalysts gave excellent results for fast cyclopropanation and subsequent in situ cis ‐to‐ trans vinylcyclopropyl isomerization. Au I and Au III catalytic species showed different abilities to tune the reactions and transform the initially formed cis product into the isomerized trans product. The appropriate choice of gold(I) or gold(III) complex enabled highly stereoselective formation of cis or trans products (up to 99 % dr ), in high yields (63–98 %). The pure cis isomers were used in isomerization studies, showing that rapid cis ‐to‐ trans isomerization took place at room temperature in the presence of BOX‐Au III catalysts.