From Allylic Substitution Catalyzed by Ruthenium Complexes to the Total Synthesis of (+)-iso-exo-Brevicomin

摘要

Pentamethylcyclopentadienyl ruthenium(II) centres are able to activate allylic halides and carbonates to give allylic rathenium(IV) complexes via oxidative addition. Such complexes, which are intermediate species in catalytic nucleophilic allylic substitution reactions in the presence of Cp*Ru(II) precursors have been fully characterized and provided regioselective nucleophilic substitution from unsymmetrical allylic substrates and lead to chiral branched isomers as major compounds. The use of optically pure bidentate nitrogen ligands, especially bis-oxazolines makes possible the enantioselective substitution reaction.