Diastereoselective Synthesis of Highly Substituted Five-Membered-Ring Oxygen Heterocycles by Zirconocene-Mediated C-C Coupling Reactions

As homoenolate equivalents, zirconocene-1-aza-1,3-diene complexes were used for the first time in stereoselective synthesis. By insertion of an unsymmetrical ketone in the Zr-C σ bond, sterically demanding trisubstituted dihydro- and tetrahydrofuran derivatives were prepared in good overall yields and with high diastereoselectivities (see below).