The Magnesium−Ene Cyclization Stereochemically Directed by an Allylic Oxyanionic Group and Its Application to a Highly Stereoselective Synthesis of (±)-Matatabiether. Allylmagnesium Compounds by Reductive Magnesiation of Allyl Phenyl Sulfides<sup>1</sup>
more easily prepared in a connective fashion than the usual allyl halide precursor. Since the presence of lithium ions encourages undesirable proton transfer to the cyclized organometallic and is detrimental to the stereochemical control, the conversion of the allylic thioether to the allylmagnesium utilizes a lithium-free method involving direct reductive magnesiation in the presence of the magnesium-anthracene
Tandem Lithium−Ene Cyclization and Thiophenoxide Expulsion to Produce Fused Vinylcyclopropanes: First Observation of Allylic Lithium Oxyanion-Induced Reactivity and Stereoselectivity in Intramolecular Carbolithiation