Influence of the Nature of Low Valent Titanium Reagents in McMurry Olefination: Stereoselective Synthesis of Symmetrical and Unsymmetrical Hydroxystilbenes

Intramolecular reductive deoxygenation of ethylenedioxy tethered symmetrical and unsymmetrical aromatic bis(ketone) ethers with the low-valent titanium (LVT) reagent (TiCl4-Zn-DME) yielded the corresponding cyclic stilbenes with excellent Z-selectivity. On the other hand, coupling of the aldehydic tethered ethers proceeded with high E-selectivity with the LVT reagent (TiCl3 / Li / KCl (2.0 eq.) / THF). Dealkylation of the cyclic stilbenes furnished the geometrically pure hydroxystilbenes.