Intramolecular reductive deoxygenation of ethylenedioxy tethered symmetrical and unsymmetrical aromatic bis(carbonyl) ethers with the low-valent titanium (LVT) reagent (TiCl4-Zn-THF) yielded chromatographically separable E/Z-isomers of corresponding cyclic stilbenes which were further dealkylated to obtain geometrically pure hydroxystilbenes. The intramolecular McMurry coupling of the tethered bis(carbonyl) ethers with TiCl3-Li-THF, on the other hand, directly provided both symmetrical and unsymmetrical phenanthrenes via in situ dealkoxylation of the phenol function. This is the first report of the synthesis of unsymmetrical phenanthrenes by the LVT route.
antitumor agents - dimerization - titanium - alkenation - McMurry coupling - stereoselective synthesis
