Preparation and reactions of new low-valent samarium reagents

New low-valent samarium reagents were prepared by the reaction of metallic samarium with bromine in a molar ratio of 4: 3 or by the reaction of samarium(III) bromide with butyllithium. These reagents exhibited reducing ability higher than that of samarium(II)iodide or metallic samarium. Aromatic acid esters were reductively dimerized by these reagents. Diethyl trans-cyclopropane-1, 2-dicarboxylate was subjected to the reductive ringopening reaction on treatment with these reagents. The reaction of dimethyl cyclopropane-1, 1-dicarboxylate with metallic samarium in the presence of mercury halides afforded bis[3, 3-bis (methoxycarbonyl) propyl] mercury.