In saturated NH4CI (aq.)-THF solution at room temperature, metallic samaritan promoted reductive dimerization cyclization of gem-diactivated alkenes, reductive debromination of vic-dibromides, and reduction of sodium alkyl thiosulfates occur to afford corresponding functionalized cyciopentenes, (E)-alkenes, and disulfides. respectively in good yield. Only sub-stoichiometric quantities of samarium are employed in the former reactions and the trans-or trans, trans-form isomer is the majority product of the polysubstituted cyclopentene products.