LAUSR

Abstract The chemoselective semi-hydrogenation of alkynes into E and Z -alkenes was studied by using Ru/TPPTS as a biphasic and recyclable catalyst in ethylene glycol-toluene solvent system. Current protocol is atom efficient and gives selectivity up to 98%. This protocol is alternative to the classical Lindlar catalyst (Pd/CaCO 3 ) for Z-alkenes and also Birch reduction process (Li/Na/K in liq. NH 3 ) used for the synthesis of E -alkenes. A variety of alkynes with different functional group can be tolerated efficiently transformed into corresponding E and Z alkenes. This catalytic system has been effectively recycled up to five consecutive cycles without appreciable loss in its activity and selectivity.