Five different Ru metal precursors were reduced in imidazolium based ionic liquids under hydrogen atmosphere (4 bar) at 50 A degrees C to obtain well-dispersed and stable Ru nanoparticles. Transmission electron microscopy (TEM) analysis confirmed size of well dispersed ionic liquid mediated Ru particles (Ru NPs) of 5 nm (+/- 0.5) in diameter. These ruthenium nanoparticles (in ionic liquids) were used for Wittig type olefination reaction under mild reaction environment (70 A degrees C and 1 h). The corresponding stilbenes were obtained in good yield with low-average selectivity. The proposed methodology is especially efficient for the synthesis of stilbenes as they were synthesized in the absence of any additive (as a hydrogen acceptor). The new catalytic system was also successfully applied for the synthesis of polymethoxylated and polyhydroxylated stilbenes, including resveratrol and DMU-212.