Improved yne–ene-cross metathesis utilizing a dihydroimidazole carbene ruthenium complex

Improved yne–ene cross metathesis with a 4,5-dihydroimidazolin-2-ylidene ruthenium benzylidene complex is described. The N-heterocyclic carbene ligands complex 2 shows significantly increased activity in the case of sterically hindered olefins when compared to 1. Even disubstituted triple bonds are transformed into 1,2,3-trisubstituted-1,3-dienes.