Improved yne-ene cross metathesis with a 4,5-dihydroimidazolin-2-ylidene ru
thenium benzylidene complex is described. The N-heterocyclic carbene ligand
s complex 2 shows significantly increased activity in the case of stericall
y hindered olefins when compared to 1. Even disubstituted triple bonds are
transformed into 1,2,3-trisubstituted-1,3-dienes. (C) 2000 Elsevier Science
Ltd. All rights reserved.