An improved 1,3-diene synthesis from alkyne and ethylene using cross-enyne metathesis

Synthesis of 1,3-diene from alkyne and ethylene (1 atm) was improved using ruthenium carbene complex 1b having heterocyclic carbene as a ligand. In this reaction, the heteroatom at the propargylic position was not required, although the reaction of alkyne with the first-generation ruthenium carbene complex 1a was affected by the substituent at the propargylic position. Various 1,3-dienes could be synthesized from alkynes and ethylene.