Novel 1,3-diene synthesis from alkyne and ethylene by ruthenium-catalyzed enyne metathesis

A novel 1,3-diene synthetic method from alkyne and ethylene was developed using ruthenium-catalyzed enyne metathesis. The reaction procedure is very simple: A CH 2 Cl 2 solution of alkyne was stirred at room temperature under ethylene gas (1 atm.) in the presence of a catalytic amount of ruthenium benzylidene complex. The yield was good and the conversion yield was high. Dienes having functional groups such as a keto-carbonyl group, silyloxy group, ester, and ketal were synthesized from the corresponding alkynes and ethylene. In this reaction, the alkyne having a hetero atom at the propargylic position gave a good result and ether oxygen or amine nitrogen that coordinate strongly to the ruthenium catalyst prevents the reaction. Novel 1,3-diene synthesis was developed from alkyne and ethylene in the presence of ruthenium carbene complex.