Implications of Active Intermediate and Olefin Attachment Position in the Piperine Metathesis

First and second generation of Grubbs catalysts (G1 and G2) were applied in the piperine olefin metathesis under different conditions. G1 was used in self-metathesis, G2 was implemented in both, self and cross-metathesis of piperine with eugenol. Results allowed to implicate about the main intermediate of the reaction and the position of olefin attachment to the catalyst, assuming that the reaction follows a pathway where 2A=B olefin leads to the formation of A=A and B=B. In addition, the results contributed to the studies of catalyst’s reactivity when the olefin metathesis product required the high electronic effect of the N-heterocyclic of G2. In this paper, the highest activity of G2 in the olefin metathesis of eugenol was observed when the first intermediate was Ru-eugenol-moiety in the cross-metathesis of the piperine with eugenol. This demonstrates that the acidity of the new carbene in the intermediate species causes inactivity only in the reaction with piperine.