Mechanistic studies on acetylene cyclotrimerization catalyzed by Grubbs first and second generation catalysts

Cyclotrimerization of acetylene catalyzed by Grubbs ruthenium catalysts can proceed through two pathways. Pathway 1 is the metathesis pathway and involves a four membered metallacycle intermediate and pathway 2 is non-metathesis pathway and has a five membered metallacycle intermediate.