Metathesis of renewable products: degradation of natural rubber via cross-metathesis with β-pinene using Ru-alkylidene catalysts

Renewable beta-pinene and natural rubber (NR) were used in the cross-metathesis reactions for the synthesis of terpene-terminated oligomers. The metathesis was carried out under solvent-free conditions using the second generation Grubbs catalyst (I). Isolated yields of oligomers were high and ranged between 80 and 90%. It was shown that the molecular weights of products may be changed in a wide range by controlling the ratio of beta-pinene to NR. The formation of beta-pinene and NR cross-metathesis products during chain transfer was confirmed using a model reaction of beta-pinene with (Z)-3-methyl-2-pentene.