Ru-catalyzed chemoselective methoxycarbonylation of methyl pentenoate: An assistant role of chloride anions

Alkoxycarbonylation of alkene has been an important basis in modern chemical industry. As the cheapest noble metal, the potential of ruthenium furnishes significant innovations in the homogeneous catalysis. However, the competitive hydrogenation of alkenes to alkanes represents the most challenge in the alkoxycarbonylation of alkene. Herein, the chloride anions-assisted Ru-catalyzed methoxycarbonylation of methyl pentenoate was investigated. The chemoselectivity of methoxycarbonylation can be improved by controlling the ratio of LiCl/ Ru3(CO)12. Mechanistic experiments show that the activation energy of hydrogenation is increased due to the change of the active species by increasing the amount of LiCl, which hinders the hydrogenation of methyl pentenoate. The di-methoxycarbonylation of 1,7-octadiene indicates that this methodology has the potential to develop the Ru-catalyzed di-methoxycarbonylation of diene substrates.