An industrially viable catalyst system for palladium-catalyzed telomerizations of 1,3-butadiene with alcohols

The telomerization reaction of 1,3-butadiene with alcohols to give alkyl octadienyl ethers in the presence of palladium–carbene catalysts has been studied in detail. Unprecedented catalyst efficiency with turnover numbers (TON) up to 1 500 000 and turnover frequencies (TOF) up to 100 000 h−1 have been obtained after optimization for the reaction of methanol in the presence of an excess of in situ generated carbene ligands. High yields (75–97 %) and catalyst productivities (TON 15 000–100 000) are observed for other aliphatic alcohols and phenols. For comparison five carbene–palladium(0) complexes have been synthesized and characterized by X-ray crystallography. Both electronic and steric effects on the stability and reactivity of the catalysts have been discussed on the basis of density functional theory calculations