Facile Pd(II)- and Ni(II)-Catalyzed Isomerization of Terminal Alkenes into 2-Alkenes

摘要

Mono- and 2,2′-disubstituted terminal alkenes can be isomerized into the more stable internal (Z)- and (E)-alkenes by treating them with catalytic amounts of [(allyl)PdCl]2 or [(allyl)NiBr]2, a triarylphosphine,and silver triflate at room temperature. The isomeric ratio (E:Z) depends on the alkenes, the E-isomer being the major one. The reaction is tolerant to a wide variety of functional groups including other reactive olefins. Unlike the more reactive Ir catalysts, monosubstituted alkenes give almost exclusively the 2-alkenes. Direct comparison to two of the best-known catalysts for this process {[Ir(PCy3)3]+[BPh4]-and Grubbs generation II metathesis catalyst} is also described.