Palladium-catalyzed enyne cyclization of 2 '-alkenyl 2-alkynoates in imidazolium type ionic liquids

摘要

The use of [bmim][BF4], [bmim][PF6], and [bmim][Cl] ILs as the solvents in Pd(II)-catalyzed enyne cyclization of 20-alkenyl 2-alkynoates in the presence of cupric chloride has been investigated. The Z/E stereoselectivity of the reaction could range from 90:10 to 4:96 by tuning the amount of LiCl in ILs. After the separation of the product, the IL-catalyst mixture could be recovered by treatment with hydrochloric acid and recycled several times without an obvious loss of catalytic activity.