Study on Rh(I)-catalyzed cycloisomerization of dienes with alkenes in ionic liquids: effect of the structure of ILs on catalyst recyclability

Abstract

A Rh(I)-catalyzed cycloisomerization of dienes with alkenes using ionic liquids (ILs) as reaction media was investigated. In contrast to the hydroacylation promoted by the same cationic Rh(I) catalyst, the structure of ILs strongly affected the recyclability of the catalyst in this cycloisomerization, and a [BDMI (1-butyl-2,3-dimethyl imidazolium)]⁺-based IL was more effective than a [BMI (1-butyl-3-methyl imidazolium)]⁺-based one. It has also been proven that the addition of 2,2,2-trifluoroethanol (TFE) to the reaction mixture prevented the loss of reactivity of the catalyst, and the IL recovered after the reaction under the present conditions could be used repeatedly.