Ionic liquids (ILs) are receiving much attention as a reaction medium in synthetic organic chemistry because they have some unique properties such as a wide liquid range with a melting point around room temperature, negligible vapor pressure, high polarity, and thermal stability. Furthermore, ILs are known to dissolve charged species such as organometallic compounds more readily than non-charged species, including most organic compounds, via ionic interactions. This property of ILs might enable easy separation of the catalyst and organic compounds by simple phase separation and recycling of the catalyst remaining in ILs. In recent years, from the viewpoint of green chemistry, various reactions catalyzed by transition metal complexes have been extensively examined using ILs as reaction media. For Rh chemistry, although there are several reports on recycling of catalysts using ILs, there has been no report on the hydroacylation of 4-pentenals,which is one of the important Rh(I)-mediated C-C bond forming reactions. Herein, we report the use of ILs as reaction media for Rh(I)-catalyzed intramolecular hydroacylation with the aim of developing environmentally benign chemical processes.
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