Ionic liquid [Dabco-C8][FeCl4] as an efficient and recyclable catalyst for direct C3 alkylation of indoles with electron-deficient olefins

Abstract

In this paper, a simple and highly efficient Friedel–Crafts Michael–type addition of indoles to electron-deficient olefins was achieved by a new magnetic ionic liquid catalyst ([Dabco-C8][FeCl4]). This catalyst system is applicable to a variety of electron-deficient olefins, including chalcones, enones, and nitro-olefins, and affords the corresponding 3-alkylindole derivatives in good to excellent yields under mild conditions within short times. The catalyst can be recycled four times without considerable activity loss.