Lactate-Based Ionic Liquid Catalyzed Reductive Amination/Cyclization of Keto Acids under Mild Conditions: A Metal-Free Route To Synthesize Lactams

Task-specific ionic liquids (ILs) have shown promising applications in catalysis. Herein we present lactate-based IL (e.g., 1-butyl-3-methyl­imidazolium lactate, [BMIm]­[Lac]) catalyzed reductive amination/cyclization of keto acids using triethoxysilane as a reducing agent, which provides a metal-free route to synthesis of lactams under mild conditions, even at room temperature. [BMIm]­[Lac] combined with (EtO)3SiH afforded a series of five- and six-membered lactams in good to excellent yields at 80 °C within 1 h, showing comparable performance to the best metal-based catalyst reported to date. The mechanism investigation indicated that the ILs (e.g., [BMIm]­[Lac]) served as a multifunctional catalyst, which could activate hydrosilanes and simultaneously catalyzed the cyclization of LA with amines.