LiAlH4: From Stoichiometric Reduction to Imine Hydrogenation Catalysis. Issue 24 (15th May 2018)

• Record Type: Journal Article
• Authors: Elsen, Holger; Färber, Christian; Ballmann, Gerd; Harder, Sjoerd
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 24(2018)
• Page Start: 7156
• Page End: 7160
• Publication Date: 2018-05-15
• Subjects: aluminium -- hydrides -- lithium -- reduction -- sustainability; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201803804
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Imine‐to‐amine conversion with catalytic instead of stoichiometric quantities of LiAlH4 is demonstrated (85 °C, catalyst loading≥2.5 mol %, pressure≥1 bar). The effects of temperature, pressure, solvent, and catalyst modifications, as well as the substrate scope are discussed. Experimental investigations and preliminary DFT calculations suggest that the catalytically active species is generated in situ: LiAlH4 +Ph(H)C=N t Bu→LiAlH2 [N( t Bu)CH2 Ph]2 . A cooperative mechanism in which Li and Al both play a prominent role is proposed. Abstract : Atom‐economical imine reduction : Classical imine‐to‐amine reduction uses stoichiometric quantities of LiAlH4, which generates Li/Al salt side products. The same reaction under an H2 atmosphere needs only catalytic LiAlH4 (2.5 mol %) and proceeds under surprisingly mild conditions (85 °C, 1 bar H2 ). The catalyst is an in‐situ‐generated LiAlH2 (NRR′)2 complex.