Efficient Synthesis of Amines by Iron‐Catalyzed C=N Transfer Hydrogenation and C=O Reductive Amination

Abstract

AbstractHere we report the catalytic transfer hydrogenation (CTH) of non‐activated imines promoted by a Fe‐catalyst in the absence of Lewis acid co‐catalysts. Use of the (cyclopentadienone)iron complex 1, which is much more active than the classical ‘Knölker complex’ 2, allowed to reduce a number of N‐aryl and N‐alkyl imines in very good yields using iPrOH as hydrogen source. The reaction proceeds with relatively low catalyst loading (0.5–2 mol%) and, remarkably, its scope includes also ketimines, whose reduction with a Fe‐complex as the only catalyst has little precedents. Based on this methodology, we developed a one‐pot CTH protocol for the reductive amination of aldehydes/ketones, which provides access to secondary amines in high yield without the need to isolate imine intermediates.magnified image