Transition Metal-Free Hydrogenolysis of Anilines to Arenes Mediated by Lithium Hydride.

Abstract

Hydrodenitrogenation (HDN) of nitrogen-containing organic compounds such as aniline and its derivatives is of scientific interest and practical importance. Major efforts have been devoted to the development and understanding of transition metal-mediated chemical processes. Herein, we report a fundamentally different strategy using a transition metal-free material, that is, lithium hydride (LiH) enabling the hydrogenolysis of aniline to benzene and ammonia via a chemical looping approach. Aniline reacts with LiH to form lithium anilide, and subsequently, the hydrogenolysis of lithium anilide yields benzene and ammonia and regenerates LiH to complete the loop. This LiH-mediated chemical looping HDN process stands in sharp contrast to the transition metal-catalyzed or -mediated processes, which commonly lead to the complete hydrogenation of aromatic rings. A highly denitrogenated product formation rate of 2623 μmol·g-1·h-1 is achieved for the hydrogenolysis of lithium anilide at 300 °C and 10 bar H2, which exceeds the catalytic rate of transition metal catalysts. Computational studies reveal that the scission of C-N bonds is facilitated by a Li-mediated nucleophilic attack of hydride to the α-sp2C atom of aniline. This work not only provides a distinctive chemical looping route for HDN, but also opens up materials space for the denitrogenation of anilines.