Lithium hydride mediates hydrogenolysis of anilines to arenes Yongli Cai 1 , Liu Wei 2 , Wu Anan 2 , Guo Jianping 1 , Chen Ping 1 1 University of Chinese Academy Sciences, China, 2 Xiamen University, China. Hydrides containing hydridic H‾ have shown promise in energy storage and chemical transformations. 1 For example, alkali and alkaline earth metal hydrides (denoted as AHs) have been studied as key components of hydrogen storage materials. And some AHs (e.g., LiH and BaH 2 ) have been shown to afford nitrogen activation to form imides. Based on this knowledge, a chemical looping ammonia synthesis process mediated by AHs have been constructed, in which the formation and mutual-conversion of Li-N and Li-H bonds are the key to fulfill the loop. 2 By virtue of this unique property, we recently found that AHs can also mediate the cleavage of C-N bond in anilines besides N≡N bond. Because of high C−N bond dissociation energy, the intense coordinating ability, and the inferior leaving ability of the NH 2 group, breaking C-N bond, specially the sp 2 C-N bond remains challenging. 3 Transition metals are commonly required for C-N cleavage. The development of new strategy or materials for C-N bond activation under mild conditions will not only deepen the understanding of reaction mechanism but also have the important application value. Recently, we have proposed a lithium hydride (LiH)-mediated chemical looping process for hydrogenolysis of aniline (denoted as CL-HDN), which decouples the overall HDN reaction into a set of separated steps. 4 In the step of the loop, LiH deprotonates aniline to form a lithium anilide and H 2 . The lithium anilide is then exposed to dihydrogen at elevated temperatures to produce benzene and lithium amide (LiNH 2 ) in the step. And in the step the LiH is regenerated by the hydrogenation of LiNH 2 in a flow of H 2 closing the chemical cycle. Benzene is the dominant denitrogenated product in this process. A high denitrogenated product formation rate is achieved under lower temperatures and pressures which is comparable to the catalytic rate of transition metal catalysts. The computational studies reveal that the cleavage of C-N bond is facilitated via a LiH-mediated pathway, in which the hydride (Hˉ) of LiH functions as a nucleophile to attack the α-sp 2 C atom and Li cation interacts with the distorted aromatic ring by a cation−π interaction. This work provides a new method for C-N bond activation and may help the development of new materials or catalysts for the C-N bond cleavage. Considering the reaction is an inverse step of C-N bond formation, this work also provides hints on the development of efficient materials or processes for the reaction of benzene and ammonia to anilines or other important C-X (X=C, O etc.) bond coupling reactions. References 1. Q. Wang, J. Guo*, P. Chen*, Joule , 2020 , 4, 705-709.
2. W. Gao, J. Guo*, P. Chen* et al., Nat. Energy ., 2018 , 3, 1067-1075. 3. D. Hu, Y. Zhou, X. Jiang*, Natl. Sci. Rev., 2022 , 9, No. nwab156. 4. Y. Cai, J. Guo*, P. Chen* et al., J. Am. Chem. Soc. , 2022 , 144, 17441−17448.
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