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LiAlH 4 ‐catalyzed Imine Hydrogenation with Dihydrogen: New DFT Mechanistic Insights
Author(s) -
Qu ZhengWang,
Zhu Hui,
Grimme Stefan
Publication year - 2021
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.202100674
Subject(s) - imine , frustrated lewis pair , chemistry , lithium amide , catalysis , amide , heterolysis , lewis acids and bases , stoichiometry , lithium (medication) , hydride , ionic bonding , reagent , photochemistry , polymer chemistry , combinatorial chemistry , organic chemistry , metal , ion , enantioselective synthesis , medicine , endocrinology
Recently, it was found that the widely used stoichiometric reducing reagent LiAlH 4 can also be used as a useful catalyst for imine hydrogenation with H 2 under relatively mild conditions. In this work, extensive state‐of‐the‐art DFT calculations are conducted to explore the detailed catalytic mechanism. In sharp contrast to the recent proposal involving heterolytic H 2 ‐activation over Al−N amide bonds after multiple imine insertion, our new mechanism highlights the dual role of the Lewis‐acidic lithium cation in frustrated‐Lewis‐pair‐like activation of both imine substrate and H 2 when combined with the aluminum‐bound hydride and amide ligands, respectively. Ionic Li−N amide bonds are about 13 kcal/mol more reactive than Al−N amide bonds for H 2 activation, thus providing a useful structural feature for rational design of active hydrogenation catalysts.