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Mechanistic Insights into Manganese (I)‐Catalyzed Chemoselective Hydroarylations of Alkynes: A Theoretical Study
Author(s) -
Wang Zheyuan,
Zhu Lei,
Zhong Kangbao,
Qu LingBo,
Bai Ruopeng,
Lan Yu
Publication year - 2018
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.201801301
Subject(s) - alkyne , chemistry , steric effects , protonation , moiety , catalysis , imine , regioselectivity , annulation , reactivity (psychology) , migratory insertion , chemoselectivity , photochemistry , bond cleavage , combinatorial chemistry , medicinal chemistry , stereochemistry , organic chemistry , alternative medicine , pathology , medicine , ion
Density functional theory calculations were employed to elucidate the mechanism of Mn‐catalyzed chemoselective hydroarylation reactions. The Mn‐catalyzed [4+2] annulation undergoes a reaction pathway involving sequential imine‐directed C−H bond cleavage, alkyne insertion into the Mn−C bond, β‐oxygen elimination and outer catalytic cycle annulation–aromatization. Computational results demonstrated that the previously proposed chelation‐assisted alkyne insertion process was unfavorable owing to the weak coordination ability of the β‐oxygen leaving group compared with that of CO. Further noncovalent interactions analysis indicated that the origin of the high regioselectivity was contributed to the steric repulsion resulting from significant nonbonding overlap between the reacting aryl moiety and the quaternary carbon group of the reactant in the alkyne insertion step. In addition, in the Brønsted‐acid‐mediated chemoselective alkenylation reaction, the used terminal alkynes had relatively enhanced reactivity in the alkyne insertion step owing to its reduced steric repulsion. From the active alkenyl‐Mn intermediate, the activation free energy of protonation and β‐oxygen elimination are approximate, thus the alkenylated product is obtained after protonation in an acidic system. We expect that this detailed mechanistic study will significantly enhance our ability to develop Mn‐catalyzed arene C−H bond functionalization reactions.