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Titanium‐catalyzed esterification reactions: beyond Lewis acidity
Author(s) -
Wolzak Lukas A.,
Vlugt Jarl Ivar,
Berg Keimpe J.,
Reek Joost N. H.,
Tromp Moniek,
Korstanje Ties J.
Publication year - 2020
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.202000931
Subject(s) - catalysis , lewis acids and bases , chemistry , titanium , carboxylate , stoichiometry , transition state , lewis acid catalysis , reaction mechanism , density functional theory , combinatorial chemistry , organic chemistry , computational chemistry
Esterification is a key reaction and is used in many synthetic and industrial processes, yet the detailed mechanism of operation of often‐used (Lewis acid) catalysts is unknown and subject of little research. Here, we report on mechanistic studies of a titanium aminotriphenolate catalyst, using stoichiometric and catalytic reactions combined with kinetic data and density functional theory (DFT) calculations. While often only the Lewis acidity of the Ti‐center is taken into account, we found that the amphoteric nature of this catalyst, combining this Lewis acidity with Brønsted basicity of a Ti‐bound and in situ formed carboxylate group, is crucial for catalytic activity. Furthermore, hydrogen bonding interactions are essential to pre‐organize substrates and to stabilize various intermediates and transition states and thus enhancing the overall catalytic reaction. These findings are not only applicable to this class of catalysts, but could be important for many other esterification catalysts.