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Absence of Non‐Linear Effects Despite Evidence for Catalyst Aggregation
Author(s) -
Geiger Yannick,
Achard Thierry,
MaisseFrançois Aline,
BelleminLaponnaz Stéphane
Publication year - 2021
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202100183
Subject(s) - catalysis , dimer , ligand (biochemistry) , chemistry , monomer , benzaldehyde , enantioselective synthesis , linearity , combinatorial chemistry , organic chemistry , polymer , physics , receptor , biochemistry , quantum mechanics
An in‐depth study of the catalytic system, consisting of the enantioselective addition of ZnEt 2 to benzaldehyde with (1 R ,2 S )‐(−)‐N‐Methylephedrine (NME) as chiral ligand, suggests the presence of dimeric and trimeric aggregates, as deduced from product ee vs. catalyst loading and NMR investigations ( 1 H, DOSY). Formation of catalyst aggregation was excluded in earlier studies as this system displays a linear product ee vs. ligand ee ‐correlation, which is usually taken as an indication for the absence of catalyst aggregation. A subsequent theoretical study, using the monomer‐dimer competition model, which we have recently developed, highlights the possible parameter configurations leading to linear product ee vs. ligand ee plots – despite the presence of catalyst dimers. It shows that, while the Kagan and Noyori models allow linearity in very specific cases only, a multitude of scenarios may lead to linearity here, especially if heterochiral dimers are catalytically active.