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Aggregation and Cooperative Effects in the Aldol Reactions of Lithium Enolates
Author(s) -
Larrañaga Olatz,
de Cózar Abel,
Bickelhaupt F. Matthias,
Zangi Ronen,
Cossío Fernando P.
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201301597
Subject(s) - aldol reaction , chemistry , lithium (medication) , tetramer , alkoxide , electrophile , adduct , dimer , density functional theory , acetone , computational chemistry , reactivity (psychology) , organic chemistry , medicine , alternative medicine , pathology , enzyme , endocrinology , catalysis
Density functional theory and Car–Parrinello molecular dynamics simulations have been carried out for model aldol reactions involving aggregates of lithium enolates derived from acetaldehyde and acetone. Formaldehyde and acetone have been used as electrophiles. It is found that the geometries of the enolate aggregates are in general determined by the most favorable arrangements of the point charges within the respective Li n O n clusters. The reactivity of the enolates follows the sequence monomer≫dimer>tetramer. In lithium aggregates, the initially formed aldol adducts must rearrange to form more stable structures in which the enolate and alkoxide oxygen atoms are within the respective Li n O n clusters. Positive cooperative effects, similar to allosteric effects found in several proteins, are found for the successive aldol reactions in aggregates. The corresponding transition structures show in general sofa geometries.