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Reversal Diastereofacial Selectivity in the n ‐Butyllithium Addition to O ‐Protected N ‐Trimethylsilylimines of (2 S )‐Lactal: Enthalpic versus Entropic Contributions
Author(s) -
Cainelli Gianfranco,
Giacomini Daria,
Galletti Paola
Publication year - 1999
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/(sici)1099-0690(199901)1999:1<61::aid-ejoc61>3.0.co;2-p
Subject(s) - diastereomer , chemistry , selectivity , enthalpy , entropy (arrow of time) , solvent , butyllithium , thermodynamics , computational chemistry , medicinal chemistry , stereochemistry , organic chemistry , catalysis , physics
Commonly observed, but rarely explored, is the possibility of modifying the diastereomeric excess ( de %) by means of temperature. A complete reversal in the diastereofacial selectivity could be obtained whenever the diastereoisomers concerned are differentially favored by enthalpy and entropy. The enthalpic or entropic dominance of a diastereoisomer depends greatly on the reaction solvent used.