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Lithiated Fluorinated Styrene Oxides: Configurational Stability, Synthetic Applications, and Mechanistic Insight
Author(s) -
Capriati Vito,
Florio Saverio,
Perna Filippo Maria,
Salomone Antonio
Publication year - 2010
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.201000897
Subject(s) - racemization , electrophile , synthon , chemistry , enantiomer , styrene , computational chemistry , medicinal chemistry , organic chemistry , catalysis , copolymer , polymer
The configurational stability of some lithiated fluorinated styrene oxides has been investigated. Chemical studies have shown that in ethereal solvents α‐lithiated ortho ‐, meta ‐, and para ‐fluorostyrene oxides ( 2‐Li , α‐ 5‐Li , and α‐ 6‐Li ) are all configurationally stable in the reaction time scale, whereas α‐lithiated ortho ‐, meta ‐, and para ‐trifluoromethylstyrene oxides ( 9‐Li , 13‐Li , and 14‐Li ) are configurationally unstable. Optically active oxiranyllithiums 2‐Li and 9‐Li , could be stereospecifically generated and quenched with electrophiles. The corresponding derivatives were then successfully subjected to regiospecific ring‐opening reactions with amines to give fluorinated β‐amino alcohols with a stereodefined quaternary carbinol center, which are useful synthons in medicinal chemistry. The barriers of inversion have been calculated (Eyring equation) for oxiranyllithiums 9‐Li , 13‐Li , and 14‐Li by determining the enantiomeric ratios after electrophilic quenching on aging the enantioenriched organolithium for different times in THF; in the case of 9‐Li , activation parameters have also been determined. Mechanisms that may be responsible of the racemization oxiranyllithiums 9‐Li , 13‐Li , and 14‐Li undergo once generated are also discussed.