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Highly Enantiomerically Enriched α ‐Haloalkyl Grignard Reagents
Author(s) -
Hoffmann Reinhard W.,
Nell Peter G.,
Leo, Roland,
Harms Klaus
Publication year - 2000
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 - 10.1002/1521-3765(20000915)6:18<3359::aid-chem3359>3.0.co;2-u
Subject(s) - chemistry , magnesium bromide , grignard reagent , grignard reaction , reagent , enantiomer , medicinal chemistry , magnesium , racemization , bromide , halide , decomposition , organic chemistry
α ‐Chloro‐ and α ‐bromoalkyl Grignard reagents 11 and 30 with >97 % ee (enantiomeric excess) were generated by a sulfoxide/magnesium exchange reaction from the enantiomerically and diastereomerically pure sulfoxides 25 and 27 . The resulting α ‐haloalkyl Grignard reagents are configurationally stable at −78 °C. Racemization sets in at or above −60 °C, especially when the solution contains bromide ions. In the absence of halide ions, the configurational stability extends up to −20 °C, when chemical decomposition commences.