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Absolute Asymmetric Synthesis of “Chiral‐at‐Metal” Grignard Reagents and Transfer of the Chirality to Carbon
Author(s) -
Vestergren Marcus,
Eriksson Johan,
Håkansson Mikael
Publication year - 2003
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.200305003
Subject(s) - enantiopure drug , chemistry , chirality (physics) , enantiomer , reagent , absolute configuration , grignard reaction , benzaldehyde , asymmetric carbon , medicinal chemistry , stereochemistry , enantioselective synthesis , organic chemistry , catalysis , alkyl , chiral symmetry breaking , physics , quantum mechanics , quark , nambu–jona lasinio model
Two new six‐coordinate Grignard reagents, cis ‐[( p ‐CH 3 C 6 H 4 )MgBr(dme) 2 ] ( 1 ) and cis ‐[MgCH 3 (thf)(dme) 2 ]I ( 2 ), have been synthesized and their crystal structures have been determined. Both reagents are cis ‐octahedral and therefore chiral. They crystallize as conglomerates and racemize rapidly in solution. By utilizing these properties, the absolute asymmetric synthesis of specifically the Δ or the Λ enantiomer was achieved for both Grignard reagents. Enantiopure 1 and 2 were then reacted with butyraldehyde or benzaldehyde to give the corresponding alcohol in up to 22 % enantiomeric excess. At −60 °C, the Grignard reagents crystallize as racemic phases instead of conglomerates. Consequently, the crystal structures of rac‐cis ‐[( p ‐CH 3 C 6 H 4 )MgBr(dme) 2 ]⋅DME ( 3 ) and rac‐cis ‐[MgCH 3 (thf)(dme) 2 ]I ( 4 ) could be determined.