title: On the configurational stability of chiral, nonracemic fluoro- and iodo-[D(1)]methyllithiums.
abstract: Enantiomerically pure fluoro-[D1]methyllithium and iodo-[D1]methyllithiums of up to 92% ee were generated by transmetalation of the corresponding stannanes with MeLi in THF at various temperatures. The intermediate halo-[D1]methyllithiums were trapped with benzaldehyde or acetophenone already present in excess in the reaction mixture to either give halohydrins or to disintegrate to carbene. The fluoro-[D1]methyllithiums were found to be microscopically configurationally stable within the tested range of -95 to 0 °C, but chemically only stable at temperatures below -95 °C due to a rapidly increasing portion disintegrating to carbene. The iodo-[D1]methyllithiums were configurationally labile relative to the rate of addition to PhCHO at all temperatures tested (-95 to -30 °C). Disintegration to carbene interfered as well.
authors.affiliation: PharmBioTec GmbH, Saarland University, Campus C2.2, Room 31, 66123 Saarbrücken (Germany).
authors.forename: Dagmar C
authors.initials: DC
authors.lastname: Kail
authors.forename: Petra
authors.initials: P
authors.lastname: Malova Krizkova
authors.forename: Anna
authors.initials: A
authors.lastname: Wieczorek
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hammerschmidt
mesh_terms: D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D009942:Organometallic Compounds; C520093:methyllithium
keywords: chemical stability; configuration; enantioselectivity; organolithium compounds; transmetalation