title: On the preparation and determination of configurational stability of chiral thio- and bromo[D1]methyllithiums.
abstract: Thio- and bromo[D(1)]methyllithiums (ee 99%) were generated from the respective stannanes by tin-lithium exchange at temperatures ranging from 0 to -95 °C. Thio[D(1)]methyllithiums 6 were found to be microscopically configurationally labile on the time scale of the thiophosphate-α-mercaptophosphonate rearrangement even at -95 °C. Thio[D(1)]methyllithiums 13a and 13b underwent a thia-[2,3]-Wittig rearrangement down to -95 °C and 13b only down to -50 °C. The former were microscopically configurationally stable below -95 °C, and the latter racemized completely at -50 °C. Chiral bromo[D(1)]methyllithiums are chemically unstable at -78 °C but microscopically configurationally stable at the time scale of their addition to benzaldehyde and acetophenone.
authors.affiliation: Institute of Organic Chemistry, University of Vienna, Währingerstrasse 38, A-1090 Vienna, Austria.
authors.forename: Anna
authors.initials: A
authors.lastname: Wieczorek
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hammerschmidt