first-order kinetics and seems to be mainly an enthalpic process with a small negative activation entropy, as revealed by polarimetric measurements at low temperatures. This is in accordance with Cα–S bondrotation as the rate-determining step. The salts [R1C(R2)SO2tBu]Li have half-lives of racemization in the order of several hours at –105 °C. The deuteriation of the salts at –105 °C with CF3CO2D
Experimental and Theoretical Investigation of the Enantiomerization of Lithium α-tert-Butylsulfonyl Carbanion Salts and the Determination of Their Structures in Solution and in the Crystal
作者:Roland Scholz、Gunther Hellmann、Susanne Rohs、Gerhard Raabe、Jan Runsink、Diana Özdemir、Olaf Luche、Thomas Heß、Alexander W. Giesen、Juliana Atodiresei、Hans J. Lindner、Hans-Joachim Gais
DOI:10.1002/ejoc.201000409
日期:2010.8
and [R 1 C(R 2 )SO 2 Ph]Li ˙ 2diglyme [R 1 = R 2 = Me, Et; R 1 -R 2 = = (CH 2 )5] showed them to be O-Li contact ion pairs (CIPs). The monomers and dimers have a C α -S conformation in which the lone-pair orbital at the C α atom bisects the O-S-O angle and a significantly shortened C α -S bond. The C α atom of [R 1 C(R 2 )SO 2 R 3 ]Li·L n (R' = Ph; R 3 = Ph, tBu) is planar, whereas the C α atom of