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
[R 1 C(R 2 )SO 2 R 3 ]Li(R 1 ,R 2 = 烷基,苯基;R 3 = Ph、tBu、金刚烷基、CEt 3 )在 [D 8 ]THF 中的动态 NMR (DNMR) 光谱已经表明 S-tBu、S-金刚烷基和 S-CEt 3 衍生物比它们的 S-Ph 类似物具有显着更高的对映异构化屏障。C α -S 键旋转最有可能是在 S 原子上带有一个庞大基团和在 C α 原子上带有两个取代基的盐的对映异构化的速率决定步骤。[Me(Ph)-SO 2 tBu] 的从头算计算给出了关于两个 C α -S 旋转势垒的信息,这两个势垒受空间效应支配。[R 1 C(R 2 )SO 2 tBu]Li 在 -108 °C 下的 THF 中的冷冻检查显示存在单体和二聚体。[R 1 C(R 2 )SO 2 tBu]Li·L n (R 1 = Me, Et, tBuCH 2 , PhCH 2 , tBu;