Correlations between nucleophilicities and selectivities in the substitutions of tetrahydropyran acetals.
Correlations between nucleophilicities and selectivities in the substitutions of tetrahydropyran acetals.
复制标题
DOI：
10.1021/jo901639b
复制
发表时间：
2009-11-06
期刊：
影响因子：
--
通讯作者：
Woerpel KA
中科院分区：
文献类型：
--
作者：
Krumper JR;Salamant WA;Woerpel KA
研究了四氢吡喃缩醛亲核取代反应中偏离SN1立体电子模型的选择性。当使用弱亲核试剂时，立体选择性符合已知的SN1立体电子模型。相反，用强亲核试剂取代缩醛的立体选择性取决于反应条件。当在没有配位反离子的情况下使用强亲核试剂时，观察到选择性的侵蚀。这些选择性的侵蚀是由于氧碳离子中间体的亲核添加速率接近扩散极限。然而，当三氟酸反离子存在时，sn2样途径可以通过强亲核试剂进入。在大多数情况下，通过sn2途径形成的主要立体异构体与通过SN1途径形成的类似反应形成的主要立体异构体相反。
Selectivities that deviate from SN1 stereoelectronic models in the nucleophilic substitutions of tetrahydropyran acetals were investigated. When weak nucleophiles were employed, stereoselectivities conformed to known SN1 stereoelectronic models. In contrast, stereoselectivities in the substitutions of acetals with strong nucleophiles depended on reaction conditions. Erosions in selectivities were observed when strong nucleophiles were employed in the absence of coordinating counterions. These erosions in selectivities are attributed to rates of nucleophilic additions to oxocarbenium ion intermediates that approach the diffusion limit. When triflate counterions were present, however, SN2-like pathways became accessible with strong nucleophiles. In most cases examined, the major stereoisomers formed from reactions that proceeded through SN2-like pathways were opposite to the major stereoisomers formed from the analogous reactions that proceeded through SN1 pathways.
登录
查看更多内容
影响因子：
5.2
作者：
Crich D;Sharma I
通讯作者：
Sharma I
影响因子：
15
作者：
BENNET, AJ;SINNOTT, ML
通讯作者：
SINNOTT, ML
影响因子：
2.1
作者：
Codee, Jeroen D. C.;de Jong, Ana R.;van der Marel, Gijsbert A.
通讯作者：
van der Marel, Gijsbert A.
影响因子：
3.6
作者：
Dinkelaar, Jasper;de Jong, Ana Rae;van der Marel, Gijsbert A.
通讯作者：
van der Marel, Gijsbert A.
影响因子：
2.1
作者：
BROWN, DS;BRUNO, M;LEY, SV
通讯作者：
LEY, SV