CHIRAL ORGANOMETALLIC REAGENTS .14. THEORETICAL INVESTIGATIONS INTO THE MECHANISM OF INVERSION OF CONFIGURATION AT THE CARBON CENTER OF ALPHA-SULFUR-SUBSTITUTED CARBANIONS

被引：32

作者：

DRESS, RK ^{[1
]}

ROLLE, T ^{[1
]}

HOFFMANN, RW ^{[1
]}

机构：

[1] UNIV MARBURG, FACHBEREICH CHEM, D-35032 MARBURG, GERMANY

来源：

CHEMISCHE BERICHTE | 1995年 / 128卷 / 07期

关键词：

RACEMIZATION BARRIER; SULFUR-SUBSTITUTED CARBANIONS; CALCULATIONS; AB INITIO;

D O I：

10.1002/cber.19951280704

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

Ab initio calculations showed that the two elementary steps in the racemization of the alpha-methylthioethyl anion (7), inversion of the pyramidal anionic center, and rotation around the C--S bond, occur in sequence and are not concerted. The former process passes over a barrier of 1.1 kcal/mol, the latter over one of 10.9 kcal/mol. MNDO calculations on the alpha-phenylthioethyl anion (8) revealed a preferred conformation of the S-alyl bond, allowing maximum delocalization of the sulfur lone pairs into the n(*) orbital of the aryl group. This orientation is maintained during rotation around the C--S bond and is the origin of steric hindrance in the racemization of certain alpha-arylthio-, alpha-arylseleno-, and alpha-aryltelluroalkyllithium compounds 1 to 6.

引用

页码：673 / 677

页数：5

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