Stereoselective Chlorination and Bromination of Enamides and Enamines via an Electrostatic Attraction Effect Using (1,1-Diacetoxyiodo)benzene and a Halide Source
详细信息 查看全文
- 作者：Linlin Xing ; Chunbao Li
- 刊名：Journal of Organic Chemistry
- 出版年：2015
- 出版时间：October 16, 2015
- 年：2015
- 卷：80
- 期：20
- 页码：10000-10008
- 全文大小：542K
- ISSN：1520-6904
文摘
The direct chlorination and bromination of (E)-enamines and (Z)-enamides to the corresponding (Z)-configurated 伪-chloroenamines, 伪-bromoenamines, and 伪-chloroenamides have been realized using NiCl2路6H2O or tetrabutyl ammonium bromide as a halide source and (1,1-diacetoxyiodo)benzene as an oxidant. The high stereoselective reactions which produce products with only (Z)-configurations can be attributed to the structure of the intermediates, the conformations of which are controlled by the electrostatic attractions between the positively charged nitrogen atoms and the oxygen atoms of the carbonyl group. This type of electrostatic effect has never been reported in olefin halogenations. For this reason, the three-membered bromonium ion is only a minor intermediate in the enamine bromination pathway. These methods open pathways to prepare 伪-chloroenamines and 伪-chloroenamides, which are not accessible via the currently used methods.