Stereoselective Chlorination and Bromination of Enamides and Enamines via an Electrostatic Attraction Effect Using (1,1-Diacetoxyiodo)benzene and a Halide Source
作者:Linlin Xing、Chunbao Li
DOI:10.1021/acs.joc.5b01603
日期:2015.10.16
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
使用NiCl 2 ·6H 2 O或四丁基铵可以实现(E)-烯胺和(Z)-酰胺直接氯化和溴化为相应的(Z)-构型的α-氯烯胺,α-溴烯胺和α-氯烯酰胺。溴化物为卤化物源,(1,1-二乙酰氧基碘)苯为氧化剂。仅产生(Z-构型可以归因于中间体的结构,其构象由带正电荷的氮原子和羰基的氧原子之间的静电引力控制。在烯烃卤化中从未报道过这种类型的静电作用。因此,三元溴离子只是烯胺溴化途径中的次要中间体。这些方法打开了制备α-氯烯胺和α-氯烯酰胺的途径,而这是目前使用的方法无法获得的。