Lithiation of Prochiral 2,2′-Dichloro-5,5′-dibromo-4,4′-bipyridine as a Tool for the Synthesis of Chiral Polyhalogenated 4,4′-Bipyridines
作者:Victor Mamane、Emmanuel Aubert、Paola Peluso、Sergio Cossu
DOI:10.1021/jo401255q
日期:2013.8.2
achiral tetrahalogenated 4,4′-bipyridine 1 with alkyllithiums was investigated. n-BuLi was found to induce either the chlorine-directed deprotolithiation reaction alone or with a concomitant halogen–lithium exchange furnishing after iodine trapping chiral 4,4′-bipyridines 2 and 6, respectively. The role of n-BuLi in the deprotolithiation process of 1 was elucidated on the basis of isolated secondary derivatives
研究了非手性四卤代4,4'-联吡啶1与烷基锂的锂化。在碘分别捕获手性4,4'-联吡啶2和6后,发现n -BuLi单独诱导氯定向脱锂反应或伴随卤素-锂交换。基于分离的二级衍生物,阐明了n -BuLi在1的去锂化过程中的作用。去原锂化后,锂化的物种可能被不同的亲电试剂(例如MeI,TMCCl,MeSSMe,R 3 SnCl(R = Me或n -Bu)和PPh 2)捕获。Cl。此外,4,4'-联吡啶2经历了交叉偶联反应(铃木和Sonogashira),选择性地发生在碳碘键上。通过手性HPLC(高效液相色谱)分离该新的对映异构体4,4'-联吡啶家族的所有化合物,并使用反常色散通过XRD(X射线衍射)确定获得的对映异构体的绝对构型。