Rearrangement or gem-difluorination of quinine and 9-epiquinine and their acetates in superacid
作者:Sébastien Debarge、Sébastien Thibaudeau、Bruno Violeau、Agnès Martin-Mingot、Marie-Paule Jouannetaud、Jean-Claude Jacquesy、Alain Cousson
DOI:10.1016/j.tet.2004.12.045
日期:2005.2
In HF-SbF5, quinine 1a or its dihydrochloride rearranges into compound 3 (89%), the preferred conformation of the substrate favouring the observed cyclization. Under similar conditions epiquinine 2a dihydrochloride yields in equal amounts two 10,10-difluoro derivatives, epimeric at C-3. In this case, the more stable conformation of the substrate in which the benzylic hydroxyl group is ‘exo’ to the
在HF-SbF 5中,奎宁1a或其二盐酸盐重排为化合物3(89%),底物的优选构型有利于观察到的环化作用。在相似的条件下,表奎宁2a二盐酸盐的收率相等,为两个10,10-二氟衍生物,在C-3处为差向异构。在这种情况下,苄基羟基对喹啉基部分“外”的底物的更稳定构象阻止了环化作用。类似地,乙酸盐1b和2b在C-3处产生相应的10,10-二氟衍生物差向异构体。宝石的形成-二氟化合物意味着在C-10处形成氯中间体,然后提取氢化物,生成α-氯鎓离子。这一个被氟离子捕获,并通过卤素交换产生产物。