A series of amido-acetals were reacted with the Brønsted superacid, CF3SO3H, to provides indolizidine derives by a cyclization cascade. A mechanism is proposed involving formation of a vinylogous enol which undergoes a 6π-electrocyclization reaction with an adjacent N-acyl iminium ion group. With aryl substituents, there is a strong tendency for the N-acyl iminium ion group to undergo Friedel-Crafts
                                    一系列酰胺基
乙缩醛与布朗斯台德超酸CF 3 SO 3 H反应,通过环化级联反应提供
吲哚并
咪唑衍
生物。提出了一种机理,该机理涉及形成
乙烯基的烯醇,该
乙烯基的烯醇与相邻的N-酰基
亚胺离子基团进行6π-电环化反应。在具有芳基取代基的情况下,N-酰基亚
氨基鎓离子基团具有与芳基基团一起进行Friedel-Crafts型环化的强烈趋势。合成方法用于制备
生物碱天然产物ipalbidine。