Trifluoromethanesulfonic (triflic) acid is an excellent catalyst for inducing overall 5-endo cyclisation of homoallylic sulfonamides [e.g.4] to give pyrrolidines [e.g.5]. In competitive experiments, pyrrolidines or homopiperidines are formed in preference to piperidines, even when the latter would be obtained by trapping a tertiary carbocation. Cationic cascades terminated by a sulfonamide group are viable for the efficient formation of polycyclic systems.
三氟甲磺酸(三
氟甲基磺酸)是一种极好的催化剂,可诱导均烯丙基磺酰胺(如 4)发生整体 5-endo 环化反应,生成
吡咯烷类化合物(如 5)。在竞争性实验中,
吡咯烷或同
哌啶类化合物比
哌啶类化合物更容易形成,即使后者是通过捕获一个叔碳位而得到的。以磺酰胺基团终止的阳离子级联可以有效地形成多环体系。