With the aid of the hydrogen-bond relay of (S)-camphorsulfonic acid, the enantioselective exo-Diels–Alder cycloaddition of cyclic enones and 2-vinyl-1H-indoles catalyzed by prolinosulfonamide was developed. The corresponding Diels–Alder cycloadducts were readily obtained by a single recrystallization, free of column chromatography. Consequently, tetracyclic tetrahydrocarbazole ring systems with three
借助(S)-
樟脑磺酸的氢键中继,开发了由脯
氨酰磺酰胺催化的环烯酮和
2-乙烯基-1H-吲哚的对映选择性exo-Diels-Alder环加成反应。相应的 Diels-Alder 环加合物很容易通过单次重结晶获得,无需柱层析。因此,以中等产率制备了具有三个连续立体中心的四环四氢
咔唑环系统,具有优异的非对映选择性(外/内高达 >20:1)和对映选择性(高达 > 99% ee)。