Base‐Mediated Sequential Annulation Reaction of <i>β</i>‐Pyrrol‐<i>α</i>,<i>β</i>‐Unsaturated Compounds with Vinylsulfonium Salts: A New Approach to Polycyclic Pyrrolizine Derivatives

Abstract In this paper, we reported a novel sequential reaction sequence consisting of two processes including domino [3+2]/[2+1] annulation and in situ Cloke‐Wilson rearrangement reaction, which enabled synthesis of a series of structurally complex polycyclic pyrrolizine derivatives in 51–96% yields and excellent diastereoselectivities. The viability of the existing protocol was additionally illustrated by gram‐scale synthesis and further modifications. In addition, some of these valuable ring‐fused pyrrolizines displayed some extent of anticancer activity, demonstrating their potential application in the medicinal chemistry.