Synthesis of Bridged Five-Membered Ring Systems by Type II [3 + 2] Annulation of Allenylsilane-ene.

The first type II intramolecular [3 + 2] annulation of allenylsilane-ene has been achieved, enabling diastereoselective and efficient construction of synthetically challenging bridged five-membered ring systems such as bicyclo[3.2.1]. This mild and direct process shows a broad substrate scope and is highly stereospecific. Particularly, this work represents the first stereoselective method for the direct synthesis of bicyclo[3.2.1] ring systems from acyclic precursors. Additionally, the first asymmetric total syntheses of (+)- and (-)-strepsesquitriol, and the efficient formation of the synthetically challenging tetracyclic core of pierisjaponol D are achieved by this type II [3 + 2] annulation reaction.