Design and Synthesis of Highly Decorated Oxa-Cage Systems via Olefin Metathesis

Here, we report diversely fused oxa-cages starting from various alkyl-substituted cyclic-ether derivatives derived via intramolecular cyclocetherification of endo-alcohol containing endo-norbornene derivatives. All these higher oxa-cage systems are assembled in good to excellent yield by employing ring-closing metathesis (RCM) or ring-opening metathesis (ROM) as a key step. Ru-based Grubbs catalysts (G-I, G-II) are effective to assemble these target molecules. In addition, a highly strained bicyclo[2.2.1]hepatane system fused oxa-cages are easily prepared by hydrogenation sequence. Also, several highly fused saturated oxa-cage derivatives are reported. A total of 22 examples are reported and all of these compounds are well-characterized by NMR and HRMS data. The target compounds reported here may find significant applications in various fields of chemistry.