An Intramolecular Cycloetherification of Unactivated Olefinic Substrates Bearing endo‐Alcohol: Access to Diversely Alkylated Oxa‐Cage Derivatives Useful for Olefin‐Metathesis

Herein, we report an efficient and rapid synthetic methodology to access diversely substituted oxa‐cages from unactivated olefinic substrates derived from endo‐norbornenes by employing Lewis acid‐ (BF3 ⋅ OEt2) or base (NaH)‐promoted intramolecular etherification. Although both BF3 ⋅ OEt2 and NaH are found to be efficient for this transformation, slightly better yields and less reaction times are achieved with NaH/DMF (0.25–1 h at 100 °C) as compared to BF3 ⋅ OEt2/DCM (2–3 h at 0 °C to rt). The evolution of this intramolecular cyclization was studied by time‐dependent NMR studies in CDCl3 solvent. Further, these observations are supported by infrared (IR) spectral data. It is worth mentioning that the present methodology enables a new route to assemble highly fused oxa‐cage systems by choosing suitably substituted oxa‐cage compounds for the olefin‐metathesis sequence. The highly fused oxa‐cage systems may have potential applications in high‐energy‐density materials (HEDMs) and supramolecular chemistry. An intramolecular etherification of unactivated olefinic substrates bearing endo‐OH has been achieved to generate diversely substituted oxa‐cages in a step‐ and atom‐economic way. Both BF3 ⋅ OEt2 and NaH bring out this transformation effectively among several Lewis‐acids and bases. Diversely substituted oxa‐cage derivatives can serve as better precursors for the olefin‐metathesis sequence to decorate higher oxa‐cage systems.