Rigid Chiral Tertiary Amine N‐Oxides in the Synthesis of Linear Heterotriquinane and 3,9a‐Methanopyrrolo[2,1‐ <i>c</i> ][1,4]oxazepine Frameworks

Stable chiral tertiary amine N‐oxide was obtained from the oxidation of hexahydro‐5 H ‐furo[2,3‐ b ]pyrrolo[1,2‐ d ][1,4]oxazin‐2(1 H )‐one by mCPBA. A Polonovski‐type intramolecular acyl transfer of N‐oxides resulted in the unexpected formation of a novel hexahydrofuro[3,2‐ d ]pyrrolo[2,1‐ b ]oxazol‐2(3 H )‐one motif, treatment of these carbinolamines with Lewis acid resulted in the generation of congested 3,9a‐methanopyrrolo[2,1‐ c ][1,4] oxazepine.