In(OTf)<sub>3</sub>‑Catalyzed (3 + 3) Dipolar\nCyclization of Bicyclo[1.1.0]butanes with <i>N</i>‑Nucleophilic\n1,3-Dipoles: Access to 2,3-Diazabicyclo[3.1.1]heptanes, 2,3-Diazabicyclo[3.1.1]heptenes,\nand Enantiopure 2‑Azabic

The investigation into the synthesis of azabicyclo[3.1.1]heptanes\n(azaBCHeps) as bioisosteres to flat aza-aromatics has garnered increasing\nattention, while it encounters significant challenges. Herein, we\nhave demonstrated the In(OTf)<sub>3</sub>-catalyzed (3 + 3) dipolar\ncyclization of bicyclo[1.1.0]butanes (BCBs) with hydrazones and π-allyl-iridium\n1,3-dipoles, engendering a diverse array of azaBCHeps. The cyclization\nof hydrazones and BCBs furnished densely substituted 2,3-diazabicyclo[3.1.1]heptanes\nand 2,3-diazabicyclo[3.1.1]heptenes under nitrogen and oxygen atmospheres,\nrespectively. A combination of experimental and computational investigations\nlends robust support for the proton-transfer-interposed sequential\nmechanism. More importantly, by integrating In(OTf)<sub>3</sub>/iridium\nrelay catalysis, enantiopure 2-azabicyclo[3.1.1]heptanes were constructed\nthrough the (3 + 3) cyclization of BCBs with aza-π-allyl-iridium\n1,3-dipoles, in situ generated from <i>N</i>-allyl carbonates.\nBoth methodologies exhibit mild reaction conditions and good tolerance\nfor various functional groups. Moreover, the copious derivatization\nof products highlights the utility of the newly synthesized heterobicyclic\nmotifs as versatile building blocks in synthetic chemistry.