Herein, we report a unified approach to azepines by dearomative photochemical rearrangement of aromatic N-ylides. Deprotonation of quaternary aromatic salts with 1,8-diaza­bicyclo­[5.4.0]­undec-7-ene (DBU) or N,N,N′,N’-tetramethyl­quanidine (TMG) under visible light irradiation provides mono- and polycyclic azepines in yields up to 98%. This ring-expansion presents a new mode of access to functionalized azepines from N-heteroarenes using two straightforward steps and simple starting materials.

We report the multigram scale synthesis of heterodimeric β-truxinic imides piperarborenines C-E using a catechol-tethered diastereoselective intramolecular [2 + 2] photocycloaddition. Key innovations lie in the use of catechol as a practical auxiliary for the synthesis of homo- and heterodimeric β-truxinates and the use of a UV-LED flow photoreactor in the [2 + 2] step. This approach is highly scalable, requiring a single column purification, no photocatalysts, and no cryogenic conditions.

We report the development of a multigram scale total synthesis of heterodimeric β-truxinic imides piperarborenines C-E using a catechol-mediated diastereoselective intramolecular [2+2] photocycloaddition. Key innovations lie in the use of (1) catechol as a highly selective auxiliary for the robust and scalable synthesis of homo- and heterodimeric β-truxinates, (2) UV LEDs for direct excitation in the [2+2] cycloaddition step, and (3) a bis pentafluorophenyl ester and LDA for the challenging installation of the syn dihydropyridinone imides. This approach is exceptionally scalable – requiring minimal chromatography, no photocatalysts, and no cryogenic conditions - and will enable thorough evaluation of the biological properties and anticancer profiles of piperaborenines C-E and derivatives thereof.