Photoexcited Nitroarenes: A Workhorse for Strategic Synthesis of N‑Heterocycles via Reductive C–N Coupling/Cyclization Cascade

Owing to their distinct electron-withdrawing properties,
a combined
nitro-assisted functionalization followed by tandem nitro group manipulation
is emerging to streamline pharmaceutical synthesis. Herein, we disclose
an expedient protocol for the synthesis of N-heterocycles,
such as N-aryl indole, oxindole, benzoxazinone, and
(tetrahydro)quinolinone, from photoexcited o-tethered
nitroarenes at ambient temperature through a tandem C–N coupling/intramolecular
cyclization. A nitrene intermediate is formed to furnish intermolecular
C–N coupling with boronic acids, followed by intramolecular
cyclization with pendant functional groups in a single operation.
This metal-free, cascade annulation reaction is scalable and has been
applied to the synthesis of APIs and drugs.