One‐Pot Synthesis of Helical Azaheptalene and Chiroptical Switching of an Isolable Radical Cation**.

A nitrogen‐centered heptalene, azaheptalene, was designed as a representative of a new class of redox‐responsive molecules with a large steric strain that originates from the adjacent seven‐membered rings. The pentabenzo derivative of azaheptalene was efficiently synthesized by a palladium‐catalyzed one‐pot reaction of commercially available reagents. Bromination led to mono‐ and dibrominated derivatives, the latter of which is interconvertible with isolable radical cation species exhibiting near‐infrared absorption. Since the azaheptalene skeleton shows configurationally stable helicity with a large torsion angle, enantiomers could be successfully separated. Thus, optically pure azaheptalenes with P‐ or M‐helicity showed strong chiroptical properties (|gabs|≥0.01), which could be changed by an electric potential. [ABSTRACT FROM AUTHOR]