Synthesis of Benzofuro- and Indolo[3,2‑b]indoles via Palladium-Catalyzed Double N‑Arylation and Their Physical Properties

Two kinds of ladder-type π-conjugated compounds, benzofuro­[3,2-b]­indoles (BFIs) and indolo­[3,2-b]­indoles (IIs), were successfully synthesized using palladium-catalyzed double N-arylation of anilines with the corresponding dihalobiaryls. Photophysical properties were evaluated by UV–vis and photoluminescence spectroscopies and theoretical calculations. BFI derivatives showed higher quantum yields (33–39%) than the II derivative (29%). The absorption bands of the II derivative were more red-shifted compared to BFI derivatives.