Metal‐Free One‐Pot Access to Benzofuran Building Blocks Toward Efficient Narrowband Blue–Cyan Emitters

ABSTRACT

A metal‐free amino‐group‐directed regioselective cyclization from α‐diketone compounds and diarylamines is reported for the synthesis of benzofuran derivatives. The transformation proceeds through sequential intermolecular and intramolecular Friedel–Crafts‐type processes under acidic conditions, enabling one‐pot construction of fused benzofuran frameworks. The method shows good substrate scope, providing products in moderate yields and demonstrating gram‐scale practicality. Based on this scaffold, two donor units are developed and incorporated into multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters, namely BNFFA and BNFFC. Both compounds exhibit narrowband emission (full with at half maximum = 20 and 25 nm) and decent delayed fluorescence. Organic light‐emitting diodes based on these emitters achieved maximum external quantum efficiencies of 23.5% and 29.3%, with blue‐cyan emissions suitable for emerging four‐primary wide‐color‐gamut displays.