Late-Stage C─N Bond Cleavage Enables Diversification of Multiple Resonance Materials

Recent advances in materials development for organic light-emitting diodes (OLEDs) have been driven by an emerging design concept known as multiple-resonance (MR), which provides the benefits of high efficiency and color purity required for commercial OLED displays. Borylation reaction constructing MR frameworks is a key step for developing new π-conjugated systems, while this reaction includes the limitation of selectivity, making it challenging to control reactions in elaborate molecular structures. Although a wide variety of MR compounds have been prepared through carefully planned synthetic schemes based on retrosynthetic analysis, these tasks typically require significant effort for each individual target. Herein, we demonstrate a successful late-stage functionalization strategy that enables structural modifications after the borylation reaction, especially in hardly accessible regions in MR structures via carbon-nitrogen bond cleavage. Our new synthetic method also allows access to new products which were never feasible before. The newly developed material, DABNA-dimer, proves the impact of late-stage functionalization on OLED characteristics. The present study serves as a proof-of-concept for a diversity-orientated synthesis in the development of MR materials.