Microwave-Assisted Buchwald-Hartwig Double Amination: A Rapid and Promising Approach for the Synthesis of TADF...

We herein report a microwave-assisted Buchwald-Hartwig double amination reaction to synthesize potential thermally activated delayed fluorescence compounds, forming C(sp²)-N bonds between donor and acceptor units. Our approach reduces reaction times from 24 h to 10-30 min and achieves moderate to excellent yields, outperforming conventional heating methods. The method is compatible with various aryl bromides and secondary amines, including phenoxazine, phenothiazine, acridine, and carbazole. Density functional theory calculations have attributed the lack of reactivity with high energy barriers in the reductive elimination (RE) steps. Electron-withdrawing groups such as CF₃ increase the RE barrier, resulting in a 0% yield, while substituting carbazole with acridine lowers the barriers and enhances higher yields. Distortion-interaction analysis highlights steric hindrance as a key factor affecting the reaction outcome when the RE barrier is low and steric hindrance is minimal. This microwave-assisted method not only demonstrates a superior performance in terms of higher yields and shorter reaction times but also offers significant potential for reducing production costs of these materials.