10-(3,5-Di-<em>tert</em>-butylphenyl)-9-Mesitylacridinium Tetrafluoroborate

9-Mesitylacridinium salts are widely recognized as efficient organic photoredox catalysts owing to their strong excited-state oxidizing power and stability under visible-light ir-radiation. In this study, a new mesityl acridinium derivative bearing a di-tert-butylphenyl substituent on the nitrogen atom was synthesized. The introduction of tert-butyl groups on the N-aryl moiety was primarily aimed at improving solubility and chemical stability of the acridinium salt. The target compound was obtained in high overall yield starting from a 9(10H)-acridinone precursor through a concise synthetic sequence. The synthesis consists of a copper-catalyzed C–N coupling reaction to install the aryl substituent on the nitrogen atom, followed by a Grignard reaction and subsequent acid treatment to afford the corresponding acridinium salt. All transformations proceeded smoothly, providing efficient access to the desired novel acridinium derivative. This work presents a practical example of structural modification of mesitylacridinium derivatives directed toward enhanced solubility and stability, and provides a useful synthetic plat-form for the preparation of structurally diverse acridinium salts.