Efficient Synthesis of Anthraquinones from Diaryl Carboxylic Acids via Palladium(II)‐Catalyzed and Visible Light‐Mediated Transformations

• DOI: 10.1002/adsc.201601057
• Publication Date: 2016-12-17T09:38:41Z
• Authors: Kiho Kim; Minsik Min; Sungwoo Hong
• Keywords: 7. Clean energy; 01 natural sciences; 0104 chemical sciences

AbstractIrradiation of 9‐ester‐substituted anthracenes with visible light results in the formation of endoperoxides in the absence of a photocatalyst, which further undergo base‐assisted fragmentation to afford anthraquinones. The excited state species of anthracene generated by energy transfer, interacts with 3O2 to afford 1O2 by energy transfer and undergoes cycloaddition with 1O2. By employing palladium(II)‐catalyzed and visible light‐mediated transformations, we have developed an efficient synthetic protocol for accessing diverse anthraquinones from readily available diaryl carboxylic acids. The optimal result was obtained with palladium(II) acetate, Ac‐Ile‐OH, benzoquinone and potassium carbonate in tert‐amyl alcohol under O2 at 90 °C with irradiation from a 30 W fluorescent light bulb.magnified image