Activation of Anthraquinone's Electrophilicity by Light for a Dynamic C-O Bond.

Coupling of photoswitching with dynamic covalent chemistry enables control of the formation and cleavage of covalent bonds by light irradiation. -Aryloxyanthraquinones feature an exclusive ability to switch electrophilicity by interconversion between - and -quinone isomers, which was used for the first time for the implementation of a dynamic C-O bond. Photogenerated -isomers undergo a concerted -Michael addition of phenols to give hitherto unknown 4-hydroxy-10,10-diaryloxyanthracen-9-ones. These species were found to be in equilibrium with the corresponding -quinones, thus forming a dynamic covalent system of a new type. Withdrawal of the colored -quinones from the equilibria by visible light irradiation resulted in two -quinones with "locked" aryloxy groups.