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            Cyclic diaryl ethers are present in multiple natural compounds, organic pollutants
               as well as in π-conjugated organic molecular materials. This short review aims at
               overviewing the main synthetic advances in the O-annulation methods for preparing
               five-, six-, and seven-membered rings through C–H cleavage.
            
            1 	Introduction
            
            2 	Five-Membered Rings: The Dibenzofuran (DBF) Motif
            
            2.1 	Palladium-Catalysed C–H Activation
            
            2.2 	Copper-Catalysed C–H Activation
            
            2.3 	Non-CH Activation Oxidant-Mediated Cyclisation
            
            2.4 	Light-Mediated Cyclisation
            
            2.5 	Acid-catalysed C–O Cleavage/C–O Formation
            
            3 	Six-Membered Rings: DBX, PXX, Xanthone, and Their Derivatives
            
            3.1 	Dibenzoxanthene (DBX)
            
            3.2 	Peri-Xanthenoxanthene (PXX)
            
            3.3 	Xanthones
            
            3.4 	Miscellaneous
            
            4 	Seven-Membered Rings: Cularine
            
            5 	Conclusion
            
         
         Key words
cyclic diaryl ether - oxidative cyclisation - cycloetherification - C–H activation
            - C–O bond formation - O-annulation - pyrans - furans - cularine