The double Friedel–Crafts acylation of readily accessible biaryls with oxalyl chloride delivers the respective phenanthrene-9,10-diones, providing an alternative to the traditional methods, which require harsh oxidizing conditions and multistep sequences. This simple method allows the synthesis of various symmetrical and non-symmetrical targets, and is even effective for the synthesis of the parent ring system from (unactivated) biphenyl.
Key words
cyclization - electrophilic aromatic - substitution - fused-ring systems - Friedel–Crafts acylation - phenanthrene-9,10-diones