The　synthesis,　properties,　and　application　of　carbonyl-bridged　phenanthrene,　namely　phenanthrenone,　are　described.　A　novel　synthetic　route　involving　palladium-catalyzed　annulation　between　4,5-dibromo-9-fluorenone　and　internal　alkynes　was　developed　to　streamline　the　synthesis　of　phenanthrenone,　an　underexplored　building　block.　The　reaction　tolerates　a　variety　of　substituents　on　the　alkynes　and　provides　moderate　yields.　Phenanthrenone　derivatives　possess　the　advantages　of　both　fluorenone　and　phenanthrene　backbones,　such　as　extended　conjugation,　good　planarity　and　rigidity,　and　tunable　energy　gaps.　These　attractive　features　make　phenanthrenone　an　ideal　electron-deficient　π-building　block　for　developing　novel　polycyclic　aromatic　hydrocarbons.　In　addition,　phenanthrenone　derivatives　can　serve　as　organic　photoredox　catalysts　for　organocatalytic　atom　transfer　radical　polymerization　and　oxidation　of　alcohol.　©　2023　The　Royal　Society　of　Chemistry.