Photobromination of indane: preparation of bromoindenones and ready access to benzo[c]fluorenone skeleton

1,1,3,3-Tetrabromoindane and 1,1,2,3,3-pentabromoindane were efficiently synthesized by photolytic bromination of indane. Subsequent dehydrobromination of them gave the corresponding tribromo- and tetrabromoindenes, which were easily converted to the corresponding bromoindenones by silver-supported hydrolysis. Thermolysis of 3-bromoindenone gave the benzo[c]fluorenone derivative.