An example of a novel formation of an oxepin

A novel formation of an oxepin, namely 9,10,11,12-tetrafluoro-5,6-dihydrobenzob]naphth2,1-f]oxepin (5) , starting from pentafluoroacetophenone and 1-tetralone is described. Also, the same synthesis using 1-indanone affords a very different ring system namely 1,2,3,4-tetrafluoro-5,11b-dihydro-7H-benzoc]fluoren-7-one (10) . Both synthesis undergo an intramolecular nucleophilic substitution of an ortho-fluorine. In one case, the oxygen displaces the fluorine to afford the oxepin 5 and the other a carbon is used as the nucleophile to give the polycyclic ring system 10 .