Spiro [fluorene-9, 3'-indazole](l), obtained along with 9-fluorenyl anthranilate (6) by aprotic diazotization of anthranilic acid in the presence of 9-diazofluorene (3), thermolyzes to fluoradene (2), lZ, lZ'-bifluoradene (81, and 9-phenylfluorene (9). Thermolysis and photolysis of 1 in solution are interpretable on the basis of formation of triplet 2-(9-fluorenylidene)-3, 5- cyclohexadienylidene (13), isomerization of 13 to 2, and hydrogen abstraction by 13 to ...