[6]Radialene (2d) and its hexa-(2a) and dodecamethyl (2c) derivatives were subjected to several novel chemical reactions. Pyrolysis of 2a under flash vacuum conditions provided a mixture of 1,5-hydrogen shift products 9 and 10, and the benzocyclobutenes 5 and 6, produced by electrocyclization of an intermediate o-xylylene derivative 7. At the higher end of the investigated temperature range (200−400°C) the formation of cyclization products 11 was also observed. The hydrocarbon 2c isomerized to the benzocyclobutene 12 under these conditions. Photolysis at 254 nm converted 2c into a novel isomer that, according to X-ray structural analysis, has the unusual twist configuration 14. Compound 2c was photoisomerized through photoinduced hydrogen shift reactions to 15, and the stable p-xylylenes 16 and 17. Dichloroand dibromocarbene add to 2d with formation of the rotaradialene anti adducts 19a and 19b, respectively, the structures of which were also established by X-ray structural analysis. With dichlorocarbene, 2a provided the three dichlorocarbene adducts 20, 22, and 23, whereas methylenation with diiodomethane/trimethylaluminium afforded a complex product