Preparation and structural study of naphtho- and anthrocyclobutene derivatives which have extremely long C–C bonds

1,1,2,2-tetraphenyl-3,8-diiodobuta[b]naphthalene (1c), 1,1,2,2-(2,2′-biphenyl)-3,8-dibromobuta[b]naphthalene (2b), 1,1,2,2-(2,2′-biphenyl)-3,8-diiodobuta[b]naphthalene (2c), and 1,1,2,2,6,6,7,7-octaphenyl-3,5,8,10-tetrachloro-4,9-dimethyldicyclobutaanthracene derivatives (3a–3d) were prepared. X-Ray analysis of 1b, 1c, 2c and 3a showed extremely long C–C bond lengths, 1.712 (5), 1.734 (5), 1.724 (5) and 1.726 (7) Å, respectively.