sp-9-[o-(β-Chloro-α,α-dimethylethyl)phenyl]fluorene: an Unanticipated Exclusive Product from the Reaction of sp-9-(o-tert-Butylphenyl)-9-fluorenol with Thionyl Chloride

The reaction of sp-9-(o-tert-butylphenyl)-9-fluorenol, (1), with thionyl chloride in CHCl₃ at room temperature quantitatively provided the title compound [(2), (C₂₃H₂₁Cl], instead of the expected 9-(o-tert-butylphenyl)-9-chlorofluorene. Chlorination of an alkyl group under the conditions in which (1) was converted into (2) is apparently unprecedented. While the unexpected structure of (2) was suggested by ¹H and ¹³C NMR, unequivocal characterization required X-ray crystallographic analysis. Surprisingly, introduction of the Cl atom in (2) imposes only a few minor changes in the bonding parameters compared with its non-chlorinated counterpart, sp-9-(o-tert-butylphenyl)fluorene.