フルオレン誘導体の回転異性 : 第 18 報 9-アリール-1-t-ブチルフルオレン誘導体の配座平衡

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Several 9-aryl-1-t-butyl-9-fluorenol derivatives (aryl- : 2'-methylphenyl-〔4〕, 3'-methylphenyl-〔5〕, 4'-methylphenyl-〔6〕, and 2'-methyl-1'-naphthyl-〔7〕) were prepared from 1-t-butylfluorenone 〔3〕 and corresponding aryllithium. The reactions of these 9-fluorenol derivatives with HI in acetic acid gave corresponding 9-fluorenone derivatives 〔8〕, 〔9〕, 〔10〕, and 〔11〕, respectively. The conformational equilibria of these compounds〔4〕, 〔11〕 between anti-and syn-conformers were investigated on their ^1H NMR spectra. Particularly, in compounds 〔5〕 and 1-t-butyl-9-(3'-methylphenyl) fluorene 〔9〕, their ^1H NMR spectra at low temperature showed equal amounts of the two conformers, and the free energy values of activation for the exchange between the two conformers were obtained (〔5〕 : ΔG_c=12.4 kcal/mol, T_c=-20℃, 〔9〕 : ΔG_c=10.9 kcal/mol, T_c=-50℃).
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