ROTATIONAL-ISOMERISM IN FLUORENE DERIVATIVES .4. SYNTHESES OF 9-SUBSTITUTED 1-METHYLFLUORENE DERIVATIVES AND RESTRICTED ROTATION AROUND THE C(9)-C SINGLE BONDS IN THESE COMPOUNDS

Reaction of l-methyl-9-fluorenone [1] with a variety of Grignard reagents or organolithium compounds gave 9-substituted l-methyl-9-fluorenols [4], 9-Alkoxy-9-aryl-l-methylfluorenes [6] were obtained by refluxing the solution of 9-bromo-l-methylfiuorenes [5] in alcohol which in turn were prepared from [4] with HBr in acetic acid. Reduction of [4] with HI in acetic acid gave 9-substituted l-methylfluorenes [7] (e.g., 9-(2-methylphenyl)-[7e], 9-(3-methylphenyl)-[7f}, 9-(4-methylphenyl)-[7g], 9-(l-naphthyl)-[7h], and 9-(2-methyl-l-naphthyl)-l-methyIfluorene [7i]). The restricted rotation around the C.pi-C.,! single bond in [7] has been investigated by means of the DNMR method. Rotational barriers around the Csp2-Csp3(n bond in [7e] (JGtwc =19.6kcal/mol) and [7h] (ΔG115°C=21.4kcal/mol) were found to be 2~3kcal/mol higher than those of 9-(2-methylphenyl)fluorene and 9-(l-naphthyl)fluorene, respectively. © 1979, The Chemical Society of Japan. All rights reserved.