2-(9H-fluoren-9-yl)benzoic acid (1H). Methyl ester precursors for 1H and its para-carboxy isomer, 4-(9H-fluoren-9-yl)benzoic acid, were prepared from fluorene and the appropriate aryl bromide following the procedure of Chen and co-workers (22). The isolated methyl ester (1.252 g, 4.17 mmol) was added to a degassed solution of ethanol (120 ml) and 3 M aqueous KOH (30 ml). This solution was brought to reflux for 25 min, after which the reaction mixture was cooled to room temperature and diluted with 1 M HClaq (100 ml), at which point a precipitate formed. The suspension was cooled in a refrigerator overnight and filtered, and the filtrate was washed with water to yield the product as a white solid (1.107 g, 3.87 mmol). The 1H NMR in CDCl3 matched a previous report (23). 1H NMR (400 MHz, CD3CN) δ [parts per million (ppm)]: 6.33 (s, 1H, Fl–9H), 6.39 (d, 1H), 7.23 to 7.34 (m, 6H), 7.42 (td, 2H), 7.90 (d, 2H), 8.03 (d, 1H), 9.77 (carboxylic acid, brs, 1H).

2-(9D-fluoren-9-yl)benzoic acid (1-d1). Following literature precedent (24), 1H (0.143 g, 0.5 mmol) was dissolved in anhydrous THF (15 ml) under an inert atmosphere and cooled to −78°C. n-Butyllithium (0.625 ml of 1.6 M solution in hexanes, 1 mmol) was added dropwise, yielding a bright red-orange solution. After stirring for 2 hours, the reaction mixture was allowed to warm to room temperature and was then quenched with D2O (0.5 ml) and stirred an additional 15 min. The reaction mixture was diluted with water (100 ml) and made acidic with HCl(aq) and then washed with DCM (3 × 30 ml). The organics were washed with water (2 × 30 ml) and then brine (30 ml) and dried with magnesium sulfate. Removal of solvent yielded a white solid product (0.133 g, 0.46 mmol). High conversion of 1 to 1-d1 was confirmed by the absence of any detectable peak at δ = 6.39 ppm (in CDCl3) in the 1H NMR spectrum.

4-(9H-fluoren-9-yl)benzoic acid. This para-carboxy isomer of 1H was prepared via the methyl ester (22) under the same conditions used for 1H. The 1H NMR spectrum in DMSO-d6 is consistent with a literature report (25). 1H NMR (400 MHz, CD3CN) δ (ppm): 9.37 (brs, 1H), 7.91 (dd, 4H), 7.44 (ddd, 2H), 7.29 to 7.32 (m, 4H), 7.18 (d, 2H), 5.26 (s, 1H).

2-(1-Phenylvinyl)benzoic acid (5). 2-(1-Phenylvinyl)benzoic acid (5) was prepared from 2-benzoylbenzoic acid, methyltriphenylphosphonium bromide, and potassium tert-butoxide after a literature procedure (26). 1H NMR (400 MHz, CDCl3) δ (ppm): 10.82 (brs, 1H), 7.94 (dd, 1H), 7.50 (td, 1H), 7.35 (td, 1H) 7.27 (dd, overlapping with solvent), 5.13 (m, 1H), 4.90 (m, 1H).

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