Trifluoroacetic acid → 2,3',5-Trimethyl-1,1'-biphenyl

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A round bottomed flask was purged with argon and charged with alcohol 1 (1.78 g, 7.0 mmol), dichloromethane (28 mL), triethylsilane (1.5 mL, 9.1 mmol), and trifluoroacetic acid (1.1 mL, 14.7 mmol). The mixture was stirred at room temperature for 1.5 h, then was quenched with solid potassium carbonate (ca 2 g). The mixture was diluted with ether (50 mL) and transferred to a separatory funnel. The mixture was washed with saturated aqueous NaHCO3 (50 mL), and the organic phase was dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo to afford a mixture of 2 and 1-(2-bromophenyl)cyclohexene. The crude material was placed into a round bottomed flask, and the flask was purged with argon. THF (2 mL) was added, and the mixture was cooled to 0° C. with stirring. A solution of BH3 in THF (7 mL, 1M, 7.0 mmol) was added dropwise to the mixture. The mixture was stirred at 0° C. for 1.5 h, then warmed to room temperature and stirred for 19 h. Acetic acid (4 mL) was added and the mixture was stirred at room temperature for 6h. The mixture was then diluted with ether (50 mL) and poured into a separatory funnel. The mixture was washed with 1M NaOH (50 mL), the layers were separated, and the aqueous phase was extracted with ether (50 mL). The combined organic phases were washed with brine (50 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. The crude material was purified by flash chromatography on silica gel to afford 555 mg of 2 which was judged to be 93% pure by GC analysis. This material was used without further purification.

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