2-Bromo-9H-fluorene → 2-Bromo-4',7'-diphenylspiro(fluorene-9,2'-indene)

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Reaction Steps

A 50 wt % aqueous NaOH solution (35 mL) is added to a solution of 2-bromofluorene (5) (2.36 g, 9.63 mmol) and 2′,3′-bis(bromomethyl)-p-terphenyl (4b) (4.0 g, 9.61 mmol) in toluene (70 mL). Subsequently, benzyltriethylammonium chloride (110 mg, 0.483 mmol) is added as a phase transfer catalyst. The reaction mixture is vigorously stirred for 5 h when an additional amount of 2-bromofluorene (5) (0.90 g, 3.92 mmol) is added. The reaction was allowed to continue until 2′,3′-bis(bromomethyl)-p-terphenyl (4b) is completely consumed, as monitored by thin-layer chromatography. The reaction mixture is then shaken with water (200 mL) and methylene chloride (200 mL). The organic phase is separated, and the aqueous phase is extracted with methylene chloride. The combined organic extracts are washed with brine and dried over anhydrous MgSO4. After the solvent is evaporated, the solid residue is washed with a large amount of acetone to yield 2.66 g of (6b) as a white solid product. After the acetone is evaporated, the solid residue is further purified on a silica gel column using petroleum ether/methylene chloride (4:1) as the eluent, yielding additional 0.45 g of (6b). The total yield is 65%.

Provenance & Evidence