Carbon tetrabromide → 2,7-Dibromo-9-(dibromomethylidene)-9H-fluorene

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Reaction Steps

Triphenylphosphine (34.89 g, 133.0 mmol) was added to a solution of 2,7-dibromofluorenone (17.94 g, 53.08 mmol) in anhydrous tetrahydrofuran (550 mL) under nitrogen and the reaction mixture was heated at just below reflux with stirring. A solution of carbon tetrabromide (35.16 g, 106.0 mmol) in anhydrous tetrahydrofuran (150 mL) was added dropwise over 1.5 h, and the reaction mixture was heated at reflux for 17 h with stirring. After cooling to room temperature, the solvent was removed under reduced pressure and dichloromethane was added forming a slurry. The solid was filtered off and washed with dichloromethane. Recrystallisation of the solid from dichloromethane afforded 2,7-dibromo-9-dibromomethylene-fluorene (2) (15.30 g, 58%) as a bright orange powder, purity 100% (GC): υmax (KBr, cm−1) 3115, 3066, 1605, 1566, 1547, 1450, 1399, 1264, 1073; 1H and 13C NMR spectra as expected; M+=494 (pent).

Provenance & Evidence