Hydrochloric Acid → 2,2,3,3-Tetrafluoro-5-nitrobenzofuran

Participants

Reaction Steps

Into a pressure bottle was placed 10.0 g (0.028 mole) 3-chloro-4-(2-bromo-1,1,2,2-tetrafluoroethoxy)nitrobenzene, 9.0 g (0.14 mole) copper powder (200 mesh), 0.45 g (0.0028 mole) 2,2'-bipyridyl, and 40 mL of dimethylsulfoxide. The pressure bottle was sealed and the reaction mixture stirred at 190°-195° C. for two hours. The pressure bottle was cooled to room temperature, opened, and the contents poured into a separatory funnel. Approximately 200 mL of a 2N hydrochloric acid solution was added to the separatory funnel. The mixture was extracted with three 150 mL portions of diethyl ether. The extracts were combined and washed in succession with 200 mL of a 2N hydrochloric acid solution, 200 mL of a saturated aqueous sodium chloride solution, and 200 mL of a 2N sodium hydroxide solution. The washed extract was dried over anhydrous magnesium sulfate and filtered. The solvent was evaporated under reduced pressure leaving an oil. The reaction described above was repeated six additional times. The residual oils from the seven experiments were combined and subjected to column chromatography on silica gel, eluting with toluene, to yield a yellow oil. This oil was dissolved in 125 mL methylcyclohexane and the solution placed in a freezer for approximately 18 hours. Crystals had formed and were collected by filtration to yield 20.7 g 2,3-dihydro-2,2,3,3-tetrafluoro-5-nitrobenzofuran. The filtrate was evaporated under reduced pressure leaving an oil. Distillation of this oil under reduced pressure provided an additional 3.0 g of product (bp 75° C./0.2 mm). Hydrogenation of 2.15 g (0.011 mole) 2,3-dihydro-2,2,3,3-tetrafluoro-5-nitrobenzofuran with a catalytic amount (0.25 g) of platinum oxide in 150 mL of methanol produced 2.15 g of 5-amino-2,3-dihydro-2,2,3,3-tetrafluorobenzofuran.

Provenance & Evidence