Carbon tetrabromide → Benzene, 1-(2,2-dibromoethenyl)-4-(phenylmethoxy)-

Participants

Reaction Conditions

Reaction Steps

Carbon tetrabromide (78.1 g, 235.6 mmole) and triphenylphosphine (123.5 g, 471.2 mmole) were combined in 460 ml dichloromethane in a flame dried 1000 ml three neck round bottom flask under nitrogen at 0° C. The mixture was stirred 1 hour at 0° C. and was treated portionwise with 4-benzyloxybenzaldehyde (25 g, 117.8 mmole). The reaction was stirred 30 minutes at 0° C. and was washed successively with 1×100 ml water and 1×100 ml saturated sodium chloride. The organics were dried over magnesium sulfate and were poured into 3 liters hexane. The supernatant was collected and the residue was dissolved in a minimum amount of dichloromethane. This solution was also poured into 3 liters hexane and the process was repeated one more time. The combined supernatants were filtered through a 125 ml plug of silica gel (230-400 mesh) in a 600 ml coarse filter funnel. The plug was washed with 1 liter 15% ethyl acetate/hexane and the combined eluents were concentrated in vacuo to provide 38.2 g (89%) of 2-(4-Benzyloxyphenyl)-1,1-dibromo-ethene as a white solid. Melting Point: 97°-98° C. The dibromo-olefin (20 g, 54.3 mmole) was dissolved in 200 ml dry tetrahydrofuran in a flame dried 500 ml three neck round bottom flask under nitrogen. The solution was cooled to -78° C. and was treated slowly dropwise with butyllithium (70 ml, 108.6 mmole). The reaction was stirred 1 h at -78° C. followed by 1 hour at 0° C. The mixture was cooled to -78° C. and was treated with methyl-chloroformate (4.6 ml, 60 mmole). The reaction mixture was stirred for 20 minutes at -78° C. and then for 1.5 hours at 0° C. The reaction was quenched with 1×100 ml 1:1 saturated ammonium chloride/saturated sodium chloride. The layers were separated and the aqueous layer was washed with 2×100 ml diethyl ether. The combined organics were dried over magnesium sulfate and were concentrated in vacuo to a red oil. The oil was crystallized and then recrystallized from hexane to provide 9.2 g (75%) of methyl-4-benzyloxyphenyl-propiolate as orange tinged flakes. Melting Point: 78° C.

Provenance & Evidence