| 85% |
With phosphorus tribromide In neat (no solvent) at 20 - 80℃; for 2.5h; Inert atmosphere; |
|
| 79% |
With phosphorus tribromide at 100℃; for 4h; |
|
| 79% |
With phosphorus tribromide at 100℃; Inert atmosphere; |
|
| 72% |
With sulfuric acid; hydrogen bromide for 3h; Heating; |
|
| 72% |
With phosphorus tribromide at 80℃; for 3h; Inert atmosphere; |
|
| 69% |
With carbon tetrabromide; triphenylphosphine In dichloromethane Inert atmosphere; |
|
| 62.9% |
With carbon tetrabromide; triphenylphosphine In dichloromethane at 15℃; for 16h; |
75.1 1. Preparation of compound 2.
To a solution of compound 1 (72.00 g, 358.10 mmol) and PPh3 (112.71 g, 429.72 mmol) in anhydrous DCM (800 mL) at 15 °C was added CBr4 (142.51 g, 429.72 mmol). The resulting mixture was stirred at 15 °C for 16 hr. TLC showed the reaction was completed. The resulting mixture was concentrated to afford the product as a light-yellow crude oil. The residue crude was purified by column chromatography on silica gel (Petroleum ether) to afford compound 2 as a light-yellow oil (59.5 g, 62.9%). ‘H NMR (400 IVIHz, CHLOROFORM-d) = 7.56 (br d, J=7.7 Hz, 1H), 7.30 - 7.24 (m, 2H), 7.17 - 7.10 (m, 1H), 3.63 - 3.56 (m, 2H), 3.30 (br t, J7.5 Hz, 2H). TLC (Petroleum ether/Ethyl acetate = 10:1) Rf= 0.78. |
|
With phosphorus tribromide |
|
|
Multi-step reaction with 2 steps
1: Et3N / tetrahydrofuran / 2 h / 0 °C
2: LiBr / tetrahydrofuran / 16 h / Ambient temperature |
|
|
With phosphorus tribromide |
1.E E.
E. o-Bromophenethyl bromide To 550.0 g of o-bromophenethyl alcohol, while stirring, is added, dropwise, 375.0 g of phosphorus tribromide. After stirring for three hours at room temperature, the reaction mixture is heated on a steam bath for three hours and then poured into 6 kg of crushed ice. The mixture is extracted with three 600 and two 200 ml portions of ether. The ether extracts are washed, dried, concentrated, and the residue is distilled to give 531.0 g of o-bromophenethyl bromide, bp. about 86°-88° (0.9mm), nD26 1.5922. |
|
With pyridine; Ph3PBr2 In diethyl ether; acetonitrile |
58.A 2-(2-Bromoethyl)bromobenzene
EXAMPLE 58A 2-(2-Bromoethyl)bromobenzene A solution of 2-bromophenethyl alcohol (5.05 g, 25.1 mmol) and pyridine (3.65 mL, 45.2 mmol) in acetonitrile (60 mL) was treated with Ph3PBr2 (13.8 g, 32.65 mmol), stirred at 0° C. for 2 h, diluted with hexanes and filtered through a plug of silica gel with 25% diethyl ether/hexanes to provide 6.0 g of the title compound. MS (DCI/NH3) m/e 263 (M+H)+. |
|
With carbon tetrabromide; triphenylphosphine In dichloromethane |
|
|
With carbon tetrabromide; triphenylphosphine In dichloromethane at 0 - 25℃; |
|
|
With phosphorus tribromide In diethyl ether at 0 - 20℃; for 16h; Schlenk technique; |
a. Synthesis of 2-bromo-1-(bromomethyl)-3-methylbenzene
General procedure: BH3·Me2S (11 mL, 116 mmol, 1.2 equiv) was slowly added to a solution of2-bromo-3-methylbenzoic acid (21.0 g, 98 mmol) in THF (150 mL). The reactionmixture was heated at reflux for 16.5 h. Then, a 2M solution of NaOH was added andthe resulting mixture was stirred for 30 min. The aqueous layer was extracted threetimes with ether. The combined organic layers were washed with water and brine, anddried over MgSO4. Evaporation of the solvent afforded(2-bromo-3-methylphenyl)methanol (18.9 g, 94 mmol, 96% yield).A solution of (2-bromo-3-methylphenyl)methanol (19 g, 94 mmol) in ether (200 mL)was cooled to 0 °C. To the solution was added phosphorus tribromide (9.4 mL, 103mmol, 1.1 equiv) dropwise and the mixture was stirred at room temperature for 16.5 h.Methanol (35 mL) and water (100 mL) were added to quench the reaction. The organicphase was washed with water and brine. The organic phase was dried over Na2SO4,filtered, and evaporated under reduced pressure to give2-bromo-1-(bromomethyl)-3-methylbenzene (23.5 g, 90 mmol, 96% yield). Spectraldata were in good agreement with literature values.7 |
|
With phosphorus tribromide at 0 - 100℃; |
To a crude material s4 was added PBr3 (0.53 mL, 5.63 mmol) at 0 °C, then heated to 100 °C. Aftercooling to room temperature, the reaction was stopped by adding H2O. The crude mixture wasextracted with CH2Cl2 (x4) and the combined organic extracts were washed with brine, dried(Na2SO4), and concentrated in vacuo to give crude s5 (1.91 g) as pale yellow oil. This crudematerial was used for next reaction without further purification. |
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