| 83% |
Stage #1: triphenylmethylphosphonium bromide With n-butyllithium In tetrahydrofuran at 0℃;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 0 - 20℃; |
36
Preparation 36 1-bromo-3-(prop-1-en-2-yl)benzene Methyltriphenylphosphonium bromide (35.7 g, 97.9 mmoles, 1.3 equiv) is suspended in tetrahydrofuran (100 mL) and cooled to 0° C. N-Butyllithium (2.5M in hexanes, 27.0 g, 97.7 mmoles, 39.2 mL, 1.3 equiv) is added slowly to the mixture via an addition funnel. The resulting solution is stirred for 1 h at 0° C. A solution of 3-bromoacetophenone (15.0 g, 75.3 mmoles, 10.0 mL, 1.0 equiv) in tetrahydrofuran (50 mL) is added slowly via an addition funnel. The resulting mixture is warmed to room temperature and stirred for 3 h. The reaction is cooled to 0° C. and quenched with saturated aqueous ammonium chloride solution. The layers are partitioned in a separatory funnel and the aqueous phase is extracted with hexanes. The combined organic phase is dried over anhydrous sodium sulfate, filtered, and allowed to stand overnight at room temperature. The organic phase is decanted from a precipitate and concentrated under reduced pressure. The resulting solid is diluted with hexanes and filtered. The precipitate is washed with hexanes. The filtrate is concentrated and the resulting mixture is purified by silica gel flash column chromatography (hexanes) to give the title compound (83% yield): 1H NMR (CDCl3, 400 MHz) δ 7.59 (t, 1H, J=1.72 Hz), 7.40-7.36 (m, 2H), 7.18 (t, 1H, J=8 Hz), 5.36 (s, 1H), 5.12-5.10 (m, 1H), 2.13-3.11 (m, 3H). |
| 83% |
Stage #1: triphenylmethylphosphonium bromide With n-butyllithium In tetrahydrofuran; hexane at 0℃;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran; hexane at 0 - 20℃; |
|
| 71% |
Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In diethyl ether for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In diethyl ether Inert atmosphere; |
|
| 64% |
Stage #1: triphenylmethylphosphonium bromide With n-butyllithium In tetrahydrofuran at 0℃; for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 0 - 20℃; Inert atmosphere; |
|
|
Stage #1: triphenylmethylphosphonium bromide With sodium bis-(trimethyl-silyl)amide In tetrahydrofuran at 0℃; for 0.5h;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at -78 - 25℃; for 0.5h; |
1.1
Intermediate 1; Step 1. Preparation of 1-bromo-3-(2-propenyl) benzene; A solution of NaHMDS in THF (1.0 M, 18.0 mL, 18.0 mmol) was added to a suspension of methyltriphenylphosphonium bromide (6.4 g, 18.0 mmol) in THF (60 mL) that was cooled with an ice bath. The resulting orange-colored suspension was stirred for 30 min and then cooled to-78 °C. 3- Bromoacetophenone (3.0 g, 15.0 mmol) was added dropwise. After 30 min at-78 C, the reaction mixture was warmed to 25 °C and quenched with acetic acid (1.0 rnL). After removal of the solvent, the residue was triturated with ethyl acetate/hexane (3: 7,100 mL) and filtered through a short column of silica gel. Concentration of the filtrate gave the title compound. HNMR (500MHz, CDCl3) o7. 62 (t, J = 2. 5 Hz, 1H), 7.50 (m 1 H), 7.41 (m, 1H), 7.22 (t, J = 8. 5 Hz, 1H), 5.40 (s, 1H), 5.15 (s, 1H), 2. 16 (s, 3H). |
|
Stage #1: triphenylmethylphosphonium bromide With sodium bis-(trimethyl-silyl)amide In tetrahydrofuran at 0℃; for 0.5h;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at -78 - 25℃; for 0.5h; |
1
A solution of NaHMDS in THF (1.0 M, 18.0 mL, 18.0 mmol) was added to a suspension of methyltriphenylphosphonium bromide (6.4 g, 18.0 mmol) in THF (60 mL) cooled with an ice bath. The resulting orange-colored suspension was stirred for 30 min and then cooled to -78 0C. 3-Bromoacetophenone (3.0 g, 15.0 mmol) was added dropwise. After 30 min at -78 C, the reaction mixture was warmed to 25 °C. and quenched with acetic acid (1.0 mL). After removal of the solvent, the residue was triturated with ethyl acetate/hexane (3 : 7, 100 mL) and filtered through a short column of silica gel. Concentration of the filtrate gave the title compound. 1H NMR (500 MHz, CDCl3) δ 7.62 (t, J = 2.5 Hz, IH), 7.50 (m 1 H), 7.41 (m, IH), 7.22 (t, J = 8.5 Hz, IH). |
|
Stage #1: triphenylmethylphosphonium bromide With n-butyllithium In diethyl ether; hexane for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In diethyl ether; hexane at 20℃; for 24h; Inert atmosphere; |
|
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Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In tetrahydrofuran at 0 - 25℃; for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 0℃; for 24h; Inert atmosphere; |
101.1 Step 1
To a suspension of Ph3PMeBr (21.4 g , 60.0 mmol) in THF (500 mL) was added i-BuOK (6.72 g, 60.0 mmol) at 0°C. The resulting mixture was stirred at rt for 1 h. To the mixture was added l-(4-bromophenyl)ethanone (10.0 g, 50.0 mmol ) dropwise at 0°C, then was stirred for 24 h. H20 (300 mL) was added, and the mixture was extracted with EtOAc (300 mL x 2). The combined organic layers were washed with brine (300 mL), dried over Na2S04, filtered and concentrated in vacuo. The residue was purified by column chromatography on silica gel (Hexanes/EtOAc: 20: 1) to afford l-bromo-4- (prop-l-en-2-yl)benzene. |
|
Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In tetrahydrofuran at 0 - 20℃; for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 0℃; for 24h; |
1-bromo-3-(prop-1-en-2-yl)benzene
To a suspension of Ph3PMeBr (21.4 g, 60.0 mmol) in THF (500 mL) was added t-BuOK (6.72 g, 60.0 mmol) at 0°C. The resulting mixture was stirred at rt for 1 h. To the mixture was added i-(4-bromophenyl)ethanone (10.0 g, 50.0 mmol) dropwise at 0 °C, then was stirred for 24h. H20 (300 mL) was added, and the mixture was extracted with EtOAc (300 mL x 2). Thecombined organic layers were washed with brine (300 mL), dried over Na2504, filtered andconcentrated to a residue that was purified by colunm chromatography on silica gel (Hexanes/EtOAc: 20:1) to afford (±) i-bromo-4- (prop-i-en-2-yl)benzene, I-75a. |
|
Stage #1: triphenylmethylphosphonium bromide With sodium bis-(trimethyl-silyl)amide In tetrahydrofuran at 0℃; for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 0 - 20℃; |
General procedure for the synthesis of alkenes by Wittig reaction
General procedure: Under N2, a two-neck 100 mL round-bottom flask was charged with Wittig reagent (13 mmol) and dry THF (10.0 mL). Then the suspension was cooled to 0 °C and sodium hexamethyldisilazide (1 M THF solution, 13.0 mL, 13 mmol) was added into the reaction mixture. The resulting solution was stirred for 1 h at 0 °C. Next, a THF (6.0 mL) solution of ketone (10 mmol) was added at 0 and stirred at room temperature overnight. Finally H2O was added into the reaction mixture, and thereaction mixture was extracted with dichloromethane. The organic layer was washed with H2O, dried (Na2SO4), and filtered. The filtrate was concentrated in vacuo and the residue was purified by flash column chromatography on silica gel to afford alkenes as a product. 1-bromo-3-(prop-1-en-2-yl)benzene (2b) 1H NMR (400 MHz, CDCl3, rt): δ 7.60 (t, 1H, J = 2.0 Hz), 7.41-7.37 (m, 2H), 7.20 (t, 1H, J = 7.5 Hz), 5.37 (s, 1H), 5.13 (s, 1 H), 2.13 (s, 3H). Spectral data was in agreement with the values reported in the literature.[2] |
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With n-butyllithium In diethyl ether; hexane at 20℃; for 25h; Inert atmosphere; |
|
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Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In tetrahydrofuran at 0℃; for 0.75h;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 0 - 20℃; for 16h; |
|
|
Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In tetrahydrofuran at 0℃; for 0.75h;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 20℃; for 16h; |
|
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Stage #1: triphenylmethylphosphonium bromide With n-butyllithium In tetrahydrofuran; hexane at 0℃; for 1h; Inert atmosphere; Schlenk technique;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran; hexane at 0 - 20℃; Inert atmosphere; Schlenk technique; |
|
|
Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In tetrahydrofuran at 20℃; for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 20℃; Inert atmosphere; |
|
|
Stage #1: triphenylmethylphosphonium bromide With potassium-t-butoxide In tetrahydrofuran at 20℃; for 1h; Inert atmosphere;
Stage #2: 1-(3-Bromophenyl)ethanone In tetrahydrofuran at 20℃; for 1h; Inert atmosphere; |
2.2 One typical example for the preparation of alkenes.
General procedure: To a suspension of tBuOK (12 mmol, 1.2 equiv.) in anhydrous THF (20 mL) was added MePPh3Br (12 mmol, 1.2 equiv.) under argon atmosphere. The suspension was stirred at room temperature for 1 h. Then corresponding ketone (10 mmol, 1.0 equiv.) was added and the reaction mixture was stirred at the same temperature for 1 h . Then the mixture was filtered through a short pad of silica gel, which was subsequently washed with ethyl acetate (200 mL). After evaporation of the organic solvent, the residue was purified by silica gel column chromatography to provide alkene 1i (1.31g, 90%). |
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