| 98% |
With potassium carbonate |
|
| 98% |
Stage #1: 1,3-dimethoxy-2-hydroxy-benzene With potassium carbonate In acetone at 0℃; for 0.0833333h;
Stage #2: allyl bromide In acetone for 6h; Reflux; |
Synthesis of 4-allyl-2,6-dimethoxyphenol (10)
To a stirred suspension of K2CO3 (8.2 g, 59 mmol) in dry acetone (30 mL) was added solution of commercially available phenol 8a (4.2 g, 27 mmol) in dry acetone (15 mL) at 0 °C. The reaction mixture was stirred at same temperature for 5 min followed by dropwise addition of allyl bromide (3.77 g, 2.64 mL, 32 mmol) and reaction mixture was then refluxed for 6 hrs. Upon completion (TLC monitoring) reaction mixture was filtered, washed with ether and concentrated to get analytically pure compound, 2-(allyoxy)-1,3-dimethoxybenzene (9) as a viscous oil (5.56 g, 98%). The compound obtained was pure enough to be used for next reaction without further purification. To the compound 2-(allyoxy)-1,3-dimethoxybenzene (9) (9 g, 43.2 mmol) was added 30 mL of dichlorobenzene (DCB) and reaction mixture was refluxed continuously for 6 hrs on completion reaction mixture was cooled and directly loaded over silica column and purified by column chromatography over silica gel using EtOAc/pet ether (0:100 to 10:90) as eluent to get pure Claisen rearranged phenolic compound 4-allyl-2,6-dimethoxyphenol (10) as viscous colorless oil (7.92 g, 88%). |
| 94% |
With potassium carbonate In acetone at 20℃; for 24h; |
|
| 94% |
With potassium carbonate In acetone at 20℃; for 24h; |
4.2. Synthesis of 2-(Allyloxy)-1,3-dimethoxybenzene (2)
To a solution of 2,6-dimethoxyphenol (syringol, 1, 3 g, 0.016 mol) in acetone (50 mL) was addedpotassium carbonate (2.5 g, 0.018 mol) and allyl bromide (2.17 g, 0.018 mol). After stirring the mixtureovernight, the solvent was removed and 3N HCl (15 mL) was added to it. The extraction was performedwith ethyl acetate, the organic fraction so obtained was washed with brine solution and then driedover anhydrous Na2SO4. The solvents were removed at reduced pressure. Purification of the residuewas performed by flash chromatography (eluent: petroleum ether/ethyl acetate, 15:1, v/v) to yieldcompound 2 (4.74 g, 94%); colorless oil: 1H-NMR (400 MHz, CDCl3): (ppm) = 3.84 (s, 6H), 4.47(d, 2H, J = 6.0 Hz), 5.13 (dd, 1H, J = 10.4, 1.0 Hz), 5.25 (dd, 1H, J = 17.2, 1.6 Hz), 6.03 (m, 1H), 6.49(d, 2H, J = 12.0 Hz), 6.91 (t, 1H, J = 12.0 Hz). 13C-NMR (100 MHz, CDCl3): (ppm) = 53.16, 74.65,105.43, 116.59, 123.36, 135.14, 136.50, 153.81. MS (EI), m/z 194 (M+) |
| 92% |
With potassium carbonate In acetone |
|
| 92% |
With potassium carbonate In acetone for 10h; Reflux; |
|
| 85% |
With potassium carbonate In acetone at 50℃; for 24h; |
|
| 83% |
With ethanol; sodium at 20℃; |
|
| 81% |
Stage #1: 1,3-dimethoxy-2-hydroxy-benzene With sodium ethanolate In ethanol at 0 - 20℃; for 2h; Inert atmosphere;
Stage #2: allyl bromide In ethanol for 16h; |
4.1; 6.1 1st step
The sodium ethoxide solution is prepared by adding sodium (4.0 g, 174 mmol) portionwise to absolute ethanol (500 mL) at 0°C. After total consumption of the sodium, 2,6-dimethoxyphenol (19.8 g, 129 mmol) is added dropwise at 0°C under an inert atmosphere. After addition, the reaction medium is stirred at room temperature for 2 hours. 3- Bromopropene (20 g, 165 mmol) is then added dropwise and the medium is stirred for 16 hours. After concentrating under reduced pressure, the residue is dissolved in water and extracted with dichloromethane. The organic phases are combined, dried over Na2SO4 andconcentrated. The residue is purified by column chromatography on silica gel (hexane/EtOAc:5/1) to give intermediate A in the form of a brown oil (20.0 g, 81% yield). |
| 75% |
With potassium carbonate In dichloromethane at 20℃; for 2h; |
|
|
With potassium carbonate; acetone |
|
| 1.86 g |
Stage #1: 1,3-dimethoxy-2-hydroxy-benzene With sodium hydroxide In acetone for 0.5h;
Stage #2: allyl bromide In acetone at 20℃; for 6h; |
|
|
With potassium carbonate In acetone |
|
|
With sodium hydroxide In acetone |
|
|
Stage #1: 1,3-dimethoxy-2-hydroxy-benzene With potassium carbonate In acetone at 20℃; for 1h;
Stage #2: allyl bromide In acetone for 4h; Reflux; |
Synthesis of 4-Allyl-2,6-dimethoxyphenol (14)
To the stirred solution of 2,6-dimethoxyphenol (1 g, 6.5 mmol, 1 equiv) in 15 mL acetone was added K2CO3 (2.25 g, 16.3 mmol, 2.5 equiv) and stirred for 1h at rt. Allylbromide (0.59 mL, 6.8 mmol, 1.05 equiv) was then added to the reaction mixture and refluxed for 4h. After the completion of the reaction (monitored by TLC) the reaction mixture was filtered through sintered funnel, solvent was evaporated under vacuum. The crude product was taken in 20 mL DMF and heated at 200 °C for 2h. Column chromatography over silica gel (60-120 mesh) of the residue using petroleum ether/ethyl acetate (85:15, v/v) as eluant afforded 14. |
|
With potassium carbonate In acetone for 12h; Reflux; |
|
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