poix
(Newbee)
09-19-02 23:52
No 358239
      2,5-dimethoxy-phenylacetone from o-Allylphenol
(Rated as: excellent)
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o-Allylphenyl Tetrahydropyran-2-yl Ether

o-Allylphenol (8.0g), 2,3-dihydropyran (5.1g), and a cristal of toluene-p-sulphonic acid were stirred at room temperature for 2 hr.; the solution was washed with aqueous 5% sodium hydroxide (2 x 10 c.c.), then with water (10 c.c.), dried, and evaporated. Distillation (bulb-to-bulb) of the residue at5 x 10-2 mm. gave the ether (8.2g, 62%) as an oil


1-(o-Hydroxyphenyl)propan-2-ol

The foregoing ether (4.36g) in THF (5 c.c.) was added to a stirred suspension of mercury(II) acetate (6.38g) in water (10 c.c.) and THF (10 c.c.); the temperature was not allowed to exceed 25. The mixture was stirred at room temperature for 10 min more, then treated with aqueous 3M NaOH (10 c.c.), and aqueous 0.5M NaBH4 (10 c.c.) was then added below 25. The suspension was saturated with NaCl and extracted with ether (2 x 20 c.c.), andthe combined extracts were washed with water (3 x 5 c.c.). Removal of the solvent left a yellow oil, which was dissolved in a mixture of aqueous 50% ethanol (100 c.c.) and 6M HCl (30 c.c.), and the solution was then stirred at room temp for 6 hr. The mixture was basified with aqueous 6M NaOH (60 c.c.), and then extracted with ether (3 x 40 c.c.). The extracts were discarded and the remaining aqueous phase was acidified with concentrated HCl, and extracted with ether (3 x 40 c.c.). The combined extracts were washed with water (20 c.c.), then with saturated aqueous sodium hydrogen carbonate (2 x 20 c.c.) and dried. Removal of the solvent and distillation of the residue gave the alcohol (2.08g, 75%) as an oil, bp 111-114/0.5 mm


1-(1,4-Benzoquinonyl)propan-2-ol

This was prepared from the foregoing phenol by a method analogous to that described for 2-(1,4-benzoquinonyl) ethanol. 1-(1,4-Benzoquinonyl)propan-2-ol (53% yield) formed yellow cristals, mp 52-55C


quinone of 2-(1,4-benzoquinonyl) ethanol

Fremy's salt (3.8 g) and 2-(1,4-benzoquinonyl) ethanol (0.60g) in ethanol (20 c.c.) were added successively to potassium dihydrogen phosphate (2.52g) in water (150 c.c.), and the mixture was shaken at room temperature for 1 hr and the saturated with NH4Cl and extracted with ether (6 x 50 c.c.). The combined extracts were washed with water, dried, and evaporated. The residual brown oil was filtered through Woelm polyamide (8g) with benzene as eluant, the solvent was removed from the eluate, and the residue was crystallised from hexane-ether to give the yellow quinone (0.37g, 52%)


1-(1,4-Benzoquinonyl)propan-2-ol

The quinone (0.25g) in benzene (25 c.c.) was irradiated (degassed solution of the quinone in dry benzene at 15 was irradiated with visible light) for 24h. The solution became colourless and a brown oilseparated. P.l.c. of the total product on silica gel with benzene-ether (9:1) as eluant followed by crystallisation from benzene gave 2,5 dihydroxyphenylacetone (0.18g 71%) mp 80-83


Methylation of this phenylacetone with any know method will get 2,5-dimethoxy-phenylacetone


source: J chem soc 1971 p 3751-3754
 
 
 
 
    Rhodium
(Chief Bee)
09-20-02 02:21
No 358299
      Odd way of arriving at the target compound, but ...  Bookmark   

Odd way of arriving at the target compound, but nevertheless it is a great post. More like this, everyone!