Monoalkylation of hydroquinone; 4-n-propoxyphenol
SyntheticPage 445
DOI:
10.1039/SP445
Submitted Jul 25, 2010, published Jul 27, 2010
Christopher Cooksey (
rsc@chriscooksey.demon.co.uk)
A contribution from
QUINTOX group
Chemicals Used
1-bromopropane (Aldrich)
hydroquinone (Aldrich)
KOH
Procedure
A mixture of hydroquinone (55 g, 0.5 mol), 1-bromopropane (24.6 g, 0.2 mol) was heated under N2 to reflux. A solution of KOH (11.2 g, 0.2 mol) in ethanol (80 cm3) was added over 20 m and heating continued for 4 h. After neutralisation (acetic acid, 20 cm3), evaporation gave a white solid which was extracted with chloroform (4 x 50 cm3). The chloroform was evaporated to give an oil containing white crystals (hydroquinone) which was dissolved in petroleum ether (60/80), filtering hot. After cooling, filtration gave white plates (9.72 g, 32%), m.p. 48-50 ºC.
Author's Comments
Recrystallisation from ethyl acetate – petroleum ether (60/80) gave the product m.p. 51 – 52 ºC (Klarmann et al 56 – 57 ºC).
The absence of air is essential since the monoanion of hydroquinone is easily oxidised to give a black material. The molar ratio of the reactants ensures that the amount of dialkoxy-hydroquinone formed is negligible. Yields are not high, but the process is quite convenient. Other alkoxy products were obtained by the reaction of chlorides, bromides, iodides or tosylates and purified in the same way or by using flash chromatography in similar yields.
The following 4-alkoxyphenols were prepared:
CH3CH2
(CH3)2CHCH2
BrCH2CH2
HOCH2CH2
HOCH2CH2CH2
HOCH2CH2CH2CH2
HOCH2CH2OCH2CH2
CH2=CHCH2
HC≡CCH2
Data
δH (CDCl3), 6.62s (4H), 5.3brs (1H), 3.78t (2H), 1.73sex (2H), 0.97t (3H)
Lead Reference
Naish-Byfield S, Cooksey CJ, Latter AM, Johnson CI, Riley PA, Melanoma Res. 1991, 1(4), 273 – 287, PMID: 1823634
Other References
Klarmann E, Gatyas LW, Shternov VA, J. Am. Chem. Soc., 1932, 54(1), 298-305, DOI: 10.1021/ja01340a045
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Keywords: akylation, alkyl/alkenyl/aryl halides, ethers, nucleophilic
