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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


			Reaction Scheme: Monoalkylation of <SPAN class=csm-chemical-name id=csm1285420180220 title=hydroquinone>hydroquinone</SPAN>

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

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