Demethylation of a methoxy arene using pyridinium hydrochloride; 1,2,4-Trihydroxy-3-methylanthraquinone
SyntheticPage 444
DOI:
10.1039/SP444
Submitted Jul 22, 2010, published Jul 23, 2010
Christopher Cooksey (
rsc@chriscooksey.demon.co.uk)
A contribution from
R J H Clark Group, UCL
Chemicals Used
1,2,4-Trimethoxy-3-methylanthraquinone page 443
pyridine
HCl
Procedure
A mixture of 1,2,4-trimethoxy-3-methyl-anthraquinone (98.3 mg, 0.31 mmol) and pyridinium hydrochloride (3.1 g, prepared by reacting pyridine in ethanol with HCl followed by evaporation) were heated on an oil bath at 160 – 180 ºC for 6 h. Water (5 cm3) was added and after stirring 0.5 h the product, a dark red crystalline solid, was filtered and dried to give 79.9 mg (95%) of product, m.p. 275 – 277 ºC (subl).
Author's Comments
Literature (De Silva SO, et al) suggests heating at 180 ºC for 8 h. Raistrick H, et al found the product was red needles, m.p. 268 – 270 ºC (subl).
Data
δH(dmso-d6) 13.85s (1H), 13.35brs (1H), 11.09brs (1H), 8.24m (2H), 7.94m (2H), 2.11s (3H)
m.p. 275 – 277 ºC (subl)
Lead Reference
De Silva SO, Watanabe M, Snieckus V, J Org Chem, 1979, 44(26), 4802-4808,
doi: 10.1021/jo00394a012
Other References
Raistrick H, Robinson R, Todd AR, J Chem Soc 1937, 80-88,
doi: 10.1039/JR9370000080
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Keywords: anthraquinone, demethylation, phenol
