A Stabilized Formulation of IBX (SIBX) for Safe Oxidation Reactions Including a New Oxidative Demethylation of Phenolic Methyl Aryl Ethers
Aurélie Ozanne, Laurent Pouységu, Dominique Depernet, Bruno François, and Stéphane Quideau
Org. Lett. 5(16), 2903-2906 (2003) (https://www.thevespiary.org/rhodium/Rhodium/pdf/eugenol.demethylation.sibx.pdf)
(https://www.thevespiary.org/rhodium/Rhodium/pdf/eugenol.demethylation.sibx.pdf)
DOI:10.1021/ol0349965 (http://dx.doi.org/10.1021/ol0349965)
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000451672-file_cqmc.gif)
Abstract
SIBX is a nonexplosive formulation of IBX that can be used as a suspension in a variety of standard organic solvents such as refluxing EtOAc and THF to oxidize safely alcohols into aldehydes and ketones. The use of hot THF is limited to the oxidation of allylic and benzylic alcohols. Most yields are comparable to those obtained with IBX or DMP. SIBX can also be used to perform oxygenative demethylation of 2-methoxyarenols into orthoquinones and catechols.
Full experimental + Prep of SIBX (http://pubs.acs.org/subscribe/journals/orlef7/suppinfo/ol0349965/ol0349965si20030623_024608.pdf)
(http://pubs.acs.org/subscribe/journals/orlef7/suppinfo/ol0349965/ol0349965si20030623_024608.pdf)
Various Preparations of SIBX using different solvents/oxidants/desensitizers (https://www.thevespiary.org/rhodium/Rhodium/pdf/sibx.us2002107416.pdf)
(https://www.thevespiary.org/rhodium/Rhodium/pdf/sibx.us2002107416.pdf)
4-Propenyl-benzene-1,2-diol [4-allylcatechol, 3,4-dihydroxyallylbenzene] (34).
To a stirred suspension of SIBX (857 mg, 1.5 mmol) in dry THF (14 mL, ca. 0.05 M) was added 4-allyl-2-methoxy-phenol [eugenol] (33) (0.7 mmol). After stirring in the dark at room temperature for 16 h, the white suspension was filtered out from the resulting red solution. The filter cake was washed with CH2Cl2 (20 mL) and the combined filtrate and washings were poured into water (30 mL). After separation, the aqueous layer was further extracted with CH2Cl2 (30 mL). The combined organic layers were washed with saturated aqueous NaHCO3 (4 x 15 mL) and treated with an aqueous solution (2 mL) of Na2S2O4 (730 mg, 4.2 mmol) for 10 min with vigorous stirring under nitrogen in the dark. The resulting yellow solution was washed with water (10 mL), brine (10 mL), dried over Na2SO4, filtered and evaporated to dryness to furnish 34 as a viscous orange solid (77%).
Phenols can also be oxidized by (S)IBX to o-quinones, which can be reduced to catechols by the same thiosulfate workup as above.
Ref: Org. Lett. 4(2), 285-288 (2002) DOI:10.1021/ol017068j (http://dx.doi.org/10.1021/ol017068j)
IBX is very versatile, and another use is the oxidation of toluenes to benzaldehydes and alkylbenzenes to aralkylketones.
Ref: J. Am. Chem. Soc. 123, 3183-3185 (2001) DOI:10.1021/ja004218x (http://dx.doi.org/10.1021/ja004218x)
The follow article was authored by several reseachers, including the man himself, Alexander T. Shulgin.
In the future, it may prove to be adaptable to a better safer method for the oxidative demethylation of eugenol.
A Convenient Synthesis of Quinones from Hydroquinone Dimethyl Ethers. Oxidative Demethylation with Ceric Ammonium Nitrate
I'eyton Jacob, 111, Patrick S. Callery, Alexander T. Shulgin, and Neal Castagnoli, Jr.*
J. Org. Chem., Vol. 41, No. 22, 1976
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_imgs/pdf.gif)
Here are two excerpts from the article:
As a part of our studies on the metabolism and mechanism of action of psychotomimetic l-phenyl-2-aminopropanes, we required a mild method for the oxidative demethylation of p -dimethoxybenzene derivatives. We have found that ceric ammonium nitrate [Ce(NH4)2(NO& CAN] in aqueous acetonitrile will oxidize a variety of hydroquinone dimethyl ethers (a) to the corresponding quinones (b) often in high yield. The reaction can be carried out in the absence of strong acid, and is generally quite fast, requiring only a few minutes reaction time at room temperature. The selectivity and mildness of the reaction is illustrated by the fact that a variety of functional groups are tolerated.
General Procedure for Oxidative Demethylation.
Unless otherwise noted, the dimethoxy compound was dissolved in acetonitrile, and an aqueous solution of ceric ammonium nitrate (2-3 equiv CeIV) was added portionwise over 5 min. In most cases a transient blue-black color was observed. After stirring for 30 min at room temperature, the reaction mixture was extracted with chloroform. The chloroform extract was concentrated on a rotary evaporator and the crude product was purified by sublimation or recrystallization.
Here are two of the experimental examples printed in the article:
p-Benzoquinone (lb).
To a solution of p-dimethoxybenzene (la, 1.38 g, 10 mmol) in acetonitrile (25 ml) was added a solution of CAN (16.5 g, 30 mmol) in H20 (25 ml). The mixture was extracted with chloroform, the extract was concentrated under reduced pressure, and the residue was sublimed (160 "C, 20 mm) to give the yellow quinone lb (0.61 g, 5.7 mmol, 57%), mp 111.5-112.5 "C (lit.lo mp 114.5 "C).
2,5-Dimethyl-1,4-benzoquinone (2b).
The dimethyl ether 2all (1.0 g, 6.0 mmol) in acetonitrile was treated with aqueous CAN (8.8 g, 16 mmol) to yield the bright yellow quinone 2b which after sublimation (145 "C, 4 mm) gave 0.78 g (5.70 mmol, 95%) of pure product, mp 122.5-123.5 "C (lit.12 mp 123.5-125 "C).