Phenols to Quinones w/H2O2 and Mn(II) acetate , Hive Methods Discourse

demorol
(Hive Bee)
12-05-03 14:16
No 474804

Phenols to Quinones w/H2O2 and Mn(II) acetate
(Rated as: excellent)

Novel Oxidation of Phenols to Quinones by Hydrogen Peroxide in the Presence of Cobalt(II) and Manganese(II) Acetate

Experimental

Oxidation of Phenols to Quinones; Typical Procedure:

Phenol (0.94g, 10 mmol) was dissolved in 20 mL glacial acetic acid and cobalt(II) acetate tetrahydrate (0.09g, 0.5 mmol) was added to this solution and then aqueous hydrogen peroxyde (30%, 5 mL, 49.0 mmol) was added portionwise over 60 minutes at room temperature along with stirring of reaction mixture. Then 15 mL water was added and the reaction mixture was neutralized with 10% aqueous NaOH. The product was extracted with DCM (3×10 mL), dried over sodium sulfate and evaporated to dryness. After sublimation 0.32g (30% yield) of benzoquinone was obtained.

Oxidation of other phenols was carried out by similar procedure. Reaction conditions and yields of isolated products are given in Table 1.

Table 1. Oxidation of phenols to quinones using hydrogen peroxide in the presence of cobalt(II) acetate and manganese(II) acetate.^a

Substrate	Product^b	Time (min)	Yield^c (%)	Yield^d (%)	Yield^e (%)
phenol	1,4-benzoquinone	60	35	30	40
2-methylphenol	2-methyl-1,4-benzoquinone	30	70	70	70
3-methylphenol	3-methyl-1,4-benzoquinone	50	65	60	65
1-naphtol	1,4-naphthoquinone	120	45	40	45
1,4-dihydroxynaphthalene	1,4-naphthoquinone	60	60	50	50
2,6-dimethylphenol	2,6-dimethyl-1,4-benzoquinone	30	75	60	65
2,3-dimethylphenol	2,3-dimethyl-1,4-benzoquinone	60	55	45	50
1,4-dihydroxybenzene	1,4-benzoquinone	60	60	50	60

^a All reactions were carried out in AcOH using 20:1 phenol/catalyst molar ratio.
^b All quinones were fully characterized by their melting points and spectral data.
^c The reactions were carried out in the presence of manganese(II) acetate at room temperature.
^d The reactions were carried out in the presence of cobalt(II) acetate at room temperature.
^e The reactions were carried out in the presence of cobalt(II) acetate at 50°C.

Reference: Acta. Chim. Slov. 2003, 50, 569-572 (Available for free at http://acta.chem-soc.si)