COMMUNICATIONS
DOI: 10.1002/adsc.200505356
Catalyst-Free Oxidation of Alcohols at Room Temperature Using
Water as Solvent
Ziqiang Lei,* Yaoxia Yang, Xiangzhen Bai
Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering,
Northwest Normal University, Lanzhou 730070, Peopleꢀs Republicof China
Received: September 12, 2005; Revised: March 17, 2006; Accepted: March 24, 2006
Abstract: An effective, cheap, environmentally be-
nign and catalyst-free oxidation of alcohols was car-
ried out at room temperature using tetra-n-butylam-
monium Oxone (TBA-OX) as oxidant with moder-
ate to high selectivity for most of the alcohols using
water as the solvent.
at room temperature in moderate to high selectivity by
the mild and cheap oxidant tetra-n-butylammonium
ꢁ
Oxone (TBA-OX). At first we developed a procedure
ꢁ
in which alcohols were oxidized with tetra-n-butylam-
ꢁ
monium Oxone in dichloromethane (Table 1). Later
we found that similar oxidation reactions could occur
entirely in water although the conversion and product
selectivity were somewhat lower (Table 2). The proce-
dure is very simple, cheap and offers other distinct ad-
vantages over the existing methods.
Keywords: alcohols; catalyst-free oxidation; oxida-
ꢁ
tion; tetra-n-butylammonium Oxone ; water as sol-
vent
TBA-OX was first used for the oxidation of sulfides
[
14]
and sulfur-containing amino acid derivatives but has
never before been used for the oxidation of alcohols.
On the basis of the smooth oxidation of benzyl alcohol
ꢁ
Alcohol oxidations have traditionally been performed with tetra-n-butylammonium Oxone , different reac-
with stoichiometric amounts of high-valent transition tion conditions including the amount of tetra-n-buty-
ꢁ
metal salts or oxidants that generate relatively large lammonium Oxone used and the ratio of alcohol to tet-
ꢁ
amounts of metal-bearing hazardous waste and are usu- ra-n-butylammonium Oxone were investigated. In wa-
[
1–3]
ally run in chlorinated solvents.
In an attempt to pro- ter the optimum ration of alcohol to the oxidant is 1:2.
In conclusion, a series of alcohols includes benzylic
vide a more environmentally benign process for alcohol
oxidations, a variety of catalytic oxidation procedures and primary aliphatic alcohols were oxidized to the cor-
using water as the only solvent has been investigat- responding aldehydes and ketones at room temperature
[
4–9]
[10]
ꢁ
ed.
Liang and co-workers reported a transition using tetra-n-butylammonium Oxone as oxidant and
metal-free catalyst system for aerobic alcohol oxida- water as solvent in good to moderate conversion and
tions in dichloromethane at high reaction temperature. with similar selectivity. The oxidation procedure is
Although molecular oxygen was used as a terminal oxi- mild, cheap and metal-free.
dant, other additives such as Br , NaNO and nitroxyl
2
2
radicals TEMPO (2,2,6,6-tetramethyl-piperidyl-1-oxy)
were used to achieve the reactions. Surendra and co-
[11,12]
workers
also reported a transition metal-free cata-
lyst system for the oxidation of alcohols with o-iodoxy-
benzoica ci d (IBX) or N-bromosuccinimide (NBS) cat-
alyzed by b-cyclodextrin in a water/acetone mixture. On
the basis of green principles, Ji reported a facile, tran-
sition metal-free and substrate-selective oxidation of al-
cohols with NaOCl catalyzed by b-cyclodextrin using
water as the solvent.
We have developed an effective, facile and catalyst-
free oxidation of alcohols using water as solvent. Benzyl
alcohol, substituted benzyl alcohols, benzhydrol, substi-
Experiment Section
[
13]
General Remarks
All of the alcohols used in the reactions were obtained from
ABCR GmbH & Co. KG and used as received without further
purification. TBA-OX was prepared from commercially avail-
ꢁ
[14]
able Oxone by a procedure described in the literature . Sim-
ꢁ
ply extracting an aqueous solution of oxone and tetra-n-butyl-
ammonium bisulfate with dichloromethane, drying, and evap-
tuted benzhydrols, cyclic and aliphatic alcohols were orating gave the product. TBA-OX is readily soluble in di-
oxidized to their corresponding aldehydes and ketones chloromethane, chloroform, acetone, acetonitrile, and water.
Adv. Synth. Catal. 2006, 348, 877 – 880
ꢂ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
877