Chemistry Letters 2000
461
oxidized (Eq. 1). Treatment of benzyl alcohol with one mole
ratio of reagent (1) in the presence of an equimolar amount of
diphenylmethanol led to exclusive oxidation of benzyl alcohol
(Eq. 2). Interestingly in the oxidation of alcohols the overoxi-
dation of products to the corresponding carboxylic acids was
not observed at all. When we treated one equimolar amount of
benzyl alcohol with reagent (1) in the presence of an equimolar
amount of phenylmethyl sulfide, only the benzyl alcohol was
selectively oxidized (Eq. 3).
C25H23O5PS: C, 64.37; H 4.97; S, 6.87%. Found: 64.20; H,
5.20; S, 6.60%.
Oxidation of alcohols (2) with reagent (1) to the correspon-
ding carbonyl compounds (3): A mixture of alcohol (2) (1
mmol), oxidizing agent (1) (1.2 mmol, 0.56 g) and AlCl3 (1
mmol, 013 g) in a mortar was ground for the time specified in
Table 1. When TLC showed complete disappearance of alco-
hol, the mixture was extracted with CH2Cl2. Evaporation of the
solvent gave corresponding carbonyl compound (3). The prod-
uct was purified by column chromatography on silica gel using
a mixture of ethyl acetate and hexane as eluent (10:90).
Competitive oxidation:Typical procedure: A mixture of
benzyl alcohol (1 mmol, 0.11 g), diphenylmethanol (1 mmol,
0.19 g), oxidizing agent (1) (1.2 mmol, 0.56 g) and AlCl3 (1
mmol, 013 g) in a mortar was ground. The mixture was ground
until TLC showed complete disappearance of benzyl alcohol
(20 min). The other competitive reactions for Eqs. 1-3 is the
same as above.
In summary, we report here the preparation of benzyltriph-
enylphosphonium peroxymonosulfate (1) as a mild, inexpensive
and stable oxidizing agent. This oxidizing reagent is very easily
prepared from commercially available starting materials and can
be stored for months without losing its activity. The reagent is
soluble in acetonitrile, chloroform and dichloromethane and
slightly soluble in carbon tetrachloride, ether and hexane. This
reagent is an efficient, rapid, mild and inexpensive reagent for
oxidation of benzylic and allylic alcohols to the corresponding
carbonyl compounds under solvent-free condition in the pres-
ence of AlCl3. This method is superior to previously reported
methods in terms of high yields, purity of products, facile work-
up, cheaper reagent and short reaction time.
The authors are thankful of the Isfahan University of
Technology (IUT), IR Iran for financial support.
References and Notes
1
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All yields refer to isolated products after purification.
Products were characterized by comparison with authentic sam-
1
ples (IR and H-NMR spectrum, thin layer chromatography,
1
melting and boiling point). All H-NMR were recorded at 90
MHz in CCl4 relative to TMS (0.00 ppm) and IR spectra were
recorded on Shimadzu 435 IR spectrophotometer. Spectra of
solid were carried out using KBr pellets. All reactions were car-
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2
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of 0.1012 M solution of sodium sulfite to the yellow endpoint.
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5
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-
weight) of active oxidizing agent (HSO5 ). Anal Calcd for
8
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