4
34 J. CHEM. RESEARCH (S), 1999
J. Chem. Research (S),
Copper(I) Chloride/Kieselguhr: a Versatile
Catalyst for Oxidation of Alkyl Halides and Alkyl
Tosylates to the Carbonyl Compoundsy
1
999, 434^435y
Mohammed M. Hashemi* and Yousef Ahmadi Beni
Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
Copper(I) Chloride adsorbed on Kieselguhr in the presence of oxygen catalyses oxidation of alkyl halides and
alkyl tosylates to the aldehydes and ketones in high yields.
The introduction of supported reagents for bringing about
various organic reactions of synthetic signi¢cance has
recently been accomplished. These reagents not only mod-
Table 2 Reusability of catalysta
Experimental trial
Yield(%)
1
ify the activities but also may impart product selectivities.
For example oxidation of alkyl halides and alkyl tosylates
to carbonyl compounds using supported reagents is an im-
portant method for preparation of aldehydes and ketones.
In this regard various reagents have been developed:
1st
2nd
90
88
87
87
86
3
4
5
a
rd
th
th
2
3
4
All reactions are carried out under similar conditions, time 2.5h.
dimethyl
sulfoxide,
N,N-dimethyl-4-nitrosoaniline
(
Krohnke oxidation), nitronate anion and PdꢀPPh3 ,
4
5
6
pyridine N-oxides and other amine oxides, chromate
8
9
and dichromate systems, silver nitrate, hexamethylene
tetraamine, pyrazinyl sulfoxides and pyridine N-oxide
with microwave irradiation.
Some of these reagents or catalysts have low yields,
others using high temperature,
bulk requirement of the solid bed and pyridine N-oxides
with microwave irradiation only oxidize benzylic halides
to aldehydes.
In recent works we have reported a mixture of cobalt and
manganese salts of p-aminobenzoic acid supported on silica
gel as a catalyst in the presence of oxygen as a mild
and e¤cient oxidizing agent for di¡erent functional groups
1
0
11
1
2
Table 1 Oxidation of alkyl halides and tosylates to carbonyl
compounds
2
;5;6;10
3;4;11
2;10
long reaction times,
CuCl=Kieselguhr
7;8
1
2
1
2
R R CHX �����������! R R CO
O2
1
2
Reaction
Solvent time/h
Entry Substrate
Yield(%)
1
2
CH3CH2Cl
CH3CH2CH2Cl
CH2Cl2
CH2Cl2
1.5
1.5
94
91
such as benzylic and allylic alcohols to their corresponding
3
Br
Hexane 2.5
99
13
carbonyl compounds,
aromatization of 1,4-dihydro-
1
4
pyridines to pyridine derivatives, conversion of xylenes
4
5
C6H5CH2Cl
p-CH3C6H4CH2Br
Hexane 2.5
90
87
1
5
16
into toluic acids and oxidation of phenols to quinones.
Hexane
Hexane
Hexane
4
2
3
However, this procedure did not work satisfactorily for
oxidation of alkyl halides and tosylates to corresponding
carbonyl compounds.
I
6
7
8
93
88
84
O
Now, we report a very simple and convenient procedure
for oxidation of primary and secondary alkyl halides and
tosylates to carbonyl compounds using molecular oxygen
and CuCl/Kieselguhr as catalyst. The catalyst is prepared
by addition of weighed amounts of Kieselguhr to a water
solution of CuCl followed by evaporation of solvent to
dryness. The oxidation conditions are shown in Table 1.
Table 2 shows the reusability of the catalyst after 5 rep-
licate oxidations of benzyl chloride to benzaldehyde. The
catalyst was recovered quantitatively after each experiment.
In conclusion, mild reaction conditions, good yields, ease
of work-up, stability and reusability of the catalyst are
the most signi¢cant aspects of this method.
Cl
Br
Hexane 2.5
N
Br
9
Toluene
4
86
Br
1
0
Toluene
4
81a
1
1
1
1
1
a
1
2
3
4
5
CH3CH2OTs
Hexane 0.75
89
85
87
85
CH3ꢀCH2 CH2OTs
Hexane
Hexane
1
3
Experimental
5
C6H5CH2OTs
p-CH3C6H4CH2OTs
C6H5CHCHCH2OTs
b
Alkyl halides were purchased from Fluka, Merck and Aldrich.
Alkyl tosylates were prepared by treatment of corresponding alcohols
with tosyl chloride in acetonitrile. All products are known compounds
and were identi¢ed by their FT-IR spectra and mps of their
2,4-dinitrophenylhydrazone derivatives. Yields reported refer to
isolated products.
Toluene 3.75
Hexane
b
4
91
The product is anthrone. Yield of 2,4-dintrophenylhydrazone
derivative.
Preparation of CuCl/Kieselguhr Reagent.öTo a water solution of
CuCl (10 mg in 100 ml of water), Kieselguhr (50 g) was added and
the mixture stirred for 30 min. Water was evaporated in vacuo and
the residue dried in an oven at 110 8C for 5 h to give 59 g of
CuCl/Kieselguhr reagent.
*
To receive any correspondence.
y This is a Short Paper as de¢ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1999, Issue 1]; there is
therefore no corresponding material in J. Chem. Research (M).