Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 6243–6245
Synthesis, characterization and structure of a tetrameric
DABCO–bromine complex: a novel oxidizing agent for oxidation
of alcohols to carbonyl compounds
Majid M. Heravi,a,* Fatemeh Derikvand,a
Mitra Ghassemzadehb and Bernhard Neumullerc
¨
aDepartment of Chemistry, School of Sciences, Azzahra University, Vanak, Tehran, Iran
bChemistry and Chemical Engineering Research Center of Iran, Tehran, Iran
cFachbereich Chemie der Universita¨t Marburg, Germany
Received 12 April 2005; revised 3 July 2005; accepted 14 July 2005
Abstract—A tetrameric DABCO–bromine complex was synthesized, characterized and utilized as a novel active bromine complex
for the oxidation of alcohols to carbonyl compounds.
ꢀ 2005 Published by Elsevier Ltd.
1. Introduction
A yellow solid appeared as bromine was taken up. The
mixture was stirred for an additional 1 h and the yellow
solid was filtered off and crystallized from acetonitrile to
give single crystals appropriate for X-ray crystallogra-
phy. The crystal structure of the DABCO–bromine
complex has been already reported by others,15 but
our data are better.
Alcohol oxidation yielding aldehydes and ketones is a
chemical transformation of primary industrial impor-
tance in the fine chemicals industry as carbonyl com-
pounds are precursors of a variety of valuable fine
chemicals including fragrances, vitamins and drugs.1
Reagents of choice for oxidation of alcohols to carbonyl
compounds are pyridinium chlorochromate (PCC),2
Swern3 and Dess–Martin4 reagents, PCC catalyzed oxi-
dation with periodic acid,5 silica gel supported InBr3
and InCl3,6 etc.7 We have recently reported the oxida-
tion of alcohols,8 deoximation,9 desemicarbonization,10
and oxidative deprotection of silyl ethers11 and THP
ethers12 using hexamethylenetetramine bromine and
used DABCO as the catalyst for the synthesis of N-aryl-
phthalimide13 and the desilylation of silyl ethers.14
The oxidation reaction was conducted by refluxing the
DABCO–bromine complex with an appropriate amount
of an alcohol in a mixture of dichloromethane and
water. The reaction mixture was stirred at room temper-
ature. The progress of the reaction was monitored by
TLC (petroleum ether/ethyl acetate 8:2). To establish
the generality of the method, various alcohols including
allylic, benzylic, primary and secondary were oxidized
with this reagent in 15 min–5 h to give the correspond-
ing carbonyl compounds in excellent yields. The results
are shown in Table 1. The oxidation of allyl alcohols
was carried out under the mildest conditions, needing
only 15 min to be completed. An allylic alcohol was oxi-
dized regioselectively in the presence of other hydroxyl
groups. No product of over-oxidation to carboxylic
acids was observed. Concerns about the safety of adding
molecular bromine to amines may be voiced, however,
the addition of bromine to DABCO was observed to
have only a moderate exotherm. The DABCO–bromine
complex was a homogeneous non-hygroscopic solid,
which was stable at room temperature and not affected
In this letter, we describe the characterization and struc-
ture of a bromine complex of its use as a selective oxi-
dant in organic chemistry. The reagent was prepared
by the exothermic addition of molecular bromine to
1,4-diazabicyclo[2.2.2] octane (DABCO) in chloroform.
Keywords: Oxidation; Alcohols; Carbonyl compounds; DABCO–
bromine complex.
*
Corresponding author. Tel.: +98 21 804 13 47; fax: +98 21 804 78
0040-4039/$ - see front matter ꢀ 2005 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2005.07.057