Journal of the Chinese Chemical Society, 2008, 55, 713-715
713
Communication
Vanadyl Sulfate (VOSO4.3H2O). An Efficient Catalyst for Acylation of
Alcohols and Phenols under Solvent Free Condition
Hossein A. Oskooie, Bita Baghernezhad, Majid M. Heravi* and Y. Sh. Beheshtiha
Department of Chemistry, School of Science, Azzahra University, Vanak, Tehran, Iran
Alcohols and phenols were efficiently acylated with acetic anhydride in the presence of vanadyl sul-
fate (VOSO4.3H2O) at room temperature in high yields.
Keywords: Vanadyl sulfate; Acylation; Acetic anhydride; Solvent free; Reusable catalyst.
INTRODUCTION
The acylation of alcohols and phenols is one of the
and phenols. The synthetic utility of vanadium-containing
compounds has been widely explored and utilized.16-19
Among them, oxovanadium(IV) (vanadyl) compounds were
normally treated as precatalysts of the corresponding VV
species.16,17,20 However, synthetic transformations that are
directly catalyzed by vanadyl species were relatively unex-
plored. Chen, C-T. et al have used vanadyl derivatives, in-
cluding vanadyl sulfate for the acylation of alcohols,19 but
there are no reports concerning the the acylation of alco-
hols and phenols under solvent free conditions. In this pa-
per, we wish to report the acylation of alcohols and phenols
by employing acetic anhydride in the presence of vanadyl
sulfate as a catalyst under solvent free conditions, as shown
in Scheme I.
most useful and versatile transformations in organic syn-
thesis.1 Acylation using acid anhydrides provides a cheap
and efficient method for protecting OH groups during oxi-
dations, coupling reactions, etc.1,2 or synthesis of esters
with high potential applications as fragrances, flavors,3
surfactants or solvents.4 In addition, the protection of hy-
droxyl functionality as acetate is preferred due to its ease of
introduction, being stable under mild acidic reaction con-
ditions and also ease of removal by mild alkaline hydroly-
sis.
Generally, these reaction are carried out in very envi-
ronmental unfriendly conditions, using homogeneous cata-
lysts such as organic bases (pyridine in triethylamine or
pyridine with 4-(dimethylamine) pyridine,5 homogeneous
Lewis acid catalysts (AlCl3, BF3, TaCl5),2,6 or inorganic ac-
ids2,7 which generate amounts of corrosive and toxic waste
products from which the catalysts are very difficult to re-
cover. They also often necessitate the presence of environ-
mentally unfriendly solvents like dichloromethane.8 In or-
der to overcome these problems, the attention has been fo-
cused on the use of heterogeneous catalysis. Some solid
acid catalysts including zeolites,9 oxides,10 K-10 montmo-
rillonite,11 Al-MCM-41,12 or supported reagents13-15 were
used for these reaction but they required high reaction tem-
perature or the use of environmentally unfriendly solvents.
In spite of these waves of interest, due to the importance
of acylation, it is necessary to develop inexpensive, eco-
friendly and reusable catalyst for acylation of alcohols
Scheme I
RESULT AND DISCUSSION
The reaction of various alcohols and phenols with
Ac2O in the presence of vanadyl sulfate afforded products
in high yields (Table 1). In all cases, the reactions pro-
ceeded efficiently at room temperature under solvent-free
conditions. This method works well with a 1:1.5 molar ra-
tio of alcohol or phenol to acetic anhydride in the presence
of a catalytic amount of vanadyl sulfate (5 mole %) without
solvent. For liquid aldehydes (Entry 10-16), we used 1
mmol of acetic anhydride to get product.
* Corresponding author. Fax: +98-21-88047861; E-mail: mmh1331@yahoo.com