94
Letters in Organic Chemistry, 2009, 6, 94-99
Zirconium Tetrakis(dodecylsulfate) as an Efficient and Recyclable Lewis
Acid-Surfactant-Combined Catalyzed C-C and C-N Bond Forming Under
Mild and Environmentally Benign Conditions
Maasoumeh Jafarpour*, Abdolreza Rezaeifard* and Marzieh Aliabadi
Catalysis Research Lab., Department of Chemistry, Faculty of Science, University of Birjand, Birjand, 97179-414, Iran
Received April 14, 2008: Revised August 16, 2008: Accepted September 01, 2008
Abstract: A green catalytic method for C-C and C-N bond forming via Michael addition of aromatic amines and indoles
to electron-deficient olefins using Zirconium tetrakis(dodecylsulfate) in water under mild conditions with high yields and
selectivity has been developed. The reusability of the catalyst has been successfully examined without any noticeable loss
of its catalytic activity.
Keywords: Lewis acid-surfactant-combined catalysts, Zirconium tetrakis(dodecylsulfate), Michael reaction, Aqueous media,
Amines, Indoles.
1. INTRODUCTION
amines and indoles to electron-deficient olefins in water at
room temperature (24-26°C) in high yields (Scheme 2).
Development of more environmental friendly synthetic
processes is a rising interest in the chemical community. In
addition to its abundance and for economical and safety rea-
sons, water has naturally become an alternative as an envi-
ronmentally benign solvent. Moreover, it has been found that
reactions in water can facilitate access to different reactivity
and selectivity patterns compared with those observed in
common organic solvents due to its unique physical and
chemical properties [1-5]. Thus, organic reactions in aqueous
media have several advantages in comparison with many
conventional synthetic procedures in organic solvents. How-
ever, the use of water in organic reactions has serious limita-
tions. For example, most organic compounds do not dissolve
in water and many reactive substrates, catalysts, reagents and
products are decomposed or deactivated in aqueous media.
To overcome these drawbacks in the use of water as solvent,
surfactants can be used successfully which solubilize organic
materials or form emulsions with them in water.
)
4
Zr4+(-O3SO
Scheme 1.
2. RESULTS AND DISCUSSION
In order to optimize the reaction conditions, initially, the
condensation of methyl vinyl ketone and less reactive p-
nitroaniline was studied as a model reaction at room tem-
perature (Table 1). In the absence of any catalyst the Michael
adduct was produced in water with very low yield (10%)
after 24 h. The similar reaction carried out in aqueous solu-
tion of sodium dodecyl sulfate (SDS) at its critical micellar
concentration (CMC), and the same unfavorable result was
obtained. Then, we evaluated the catalytic activity of
Zr(NO3)4 in this reaction in aqueous solution in the absence
and in the presence of SDS in its CMC which led to desired
product in 70 and 75% yield, respectively, after 24 h. While,
the condensation of methyl vinyl ketone (3 mmol) and p-
nitroaniline (1 mmol) under the influence of prepared
Zr(DS)4 catalyst (10 mol%) in water (2 mL) led to the de-
sired condensed adduct in 95% isolated yield after 2.5 h (Ta-
ble 1). It seems to the Lewis acid part of the catalyst acti-
vates the substrate molecules and the surfactant part, affect-
ing the solubility of the substrates in water at the same time.
When these two factors play together, a drastic enhancement
of the rates and the yields of the products is observed.
Recently, Lewis acid-surfactant-combined (LASCs) such
as scandium tris(dodecyl sulfate) (Sc(DS)3), scandium
trisdodecane sulfate [6-7], copper bis( dodecyl sulfate)
(Cu(DS)2) [8] and aluminum tris (dodecyl sulfate) trihydrate
(Al(DS)3.3H2O) [9-10] have been developed which formed
stable colloidal dispersion systems with organic substrates in
water and efficiently catalyzed organic reactions.
In the course of our research on development of new
applications of zirconium salts [11-16] in synthetic methods
due to low toxicity ( LD50[Zr(NO3)4, oral rat]= 2290 mg kg-
1) [17], low cost, ease of handling and high catalytic activity,
we found zirconium tetrakis(dodecylsulfate) (Scheme 1) as a
LASC which efficiently and selectively catalyzed C-C and
C-N bond forming using the Michael addition of aromatic
However, we have examined the effect of other solvents
on this catalytic system. It was observed that the reaction
proceeded tediously in organic solvents such as CH2Cl2,
CHCl3, CH3CN and EtOH.
Next, the generality of the procedure was evaluated by
the reaction of a number of aromatic amines and indoles with
structurally diverse electron-deficient olefins. The reactions
proceeded efficiently and adducts were isolated in excellent
*Address correspondence to these authors at the Catalysis Research Lab.,
Department of Chemistry, Faculty of Science, University of Birjand, Bir-
jand, 97179-414, Iran; Tel: +98 0561 2502516; Fax: +98 0561 2502515;
E-mail: mjafarpour@birjand.ac.ir; rrezaeifard@birjand.ac.ir
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