ZrCl4 Catalyzed Crossed-aldol Condensation
J. Chin. Chem. Soc., Vol. 54, No. 3, 2007 809
The results are summarized in Table 1. The reactions
were completed within 2-6 h and excellent yields of the
products were obtained (entries 1-12). The control experi-
ment indicates that no product of the crossed-aldol conden-
sation could be obtained in the absence of the catalyst. It
was found that a catalyst loading of only 0.2 mmol was re-
quired to perform the reaction. Under these conditions, no
self-condensation of the starting materials was observed.
Attempt for monocondensation from one side of the cyclo-
alkanones, in the presence of lower amounts of the alde-
hydes, was not successful.
ble 1). On completion of the reaction, as indicated by TLC,
the mixture was cooled to room temperature. Then 20 mL
of water was added to the reaction mixture, and the precipi-
tate thereby formed was filtered. The product was washed
with ethanol and recrystallized from ethanol to give the
pure products in 85-98% yields.
ACKNOWLEDGEMENT
We are grateful to the Razi University Research Coun-
cil for partial support of this work.
The reactions of acyclic ketones such as 2-acetylnaph-
thalene with aromatic aldehydes were also examined and
the products were obtained in excellent yields (Table 1, en-
tries 13 and 14).
Received September 6, 2006.
When the reactions were examined in different or-
ganic solvents such as acetonitrile, dichloromethane, chlo-
roform, water and n-heptane, we found that ethanol was
the best solvent due to high yield and shorter reaction
times.
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EXPERIMENTAL SECTION
General
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General procedure for crossed-aldol condensation
In a 25 mL round bottomed flask, ketone (1 mmol),
aromatic aldehyde (2 mmol) and ZrCl4 (0.4 mmol, 0.092 g)
were added, and the solution was stirred magnetically un-
der reflux conditions for an appropriate period of time (Ta-
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