KNOEVENAGEL CONDENSATION CATALYZED BY [TBA]2[W6O19
]
1025
TABLE 2
The Knoevenagel condensation catalyzed by [TBA]2[W6O19]a (continued)
Entry
10
Ar
Productsb
Time (min)
Yield (%)c
89
5
3j
11
5
92
3k
a1 mmol Benzaldehyde, 1 mmol malononitrile, and 0.07 g [TBA]2[W6O19] in ethanol under reflux.
bAll the products were characterized by IR spectral data and comparision of their melting points with those of authentic samples. Also, the
structures of some products were confirmed by 1H NMR spectral data.
cIsolated yields.
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ence of [TBA]2[W6O19] as catalyst
16. Hosseini-Sarvari, M.; Sharghi, H.; Etemad, S. Chin. J. Chem., 2007, 25,
[TBA]2[W6O19] can activate both reactants. Under these condi-
tions, attempts to isolate the intermediate [I] failed after careful
monitoring of the reactions.
1563.
17. Sun, Q.; Shi, L.X.; Ge, Z.M.; Cheng, T.M.; Li, R.T. Chin. J. Chem., 2005,
23, 745.
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CONCLUSION
In conclusion, [TBA]2[W6O19] was found to be an efficient
heterogeneous catalyst for the Knoevenagel condensation re-
action of aromatic aldehydes with malononitrile, which gives
electrophilic alkenes in high yields in refluxing ethanol. High
yields, simple work-up procedure, short reaction times, and re-
cyclability and reusability of the catalyst makes this protocol
distinctly superior over to many other protocols reported earlier.
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