Facile Microwave-Promoted Knoevenagel Condensation
Letters in Organic Chemistry, 2011, Vol. 8, No. 8
557
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EXPERIMENTAL
All the experiments were carried out in MATTHEWS,
NC- MADE IN USA. MODEL-DISCOVER-S. MODEL
NO-NP-1009, Microwaves Digester in closed vessel. Melt-
ing points were determined in open capillaries and are uncor-
rected. IR spectra were recorded on Spectrum BX FT-IR,
Perkin Elmer (ꢀmax in cm-1) on KBr disks. 1H NMR and 13C
NMR (400 MHz and 100 MHz respectively) spectra were
recorded on Bruker Avance II-400 spectrometer. Mass spec-
tra were recorded on Waters 2695. CHN were recorded on
CHN-OS analyzer (Perkin Elmer 2400, Series II). Silica gel
G (E-mark, India) was used for TLC. Hexane refers to the
fraction boiling between 60 and 80 ꢁC.
dium(0)-catalyzed
reaction.
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[5]
[6]
General Procedure for the Synthesis of Compound 3a-l,
6a-e, 9a-h
[7]
[8]
Aryl aldehyde 2 (1 mmol) and 1, 3, dicarbonyl 1, 5 (2
mmol) and 8 (1 mmol) were added to an aqueous solution of
AOT (15 mmol) successively and mixed thoroughly. The
resulting mixture was irradiated under microwave at 150
o
watt and 60 C until the TLC showed the dissappearance of
[9]
the starting materials. On completion, the resulting mixture
was cooled to room temperature, filtered and washed with
water (3 ꢂ 5 ml). The residue obtained was recrystalized
from ethanol to get pure crystalline products (3a-l, 6a-e and
9a-h).
[10]
[11]
Genaral Procedure for the Synthesis of Compound 4a-e
Aryl aldehyde 2a-e (1.0 mmol), dimedone 1 (2.0 mmol)
and catalytic amount of concentrated sulfuric acid were
added to an aqueous solution of AOT (15 mmol) and mixed
thoroughly. The resulting mixture was irridiated at 150 watt
[12]
[13]
[14]
o
and 60 C temperature for the time mentioned in Table 2.
The progress of the reaction was monitored by TLC and after
completion, the resulting mixture was cooled to room tem-
perature and filtered. The residue was washed with water (3
ꢂ 5 ml) and recrystalized from ethanol to get pure crystalline
products (4a-e).
[15]
[16]
[17]
ACKNOWLEDGEMENTS
We thank the Department of Chemistry and Sophisticated
Analytical and Instrumentation Facility (SAIF) of North-
Eastern Hill University for providing necessary facilities and
the UGC, New Delhi for supporting this work under Special
Assistance Programme (SAP).
[18]
[19]
SUPPLEMENTARY MATERIAL
Wang, Q.; Chittabonia, S.; Hannah, N. B. Highlights in Organic
Chemistry Advances in 1,3-Dipolar Cycloaddition Reaction of Az-
ides and Alkynes - A Prototype of “Click” Chemistry. Lett. Org.
Chem., 2005, 2, 293-301.
Supplementary material is available on the publishers
Web site along with the published article.
[20]
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manganese sulphate/oxone/water. J. Mex. Chem. Soc., 2007, 51,
213-216.
(a) Bahrami, K.; Khodaei, M. M.; Nejati, A. Synthesis of 1,2-
disubstituted benzimidazoles, 2-substituted benzimidazoles and 2-
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