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Experimental Section
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General Procedure for the Preparation of 5a–i: To the solution of
2-imino-2H-chromene-3-carboxamides 3a–c (0.8 mmol) and TFA
(1.2 mmol) in ethanol (6 mL) was added an excess amount of isocy-
anides 4a–c (1.2 mmol). The resulting mixture was stirred for 1.5 h
at ambient temperature and monitored by TLC (n-hexane/ethyl
acetate, 1:2). Then, the solution was poured into saturated aqueous
solution of NaHCO3 (20 mL) and extracted with ethyl acetate
(2ϫ20 mL). The combined organic phases were dried with anhy-
drous MgSO4, filtered, and concentrated in vacuo. Crude products
5a–i were purified by flash chromatography (n-hexane/ethyl acet-
ate).
MCR Procedure: To a solution of salicylaldehydes 1a–c (0.8 mmol)
and a catalytic amount of piperidine (0.08 mmol) in ethanol (6 mL)
was added 2-cyanoacetamide (2; 0.8 mmol). The resulting mixture
was stirred for 2 h at room temperature. When the Knoevenagel
reaction was carried out, TFA (1.28 mmol) and isocyanides 4a–c
(1.2 mmol) were added, and stirring was continued for another
1.5 h at room temperature. Next, the solution was poured into a
saturated aqueous solution of NaHCO3 (20 mL) and extracted with
ethyl acetate (2ϫ20 mL). The combined organic phases were dried
with anhydrous MgSO4, filtered, and concentrated in vacuo. After-
wards, target compounds 5a–i were purified by flash chromatog-
raphy (n-hexane/ethyl acetate).
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Supporting Information (see footnote on the first page of this arti-
cle): Copies of the NMR spectra and characterization data for all
compounds.
Acknowledgments
This work was supported by grants from Avidin (AVINOMID) and
the National Technology Program (GLINOLID; National Re-
search and Technology Office, Hungary); Avicor: GOP-1.1.1-08/1-
2008-0001.
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Received: November 9, 2010
Published Online: December 30, 2010
Eur. J. Org. Chem. 2011, 848–851
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
851