Ultrasound-Assisted, One-Pot, Four-Component Synthesis of 1,4,6,8-Tetrahydroquinolines in Aqueous Medium

Abstract

A series of 2-amino-3-cyano-4-aryl-5-oxo-7,7-dimethyl-1,4,6,8-tetrahydroquinolines were prepared by a one-pot, four-component condensation of aromatic aldehydes, dimedone, malononitrile, and ammonium acetate using K₂CO₃ as a catalyst in aqueous medium under sonic conditions. This protocol, being a single-step reaction, has the advantages of operational simplicity and minimal environmental impact. The synthesized compounds were confirmed through spectral characterization using infrared, ¹H NMR, ¹³C NMR, and CHN analysis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

GRAPHICAL ABSTRACT

Keywords:

• 2-Amino-3-cyano-4-aryl-5-oxo-7,7-dimethyl-1,4,6,8-tetrahydroquinolines
• aromatic aldehydes
• malononitrile
• potassium carbonate
• ultrasonication
• water

ACKNOWLEDGMENTS

One of the authors, S. H. S. A., gratefully acknowledges the Sana University, Yemen, for a fellowship, and the authors thank the VGST Department of Science and Technology, government of Karnataka, for the CESEM Award Grant No. 24 (2010-2011).

Notes

^a 10 mol%. Ultrasound (at 26 °C).

^b Isolated yields.

^c Reflux in water. ND, not detected.

^a Isolated yields.

^a K₂CO₃ (5 mol%).

^b Ultrasound (at 26 °C).

^c Isolated yields.

^a Isolated yields.

^b Novel compounds.ND, not detected.