GREEN SYNTHESIS AND <i>Z</i>/<i>E</i>-ISOMERIZATION OF NOVEL COUMARIN ENAMINES INDUCED BY ORGANIC SOLVENTS

Authors

  • Abolfazl Olyaei Department of Chemistry, Payame Noor University, PO BOX 19395-4697, Tehran
  • Soheila Javarsineh Department of Chemistry, Payame Noor University, PO BOX 19395-4697, Tehran
  • Mahdieh Sadeghpour Department of Chemistry, Takestan Branch, Islamic Azad University, Takestan

DOI:

https://doi.org/10.1007/4715

Keywords:

chromane, 4-hydroxycoumarin, ketoenamine, triethyl orthoformate, Z/E-isomerization

Abstract

An efficient and straightforward synthesis of novel (Z/E)-3-[(heteroarylamino)methylidene]chromane-2,4-dione derivatives via a one-pot three-component condensation of 4-hydroxycoumarin, triethyl orthoformate, and heteroaryl amines in the presence of guanidinium chloride as organocatalyst under solvent-free conditions is described. Investigation of spectroscopy data indicated that coumarin enamines exist in the ketoenamine tautomeric form and undergo Z/E-isomerization in respect to the C=C bond in CDCl3 and DMSO-d6 at room temperature. Furthermore, intramolecular hydrogen bonds have been observed in the synthesized compounds. Also, 1H NMR spectra indicated that E-ketoenamines are the major isomers. High to excellent yields, short reaction times, simple workup, and very easy purification of products by non-chromatographic methods are advantages of this synthetic procedure.

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Published

2018-11-09

Issue

Vol. 54 No. 10 (2018)

Section

Original Papers