Expedient Synthesis of Biologically Potent Aryloxycoumarins and (Aryloxyimino)ethylcoumarins via Copper(II)-Promoted Chan–Lam Coupling Reaction

Abstract

A convenient protocol for the efficient synthesis of aryloxycoumarins and (aryloxyimino)ethylcoumarins is described. The synthetic route developed involves the Cu-promoted C-O and N-O coupling reactions from readily available hydroxycoumarin and (hydroxyimino)ethylcoumarin derivatives in the presence of the catalytic system Cu(OAc)₂/Et₃N. By applying this condition, a series of arylboronic acids have been successfully reacted to afford the coupled products in fair to good yields.

GRAPHICAL ABSTRACT

Keywords:

• Arylboronic acids
• Chan–Lam protocol
• coumarin
• cross-coupling reactions
• Cu(OAc)₂

ACKNOWLEDGMENTS

We acknowledge the financial support from the University Grants Commission and University of Calcutta. G. P. thanks the Council of Scientific and Industrial Research, New Delhi, India, for her fellowship (Grant No. 09/028(792)/2010 EMR-I).

Notes

^a Conditions: 1 (1 mmol), 2a (2 mmol), Cu(OAc)₂ (1 mmol).

^b Isolated yield (in some cases minor amounts of biaryl ether and/or phenol products were isolated).

^c Amount of CuI and Cu(acac)₂ used: 1 mmol.

^d Conditions: 1 (1 mmol), 2a (2 mmol), Cu(OAc)₂ (0.5 mmol).

All products showed analytical and spectral characteristics consistent with their structures.

All products showed analytical and spectral characteristics consistent with their structures.

All products showed analytical and spectral characteristics consistent with their structures.

All products showed analytical and spectral characteristics consistent with their structures.