Efficient Synthesis of Ferrocenylquinolines via the Friedländer Reaction

Abstract

Acylferrocenes 2a–c reacted with ortho-aminoarylaldehydes 1a–e via the Friedländer condensation reaction to afford the corresponding ferrocenylquinolines 3a–o in moderate yields in the presence of sodium ethoxide (30 mmol%) under mild reaction conditions. Under the same reaction conditions, 1,1′-diacetylferrocene 2d and 1,1′-dipropionylferrocene 2e reacted with ortho-aminoaldehydes 1a–e to afford the corresponding 1,1′-bis(substituted quinolin-2-yl)ferrocene derivatives 3p–t. The structures of compounds 3a–t were determined and characterized by infrared, ¹H NMR, mass spectrometry, and elemental analysis. The crystal structures of 3e and 3q were determined by x-ray crystallography.

GRAPHICAL ABSTRACT

Keywords:

• Acylferrocene
• ferrocenylquinoline
• Friedländer reaction
• o-aminoarylaldehyde
• sodium ethoxide catalysis

ACKNOWLEDGMENTS

We are grateful to the National Natural Science Foundation of China (Nos. 2117208, 20772036, and 20802021) and the Natural Science Foundation of Guangdong Province (Nos. 8251063101000002 and 7005804) for financial support.

Notes

^a Isolated yield after silica-gel column chromatography.

^b 100 mmol% EtONa was used.

^c 10 mmol% EtONa was used.