Synthesis of new 7-ferrocenyl-β-enaminone-coumarins and ferrocenyl-pyrano[3,2-g]quinolin-2-ones from coumarin and ferrocenyl-α-ketoalkynes using Ni(CN)2/NaOH/H2O/CO/KCN aqueous catalytic system

New ferrocenyl-β-enaminone-coumarins (1a–5a) and ferrocenyl-pyrano[3,2-g]quinolin-2-ones (1b–5b) were obtained through a heterocyclization reaction from 7-amino-4-methyl-2H-chromen-2-one and several ferrocenyl-α-ketoalkynes in a nickel homogeneous aqueous catalytic system formed by Ni(CN)2/CO/NaOH/KCN. In the absence of this catalytic system neither ferrocenyl substituted chromenone nor ferrocenyl-heterocycle was obtained. A possible mechanism is suggested for the synthesis of -β-enaminone-coumarins and pyrano[3,2-g]quinolinones. Molecular structure of 7-(1-ferrocenyl-3-(4-bromophenyl)-3-oxoprop-1-enylamino)-4-methyl-2H-chromen-2-one (5a) has been determined.

Graphical abstractNew ferrocenyl-β-enaminone-coumarins (1a–5a) and ferrocenyl-pyrano[3,2-g]quinolin-2-ones (1b–5b) were obtained through a heterocyclization reaction from 7-amino-4-methyl-2H-chromen-2-one and several ferrocenyl-α-ketoalkynes in a nickel homogeneous aqueous catalytic system formed by Ni(CN)2/CO/NaOH/KCN. In the absence of this catalytic system neither ferrocenyl substituted chromenone nor ferrocenyl-heterocycle was obtained.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Nickel homogeneous aqueous catalytic system is formed by Ni(CN)2/CO/NaOH/KCN. ► Reaction of 7-amino-4-methyl-coumarines with ferrocenyl-α-ketoalkynes is shown. ► With catalyst ferrocenyl-enaminone-coumarines and pyranoquinolinones were obtained. ► Mechanism for synthesis of ferrocenyl-enaminone-coumarines and pyranoquinolinones.