Structural and biological investigation of ferrocene-substituted 3-methylidene-1,3-dihydro-2H-indol-2-ones

The Knoevenagel condensation of 1,3-dihydro-2H-indol-2-one 1 with ferrocene carboxaldehyde 2 afforded an approximate 2: 1 mixture of the geometrical isomers (E)- and (Z)-3-ferrocenylmethylidene-1,3-dihydro-2H-indol-2-one 3 respectively in an overall 67% yield; the air and solution-stable isomers were readily separated by preparative thin layer chromatography and their structures were unequivocally elucidated in solution, by H-1 NMR spectroscopy, and in the solid phase, by X-ray crystallography; both isomers of 3 displayed in vitro toxicity against B16 melanoma and Vero cell lines in the micromolar range and inhibited the kinase VEGFR-2 with IC50 values of ca. 200 nM.