Reactions of 2-cyano-3-ferrocenylacrylonitrile with malononitrile: Formation of 4-ferrocenylpyridine-3,5-dicarbonitrile derivatives and sodium polymeric complexes containing carbanionic ligands

The reactions of 2-cyano-3-ferrocenylacrylonitrile with malononitrile in a EtOH/H₂O or MeOH/H₂O medium in the presence of Na₂CO₃ afforded 6-alkoxy-2-amino-4-ferrocenylpyridine-3,5-dicarbonitriles 3a,b (multi-component condensation), 6-alkoxy-2-amino-4-ferrocenyl-3-ferrocenylmethyl-3,4-dihydropyridine-3,5-dicarbonitriles 4a,b (multi-component cyclodimerization) and Na⁺ polymeric complexes: {[Na⁺(2-ferrocenyl(tetracyano)propenyl)^–L]_∞5a,b and [Na⁺(2-amino-3,5-dicyano-4-ferrocenyl-6-pyridyl-dicyanomethyl)^–L]_∞6a,b, where L = ethanol, methanol. Complexes with L = acetonitrile, dimethylformamide, acetone, ethyl acetate were prepared by recrystallization. The structures of the compounds 3b, 4b and Na⁺ polymeric complexes were established by the spectroscopic data and X-ray diffraction analysis. Two compounds 3a and 4a were tested in vitro against six human tumor cell lines U-251, PC-3, K-562, HCT-15, MCF-7 and SKLU-1 to assess their in vitro antitumor activity. The results suggest biological specificity towards PC-3, K-562 and HCT-15 cells for compound 3a, and towards PC-3 cell for compound 4a at doses of 50 μM, which are lower than cis-platin.