Synthesis, characterization and X-ray crystal structures of chiral ferrocene-containing β-diketones

Three new chiral ferrocene-containing β-diketones have been synthesized by reacting 1-ferrocenyl ethanol with the corresponding 1,3-diketone reagent MeCOCH₂COR (R = Me, 4-C₆H₄OMe, Fc; Fc = (η⁵-C₅H₅)Fe(η⁵-C ₅H₄)), using cerium(IV) ammonium nitrate (CAN) mediated C-C bond formation. These compounds identified as 3-(1-ferrocenylethyl)-pentane- 2,4-dione (1), 1-(4-methoxyphenyl)-2-(1-ferrocenylethyl)-butane-1,3-dione (2), and 1-ferrocenyl-2-(1-ferrocenylethyl)-butane-1,3-dione (3), have been isolated as air and thermally stable microcrystalline solids in 79, 63 and 44% yields, respectively. Compounds 2 and 3 were formed in 63:37 and 88:12 diastereomeric ratios, respectively. They have been fully characterized by elemental analyses, FT-IR spectra, mass spectrometry, and their complete assignments have been conducted using 2D NMR experiments. In addition, their molecular identity and geometry have been confirmed by single-crystal X-ray diffraction, and both solution and solid state measurements have shown that the three complexes exist solely as their diketo tautomers.