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

• CAN-mediated oxidative CC coupling between 1-ferrocenylethanol and β-diketones.
• Synthesis of three new 2-substituted 1-ferrocenylethyl-1,3-diketones.
• Complete 1H and 13C assignments using 2D NMR experiments.
• Structures of the three compounds were determined by X-ray diffraction.
• Solely the diketo tautomers are observed in liquid and solid phases.

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-C5H4)), 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.

Chiral ferrocene-containing β-diketones, 3-(1-ferrocenylethyl)-pentane-2,4-dione, 1-(4-methoxyphenyl)-2-1-(ferrocenylethyl)-butane-1,3-dione, and 1-ferrocenyl-2-(1-ferrocenylethyl)-butane-1,3-dione (illustrated), have been synthesized using CAN-mediated oxidative CC coupling reaction between 1-ferrocenyl ethanol and the corresponding 1,3-dione reagent; the compounds exist solely as their diketo tautomer form both in solution and in the solid state.Figure optionsDownload as PowerPoint slide