Reactions of aldehydes RCHO with 2,2,2-trimethoxy-4,5-dimethyl-1,3,2- dioxaphospholene are known to form trimethylbiacetyl-aldehyde-phosphite adducts which upon methanolysis gave rise to the corresponding symmetrical 3-R-2,4-pentanediones (R = aryl, alkyl). Reactions between ferrocenecarboxaldehyde and the biacetyl-trimethylphosphite adduct, whatever the experimental conditions used, afforded three new oxygenated C3 and C4 side-chain containing ferrocenyl complexes, namely, 1-ferrocenyl-1,2-propanedione (1, Fc-C(O)C(O)CH3; Fc = (η5-C5H5)Fe(η5-C 5H4)), 4-methoxy-4-ferrocenyl-3-hydroxy-3-methyl-2- butanone (2, Fc-CH(OCH3)C(CH3)(OH)C(O)CH3) as a single diastereoisomer, and the ferrocenyl enone 4-ferrocenyl-3-methyl-3-buten- 2-one (3, Fc-CHC(CH3)C(O)CH3) with the enone portion adopting the s-trans conformation in the solid state. The compounds readily purified by silica gel packed column chromatography were isolated in 31-44% yields, and their constitution is in agreement with elemental analyses, IR and multinuclear NMR spectroscopy, and electrospray mass spectrometry. Their molecular identity and geometry have been confirmed by single-crystal X-ray diffraction.
- X-ray structure