Ferrocenecarboxaldehyde is readily transformed into the acetal of (S)-1,2,4-butanetriol (1,3-dioxane structure) and further methylated to give acetal 15. This can then be ortho-lithiated using t-BuLi with very high diastereoselectivity (98% de). Electrophilic quenching provided a large array of compounds of established stereochemistry. Controlled hydrolysis leads to many ortho-substituted ferrocenecarboxaldehydes (98% ee) which themselves are starting materials in the synthesis of various classes of enantiopure ferrocene derivatives with planar chirality of predictable absolute configuration.

Flash chromatography on silica gel of several sulfoxides of varying ee's shows a strong enantiomeric fractionation. For example (R)-methyl p-tolyl sulfoxide of 86% ee gives 99% ee (R) in the first fraction and 63 % ee (R) in the last fraction, respectively, while (fi)-ferrocenyl phenyl sulfoxide (65 % ee) provides (S) enantiomer (79% ee) in the first fraction and (R) enantiomer (94% ee) in the last fraction. Various aspects of the phenomena are discussed. This method provides a simple procedure to obtain high ee for sulfoxides prepared by asymmetric synthesis of only modest enantioselectivity.Chiral sulfoxides are extremely useful chiral auxiliaries in asymmetric synthesis.1-4 For this purpose, it is of interest to prepare sulfoxides of various structural types. The conversion of chiral sulfinates to sulfoxides