AN EFFICIENT ASYMMETRIC-SYNTHESIS OF 2-SUBSTITUTED FERROCENECARBOXALDEHYDES

Ferrocenecarboxaldehyde is readily transformed into the acetal of (S)- 1,2,4-butanetriol (1,3-dioxane structure) and further methylated to gi ve 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 h ydrolysis leads to many ortho-substituted ferrocenecarboxaldehydes (98 % ee) which themselves are starting materials in the synthesis of vari ous classes of enantiopure ferrocene derivatives with planar chirality of predictable absolute configuration.