Diastereoselective addition of organozinc and organomagnesium reagents to 2-(2′-pyrimidyl)ferrocenecarbaldehyde

Addition of diisopropylzinc, diethylzinc, and isopropylmagnesium chloride to readily available 2-(2′-pyrimidyl)ferrocenecarbaldehyde takes place with high diastereoselectivity to afford exclusively the α-ferrocenyl alcohol of (R∗,pR∗) configuration. On the other hand, the addition of ethyl- and methylmagnesium bromide leads to diastereomeric mixtures in which the major isomer has the (S∗,pR∗) configuration. A unified mechanistic model accounting for this stereochemical outcome is proposed.