Exclusively planarchirality is exhibited by the ferrocenes obtained in a highlyenantioselectivesynthesis in which a chiral aminoamide acts as a temporary protecting/directing group. This method was used to obtain an enantiomerically pure tetrasubstituted ferrocene, which was transformed into the first C2 -symmetric disubstituted ferrocenophane [Eq. (1)].
The chiral 1,1'-bis-acetals, bis-1,1'-[(2S, 4S)-(hydroxymethyl)-2-dioxanel,3]-ferrocene (3) and 1,1'-bis-1,1'-[(2S, 4S)-(methoxymethyl)-2-dioxanel,3]-ferrocene (4) were synthesized. (3) was crystallographically characterised. The ortholithiation of (4) was studied in various conditions. Fair yields of monosubstituted compounds could be obtained with a complete regioselectivity in favor of the 2 position but the diastereoselectivities were moderate (up to 35%). Some disubstituted compounds can be isolated but in low yields (up to 8%). The regioselectivity is complete in favor of the 2,2'-disubstituted isomer. Only the diastereoisomer with two opposite planar chiralities is observed. (C) 1998 Elsevier Science S.A. All rights reserved.