A new synthetic route to optically active cyclomercurated ferrocenylimines

An adaptation of Kagan’s method for preparing 2-substituted ferrocenecarboxaldehydes has allowed us to directly prepare enantiopure (Sp)-2-chloromercurio-ferrocenecarboxaldehyde, (Sp)-3. Subsequent condensation of this aldehyde with (1R,2R)-(+)-1,2-diphenyl-1,2-ethanediamine ((R,R)-4) yielded a novel, enantiopure bis-cyclomercurated ferrocenylimine, (Sp,Sp,Rc,Rc)-N,N-bis(2-(chloromercurio)ferrocenylidene)-1,2-diphenylethane-1,2-diimine ((Sp,Sp,Rc,Rc)-5). In addition to the chiroptical data collected for both (Sp)-3 and (Sp,Sp,Rc,Rc)-5, the solid-state structure and absolute configuration of (Sp,Sp,Rc,Rc)-5 were confirmed by X-ray crystallography.