First synthesis of 1,1′-ferrocene bis-aminophosphonic esters

The series of aminophosphonates bearing the 1,1′-bis-substituted ferrocenyl moiety was obtained by the addition of dialkyl phosphites to an azomethine bond of Schiff bases derived from 1,1′-ferrocene-bis-carboxaldehyde. This addition led to both diastereoisomeric forms demonstrating its behaviour to be contrary to the addition to terephthalic Schiff bases, which led exclusively to a meso-form.