Abstract Reaction of ethylenediamine with phosphorous acid and formaldehyde in molar ratio 1: 2: 2 gives [[(2-aminoethyl) imino] bis (methylene)] bisphosphonic acid (2a) as the major product. Similarly, reaction of hexamethylenediamine with phosphorous acid and formaldehyde in molar ratio 1: 2: 2 yields [[(6-aminohexyl) imino] bis (methylene)] bisphosphonic acid (2b) which is isolated either as [[(6-carbobenzoxyaminohexyl) imino] ...
