Microwave-assisted synthesis of (aminomethylene) bisphosphine oxides and (aminomethylene) bisphosphonates by a three-component condensation

A practical method was elaborated for the synthesis of (aminomethylene) bisphosphine oxides comprising the catalyst-and solvent-free microwave-assisted three-component condensation of primary amines, triethyl orthoformate and two equivalents of diphenylphosphine oxide. The method is also suitable for the preparation of (aminomethylene) bisphosphonates using (MeO)(2)P(O)H/(MeO)(3)CH or (EtO)(2)P(O)H/(EtO)(3)CH reactant pairs and even secondary amines. Several intermediates referring to the reaction mechanism together with a few by-products could also be identified.