Microwave-Assisted Kabachnik⁻Fields Reaction with Amino Alcohols as the Amine Component

In this paper, the microwave (MW)-assisted catalyst-free and mostly solvent-free Kabachnik-Fields reaction of amino alcohols, paraformaldehyde, and various >P(O)H reagents (dialkyl phosphites, ethyl phenyl-H-phosphinate, and secondary phosphine oxides) is reported. The synthesis of N-2-hydroxyethyl-α-aminophosphonate derivatives was optimized in respect of the temperature, the reaction time, and the molar ratio of the starting materials. A few by-products were also identified. N,N-Bis(phosphinoylmethyl)amines containing a hydroxyethyl group were also prepared by the double Kabachnik-Fields reaction of ethanolamine with an excess of paraformaldehyde and secondary phosphine oxides. The crystal structure of a 2-hydroxyethyl-α-aminophosphine oxide and a bis(phosphinoylmethyl)ethanolamine was studied by X-ray analysis.