A green synthesis of α-aminophosphonates in glycerol

A simple and efficient method is described using glycerol as a solvent in the catalyst-free synthesis of α-aminophosphonates in high purity. Products are prepared by the Kabachnik– Fields reaction from amines, phosphites, and carbonyl compounds. The method does not require a toxic catalyst.α-Aminophosphonic acids and their derivatives exhibit a widerange of biological properties,(1) and are able to function as α-aminocarboxylic acid surrogates.(2)α- Aminophosphonate esters haveattracted attention because not only are they biologically attractivepeptide mimics of α-amino acids, but they also exhibit intriguing biological activities.(3)Glycerol can be considered as‗organic water‘ since, like water, it is abundant, biodegradable,inexpensive, nontoxic, highly polar, immiscible with hydrocarbons,is able to form strong hydrogen-bond networks, and can dissolve awide range of organic and inorganic compounds, including transitionmetal catalysts.(4)In addition, compared to water, it has the advantage of a higherboiling point, lower vapor pressure, and is able to dissolve organiccompounds usually immiscible with water.(5)