Amino acids as suitable N-nucleophiles for the aza-Michael reaction of vinylphosphoryl compounds in water

Application of water as a sole solvent promotes the aza-Michael reaction of diethyl vinylphosphonate and diphenylvinylphosphine oxide with α-substituted amino acid sodium salts generated in situ to afford the corresponding β-aminophosphonates and β-aminophosphine oxides in excellent yields and of high purity. The approach is equally suitable for the synthesis of both racemic and optically active compounds. In the case of glycine, the mono and bis(phosphonoethyl)-substituted products are formed in 6:4 ratio and when using a stoichiometric amount of the reactants, N,N-bis[2-(diethoxyphosphoryl)ethyl]glycine was the only product. In contrast, to perform the double phosphonoethylation of d,l-alanine, prolonged heating of the reaction mixture was required.