Prototropic Isomerizations in the 2-Azaallylic Triad of Imidoylphosphonates

In the present review we attempt to systematize and generalize the available data on prototropy in imidoylphosphonates containing α-hydrogen atoms in the N- or C-alkyl groups of the C=N bond. Prototropic transitions in C=N-CH triad of imidoylphosphonates leading to biorelevant α-aminophosphonates are in main focus of the review. Central to this endeavour is elucidation of the effect that the phosphoryl or phosphonium moiety exerts on prototropy in the phosphorylated 2-azaallylic triad.