3-Imidoallenylphosphonates: In Situ Formation and β-Alkoxylation

3-Imidoallenylphosphonates, allenes bearing both an electron-withdrawing and -donating group, were isolated for the first time. An alkoxy substituent was introduced into these unprecedented intermediates in a one-pot approach, yielding β-functionalized aminophosphonates in excellent yields and short reaction times. The mechanistic insights gained are important additions to the domain of allene chemistry. Addition of biologically important molecules, including monoglycerides, amino acids, and nucleosides, proves the general applicability of the developed method.