The addition of dialkyl phosphites or diphenylphosphine oxide to the triple bond of dialkyl acetylenedicarboxylate may result in mono- and/or bisadducts. The ratio of the products may be influenced by the molar ratio of the reactants and the conditions (temperature of microwave irradiation and reaction time). Stereospecific 3JPP couplings were utilized in the assignments to the meso and racemic forms of the bisadducts. The bis(dialkylphosphonyl)-succinates were formed as a mixture of the corresponding meso form and racemate, while bis(diphenylphosphinoyl)-succinate was obtained as a racemate. The 31P–12CH–13CH–31P spin system of bis(dialkylphosphonyl)-succinates was subjected to a detailed NMR analysis supported by simulation.