Facile Diastereoselective Synthesis of Phosphonate Esters Bearing Cyclic or Acyclic Amides

Phosphonate esters were obtained in excellent yields from a 1:1:1 addition reaction between triphenyl phosphite, dialkyl acetylenedicarboxylate and NH acids (maleimide, succinimide and N-phenylacetamide). The stereochemistry was established by solution NMR and single X-ray crystallography for two of the phosphonate esters. Dynamic effects of the maleimide moiety was observed and determined by 1 H and 13 C NMR. The free energy of activation is established for the rotation of the maleimide moiety around the N-C bond in dimethyl (2S * ,3R * )-2-(2,5-dioxo-2,5-dihydropyrrol-1-yl)-3-(diphenoxyphosphoryl)butanedioate as 47 ± 2 kJ/mol.