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 1H and 13C 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.