Synthesis of 4-phosphazenyl-2,3-dihydropyrrol-2-ones and 5-phosphazenyl-2-pyridones from β-[(N-acyl)phosphazenyl]enamines and dimethyl acetylenedicarboxylate

Abstract

4-Phosphazenyl-2,3-dihydropyrrol-2-ones and 5-phosphazenyl-2-pyridones are obtained by addition of dimethyl acetylenedicarboxylate to [(N-acyl)phosphazenyl]enamines. In refluxing dichloromethane the reaction affords exclusively 2,3-dihydropyrrol-2-ones, while in toluene at 110 °C a mixture of 2-pyridones and 2,3-dihydropyrrol-2-ones is formed. They are easily separated by fractional recrystallization. The structures of all new compounds have been unequivocally assigned based on two-dimensional ¹H,¹³C correlation and steady-state nuclear Overhauser enhancement experiments. For 2-pyridones the absolute sign of ⁴J_PH has been determined.