Influence of substituents in the aromatic ring on the spectral and chemical properties of 5-aryl-Δ3-1,3,4λ5-oxazaphospholin-2-ones

Cycloadducts formed in the reactions of dialkyl phosphorisocyanatidites with ortho-, meta-, and para-substituted aromatic aldehydes have the structure of 5-aryl-Δ3-1,3,4λ5-oxazaphospholin-2-ones. Differences were found between the chemical and spectral properties of the ortho compounds and the para and meta compounds. In the crystals and in solution oxazaphospholinones with ortho-substituted aryl groups exist in the stable form with a polarized P=N bond. Their para and meta analogs exist in the metastable form in the crystalline state, but in solution at temperatures above 00C they exist in the stable form. The 1H, 13C, and 31P NMR spectra were recorded on a Bruker WM-250 spectrometer. For the stabilization of the resonance conditions we used CDCl3. The mass spectra were determined on a MAT-212 spectrometer with 50-eV ionizing electrons