Structural implications of nuclear magnetic resonance and infrared investigations on 2-substituted 1,3,2-dioxaphosphorinan-2-ones

Abstract

The ¹H n.m.r. spectra of twenty one 2-substituted 5,5-disubstituted 1,3,2-dioxaphosphorinan-2-ones (2-substituent = CPh₃, CMe₂·OH, OMe, OBu^t, NC₅H₁₀, Me, Et, Prⁿ, Ph, CH₂Ph, Br, Cl, H), many of which were examined at more than one temperature or concentration or in more than one solvent, are shown to be most consistent with the presence of one dominant chair conformer (2-substituent = alkoxy, Br, Cl, H) or with an equilibrium of rapidly interconverting chair conformers (2-substituent = alkyl, aralkyl, phenyl). The assignment of i.r. phosphoryl stretching bands for some of these derivatives is shown to be qualitatively consistent with the ¹H n.m.r. results.

Predictions of the dispositions of exocyclic substituents based on these ¹H n.m.r. and i.r. spectra are made and a classification of 1,3,2-dioxaphosphorinan-2-ones based on the sum of the two J(POCH) values associated with the 4,6-methylene protons is established.