Anomeric-like Substituent Effects on the Chair-Chair Conformational Equilibrium of the 2-Oxo-1,3,2-oxazaphosphorinane Ring System

Article abstract of DOI:10.1021/jo00021a031

The chair-chair equilibria for a series of 5,5-dimethyl-2-oxo-(2-p-X-anilino)-1,3,2-oxazaphosphorinanes were determined by 1H NMR. The percentage of chair conformer with the p-X-anilino group axial is increased by the presence of electron withdrawing X, while the opposite is true for electron-donor para X.Reasonably good linear plots of log K vs ? were obtained in the solvents acetone-d6, CD3CN, and CD3NO2 with ρ = 0.28-0.36.These results are interpreted in terms of the dominance of the endo anomeric effect involving overlap of the endocyclic N(3) and O(1) p lone pairs with the axial P-N ?* orbital (p-XC6H4NHP).