Synthesis, X-ray Geometry, and Anodic Behavior of Tris[2-(hydroxymethyl)phenyl]phosphane

Abstract

Tris[(monohydroxymethyl)phenyl]phosphanes 5a and 5b were prepared, and the geometry of the ortho-isomer 5a was determined by X-ray diffraction. 5a was found to be propeller-like in shape, exhibiting a helical conformation with the three hydroxymethyl substituents standing on the same side as that with the phosphorus lone pair. Phosphanes 5a and 5b underwent electrochemical one-electron oxidation, giving rise to nonpersistent phosphoniumyl cation radicals 5a·+ and 5b·+. The low value of the anodic peak potential of 5a was explained by the fast decay of 5a·+, which was rapidly rearranged to a phosphoranyl radical through the formation of a strong P−O bond. The fast oxidation of this intermediate phosphoranyl radical followed by a second cyclization led to the 1-[2-(hydroxymethyl)phenyl]spirobi[1H,3H-2,1-benzoxaphosphole] 7a, which was isolated in significant yield.