The Stereochemistry of Organmetallic Compounds. XXV. The Stereochemistry of Displacements of Secondary Methanesulfonate and p-Toluene-sulfonate esters by Diphenylphosphide Ions. X-ray Crystal Structure of (5α- Cholestan- 3α-yl)diphenylphosphine Oxide

Abstract

Reactions of both axial and equatorial cholestan-3α- and -3β-yl mesylates and tosylates with sodium diarylphosphides give cholestanylphosphines in good yield and with complete inversion of stereochemistry. The stereochemistry has been established by an X-ray crystal structure of (5α-cholestan-3α-yl) diphenylphosphine oxide, and a general method for distinguishing between axial and equatorial phosphines based on ³¹P N.M.R . spectra is presented. The monophosphines were used as ligands in asymmetric hydrogenation, but only low optical yields were obtained.