Preparation and nuclear magnetic resonance studies of diaryloxytriphenylphosphoranes. Correlation of substituent effects with ³¹P N.M.R. chemical shifts

Abstract

Triphenylphosphine and diisopropyl azodicarboxylate react with phenols in tetrahydrofuran or chloroform at 0° to give diaryloxytriphenylphosphoranes. A linear free-energy relationship has been found between the ³¹P n.m.r. chemical shifts of many of these phosphoranes and the acid dissociation constants of the corresponding phenols. In general, electron-withdrawing groups on the phenol result in downfield ³¹P n.m.r. chemical shifts, while electron donating groups result in up-field shifts.