Preparation of new sulfonated triarylphosphanes:: Control of the selectivity by structural assistance

A synthetic approach for the selective preparation of tri-, di-, and monosulfonated triarylphosphanes is presented. PPhnAr3-n parent phosphanes (1a-8a) having aryl rings (Ar) activated by simple electron donating groups (CH3, CH3O) were prepared by the standard Grignard method. The activated rings could be sulfonated selectively under mild conditions and with short reaction times (0.8-3 h). Using a very simple workup procedure, the corresponding tri-, di-, and monosulfonated phosphanes (1b-8b) were isolated in outstanding yields (88-99%) and found to contain negligible amount of phosphane oxides (0-4%). (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.