Synthesis, characterization, and applicability of neutral polyhydroxy phospholane derivatives and their rhodium(I) complexes, for reactions in organic and aqueous media

Two different protocols for the preparation of water-soluble, enantiomerica lly pure polyhydroxybisphospholanes from acid-labile acetal and tert-butyld imethylsilyl-protected derivatives are reported. These procedures circumven t two of the commonly encountered limitations in the synthesis of these pot entially important ligands: (a) formation of phosphonium salts from the hig hly basic phosphine under acidic conditions, and (b) the need to start with preformed, fully protected cationic metal complex. Thus, cationic Rh compl exes of these ligands have been prepared in a separate step, and they have been found to be excellent catalysts for organic and aqueous phase hydrogen ation of dehydroamino acids. The viability of catalyst recovery has been de monstrated in three different systems, including two cases where > 99% ee c an be achieved under recycling conditions.