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, enantiomerically pure polyhydroxybisphospholanes from acid-labile acetal and tert-butyldimethylsilyl-protected derivatives are reported. These procedures circumvent two of the commonly encountered limitations in the synthesis of these potentially important ligands: (a) formation of phosphonium salts from the highly basic phosphine under acidic conditions, and (b) the need to start with preformed, fully protected cationic metal complex. Thus, cationic Rh complexes of these ligands have been prepared in a separate step, and they have been found to be excellent catalysts for organic and aqueous phase hydrogenation of dehydroamino acids. The viability of catalyst recovery has been demonstrated in three different systems, including two cases where > 99% ee can be achieved under recycling conditions.
RajanBabu
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Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, USA.
Yan
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Shin
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