Electronic and steric effects of ligands as control elements for rhodium-catalyzed asymmetric hydrogenation

Substituent electronic effects in chiral ligands for asymmetric catalysis

“…Electronic tuning of such bis(diphenylphosphino)pentane ligands was reported by Bakos et al in 2004 [37]. They varied the substitution pattern of the aryl groups to modify the donor phosphine basicity and applied rhodium complexes of the resulting ligands in the asymmetric hydrogenation of (Z)-a-acetamidocinnamic acids and esters, Scheme 31.…”

Phosphines and Related Tervalent Phosphorus Systems

“…361 Twenty new chiral aminoalkylphosphines of type (154) have been prepared by transformations of related chiral phosphinoalkanoic acids. 362 An eight stage route to the diphosphine (155) has been developed, starting from 5-amino-isophthalic acid dimethyl ester, involving Arbuzov and trichlorosilane reduction stages, and subsequent elaboration of the arylamino group. Covalent binding to silica is then possible via the succinimide ester group.…”

“…A convenient general procedure has been developed for the synthesis of a range of long chain a,o-bis(diphenylphosphino)alkanes involving 18-32 methylene bridges. 149 Also reported are the linear tetraphosphine (77), 150 a series of new linear arene-bridged bis(1,4-diphenylphosphinoethoxy) systems, e.g., (78), 151 unsymmetrical bis (diarylphosphino)propanes having partly fluorinated aryl substituents, 152 and various unsymmetrical arsino(phosphino)ethanes having bulky groups at phosphorus and arsenic, together with new chiral diphosphino-ethane 153 andpropane 154,155 systems, e.g., (79). Further reports have appeared of the synthesis of carbohydrate-based diphosphines, e.g., the rigid isomannide-based system (80), 156 the water-soluble a,a-trehalose-based phosphinophosphinite (81) 157 and both a diphosphino-and a tetraphosphino-a-cyclodextrin system.…”

New, efficient, heterogenized catalysts for asymmetric hydrogenation of dehydroamino acid derivatives

“…[Rh(NBD)(2S,4S)-BDPP]PF 6 and [Rh(NBD)(2S,4S)-3,5-diMe-BDPP]PF 6 complexes were prepared according to a published process [9]. (Z)-a-acetamidocinnamic acid was purchased from Aldrich and methylester was prepared by a standard procedure [10].…”

“…A Rh complex of this chiral ligand, the [Rh(NBD)(2R,4R)-BDPP]ClO 4 was successfully applied in the hydrogenation of methyl (Z)-a-acetamidocinnamate with excellent activity and selectivity [8]. An even higher activity was found using dimethylated derivatives of BDPP in the hydrogenation reaction [9]. Full potential of this remarkable catalytic system can be applied if the above catalyst will be heterogenized.…”