Preparation and use of MeO-PEG-supported chiral diphosphine ligands: soluble polymer-supported catalysts for asymmetric hydrogenation

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

“…Similar increases in activity have been found for other related systems in which the (2S,4S)pentanediol component was substituted by polyethyleneglycol chains. 222,223 Soluble polymer-supported chiral phosphoramides (159 and 160) have been reported to be significantly more efficient than the corresponding homogeneous analogue (161) for the organocatalytic allylation of benzaldehyde with allyltrichlorosilane ( Fig. 34).…”

“…53). 319 They assembled several columns packed with suitable supported reagents, catalysts and scavengers (220)(221)(222) required for the different synthetic and purification steps. The system could be reused sixty times with no significant loss in selectivity or yield (90% ee and 62% yield for the 60th run, in comparison with 99% ee and 65% yield for the first cycle) after following the proper protocols of washing and regeneration.…”

Phosphino-carboxamides: the inconspicuous gems

“…249,250 Pyrphos analogues bearing P-chiral donor groups were also reported. 251 Amidation reactions with (3R,4R)-142 (or the corresponding (S,S)-enantiomer and P-chiral analogues) and (3R,4R)-144 were employed to anchor the chiral, C 2 -symmetric diphosphine unit onto poly(acrylic acid), 252 poly(ethylene glycol) (MeO-PEG-OH) 253 or PEG-chains in a PEG-grafted poly(styrene) (PS-PEG-NH 2 ). 254 In the same manner, phosphinoamine 142 was modified with water-solubilising acyl tags 252b or appended to terminal positions of PPI and poly(amido amine) (PAMAM) dendrimers, 255 to focal points of etheric dendrons 256 and even to protein-directing biotin units 257 and oligonucleotides.…”

“…Ru-catalysts prepared from this polymer catalyzed hydrogenation of 172 in methanol under homogenous conditions (ee > 90%) and could be recovered unaffected by solvent precipitation. 340 Another co-polymer prepared by polycondensation of (R)-171, terepthaloyl chloride and poly(ethylene glycol) (MW = 4000) was evaluated in hydrogenation of 172 and some related substrates under homogenous and two-phase conditions. 341 (Note: a BINAP derivative bearing one MeO-PEG-CO(CH 2 ) 3 CONHCH 2 -and one charged NH 3 CH 2 -modifying group was prepared by Geneˆt et al and used as a ligand in asymmetric hydrogenations.)…”

Synthesis of MeO-PEG-Supported Ferrocenyloxazoline Ligands and Their Application in Asymmetric Catalysis

“…[2,3] As soluble polymer modified poly(ethylene glycol)s (PEGs) recently emerged as readily functionalized, commercially available polymers that are soluble in some solvents and insoluble in a few other solvents for example ether and n-hexane. [4][5][6][7][8][9][10][11][12][13] Recently, the monomethyl ether of PEG (MeO-PEG) has successfully being used for supporting chiral ligands to be transformed in catalysts for some catalytic asymmetric reactions. MeO-PEG has also been employed by us for the immobilization of MeO-PEGsupported tunable axial chiral bisphosphine ligands which were applied in asymmetric hydrogenation of quinolines with up to 92% ee.…”