93-53-8Relevant articles and documents
Chiral diphosphite-modified rhodium(0) nanoparticles: Catalyst reservoir for styrene hydroformylation
Axet, M. Rosa,Castillon, Sergio,Claver, Carmen,Philippot, Karine,Lecante, Pierre,Chaudret, Bruno
, p. 3460 - 3466 (2008)
The organometallic synthesis of rhodium nanoparticles stabilized with diphosphite ligands is described. These nanoparticles were investigated as catalysts in the styrene hydroformylation reaction, and their activity and selectivity were compared with those of similar molecular complexes. NMR spectroscopic studies performed during the course of the catalytic reaction showed that the synthesized nanoparticles are not stable and produce molecular species. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Rhodium catalysed asymmetric hydroformylation with diphosphite ligands based on sugar backbones
Buisman,Martin,Vos,Klootwijk,Kramer,Van Leeuwen
, p. 719 - 738 (1995)
Chiral disphosphite ligands (PP) prepared from {(2,2'-biphenyl-1,1'-diyl), (4,4',6, 6'-tetra-t-butyl-2,2'-biphenyl-1,1'-diyl), 4,4'-di-t-butyl-6,6'-dimethoxy-2,2'-biphenyl-1,1'-diyl) and di(2-t-butyl, 6-methylphenyl)} phosphorochloridites and sugar backbones {1,2-O-isopropylidene-D-xylofuranose, methyl-2,3-O-isopropylidene-α-D-mannopyranoside and (methyl-3,6-anhydro)-α-D-mannopyranoside, α-D-glucopyranoside and β-D-galactopyranoside} have been used in the rhodium catalysed asymmetric hydroformylation of styrene. Enantioselectivities up to 64% have been obtained with stable hydridorhodium diphosphite dicarbonyl catalysts (HRhPP(CO)2). High regioselectivities (up to 97%) to the branched aldehyde were found at relatively mild reaction conditions (T = 25-40°C, 9-45 bar of syngas pressure). The solution structures of HRhPP(CO)2 catalysts have been studied by 31P and 1H NMR spectroscopy. Bidentate coordination of the diphosphite ligand to the rhodium centre takes place in a bis-equatorial way. A relation between the trigonal bipyramidal structure and the enantioselectivity of the HRhPP(CO)2 complex is found. Rigid ligands with unsuitable geometries for bidentate coordination probably coordinate as monodentates and give rise to unstable catalysts and low selectivities during catalysis.
Tunable furanoside diphosphite ligands. A powerful approach in asymmetric catalysis
Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen
, p. 2957 - 2963 (2003)
A series of highly tunable furanoside diphosphite ligands, derived from readily available D-(+)-xylose and D-(+)glucose, are discussed. Their modular nature allows a facile systematic variation in the configuration of the stereo-centres at the ligand bridge and in the biaryl substituents. This enabled to select a ligand for each particular reaction that provided enantioselectivities that are comparable to those of the best catalysts previously reported in different asymmetric reactions. The Royal Society of Chemistry 2003.
Deracemization through photochemical E/Z isomerization of enamines
Huang, Mouxin,Luo, Sanzhong,Pan, Tianrun,Zhang, Long
, p. 869 - 874 (2022/03/07)
Catalytic deracemization of a-branched aldehydes is a direct strategy to construct enantiopure a-tertiary carbonyls, which are essential to pharmaceutical applications. Here, we report a photochemical E/Z isomerization strategy for the deracemization of a-branched aldehydes by using simple aminocatalysts and readily available photosensitizers. A variety of racemic a-branched aldehydes could be directly transformed into either enantiomer with high selectivity. Rapid photodynamic E/Z isomerization and highly stereospecific iminium/enamine tautomerization are two key factors that underlie the enantioenrichment. This study presents a distinctive photochemical E/Z isomerization strategy for externally tuning enamine catalysis.
Chelation and Stereodirecting Group Effects on Regio- And Diastereoselective Samarium(II)-Water Allylic Benzoate Reductions
Leitch, Michael A.,O'Neil, Gregory W.,Stockdale, Trevor F.
, p. 1544 - 1560 (2020/05/19)
SmI 2 (H 2 O) n reductions of allylic benzoates adjacent to a trisubstituted alkene occur in high yields with complete regioselectivity and good diastereoselectivity (up to 90:10) for substrates containing properly positioned stereodirecting- and chelating groups. The outcome of these reactions can be rationalized by ring conformation considerations of a proposed chelated organosamarium intermediate, and a mechanism involving intramolecular protonation by a samarium-bound water.