Chiral biphosphine ligands

Matteoli, U., Beghetto, V., Schiavon, C., Scrivanti, A., and Menchi, G. Synthesis of the new chiral biphosphine ligand 2,3-bis(diphenylphosphino)butane (CHIRAPHOS), Tetrahedron Asymmetry 1997, 8, 1403-1409. 

A new type of iodonium salts constitute the conformationally rigid, tetranu-clear macrocyclic ring systems dubbed molecular boxes. The relatively simpler tetraaryltetraiodonium salts were obtained from 4,4 -bis(diacetoxyiodo)bi-phenyl and 4,4 -bis(trimethylsilyl)biphenyl [119]. The iodonium salt derived from 4-(4 -lithiophenyl)pyridine was made using the method of /J-(dichloroio-do)chloroethylene and it was used for the construction of hybrid iodonium-platinum (or palladium) cationic tetranuclear macrocyclic squares including some in which the ligand of the metal was a chiral biphosphine [120,121]. 

Modified chiral biphosphinic dioxolane ligands and their use in the asymmetric synthesis of natural lignans 92H(33)435. 

Chiral amine/dipeptide ligands Biphosphine Ligands Carbene Ligands... 

Hydrogenation of iV-acyl a-amino acids in 87-91% ee has been accomplished with Rh bound to copolymers (43) with chiral phosphine ligands, as shown in Scheme 16. The same % ee was obtained with Rh catalysts prepared from analogous soluble ligands. Hydrophilic poly(2-hydroxy-ethyl methacrylate) and poly(iV,iV-dimethylacrylamide) provided polar environments for the hydrogenations. The chiral polymeric catalyst can be recycled. Earlier studies with polymers based on chiral biphosphine monomer (44) showed that polar comonomers were required for high % ee catalysis. ... 

Numerous biphosphines appear to be good chiral ligands for the near-quantitatively enantioselective hydrogenation of amino acid precursors The two phosphorus atoms are connected by a chiral backbone having one asymmetric center or two. The general structure is easily prepared by alkylation of a disubstituted phosphide ... 

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