88057-05-0Relevant articles and documents
Efficient novel 1,2-diphosphite ligands derived from D-mannitol in the Pd-catalyzed asymmetric allylic alkylation
Xing, Ai-Ping,Pang, Zeng-Bo,Li, Hai-Feng,Wang, Lai-Lai
, p. 8822 - 8828 (2015/03/05)
A novel Pd/1,2-diphosphite catalyzed asymmetric allylic alkylation of 1,3-diarylpropenyl acetate with malonates was developed. Catalyst optimization via a variation in the protecting groups at the 1,2- and/or 5,6-positions of d-mannitol skeleton and in bi
Synthesis and reactivity of chiral, wide-bite-angle, hybrid diphosphorus ligands
Czauderna, Christine Fee,Cordes, David B.,Slawin, Alexandra M. Z.,Müller, Christian,Van Der Vlugt, Jarl Ivar,Vogt, Dieter,Kamer, Paul C. J.
, p. 1797 - 1810 (2015/04/27)
Effective and modular synthetic approaches toward phosphine-phosphite ligands and phosphine-phosphonite ligands featuring a diphenyl ether backbone have been developed. The phosphine-phosphite ligands are obtained by a two-step protocol from 2-bromo-2′-methoxydiphenyl ether. The phosphine-phosphonite ligands are prepared in a four-step synthetic protocol that involves a novel, unsymmetrical diphenyl ether derived phosphine-phosphorusdiamide as key building block. Structural studies on PtII complexes with either phosphine-phosphite or phosphine-phosphonite ligands indicate strict cis coordination for these ligand systems. High-pressure NMR spectroscopy studies of Rh complexes under syngas indicate the presence of two ea isomers for Rh(H)(CO)2(PP). The existence of this mixture is further supported by high-pressure IR spectroscopy studies. In order to benchmark the activity and selectivity of these novel, wide-bite-angle, mixed-donor ligands, they were screened in Pd-catalyzed asymmetric allylic alkylation as well as Rh-catalyzed hydrogenation and hydroformylation reactions. The ligands give 100-% conversion and low-to-moderate enantioselectivity in the allylic alkylation of 1,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate with dimethyl malonate. In the hydroformylation of styrene, good conversion and regioselectivities are achieved but only moderate enantioselectivity. The ligands give good conversions in asymmetric hydrogenation of typical substrates, with good-to-excellent enantioselectivities of up to 97-% depending on the substrate. The design of two subclasses of chiral, mixed-donor diphosphorus ligands with a diphenylether backbone is described. Both phosphine-phosphonite and phosphine-phosphite derivatives are accessible. Coordination to PtII and RhI is described, and high-pressure spectroscopy under syngas provides information on coordination geometry. The chiral ligand systems are benchmarked in Pd-catalyzed allylic alkylation and Rh-catalyzed hydrogenation and hydroformylation.
Platinum-catalysed allylic alkylation: Reactivity, enantioselectivity, and regioselectivity
Blacker, A. John,Clarke, Matthew L.,Loft, Michael S.,Mahon, Mary F.,Humphries, Mark E.,Williams, Jonathan M. J.
, p. 353 - 360 (2007/10/03)
The use of platinum complexes as catalysts for allylic substitution has been studied. A variety of different complexes catalyse the reaction, and several substrates have been tested. In the alkylation of mono(alkyl)-substituted allylic acetates, regioselectivity is highly dependent on ligand choice. By using tricyclohexylphosphine as the ligand, almost complete formation of branched products is observed. The development of a highly enantioselective (ca. 80-90% ee) reaction that makes use of chiral diphenylphosphinooxazoline ligands (abbreviated as (S)-P∧N) is also described. The enantioselectivity is highly dependent on the ratio of ligand to platinum (when the ratio ligand/Pt is greater than 1:1, the ee drops off dramatically). This is in contrast to palladium and is interpreted in terms of differing coordination chemistry for the two metals ((S)-P∧N is hemilabile when complexed to platinum) and should be of significance to future systems that utilise heterobidentate ligands. The crystal structures of two isoelectronic platinum and palladium complexes [{(S)-P∧N}MCl2] are also described.
