Phosphine ligands asymmetric

Hydrosilylation of monosubstituted alkenes with palladium catalysts and trichlorosilane follows a course which favors branched products. By using a chiral phosphine ligand, asymmetric reaction is feasible. Initially, menthyldiphenylphosphine (MDPP, 93) and neomenthyldiphenylphosphine (NMDPP, 94) were employed with little success. Later, (/ )-/VA -dimethyl-l-[(S)-2-diphenylphosphinoferroce-nyl]ethylamine [(R)-(S)-PPFA] (95) and its enantiomer were prepared, and these have proved to be the... 

Asymmetric allylation of carbon nucleophiles has been carried out extensively using Pd catalysts coordinated by various chiral phosphine ligands and even with nitrogen ligands, and ee > 90% has been achieved in several cases. However, in most cases, a high ee has been achieved only with the l,3-diaryl-substitiitcd allylic compounds 217, and the synthetic usefulness of the reaction is limited. Therefore, only references are cited[24,133]. 

Borane complexes of P-heterocycles as versatile precursors for the synthesis of chiral phosphine ligands used for asymmetric catalysis 98S1391. 

Synthesis of novel optically active cyclic phosphine ligands and their use in catalytic asymmetric reactions 98YGK511. 

Cr6py KVL, Imamoto T (2003) New P-Chirogenic Phosphine Ligands and Their Use in Catalytic Asymmetric Reactions. 229 1-40 Cristau H-J, see Taillefer M (2003) 229 41-73... 

New P-Chirogenic Phosphine Ligands and their Use in Catalytic Asymmetric Reactions... 

A number of excellent reports which deal with synthesis of optically active phosphine ligands are available to date, and have been referenced in this chapter. Therefore it is not the intention here to overlap with them, but rather to describe recent advances in the field. Thus, this chapter is intended to serve as a review to the preparation of some efficient P-chirogenic compounds which have been developed over the past ten years, by either resolution or asymmetric synthesis. Considerable progress has been made in the preparation and use of P-stereogenic compounds. Use of newer methods is stressed here however an at-... 

Scheme 1. First use of P-chirogenic phosphine ligands in asymmetric hydrogenation reaction...

The hydroboration of enynes yields either of 1,4-addition and 1,2-addition products, the ratio of which dramatically changes with the phosphine ligand as well as the molar ratio of the ligand to the palladium (Scheme 1-8) [46-51]. ( )-l,3-Dienyl-boronate (24) is selectively obtained in the presence of a chelating bisphosphine such as dppf and dppe. On the other hand, a combination of Pdjldba), with Ph2PC6p5 (1-2 equiv. per palladium) yields allenylboronate (23) as the major product. Thus, a double coordination of two C-C unsaturated bonds of enyne to a coordinate unsaturated catalyst affords 1,4-addition product On the other hand, a monocoordination of an acetylenic triple bond to a rhodium(I)/bisphosphine complex leads to 24. Thus, asymmetric hydroboration of l-buten-3-yne giving (R)-allenyl-boronate with 61% ee is carried out by using a chiral monophosphine (S)-(-)-MeO-MOP (MeO-MOP=2-diphenylphosphino-2 -methoxy-l,l -binaphthyl) [52]. 

In the same context, Kang et al. have examined several bidentate thiol derivatives as ligands in the same reaction to that described above. A nickel complex derived from the p-amino thiol depicted in Scheme 2.31 catalysed the reaction in a useful asymmetric level of 74% ee, whereas the use of the thiol phosphine ligand depicted in Scheme 2.31 gave a lower enantioselectivity of 27% ee. In this study, the authors found that the enantioselectivity was strongly dependent on the ligand concentration and on the nickel-to-ligand ratio. 

In addition, various chiral (p-A -sulfonylaminoalkyl)phosphine ligands were earlier employed by Achiwa et al. for the asymmetric palladium-catalysed hydrosilylations of cyclopentadiene and styrene, affording the corresponding... 

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