Novel diphosphines, their complexes with transisition metals and their use in asymmetric synthesis
申请人:——
公开号:US20040260101A1
公开(公告)日:2004-12-23
The invention relates to novel diphosphines, in optically pure or racemic form, of formula (I):
1
in which:
R
1
and R
2
are a (C
5
-C
7
)cycloalkyl group, an optionally substituted phenyl group or a 5-membered heteroaryl group; and
A is (CH
2
—CH
2
) or CF
2
.
The invention further relates to the use of a compound of formula (I) as a ligand for the preparation of a metal complex useful as a chiral catalyst in asymmetric catalysis, and to the chiral metal catalysts comprising at least one ligand of formula (I).
reducing alkenes bearing metal-coordinating groups. In the present system, selectivity was pressure-dependent: In most cases, a decrease in the H2 pressure to 3 bar resulted in an increase in enantioselectivity. Moreover, the process can be carried out in environmentally friendly solvents, such as methanol and ethyl acetate, with no loss of selectivity.
MaxPHOX-Ir 催化剂系统为 α-和 β-四氢萘酮衍生的环状烯酰胺的还原提供了迄今为止报道的最高选择性。该结果表明铱催化剂也能有效还原带有金属配位基团的烯烃。在本系统中,选择性取决于压力:在大多数情况下,氢气压力降低至 3 bar 会导致对映选择性增加。此外,该过程可以在甲醇和乙酸乙酯等环保溶剂中进行,而不会损失选择性。
Phosphite-Thiother Ligands Derived from Carbohydrates allow the Enantioswitchable Hydrogenation of Cyclic β-Enamides by using either Rh or Ir Catalysts
Phosphite‐thioether ligands with a simple modular architecture, derivedfrom inexpensive l‐(+)‐tartaric acid and d‐mannitol, have been for the first time successfully applied (ee values up to 99 %) in the synthesis of 2‐aminotetralines and 3‐aminochromanes by metal‐catalyzed asymmetric hydrogenation of cyclic β‐enamides. The ligands have the advantages of the robustness of the thioether/phosphite moieties
Several enantiopure diphosphanes 21 were synthesized in three steps from a common precursor 19. The cationic rhodium complexes 22 were screened as catalysts for asymmetric hydrogenation of various alkenes. Enantioselectivities up to 95−98% have been observed in some cases. Enantioselectivities are modest in allylic substitution catalyzed by the corresponding palladium complexes.
Rhodium-P,O-bidentate coordinated ureaphosphine ligands for asymmetric hydrogenation reactions
作者:Jurjen Meeuwissen、Remko J. Detz、Albertus J. Sandee、Bas de Bruin、Joost N. H. Reek
DOI:10.1039/b926043a
日期:——
We present new ureaphosphine ligands that coordinate in a P,O-bidentate fashion to rhodium(I). The ureaphosphine-Rh(I)-complexes were effectively used in the asymmetric hydrogenation of cyclic enamides giving high conversions and enantioselectivity.