Enantiomerically pure &bgr;-hydroxy esters are prepared by a process in which &bgr;-keto esters are reacted with hydrogen in the presence of catalysts of the formula LRuX2 where
X is halogen, acetate, allyl, methallyl, 2-phenylallyl, perchlorate, trifluoroacetate, tetrafluoroborate, hexafluoroantimonate, hexafluorophosphate, hexafluoroarsenate or trichloroacetate,
L is a bidentate phospholane of the formula I
where
B=a bridging link with 1-5 carbon atoms between the two phosphorus atoms,
R1=H, C1-C6-alkyl, aryl, alkylaryl or SiR23,
R2=alkyl or aryl,
m=0 or 1,
R3=H or OR4, and
R4=R1,
with the proviso that if m=1 then R3=H and if m=0 then R3 ≠ H.
Synthesis of C2-symmetric analogues of 4-(pyrrolidino)pyridine: new chiral nucleophilic catalysts
作者:Alan C. Spivey、Adrian Maddaford、Tomasz Fekner、Alison J. Redgrave、Christopher S. Frampton
DOI:10.1039/b004704j
日期:——
The syntheses of a series of enantiomerically pure C2-symmetric 4-(pyrrolidino)pyridine (PPY) derivatives by SNAr of 4-halo-/4-phenoxypyridines and by cyclocondensation from 4-aminopyridine are described. Preliminary results pertaining to their use as catalysts for acylative kinetic resolution of 1-phenylethanol are also presented. A single-crystal X-ray analysis of PPY If is reported.
Phospolanes and diphospholanes of the general formula I
where:
is H, C1-C6-aryl, alkylaryl, SiR32,
R2 is alkyl or aryl,
A is H, C1-C6-alkyl, aryl, Cl or
B is a linker with 1-5 C atoms between the two P atoms, and their use as catalyst in asymmetric synthesis.
derivatives of the prominent DuPHOS or BPE ligands. D-Mannitol was used as the starting material for these ligands. New bisphospholanes were used as ligands in the enantioselective rhodium(I)-catalyzedhydrogenation of functionalized olefins like unsaturated α- and β-amino acid derivatives, itaconates, and an unsaturated phosphonate. A relevant ruthenium(II) catalyst was used for the reduction of prochiral β-oxo