ISSN:
0009-2940
Keywords:
Cross-Coupling
;
Grignard reactions
;
Nickel
;
Pyrollidinephosphane
;
Cooperative effects
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The preparation of both diastereomeric derivatives of 3-(diphenylphosphanyl) pyrrolidine with chiral (tetrahydrofuran-2-yl)methyl and [(N-neopentyl)pyrrolidin-2-yl]methyl groups as substituents on the pyrrolidine nitrogen atom and of (2S,4S)-1-benzyl-4-(diphenylphosphanyl)-2-(methoxymethyl) pyrrolidine is reported. [3S,P(RS)]-3-(phenylphosphanyl) pyrrolidine, bearing an additional chiral center on phosphorus, is the starting material for the preparation of phosphanes, in which one phenyl group of the PPh2 moiety is substituted by an 2-methoxyphenyl (=An) or 2,4,6-trimethoxyphenyl (=TMP) group. PdI2 complexes of these ligands were separated into diastereomers by chromatography on silica gel columns. The structural chemistry of these novel phosphane diastereomers and their PdI2 complexes is investigated by X-ray crystallography and NMR. At the P,N-coordinated palladium center displacement of an iodide anion is found for P,N,N′ ligands only. In the nickel complex catalysed cross-coupling reaction, yielding 3-phenyl-1-butene, we obtain the highest enantioselectivities in the case of simple 1-alkyl-3-(diphenylphosphanyl)pyrrolidine ligands. The enantioselectivity obtained with diastereomeric derivatives, bearing additional ether or amine ligating sites is mainly determined by the chiral center in 3-position of the 3-(phosphanyl) pyrrolidine part of these ligands. Optimisation of enantioselectivity with these ligands can be carried out by a variation of the ligand to nickel ratio and by the choice of the vinyl halide used as starting compound. The catalytic cycle must contain at least one catalytically active species, bearing more than one β aminoalkylphosphane ligand.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19971300729
