ENANTIOSELECTIVE CATALYSIS .15. PREPARATIVE AND STRUCTURAL CHEMISTRY OF DIASTEREOMERIC DERIVATIVES OF 3-PHOSPHANYLPYRROLIDINE AND THEIR PALLADIUM(II) COMPLEXES - ASYMMETRIC GRIGNARD CROSS-COUPLING REACTION

The preparation of both diastereomeric derivatives of 3-(diphenylphosp hanyl)pyrrolidine with chiral (tetrahydrofuran 2-yl)methyl and [(N-neo pentyl)pyrrolidin-2-yl]methyl groups as substituents on the pyrrolidin e nitrogen atom and of -(diphenylphosphanyl)-2-(methoxymethyl)pyrrolid ine is reported. [3S,P(RS)]-3-(phenylphosphanyl)pyrrolidine, bearing a n 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-trimethoxy phenyl (= TMP) group. PdI2 complexes of these Ligands were separated i nto diastereomers by chromatography on silica gel columns. The structu ral chemistry of these novel phosphane diastereomers and their PdI2 co mplexes is investigated by X-ray crystallography and NMR. At the P,N-c oordinated palladium center displacement of an iodide anion is found f or P,N,N' ligands only. In the nickel complex catalysed cross-coupling reaction, yielding 3-phenyl-1-butene, we obtain the highest enantiose lectivities in the case of simple 1-alkyl-3-(diphenylphosphanyl)pyrrol idine ligands. The enantioselectivity obtained with diastereomeric der ivatives, bearing additional ether or amine ligating sites is mainly d etermined by the chiral center in 3-position of the 3-(phosphanyl)pyrr olidine part of these ligands. Optimisation of enantioselectivity with these ligands can be carried out by a variation of the ligand to nick el ratio and by the choice of the vinyl halide used as starting compou nd. The catalytic cycle must contain at least one catalytically active species, bearing more than one beta-aminoalkylphosphane ligand.