Phosphinite-oxazoline ligands

Reactions of the same substrate with several nucleophiles were also catalyzed by the water-soluble Pd-complex of a phosphinite-oxazoline ligand which was prepared from natural D-glucosamine (Scheme 6.23) [53]. The catalyst dissolves weU both in water and in CH3CN but not in diethyl ether. Therefore the reactions could be ran either in water/toluene biphasic systems or in homogeneous water/CHaCN solutions. In the latter case, phase separation could be induced by addition of diethyl ether upon which the catalyst moved quantitatively to the aqueous phase. The product was obtained from the organic phase by evaporation of the solvent(s) and the aqueous solution of the Pd-complex was recycled. In aqueous systems the... 

Yonehara, K., Mori, K., Hashizume, T. et al. (2000) Palladium-catalyzed asymmetric inter-molecular arylation of cyclic or acyclic alkenes using phosphinite-oxazoline ligands derived from D-glucosamine. J. Organomet. Chem., 603, 40-9. 

The oxazoline-derived P,N ligands can be classified into four groups according to structure phosphino-oxazolines phosphite- and phosphinite-oxazolines catalysts containing a P-N bond and structurally related non-oxazoline catalysts. 

The extraction concept is also applicable to sophisticated syntheses of fine-chemicals as recently shown by Ohe, Uemura and co-workers [35], They prepared a novel amphiphilic phosphinite-oxazoline chiral ligand based on D-glucosamine. The corresponding palladium complex was an efficient catalyst for asymmetric allylic substitution reactions and could be recycled by simple acid/base extraction and reused in the second reaction without loss of enantioselectivity. 

Recent developments in chirality induced by ligands, and in efficient synthetic methods for ligands such as diphosphines, chiral diamines, amino-phosphine-phosphinites, phosphino-oxazolines and diimino-diphosphines, are available in the literature.105-107... 

Numerous complexes possess P,N-chelating ligands that form six-membered ring systems. Depending on the relative position of the phosphorus (including phosphines, phosphinites, and aminophosphines) and oxazoline/thiazoUne donor groups, four types of subunits can be considered (Scheme 14.14). 

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