Chiral aminophosphine-phosphinite ligands

If Q-symmetric ligands are employed in asymmetric hydrogenation instead of the corresponding C2-symmetric ligands, there coexist principally four stereoiso-meric substrate complexes, namely two pairs of each diastereomeric substrate complex. Furthermore, it has been shown that, for particular catalytic systems, intramolecular exchange processes between the diastereomeric substrate complexes should in principle be taken into account [57]. Finally, the possibility of non-estab-hshed pre-equilibria must be considered [58]. The consideration of four intermediates, with possible intramolecular equilibria and disturbed pre-equihbria, results in the reaction sequence shown in Scheme 10.3. This is an example of the asymmetric hydrogenation of dimethyl itaconate with a Rh-complex, which contains a Q-symmetrical aminophosphine phosphinite as the chiral ligand. 

Cyclic chiral aminophosphine and phosphinite ligands in enantioselective catalysis 03CCR(242)145. 

Chiral ligands containing tervalent phosphorus acid derivatives as coordination sites continue to be explored for asymmetric metal catalysed reactions. New examples this year include the phosphite (119) and stereoisomers, the phosphites (120), 2 the diphosphinite TADDOP (121), the diphosphites (122) containing crown ethers, the aminophosphine-phosphinites AMPP s (123) and... 

Certain chiral phosphinite or aminophosphine ligands are also useful for amino acid synthesis. Hydrogenation with a CYCPHOS-Rh complex occurs rapidly to produce high optical yields. The efficacy of this reaction is ascribed to the flexibility of the ligand, which speeds the reaction and gives a fixed chelate ring conformation (26). 

FIGURE 29.1. Examples of chiral monodentate phosphorous-containing ligands phosphites, phos-phoramides, phosphordiamides, phosphinites, phosphonites, aminophosphonites, and aminophosphines. 

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