Asymmetric catalysis privileged ligands

In large-scale processes, a limited number of phosphines and phosphites are used, which can be called, in analogy to ligands in asymmetric catalysis, privileged hgands. Somewhat more variants are available from commercial suppliers. 

Li H, Chen YG, Deng L (2011) Cinchona Alkaloids. In Zhou QL (ed) Privileged Catalysts and Ligands in Asymmetric Catalysis. Wiley-VCH, Weinheim, p 361... 

Oxazolines are nowadays essential ligands in asymmetric catalysis and also important synthons for stereoselective synthesis [8]. The success of the Cj-symmetric bis(oxazolines) ( BOX ) and pyridine-bis(oxazolines) ( Pybox ) discovered in the early 1990s has established them as a privileged class of ligands [9]. In contrast, the development and application of trisoxazolines lagged behind for a long time. Katsuki and collaborators [10] reported the first example of a chiral trisoxazoline in 1995 and their use in the allylic oxidation of alkenes (Kharasch-Sosnovsky reaction), as well as the enantioselective addition of diethylzinc to aldehydes. 

Teichert JF, Feringa BL (2010) Phosphoramidites privileged ligands in asymmetric catalysis. 

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