PHOX type ligand

While virtually all of the research described above has focused on the inter-molecular cycloaddition of azomethine ylides, the intramolecular process holds considerable promise for the synthesis of polycyclic natural products. The Pfaltz group reported an intramolecular catalytic asymmetric cyclization of aryl iminoesters 112 using a complex of silver acetate with PHOX type ligand 100 (Scheme 2.29,... 

In situ catalysts formed from Pd(dba)2 precursor and PHOX-type ligands have shown high enantioselectivities in Heck reactions (280). It has to be noted that no C=C double bond migration, a common sidereaction in Pd-phosphine catalyzed reactions, has taken place. 

The ligand synthesis requires only two steps from simple starting materials. As with the PHOX type catalysts, chirality is built in through the use of a chiral amino alcohol (Scheme 29.5). 

Among the potentially bidentate, P,N ligand derivatives of quite different structure can be found. The electronic and steric parameters of 2-(2 -diarylphosphino-phenyl)oxazoline-type ligand, PHOX) (81) may be varied both... 

J.-D. Lee, T. T. Co, T.-J. Kim, S. O. Kang, New types of o-carborane-based chiral phosphinooxazohne (Cab-PHOX) ligand systems synthesis and characterization of chiral Cab-PHOX ligands and their application to asymmetric hydrogenation, Synlett2WS9, 5, 771. 

---