Cycloisomerization diphosphine ligands

Moreover, deconstructing the tridentate architecture of the triphos ligand into chiral diphosphines such as xyl-BINAP or SEGPHOS provided an enantios-elective cycloisomerization with enantio-ratios up to 98 2 (Scheme 31) (68). 

Complexes C3 have been used as pre-catalysts for the cycloisomerization of a model 1,6-enyne which contains a tosylamide function in the tethering chain (Fig. 10.43). The catalytically active species was generated by iodide abstraction from C3 by addition of a silver salt (AgBp4). The reaction affords the expected 3-azabicyclo[4.1.0]heptene derivative. An extensive catalytic screening highlighted (S. S -Chiraphos as the most effective chiral diphosphine and demonstrated that suitable modulation of the NHC ligand allows increasing of the... 

Brissy D, Skander M, Retailleau P, Frison G, Marinetti A (2009) Platinum(II) complexes featuring chiral diphosphines and N-hetetocyclic carbene ligands synthesis and evaluation as cycloisomerization catalysts. Organometallics 28 140-151... 

---