“…Various chiral oxo-and oxy-functional diphosphines, e.g., (83), have been prepared from the camphor system. 165,166 Chiral C 2 -symmetric 1,4-dioxanyldiphosphines, e.g., (84), have been prepared from tartrate esters. 167 Routes to a number of P,P,N-donor systems have been developed, including a trans-chelating 1,5-bis(di-t-butylphosphino)-2-(S)-dimethylaminopentane, 168 2,2 0 -bis(diphenylphosphino)diphenylamine, 169 and a series of tripod ligands (85) involving phosphine and dialkylamine or N-pyrazolyl donors.…”