Chiral Metal Complex-Promoted Asymmetric Hydrophosphinations

Abstract

A review. This chapter provided an account of the synthesis of a series of chiral tertiary phosphines via the metal complex-assisted asym. hydrophosphination methodol. which involves secondary phosphines as the nucleophiles. Chiral aza- and phosphapalladacycles were found to function as highly efficient templates or catalysts for the asym. P-H addn. reaction. The versatile protocol allows for the asym. hydrophosphination of olefinic C:C bonds of monophosphines thus yielding a family of tertiary C*-diphosphines as well as C*P*-diphosphines, depending on the nucleophile employed. The addn. of two equiv. of HPPh2 to sym. bifunctionalized alkynes leading to generation of two new C* centers was also supported. The air-sensitive nucleophiles and the unsatd. substrates contg. unprotected functionalities such as aldehyde, keto, ester, cyano, and alc. can be utilized directly under this mild and facile reaction conditions. The methodol. is equally efficient when applied to the generation of P-N ligand systems via hydrophosphination of unsatd. pyridyl-based substrates as well as systems with C:N moieties. The protocol has also the added advantage of allowing the selective formation of 1,1-, 1,2-, and 1,3-diphosphines simply by judicious control of reaction conditions. This reaction can also be extended to the synthesis of chiral triphosphine systems. This synthetic strategy therefore promises to be a versatile approach for the generation of a wide range of chiral tertiary phosphine ligands with potential applications in catalysis. [on SciFinder(R)]