Arylation of Phosphines, Phosphonates, and Phosphinates

Pd-catalyzed arylation of various phosphorus compounds containing P—H bonds with aryl and alkenyl halides, or triflates offers useful methods of C— P bond formation. After pioneering work on Pd-catalyzed arylation and alkenylation of dialkyl phosphonates by Hirao etal., extensive studies have been carried out on arylation of various phosphorus compounds. The methods are particularly useful for the synthesis of various chiral phosphines used in Pd-catalyzed asymmetric reactions. 

Arylations of phosphines and phosphine oxides are carried out as shown by the following general equations. The reactions are explained by oxidative addition of aryl halides, followed by ligand exchange with Ph2P-H, which is similar to transmetallation. Finally, reductive elimination affords arylated products. 

Recently, extensive synthetic studies on multiply functionalized chiral arylphosphines by Pd-catalyzed arylation of primary and secondary phosphines with aryl halides have been carried out by Stelzer [2]. The synthetic methods can be summarized by the following general schemes. 

A racemic phosphine 28 was obtained by consecutive displacement of hydrogen atoms of phenylphosphine (8) with two different aryl iodides 25 and 27. For the coupling of diphenylphosphine with aryl iodides, Pd on carbon is a good catalyst in DMF under microwave dielectric heating in DMF [3]. 

A P-chirogenic phosphine can be synthesized by Pd-catalyzed asymmetric phos-phination. Coupling of the racemic phosphine 28a with iodobenzene afforded the 

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