Hydrophosphinations palladium

Hydrophosphination catalyzed by a palladium(II) precursor has been reported. The P-H bonds of a protected bis(phenylphosphino)pyrrolidine added to acrylonitrile in the presence of catalytic amounts of PdCl2 and K2CO3 (Scheme 5-9). Without palladium, using KOH or K2CO3 as base gave only 30-40% yield. Similar catalytic chemistry was reported briefly for methyl acrylate [10]. 

Scheme 5-9 Palladium-catalyzed hydrophosphination of aery lonitrile with a disecondary phosphine...

Metal complex chemistry, homogeneous catalysis and phosphane chemistry have always been strongly connected, since phosphanes constitute one of the most important families of ligands. The catalytic addition of P(III)-H or P(IV)-H to unsaturated compounds (alkene, alkyne) offers an access to new phosphines with a good control of the regio- and stereoselectivity [98]. Hydrophosphination of terminal nonfunctional alkynes has already been reported with lanthanides [99, 100], or palladium and nickel catalysts [101]. Ruthenium catalysts have made possible the hydrophosphination of functional alkynes, thereby opening the way to the direct synthesis of bidentate ligands (Scheme 8.35) [102]. 

The binuclear palladium complex [(tBu2PH)PdPtBu2]2 with oxygen gave a very efficient catalyst for the hydrogenation of a,/3-unsaturated carbonyls. 0 Glueck and co-workers have undertaken studies on aspects of platinum-catalyzed hydrophosphinations of activated olefins.71,72... 

The Duphos ligand (157) has been used to prepare organometallic complexes of palladium.385 Rhodium complexes of ligands (156), (157), or (159) are efficient catalysts for enantioselective hydrogenations337-341,343,345,386-388 and furthermore, in the case of platinum complexes with (157), as catalysts for the asymmetric hydrophosphination of activated olefins.71... 

Keywords Cross-coupling Hydrophosphination Mechanism Palladium Phosphination Phosphine... 

Scheme 34 Proposed mechanism for nickel- or palladium-catalyzed hydrophosphination via attack on a complex of an electron-rich alkene...

Examples of electrophilic addition of secondary phosphines to alkenes or alkynes were described. [114, 124, 125, 135]. Glueck [124-126] reported enantioselective tandem reaction of alkylated/arylation of primary phosphines catalyzed by platinum complex, proceeding with formation of chiral phosphaace-naphthenes. Palladium-catalyzed hydrophosphination of alkynes 219 tmder kinetic resolution conditions gave access to 1,1-disubstituted vinylphosphine boranes 220. However, despite screening several chiral ligands, temperatures, and solvents, the... 

Yuan M, Pullarkat SA, Li Y, Lee Z-Y, Leung P-H (2010) Novel synthesis of chiral 1,3-diphosphines via palladium template promoted hydrophosphination and fimctional group transformation reactions. Organometallics 29 3582-3588... 

Yuan M, Zhang NA, Pullarkat S, Li Y, Liu F, Pham P-T, Leung P-H (2010) Asymmetric synthesis of functionalized 1,3-diphosphines via chiral palladium complex promoted hydrophosphination of activated olefins. Inorg Chem 49 989-996... 

The same reaction was performed in the presence of a source of Pd and a bidentate phosphine in toluene at 50 °C. Methylphenylphosphine borane (41a) was reacted with 1-octyne in the presence of palladium acetate (5%) and dppp (10%) for 35 minutes. Interestingly, the Markovnikov product 43a is obtained in 85% yield, with no trace of 42, meaning that in this case the phosphorus attacks the internal carbon of 1-octyne. The same reaction using bdpp (2,4-dw(diphenylphosphino)pentane) and phenylacetylene (39, R = Ph) also yields regioisomer of 43 with 53% yield. Several experiments with diphenylphosphine borane under different reaction conditions (palladium source, temperature, alkyne) showed that the reaction does not occur in the absence of palladium (0) and that hydrophosphination of 1-ethynylcyclohexene (42) undergoes selective hydrophosphination at the triple bond, with the alkeneic bond untouched. 

In 2007, Glueck s group reported a catalytic DKR process in which secondary phosphines were converted into the corresponding enantio-enriched tertiary phosphines through palladium-catalysed asymmetric hydrophosphination of aryliodides using secondary phosphines. The key intermediates were diaster-eomeric phosphide complexes with chiral ancillary ligands (L Pd PRR ). Their relative rates of P-inversion and phosphorus-carbon bond formation controlled the enantioselectivity of the prodnct formation. As shown in Scheme 2.63, the reaction allowed moderate enantioselectivities of up to 70% ee to be achieved. 

A route to non-racemic P-stereogenic vinylphosphine-boranes, e.g., (100), is afforded by the addition of methylphenylphosphine-borane with alkynes in the presence of a chiral diphosphine-palladium catalyst. The ehiral diphosphine-platinum complex-catalysed addition of diethylphosphine to the diene cis,cis-muco-nitrile has given the new diphosphine (101) as a 3 2 mixture of diastereoisomers. Further work has been reported on the use of cyclopentadienyliron complexes that act as metal templates for the intramolecular hydrophosphination of coordinated vinylphosphines with 1,2-diphosphino-alkanes and -benzenes, leading to 1,4,7-triphosphacyclononanes, e.g., (102), capable of further elaboration to form new cyclic phosphines. 

Apart from being air sensitive, the generally stable M-P coordination renders technical difficulties in the elimination of the tertiary phosphine product in catalytic process involving transition metal ions as catalysts. However, the asymmetric hydrophosphination of aromatic enones could be catalyzed by the same organo-palladium (II) complex with high yields and stereoselectivity (Table 1). 

Glueck et al. have reported the addition reaction to activated alkenes (Michael acceptors) and have carried out detailed mechanistic studied [121,122]. An important mechanistic study was also carried out for the palladium catalyzed asymmetric phosphination [123, 124]. Hydrophosphination of less activated olefins was achieved for the first time by Ni-catalyzed reaction using phosphite ligands (Scheme 8.44) [125],... 

Scheme 8.58 Asymmetric hydrophosphination of diphenylphosphinoalkenols using organo palladium complex...

Hoye PAT, Pringle PG, Smith MB, Worboys K (1993) Hydrophosphination of formaldehyde catalysed by tris-(hydroxymethyl)phosphine complexes of platinum, palladium or nickel. J Chem Soc Dalton Trans 269-274... 

---