Supported arylphosphines

Another method is the hydroformylation with the addition of water soluble den-drimers which gave high activity and selectivity in the hydroformylation of 1-oc-tene and styrene [189]. Cyclodextrins can also be used to enable a strong exchange between the two layers [190]. In addition, hydroformylation has been tested in flu-orous biphasic systems with good results, however, very special fluorocopolymer-supported arylphosphines had to be prepared [191]. 

In a related strategy, ethynylphosphines (81) have been prepared with a view to synthesising polyphosphacyclopolyyne materials such as (82) (Scheme 24) [70]. Interaction between the phosphorus lone pairs and the organic 71-systems is supported by the fact that the phosphorus atoms of mono- and di-silyl-capped analogues of bis(arylphosphine) derivative (81) exhibit an unusually low inversion barrier (65 kj mol versus 130-140 kj mol for classical alkyl-or aryl-phosphines). Indeed, the rings (82) exhibit values of at ca. 300 nm, consistent with this assumption. 

The Uozumi group developed unique recyclable amphiphilic resin-supported tri-arylphosphines (PEP) attached to polyethylene glycol-polystyrene graft copolymer (PEG-PS), and found that Pd(PEP) is an active catalyst for allylation in water [40a]. They immobilized a chiral amine on PS-PEG-NH2 resin to give PS-PEG resin-supported chiral P,N-ligand R,S) 106. Asymmetric allylation of diethyl malonate... 

A general and efficient method for the microwave-assisted synthesis of mono- and diarylphosphinic acids (579) and (581) from anihnium 7f-phosphinate (580) and aryl halides, using Pd(0) and Xantphos as a supporting ligand, has been developed by Stawihski and Kalek (Scheme A2)P The procedure was highly efficient and provided a rapid access to a broad spectrum of arylphosphinate derivatives. 

Phosphorus donor ligands have also been used to activate Ru3(CO)i2 in the catalytic reduction of nitrobenzene by CO/H2O in the presence of sodium hydroxide [32], Reaction conditions are mild (room temperature and one atmosphere of CO). In a three hours reaction, a turnover of 95 was observed by adding l,2-bis(diphenylphosphino)ethane (DPPE) to Ru3(CO)i2 in a 0.5 molar ratio. By adding PPh3 or in the absence of any phosphorus ligand, the observed turnover was 43 and 51 respectively. However, better results have been obtained with rhodium catalysts (see later) [32]. Preformed phosphine-substituted clusters of the type Ru3(CO)9L3 (L = arylphosphine) have also been used as catalysts for the same reaction [33] and the same complex was also supported on a polystyrene-divinylbenzene copolymer. 

Secondary phosphine oxides have been used in nickel-catalyzed cross-coupling reactions with aryl tosylates and mesylates for the preparation of arylphosphine oxides (Scheme 4.205) [341], These substrates are typically more stable than aryl triflates and can be readily prepared from a wide range of phenols. In terms of the metal catalyst, the authors used a discrete species ((dppONiCl ) and added extra supporting ligand (2 equiv per metal center) to prevent catalyst decomposition. The addition of zinc dust was essential to the success of the reaction, and no arylphosphine oxide was observed without it. 

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