Functional phosphines

Similarly to the P-CHj group, secondary phosphine-boranes react smoothly in the presence of a base (BuLi, NaH) under mild conditions to afford other kinds of functionalized phosphine-boranes in good to high yields, without racemi-zation. Yet the success of deprotonation/treatment with an electrophile process to afford substituted phosphine derivatives without any loss in optical purity may depend on the deprotonation agents employed. Use of butyllithium usually provides the products with high enantiomeric excess in good to high yields [73]. 

Keywords. Primary phosphines, Thioether phosphines, Amido phosphines, Carboxylate phosphines, Functionalized phosphines... 

The functionalized phosphine coordinates to the iridium center as a 6+2 electron donor ligand. This dihydrido iridium]111) complex reacts with ethene or propene to yield ethane or propane and formation of the iridium(l) complexes [(t -QH5CH2CH2PTr2-K-P)lr(CH2=CHR)]BF4 (R=H, Me) (Scheme 2.27). 

When the catalyst is located in the core of a dendrimer, its stability can also be increased by site-isolation effects. Core-functionalized dendritic catalysts supported on a carbosilane backbone were reported by Oosterom et al. 19). A novel route was developed to synthesize dendritic wedges with arylbromide as the focal point. These wedges were divergently coupled to a ferrocenyl diphosphine core to form dppf-like ligands (5). Other core-functionalized phosphine dendritic ligands have also been prepared by the same strategy 20). 

As adenine analogous donor-acceptor ligands the heterocycle functionalized phosphines 10a and 15-18 were chosen. As T analogous acceptor-donor ligands the knovm isoquinolone Ila and the new 7-azaindole system 19 were selected [23]. 

Recently, we [53] and others [54] simultaneously reported an example of a complex in which the transition metal dictates the coordination mode, viz. urea-functionalized phosphine 20, which forms a trans palladium complex, complemented by hydrogen bonding ofthe urea fragments (Figure 10.6). Bear in mind that any monophosphine, and even wide bite angle diphosphines, give trans complexes with a hydrocarbyl palladium halide. More interestingly, the urea moieties can function as a host for another halide ion. 

The most direct synthesis is performed by reaction of a dihalo compound with a tricoordinated phosphorus compound including a reactive P—Y bond (reaction 101). This synthesis, first used with secondary phosphines, the corresponding phosphides or diphosphines (Y = H, Na, K, PPh2)2b,38°, has subsequently been developed also with silylphosphines (Y = SiMe3),132,381-383 which are easier to handle (reaction 102). The same kind of cyclization by intramolecular alkylation can be achieved using a functional phosphine prepared in a multi-step synthesis380,384,385 (reaction 103). 

Phosphine-boronates featuring rigid backbones have been accessed by condensing adequately functionalized phosphines and boronic acids. This strategy was first developed by Kagan6 and Jacobsen62 who independently reported the synthesis of the tartrate-derived boraDIOP compounds 50 (Scheme 32). The key precursor 49 was readily obtained by acidic hydrolysis of the diphosphine (R,R)-DIOP (DIOP = 2,3-O-isopro-pylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)butane). Upon reaction with PhB(OH)2 or PhBCU the phosphine-boronate 50a was isolated in... 

In recent years, polycyclic P-Si and P-Ge clusters respectively have been obtained by reaction of organosilyltrihalides v th threefold functionalized phosphines [1-3]. A decisive influence on the nature and the steric hindrance of the ligand R of the adequately substituted RECI3 on the reaction can be observed. 

A new synthetic route to bis-methylene analogues of triphosphate esters has been reported. Lithiated methaneselenophosphonate and methanethiophos-phonate anions can condense several times with polyfunctional substrates such as chlorophosphites and phosphoramidous chlorides prior to esterifica-tion/trans-esterification and selenation or oxidation. A water-soluble phos-phonate-functionalized phosphine ligand (361) has been prepared in eight steps... 

A second approach relies on the traceless Staudinger ligation between an appropriately functionalized phosphine and an azide to produce a new amide bond [54]. This method has found extensive utility in the labeling of peptides and proteins [215]. Importantly, this method has also been used for the construction of native iV-linked glycans through the reaction between a glycosyl azide and a phosphine containing amino acid [216,217]. 

Functionalized tertiary phosphines continue to attract considerable interest for their unusual coordination chemistry and their increasing importance in catalysis. Whilst this subject area is extensive, only a few types of functionalized phosphines will be discussed here, including brief details regarding preparative procedures. 

Miscellaneous. The addition of Grignard reagents to the functionalized phosphines (93) leads to the magnesium alkoxides (94), which react with methyl iodide selectively at phosphorus. The magnesium salts (95) of the resulting betaines undergo elimination, on heating with potassium t-butoxide, to form the olefins (96) and methyldi-phenylphosphine oxide.i ... 

Table 1.4 Examples of functionalized phosphines for biphasic aqueous hydroformylations.

Rhodium complexes generated from the polyethylene glycol)-functionalized phosphine 9 (n = 1, x = 0, R = Me, Bu), which should behave as a nonionic surfactant and be able to induce micelle formation, have been used as catalysts in the hydroformylation of 1-dodecene in an aqueous/organic two-phase system [31]. The conversion of 1-dodecene was 80% and the n/iso ratio 60 40, with no carryover of the rhodium catalyst into the organic phase. The Rh/9 (n = 1, x = 0, R = Me, Bu) catalyst remained active after one recycle step [31],... 

The important stabilizing effect of the palladated 8-methyIquinoline ligand [hereafter the Pd compounds derived from this ligand are referred to as Pd(8-mq) has been used to build an original chemistry on the positions trans to it. Thus it is possible to isolate phosphoenolates, when functionalized phosphines are bound to palladium, by direet reaction of a lithium phosphoenolate on the palladium compound , the nuclearity of the product depending upon the stoichiometry ... 

Trimethylsilyl esters of both functionalized and non-functionalized phosphinic acids, R2P(0)0SiMc3, have been prepared from the respective alkyl halides and bis(trimethylsi-lyl) alkylphosphonites, RP(OSiMe3)2, (Michaelis-Arbuzov alkylation) as part of a novel sequence in which the latter are obtained in situ from alkyl halides and bis(trimethylsilyl) hypoghosphite [HP(OSiMe3)2] in the presence of Et3N (Michaelis-Becker-like alkyla-... 

The synthesis of functionalized phosphinic and phosphonic acids and their derivatives. Part A halo, hydroxy, epoxy, mercapto, carboxy and oxo functionalized acids... 

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