Catalysts triphenylphosphite

Conventional triorganophosphite ligands, such as triphenylphosphite, form highly active hydroformylation catalysts (95—99) however, they suffer from poor durabiUty because of decomposition. Diorganophosphite-modified rhodium catalysts (94,100,101), have overcome this stabiUty deficiency and provide a low pressure, rhodium catalyzed process for the hydroformylation of low reactivity olefins, thus making lower cost amyl alcohols from butenes readily accessible. The new diorganophosphite-modified rhodium catalysts increase hydroformylation rates by more than 100 times and provide selectivities not available with standard phosphine catalysts. For example, hydroformylation of 2-butene with l,l -biphenyl-2,2 -diyl... 

The first iridium catalysts for allylic substitution were published in 1997. Takeuchi showed that the combination of [fr(COD)Cl]2 and triphenylphosphite catalyzes the addition of malonate nucleophiles to the substituted terminus of t -allyliridium intermediates that are generated from allylic acetates. This selectivity for attack at the more substituted terminus gives rise to the branched allylic alkylation products (Fig. 4), rather than the linear products that had been formed by palladium-catalyzed allylic substitution reactions at that time [7]. The initial scope of iridium-catalyzed allylic substitution was also restricted to stabilized enolate nucleophiles, but it was quickly expanded to a wide range of other nucleophiles. 

Although most of these early reactions were conducted with allylic acetates, reactions of allylic carbonates, trifluoroacetates, and phosphates also occur. Sodium diethylmalonate also reacts with allylic alcohols in the presence of the iridium-triphenylphosphite catalyst. However, the alcohol itself does not act as a leaving group. Instead, transesterification occurs with one equivalent of malonate nucleophile to form a more labile ester leaving group. 

Addition to linear 1,1-disubstituted allylic acetates is slower than addition to monosubstituted allylic esters. Additions to allylic trifluoroacetates or phosphates are faster than additions to allylic carbonates or acetates, and reactions of branched allylic esters are faster than additions to linear allylic esters. Aryl-, vinyl, alkynyl, and alkyl-substituted allylic esters readily undergo allylic substitution. Amines and stabilized enolates both react with these electrophiles in the presence of the catalyst generated from an iridium precursor and triphenylphosphite. 

Jeong and co-workers devised the method by using a phosphite-modified cobalt catalyst, which was obtained m situ by mixing of dicobalt octacarbonyl (3 mol%) and triphenylphosphite (10mol%) prior to the addition of reactants. Best results were obtained under mild pressure of GO (3 atm). ... 

A variety of condensing agents, such as triphenylphosphite/pyridine [4,5] and DBOP/triethylamine [6], which are used in amounts equivalent to functional groups on monomers, had been developed by the 1980s, whereas new catalysts that promote condensation polymerization exactly with a catalytic amount were developed in the last decade. 

Ligands with good acceptor character (e.g., triphenylphosphite, Table IX) stabilize the m-7r-allyl, cr-alkyl intermediate (XLVIb) and only CDD is formed. The stabilization introduced by triphenylphosphite is so effective that even at elevated temperatures (60° C) practically no DT results, while a naked-nickel catalyst at the same temperature produces DT and CDD in about equal proportions. 

Scheme 7. The catalytic reaction mechanism of trans-1,4 polymerization of butadiene with the bis(triphenylphosphite) complex [Ni(7 -RC3H4)(P(OPh3)2]PF6 as the catalyst.

For the reaction of alkyl-substituted alkenes, chloro(triphenylphosphite)copper can be used as a catalyst.Vinylcyclopropanes are formed at low temperature in yields of 55-77% for disubstituted alkenes (see Houben-Weyl, Vol. E19b, p763). 

Further studies of regioseleclive syn hydrocyanation of various alkynes and alkynols used nickel-based catalyst systems of the type NiL4 with either L = triphenylphosphite or L2 = a,a-bis(diphenylphosphino)-2-xylene (PHMEP)26. The regioselectivities observed with the phos-phane catalyst reflect dominant steric effects, whereas results with the phosphite catalyst system show some evidence for chelation control. Similar conversions of various amino alkynes also occur exclusively in a syn fashion with comparable regioselectivity trends, as in the alkynol case28. The products are used as precursors for the synthesis of saturated and unsaturated amino acids28. 

These cfs-complexes were shown to have latent behavior they were inactive at room temperature in model olefin RCM and CM reactions, as well as in enyne metatheses [60], yet the catalytic activities became very high when the reactions were carried out at 80 °C in toluene [60, 61]. Triisopropylphosphite and triphenylphosphite complexes led to the most active catalysts, the former being faster. In addition, both cis- and trans-NHC-phosphite catalysts were found to... 

If triphenylphosphite [149] or some other phosphorus compounds [928, 1037] with a more complicated structure [928] are used as catalyst modifiers, no such hydrogenation is observed but high yields of aldehydes are obtained. 

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