Reaction with triarylphosphines

The formation of acylcobalt tetracarbonyls from alkylcobalt tetracarbonyls and carbon monoxide described above is an example of this type of reaction. The similar reactions with triarylphosphines and phosphite esters have been thoroughly studied because the equilibria are far on the side of the acyl compounds and the products are convenient derivatives to prepare from the alkylcobalt tetracarbonyls (7,10), The triarylphosphine and phosphite ester derivatives are much more thermally and oxidatively stable than the alkylcobalt tetracarbonyls themselves. 

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

A related preparation of specific stabilized phosphonium yUdes corresponds to the reaction of triarylphosphines with acetylene dicarboxylic esters in presence of fullerene, which affords a cyclopropanyl-fullerene substituted stabilized phosphonium ylide [9] or the corresponding evolution products [10]. 

Phosphines may react with certain conjugated systems. This reaction may be conducted deliberately [25] to selectively remove an alkyldiarylphosphine in the presence of a triarylphosphine. Phosphines may react similarly with a, -conjugated carbonyl reaction byproducts such as methacrolein or ethylpropylacrolein. A further concern is reaction with the conjugated system of a feedstream. This chemistry is undesirable when it consumes reagents. Additional harm arises when the reaction product promotes further side reactions, which consume the product.[26]... 

The first investigations of rhodium-catalyzed hydroformylation in room-temperature Hquid molten salts were published by Chauvin et al. in 1995 [6, 67]. The hydroformylation of 1-pentene with the neutral Rh(CO)2(acac)/triarylphosphine catalyst system was carried out as a biphasic reaction with [BMIM][Pp6] as the ionic liquid. 

Certain thietane derivatives such as (54) (67JOC2009), (55) (81JCR(M)1132) and (56) (80JOC2962) are desulfurized on treatment with triarylphosphines. These reactions probably involve initial attack by phosphorus on sulfur. 

The nickel-catalyzed transformation of aromatic halides into the corresponding nitriles by reaction with cyanide ions is reported. Both tris(triarylphosphine)nickel(0) complexes and tY2ins-chloro( aryl )bis( triarylphosphine )nickel(II) complexes catalyze the reaction. The influence of solvents, organophos-phines, and substituents on the aromatic nucleus on catalytic cyanation is studied. A mechanism of the catalytic process is suggested based on the study of stoichiometric cyanation of ti3ins-chloro(aryl)bis(triphenylphosphine)nickel-(II) complexes with NaCN and the oxidative addition reaction of Ni[P(C6H5)3]s with substituted aryl halides. 

Triarylphosphines, which are often employed with palladium in catalysts, also can transfer aryl groups to the palladium and cause vinyl substitution reactions with alkenes.49,30 Fortunately, this reaction is usually slower than other methods for generating arylpalladium derivatives so that it usually is not a problem, but there are exceptions (equation 16). 

By combining the methods reported above, Cook and Andrews in 1996 discovered the first catalytic process based on the stoichiometric reactions with rhenium (V) diolate complexes reported in the 10 years before. The use of a reductant in the form of a triarylphosphine was found to be critical to close the deoxydehydration... 

Ni(0) catalysis is able to induce reactions of methylenecyclopropane with olefins activated by electron-withdrawing groups (equation 193). These cycloadditions work with the utmost efficiency in the case shown, whereas more substituted components might give lower yields due to competing side reactions such as cyclo- and codimerization. These problems could be circumvented by employing new Ni(0) systems with triarylphosphines as cocatalysts (equation 193). Similar conditions lead to the smooth addition of dialkylmethylenecyclopropanes to electron-deficient olefins. ... 

Aryl coupling reactions. A new catalyst for Heck and Sonogashira couplings and allylic displacements is made from glass beads coated with triarylphosphine (1) that carry a dimethylguanidinyl group in each benzene ring. ... 

Chlorination of phosphines. Both trialkyl- and triarylphosphines afford the dichlorides on reaction with triphosgene, which can then be used to convert epoxides to 1,2-dichloroalkanes, aldehydes to gem-dichlorides, amides to nitriles, formamides to isonitriles, ureas to carbodiimides, and amines to triphenylphosphoranylimines. 

Nucleophilic attack at nitrogen has also been identified in a study of the reactions of triarylphosphines with tetracyanoethylene in aqueous acetonitrile. In contrast, the related reactions with tetracyanoquinodimethane (TCNQ) involve one electron transfer from phosphorus to the TCNQ molecule. Full details of the reactions of tertiary and ditertiary phosphines with bromophenyldiazirines have now appeared. Interest in the Staudinger reaction of tertiary phosphines with azides has also been maintained. A spectroscopic study has shown that the sequence of addition of reactants alters the course of the Staudinger reaction of azides in the presence of acyl derivatives. The Staudinger reaction of a-azidophenylacetonitrile with triphenylphosphine unexpectedly results in the formation of the salt (135). Applications of the Staudinger reaction in synthesis... 

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