Nickel complexes nitriles

Vinylic copper reagents react with CICN to give vinyl cyanides, though BrCN and ICN give the vinylic halide instead." Vinylic cyanides have also been prepared by the reaction between vinylic lithium compounds and phenyl cyanate PhOCN." Alkyl cyanides (RCN) have been prepared, in varying yields, by treatment of sodium trialkylcyanoborates with NaCN and lead tetraacetate." Vinyl bromides reacted with KCN, in the presence of a nickel complex and zinc metal to give the vinyl nitrile. Vinyl triflates react with LiCN, in the presence of a palladium catalyst, to give the vinyl nitrile." ... 

The reaction between aryl halides and cuprous cyanide is called the Rosenmund-von Braun reactionP Reactivity is in the order I > Br > Cl > F, indicating that the SnAt mechanism does not apply.Other cyanides (e.g., KCN and NaCN), do not react with aryl halides, even activated ones. However, alkali cyanides do convert aryl halides to nitrilesin dipolar aprotic solvents in the presence of Pd(II) salts or copper or nickel complexes. A nickel complex also catalyzes the reaction between aryl triflates and KCN to give aryl nitriles. Aromatic ethers ArOR have been photochemically converted to ArCN. 

Pyridine compounds 45 can also be produced by the NHC-Ni catalysed cycloaddition between nitriles 43 and diynes 44 (Scheme 5.13) [16]. The SIPr carbene was found to be the best ligand for the nickel complex in this reaction. The reaction required mild reaction conditions and low catalyst loadings, as in the case of cycloaddition of carbon dioxide. In addition to tethered aUcynes (i.e. diynes), pyridines were prepared from a 3-component coupling reaction with 43 and 3-hexyne 23 (Scheme 5.13). The reaction of diynes 44 and nitriles 43 was also catalysed by a combination of [Ni(COD)J, NHC salts and "BuLi, which generates the NHC-Ni catalyst in situ. The pyridines 45 were obtained with comparable... 

Hydrocyanation of aliphatic conjugated dienes in the presence of Ni(0) complexes gives diene rearrangement products and /i.y-unsaUiratcd nitriles in 10-90% yields10. Dienes other than 1,3-butadiene do not produce terminal nitriles, implying that the more highly substituted jr-allyl nickel complex is favored. Thus, reaction of 1-phenylbuta-l,3-diene (1) affords ( )-2-methyl-4-phenylbut-3-enenitrile (2) as the sole product (equation 5). The... 

We believe that this intermediate is a five coordinated nickel complex. This is in agreement with the general finding that substitution reactions of ds square planar complexes take place via a five-coordinated intermediate (24, 25). During the formation of the nitrile there is a reductive elimination in which the oxidation state of nickel is reduced to zero. This process is obviously favored by electron-releasing substituents on the aryl group. This is exactly what has been observed. 

In recent years there has been considerable interest in the reactions of nitriles in the coordination sphere of metal ions. Breslow et al.312 first reported that the hydrolysis of 2-cyano-l,10-phenanthro-line to the corresponding carboxamide is strongly promoted by metal ions such as copper(II), nickel(II) and zinc(II). Base hydrolysis of the 1 1 nickel complex is 107 times faster than that of the uncomplexed substrate. The entire rate acceleration arises from a more positive value of AS. Somewhat similar effects have been observed for base hydrolysis of 2-cyanopyridine to the corresponding carboxamide. In this case rate accelerations of 109 occurred with the nickel(II) complex.313... 

Negishi reaction, 269 Negishi reagent, 129 Nickel complexes, 43 15 Nitrile reactions with... 

Successful development of the asymmetric hydrocyanation reaction may provide a versatile route to chiral nitriles, amines, and acids. As we have seen, the mechanistic details of the hydrocyanation reaction of butadiene with zero-valent nickel complexes are well established. By using a nickel complex of a chiral bidentate phosphinite ligand, 9.53, good conversion and enantioselectiv-ity (>85% e.e.) for the hydrocyanation of 6-methoxy 2-vinyl naphthalene have been obtained. 

Recently, ee s of 85-90% have been obtained for the asymmetric hydrocyanation of 6-methoxy-2-vinyhiaphthalene using nickel complexes of chiral bidentate phosphinites derived from glucose (abbreviated PP, equation 12). This reaction is of great interest to the pharmaceutical industry because the (S) enantiomer of the product nitrile is a useful precursor for the widely marketed antiinflammatory dmg naproxen (equation 13). The same reaction can be applied to a number of other vinyl aromatic compounds, including the precursor for the antiinflammatory drug ibuprofen (6) however, the ee is not as high. 

When an alkene is treated with MesSiCN and AgC104, followed by aq. NaHCOs, the product is the isonitrile (RNC) formed with Markovnikov selectivity isos alternative reagent is the cyanohydrin of acetone, which adds to alkenes to give a nitrile in the presence of a nickel complex. 

In the first stage Lewis acids are absent and further hydroeyanation of the monoolefm products 3-PN 40 and 2M3BN 41 does not readily oeeur. The monoeyanation of butadiene is similar to HCN addition to olefins. An individual feature of hydrocyanation of conjugated dienes is the intermediate appearance of TT-allylic complexes 43, which participate in the successive carbon-carbon coupling. Equations (12) and (13) demonstrate the reaction of butadiene with the hydrido-nickel complex 42 leading to formation of nitrile 40 (a) and explain the generation of byproducts, i.e., the branched nitrile 41 via an alternative pathway (b) [68-70]. 

Use of nickel carbonyl to add 1 mol of HCN to 1,3-butadiene may be the first example of hydrocyanation by a homogeneous nickel catalyst. That work also recorded the important observation that substantial improvement in nitrile product yield results from conducting the reaction in the presence of ( 115)3 or (C H5)3As. This work led to extensive studies to develop effective nickel hydrocyanation catdysts. Virtually all subsequent developments have focused on finding the most effective nickel complex and the identification and application of promoters to improve catalyst efficiency and life. ... 

As an unexpected result of our investigations on the arylation of amines, a new catalysis with nickel complexes was pointed out for the aminolysis of nitriles indeed, in the reaction of the p-bromobenzonitrile with the 4-phenylpyridine in the presence of catalytic amounts of NiBr2, in addition to the expected arylamine, the amide resulting from the aminolysis of the cyano group (and subsequent hydrolysis during the work-up) was isolated (eqn. 8). 

But, till now, to the best of our knowledge, there is no example for the aminolysis of nitriles catalyzed by nickel complexes. 

Twieg and coworkers, reported preparation of poly(norbomene) copolymers functionalized with nonlinear optical chromophore side groups. Use was made of (ri -toluene)Ni(C6F5)2, catalyst in the polymerization of norbomene. The nickel complex used to polymerize the norbomene monomers is tolerant to many functional groups found in nonlinear optical chromophores. On the other hand, nitriles and amines other than trisubstituted amines strongly inhibit the reaction. A copolymer of hexylnorbomene and a norbomene-functionalized Disperse Red I chromophore was scaled up and studied in detail. Initial studies indicate that electric field poling is effective but that relaxation of polar order in the poly(norbomene) is faster than in a comparable methacrylate copolymer. The copolymer can be illustrated as follows ... 

The addition of HCN to olefins catalyzed by complexes of transition metals has been studied since about 1950. The first hydrocyanation by a homogeneous catalyst was reported by Arthur with cobalt carbonyl as catalyst. These reactions gave the branched nitrile as the predominant product. Nickel complexes of phosphites are more active catalysts for hydrocyanation, and these catalysts give the anti-Markovnikov product with terminal alkenes. The first nickel-catalyzed hydrocyanations were disclosed by Drinkard and by Brown and Rick. The development of this nickel-catalyzed chemistry into the commercially important addition to butadiene (Equation 16.3) was conducted at DuPont. Taylor and Swift referred to hydrocyanation of butadiene, and Drinkard exploited this chemistry for the synthesis of adiponitrile. The mechanism of ftiis process was pursued in depth by Tolman. As a result of this work, butadiene hydrocyanation was commercialized in 1971. The development of hydrocyanation is one of tfie early success stories in homogeneous catalysis. Significant improvements in catalysts have been made since that time, and many reviews have now been written on this subject. ... 

Nickel complexes containing acrylonitrile and acrolein, i.e., [Ni(AN)2] and [Ni(CH2CHCHO)2], are rapidly oxidized in air. Depending upon dispersion, their color may be light yellow to red for the weakly dispersed forms. IR spectra, as well as chemical and physical properties such as nonsolubility, nonvolatility of [Ni(AN)2], and readiness to react with Lewis bases, show that this compound is polymeric in the solid state. It is not possible to exclude that acrylonitrile constitutes a bridge which coordinates through the double bond and the nitrile group. 

Well-defined 1 1 and 1 2 adducts with triphenylphosphine are formed with ease 42,45, 46). The yellow 1 1 adduct is more stable than bis(acrylo-nitrile)-nickel itself (dec. p. 185° C) and represents one of the first examples of a nickel complex with the coordination number three. The 2 1 adduct is monomeric in benzene and has a dipole moment of 6 Debye units (46). Unstable bis(pyridine) adducts were also isolated, but were found to decompose at room temperature, depositing metallic nickel (46). 

Since cyclooctadiene has no suitable low-lying unoccupied orbitals some of the 3d electrons of nickel are expected to have a relatively high antibonding character. It is therefore not surprising that the nickel complex is extremely reactive, air-sensitive, and very unstable in solutions even in the absence of oxygen. Carbon monoxide at room temperature completely displaces the cyclooctadiene molecules and yields nickel carbonyl (99). Acrylonitrile reacts with (LII) under similarly mild conditions, forming bis(acrylo-nitrile)-nickel 101), while duroquinone, well below room temperature, affords cyclooctadiene-duroquinone-nickel 101). These reactions uniquely demonstrate the close interrelationship between all complexes of zero-valent nickel. 

The reaction chemistry of 1-5 could also be useful for construction of iV-het-erocycles. The reactions of 1-5 with ketone, nitrile, isocyanate, and carbodiimide all lead to P P C-C bond cleavage and eliminate ethylene. Various iV-heterocycles or (9-heterocycles 1-7-1-10 could be thus synthesized. TransmetaUation of 1-7-1-10 with nickel complexes followed by treatment with alkyne readily affords pyridine, pyridine, or 2-iminopyridine derivatives [37-39]. 

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