Nickel-complex-catalyzed reactions dienes

The catalytic cyclo-oligomerization of 1,3-butadiene mediated by transition-metal complexes is one of the key reactions in homogeneous catalysis.1 Several transition metal complexes and Ziegler-Natta catalyst systems have been established that actively catalyze the stereoselective cyclooligomerization of 1,3-dienes.2 Nickel complexes, in particular, have been demonstrated to be the most versatile catalysts.3... 

After that, studies on the palladium-catalyzed reactions of conjugated dienes attracted little attention. They have only been reexamined since the late 1960 s. The scope of the reaction of butadiene catalyzed by palladium complexes has gradually been established. The catalysis by palladium is different from those of other transition metals. Although palladium is located below nickel in the periodic table, the catalytic... 

Recently, four-component coupling reactions of aldehydes, alkynes, dienes, and dimethylzinc catalyzed by a nickel complex have been reported (Equation (78)).435 Similarly, l,c< -dienynes react with carbonyl compounds and dimethylzinc in the presence of an Ni catalyst to afford the corresponding cyclized products. 

Nickel is frequently used in industrial homogeneous catalysis. Many carbon-carbon bond-formation reactions can be carried out with high selectivity when catalyzed by organonickel complexes. Such reactions include linear and cyclic oligomerization and polymerization reactions of monoenes and dienes, and hydrocyanation reactions [1], Many of the complexes that are active catalysts for oligomerization and isomerization reactions are supposed also to be active as hydrogenation catalysts. 

Another example is butene dimerization catalyzed by nickel complexes in acidic chloroaluminates 14). This reaction has been performed on a continuous basis on the pilot scale by IFF (Difasol process). Relative to the industrial process involving homogeneous catalysis (Dimersol process), the overall yield in dimers is increased. Similarly, selective hydrogenation of diene can be performed in ionic liquids, because the solubility of dienes is higher than that of monoene, which is higher than that of paraffins. In the case of the Difasol process, a reduction of the volume of the reaction section by a factor of up to 40 can be achieved. This new Difasol technology enables lower dimer (e.g., octenes) production costs 14). 

Mori has reported the nickel-catalyzed cyclization/hydrosilylation of dienals to form protected alkenylcycloalk-anols." For example, reaction of 4-benzyloxymethyl-5,7-octadienal 48a and triethylsilane catalyzed by a 1 2 mixture of Ni(GOD)2 and PPhs in toluene at room temperature gave the silyloxycyclopentane 49a in 70% yield with exclusive formation of the m,//7 //i -diastereomer (Scheme 14). In a similar manner, the 6,8-nonadienal 48b underwent nickel-catalyzed reaction to form silyloxycyclohexane 49b in 71% yield with exclusive formation of the // /i ,// /i -diastereomer, and the 7,9-decadienal 48c underwent reaction to form silyloxycycloheptane 49c in 66% yield with undetermined stereochemistry (Scheme 14). On the basis of related stoichiometric experiments, Mori proposed a mechanism for the nickel-catalyzed cyclization/hydrosilylation of dienals involving initial insertion of the diene moiety into the Ni-H bond of a silylnickel hydride complex to form the (7r-allyl)nickel silyl complex li (Scheme 15). Intramolecular carbometallation followed by O-Si reductive elimination and H-Si oxidative addition would release the silyloxycycloalkane with regeneration of the active silylnickel hydride catalyst. 

The most outstanding example for the applieation of homogeneously catalyzed hydrocyanation is the DuPont adiponitrile process. About 75 % of the world s demand for adiponitrile is covered by hydrocyanation of butadiene in the presence of nickel(O) phosphite species. This process is discussed for the addition of HCN to dienes as an example, because in this case a well-founded set of data is available. Though it was Taylor and Swift who referred to hydrocyanation of butadiene for the first time [45], it was to Drinkard s credit that this principle was fully exploited for the development of the DuPont adiponitrile process [18]. The overall process is described as the addition of two equivalents of HCN to butadiene in the presence of a tetrakisphosphite-nickel(O) catalyst and a Lewis acid promoter. A phosphine-containing ligand system for the catalyst is not suitable, since addition of HCN to the tetrakisphosphine-nickel complex results in the formation of hydrogen and the non-aetive dicyano complex [67], In general the reaction can... 

The bond between the carbon atoms a and (3 to a C-C double bond can be broken by a transition metal with formation of a Jt-allyl intermediate providing the driving force. Whereas stoichiometric reactions of this sort are yet to appear, jt-(allyl)metal intermediates are occasionally involved in catalytic C-C bond cleaving reactions. The nickel catalyzed skeletal rearrangement of 1,4-dienes involves the formation of an olefin coordinated Jt-(allyl)nickel complex (99) [118]. 

When phosphane-free nickel complexes, such as bis(cycloocta-l,5-diene)nickel(0) or te-tracarbonylnickel, are employed in the codimerization reaction of acrylic esters, the codimer arising from [2-1-1] addition to the electron-deficient double bond is the main product. The exo-isomer is the only product in these cyclopropanation reactions. This is opposite to the carbene and carbenoid addition reactions to alkenes catalyzed by copper complexes (see previous section) where the thermodynamically less favored e Jo-isomers are formed. This finding indicates that the reaction proceeds via organonickel intermediates rather than carbenoids or carbenes. The introduction of alkyl substituents in the /I-position of the electron-deficient alkenes favors isomerization and/or homo-cyclodimerization of the cyclopropenes. Thus, with methyl crotonate and 3,3-diphenylcyclopropene only 16% of the corresponding ethenylcyc-lopropane was obtained. Methyl 3,3-dimethylacrylate does not react at all with 3,3-dimethyl-cyclopropene, so that the methylester of tra 5-chrysanthemic acid cannot be prepared in this way. This reactivity pattern can be rationalized in terms of a different tendency of the alkenes to coordinate to nickel(O). This tendency decreases in the order un-, mono- < di-< tri- < tet-... 

Indeed, methyl rw-6,6-dimethyl-2-(triphenylphosphanyl)-2-nickelabicyclo[3.1.0]hexane-3-carboxylate (13) [and the corresponding ethenebis(dimethylphosphane) complex] was isolated in 65% yield from the conversion of (/7 -methylacrylate)bis(triphenylphosphane)nickel and 3,3-dimethylcyclopropene. The former complex catalyzes the cotrimerization of dimethylcyclo-propene with methyl acrylate with almost identical activity as earlier observed with an in situ catalyst obtained by mixing bis(cycloocta-l,5-diene)nickel and triphenylphosphane (1 1). Thus, this metallacyclic system can be regarded as an intermediate in the co-cyclotrimerization reaction. ... 

Recently, the nickel-catalyzed isomerization of geraniol and prenol has been investigated in homogeneous and two-phase systems. The best results with respect to activity and selectivity have been obtained in homogeneous systems with a bis(cy-cloocta-l,5-diene)nickel(0)/l,4-bis(diphenylphosphanyl)butane/trifluoroacetic acid combination. Catalyst deactivation occurs in the course of the reaction owing to coordination of the aldehyde group that is formed to the nickel species or as a result of protonolysis of hydrido or (jr-allyl)nickel complexes [2],... 

Thermolysis of (44) in the presence of alkynes results in 1,4-disilanaphthalenes <9lOM3l73>. As already mentioned, they can be formed in higher yields during the nickel <92JOM(439)l9) and platinum catalyzed reactions <930M4987> of the (44) with diphenylalkyne and ethene respectively. Platinum-complex catalyzed dehydrogenative double silylation of alkynes, alkenes, and dienes with... 

Insertion of dienes into M-H bond or M-alkyl bond affords r -allylic complexes or its )7 -alken-J7 -yl resonance form. The allylic complex may further undergo insertion of other unsaturated compounds such as alkene or diene into the unsubstituted or substituted terminal of the allyhc ligand. If successive butadiene insertion takes place, polymers with internal unsaturated bonds are produced as will be described later. A nickel-catalyzed reaction of butadiene with 2 mol of HCN affords adiponitrile, an important feedstock in polymer synthesis (Eq. 1.15). 

The paUadium-catalyzed reactions occurred with the simple combination of [Pd(allyl) Cl]j and added phosphine, or with Pd(PPh3) and an acid co-catalyst. The scope of these reactions encompassed the additions of arylamines. As shown in Equation 16.81, reaction of various arylamines with cyclohexadiene occurred with high enantioselectivity using Trost s ligand. This ligand is discussed in more detail in Chapter 20. These reactions, and nickel-catalyzed reactions, occur by nucleophilic attack of amines on ir-allyl intermediates generated by protonation of diene complexes or insertion of dienes into palladium hydrides. 

In homogeneous catalysis telomerization is defined as the oligomerization of dienes with incorporation of a nucleophile. For example, two molecules of butadiene react with one nucleophile HY to form telomers. This reaction is catalyzed by various organometallic compounds of the transition metals, especially by palladium and nickel complexes. 

The nickel-catalyzed [4 + 4]-cycloaddition of butadiene to form cyclooctadiene was first reported by Reed in 1954.90 Pioneering mechanistic and synthetic studies largely derived from the Wilke group advanced this process to an industrially important route to cyclodimers, trimers, and other molecules of interest.91-94,943 95,96 While successful with simple dienes, this process is not useful thus far with substitutionally complex dienes as needed in complex molecule synthesis. In 1986, Wender and Ihle reported the first intramolecular nickel-catalyzed [4 + 4]-reaction of... 

Silastannative coupling of 1,3-diene and aldehydes is achieved both in inter- and intramolecular fashions (Equations (116) and (117)).277 Interestingly, the reaction is catalyzed by nickel(0) complexes, whereas a platinum complex is used for simple 1,4-silastannation of 1,3-diene.278... 

Equations 1 to 3 show some of fixation reactions of carbon dioxide. Equations la and lb present coupling reactions of CO2 with diene, triene, and alkyne affording lactone and similar molecules [2], in a process catalyzed by low valent transition metal compounds such as nickel(O) and palladium(O) complexes. Another interesting CO2 fixation reaction is copolymerization of CO2 and epoxide yielding polycarbonate (equation 2). This reaction is catalyzed by aluminum porphyrin and zinc diphenoxide [3],... 

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