Adiponitrile formation

With all these substitutions, explicit equations for 4-pentenenitrile consumption and adiponitrile formation are obtained from eqns 8.98 and 8.99. The equations are more lengthy, but of same algebraic form as eqn 8.53 for the network 8.49 without by-product formation. 

Enone formation-aromatization has been used for the synthesis of 7-hydro-xyalkavinone (716)[456]. The isotlavone 717 was prepared by the elimina-tion[457]. The unsaturated 5-keto allyl esters 718 and 719, obtained in two steps from myreene. were subjected to enone formation. The reaction can be carried out even at room temperature using dinitriles such as adiponitrile (720) or 1,6-dicyanohexane as a solvent and a weak ligand to give the pseudo-ionone isomers 721 and 722 without giving an allylated product(458]. 

The main point to note is that the use of an additional ligand such as adiponitrile, vinyl acetate or methyl vinyl ketone is useless similar yields were obtained. Considering the fact that the presence of an additional ligand did not raise the reaction yields and could have negative effects if the optimal amount is not present in the reaction mixture, it was decided to work without any ligand. The use of dimethylformamide or dimethylacetamide instead of acetonitrile did not lead to organozinc species formation when these solvents were used without addition of pyridine. 

In the course of the catalytic hydrogenation of a,us dinitriles over Raney nickel, by-products are obtained from C-N and C-C bond formation. The mechanism of the formation of these compounds was investigated. Cyclic and linear secondary amines can result from the same secondary imine through a transimination process involving a ring-chain tautomerism. Stereochemical results for 2-aminomethyl-cyclopentylamine (AMCPA) are in accordance with a specific cyclisation pathway favored by an intramolecular hydrogen bond giving rise to the cis isomer from aminocapro-nitrile, unfavored in the case of adiponitrile which leads to the trans AMCPA as the major isomer. 

TAA+ have been reported to enhance dimerization within the potential window . Specifically TAA+ favor the formation of adiponitrile from acrylonitrile 5-l9). However, since TAA+ are inactive in this potential region their involvement may be different than described above. 

The hydrocyanation of alkenes [1] has great potential in catalytic carbon-carbon bond-formation because the nitriles obtained can be converted into a variety of products [2]. Although the cyanation of aryl halides [3] and carbon-hetero double bonds (aldehydes, ketones, and imines) [4] is well studied, the hydrocyanation of alkenes has mainly focused on the DuPont adiponitrile process [5]. Adiponitrile is produced from butadiene in a three-step process via hydrocyanation, isomerization, and a second hydrocyanation step, as displayed in Figure 1. This process was developed in the 1970s with a monodentate phosphite-based zerovalent nickel catalyst [6],... 

A drastic example of this phenomenon is encountered in the cathodic hydrodimerization 76>8°1 of acrylonitrile to adiponitrile. This can be accomplished in very high yield in a concentrated solution of a tetraalkylammonium tosylate in water. Practically no propionitrile, the product of hydrogen addition, is formed. The reaction is believed to occur via formation of the acrylonitrile anion radical (6), which then attacks a second molecule of acrylonitrile. Further reduction of the resulting anion radical (7) followed by protonation of the dianion gives adiponitrile (Eqs. (21), (22) and (23) ). 

The catalytic cycle for the hydrocyanation of 4PN to desired adiponitrile and undesired 2-methyl glutaronitrile (MGN) is shown by Fig. 7.15. The intermediates that lead to the formation of 7.56 or 7.57 from NiL3 are not shown... 

An aliphatic dinitrile sebaconitrile has been converted to 1,10-decanediamine in 79-80% yields with addition of an 8 molar ratio of ammonia to the nitrile (7.20).34 In this hydrogenation, the presence of ammonia at least in 5 molar ratio to the nitrile was claimed to be necessary to minimize the formation of secondary amine. The hydrogenation of a number of dinitriles, including industrially important adiponitrile and m-... 

Scheme 7.2 The formation pathways of the carbocyclic byproducts in the hydrogenation of adiponitrile.

Cyclization also occurs extensively with glutaronitriles. In hydrogenation of 1,3-dicyano-2-propanol with Raney Ni, the formation of 4-hydroxypiperidine predominated over the formation of l,5-diamino-3-propanol even in the presence of liquid ammonia.114 Hydrogenation in the absence of ammonia further increased the yield of the piperidine (eq. 7.62). Adiponitrile was transformed to azacycloheptane in high selectivity in the hydrogenation over y-Al203-supported Ni catalysts in a continuous process at 170°C and 0.1 MPa H2 in the absence of ammonia.115... 

This type of reaction is now of major industrial importance because it constitutes a straiglitforward synthesis of nitriles. Wlien it is applied to a diolefm, such as butadiene, it leads to the formation of dinitriles, which are precursors of valuable monomers for the preparation of polymers (butadiene leads to adipo-nilrile. a nylon-b, fvprecursor). Du Font developed the first commercial process using butadiene and HCN for adiponitrile synthesis from butadiene, but this process does nut proceed through a hydrocyanation reaction it is. in fact, a copper-catalyzed halogenation reaction followed by a cyanaikm reaction (tquaiion (16)) of the chlorinated intermediate (Fquation (17)). 

Example 8.12. By-product formation in hydrocyanation of 4-pentenenitrile [44]. Hydrocyanation of 4-pentenenitrile (4-PN) to adiponitrile (ADN) was examined in some detail Example 8.7. The du Pont process maximizes the yield of adiponitrile, the desired product, by addition of a Lewis acid such as zinc chloride or tri-alkylborane, but nevertheless some 2-methyl-glutaronitrile (2-MGN) is formed as byproduct ... 

Catalytic tests were run in a pulse reactor, at 400 °C, with a cyclohexane/ oxygen/ammonia feed composition in mol% of 3/6/4 (the balance being He). The main products obtained were adiponitrile (ADN) and benzene, with an overall selectivity of more than 90% (the cyclohexane conversion is not reported). The rates of benzene and ADN formation are plotted in Figure 20.10 as functions of the Sb20s content of catalysts. It is shown that the overall formation of benzene considerably decreased on increasing the amount of Sb in catalysts. The formation of ADN decreased, but the decrease was less pronounced than that of... 

Figure 20.10 Rates of adiponitrile (ADN) ( ) and benzene ( ) formation as functions of the content of Sb205 in catalysts for cyclohexane ammoxidation. Elaborated from [127a].

The presence of a catalyst led to the formation of C4 dinitriles (maleonitrile, fumaronitrile, succinonitrile), C5 dinitriles (glutaronitrile) and dinitriles (muco-no nitrile, adiponitrile), but the yield of these compounds was very low. In the best case, with a V/Mo/O catalyst (atomic ratio V/Mo 4/1 phase V2O5), the yield to maleonitrile was 1.9% and 0.8% to fumaronitrile, 17% to benzene, 23% to CO, , with traces of mucononitrile, at a conversion of 57% at 460 °C. With the same catalyst, the initial selectivity (extrapolated at zero conversion) to C4 nitriles was approx 5% (negligible to other nitriles), while the predominant primary products were benzene and carbon oxides. For temperatures lower than 420 °C the predominant product was cyclohexene, while at higher temperatures benzene and CO prevailed (Figure 20.11). 

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... 

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