Dinitriles from nitriles

Using supported y-Mo2N as a surface-mediated catalyst, a new proposal for the manufacture of aromatic nitriles and dinitriles from the relatively cheap aldehydes was made [16, 17]. Thus, isophthalic dinitrile can be produced in a gas-phase amm(on)dehydrogenation (cf. Section 3.3.12.2) at 400 °C according to eq. (11) with 80% conversion when a 50-fold excess of ammonia is used [16]. It is obvious that imine intermediates are formed (from the aldehyde and ammonia) which then dehydrogenate under the reaction conditions. 

Table 16.3. Selectivities for formation of the linear dinitrile from nickel-catalyzed hydrocyanation of 4-pentene nitrile in the presence of a series of boron Lewis acids.

A nitrilase from the hyperthermophile Pyrococcus abyssi, which exhibits optimal growth at 100 °C, was cloned and overexpressed. Characterization of this nitrilase revealed that it is operational as a dimer (rather than the more common multimeric structure for nitrilases), with optimal pH at 7.4 and optimal apparent activity at 80 °C with Tm (DSC) at 112.7 °C. The substrate specificity of the nitrilase is narrow and it does not accept aromatic nitriles. The nitrilase converts the dinitriles fumaronitrile and malononitrile to their corresponding mononitriles [58],... 

The nitrilase from cyanobacterium Synechocystis sp. PCC6803 was found to effect the stereoselective hydrolysis of phenyl-substituted /3-hydroxy nitriles to (S)-enriched /3-hydroxy carboxylic acids. The enzyme also effected the conversion of y-hydroxynitrile, albeit with lesser enantioselectivity (Table 8.10). Interestingly, this enzyme was also was found to hydrolyze aliphatic dinitriles, such that for 1,2-dicyanoethane and 1,3-dicyanopropane the... 

Bis(nitrile oxides) obtained from dialkylbenzenes have been claimed as low-temperature rubber vulcanization agents (517). Curing of poly(butadiene-co-acrylonitrile) with 2,4,6-trimethylisophthalodinitrile N-oxide produces rubbery material of good quality, however, curing of (polybutadiene) was unsuccessful (518). The solubility of dinitrile oxides and stability of their ketone solutions has been studied for their application as vulcanizing agents in the production of mbberized materials (519). 

Other nucleophile-electrophile pairs for which the pm-disubstituted naphthalene system has been used to monitor potential bonding interactions are illustrated in [35] and [36], The methoxynitrile [35], for example, shows the same sort of evidence for a bonding interaction, marked by a 7° distortion from linearity at the nitrile carbon, in plane, and exactly away from the methoxyl oxygen (Procter et al., 1981) so also does the bipyridyl dinitrile [37] (Baxter et al., 1991). In the unique case of the 8-diazonium quinoline-N-oxide [36] the proximity of a formally negatively charged oxygen induces a distortion from linearity of 10.4° in the diazonium group (Wallis and Dunitz, 1984). 

Much the same activity is displayed in a compound in which the nitriles are attached to aliphatic (and highly stericaUy hindered ) carbon. The displacement of benzUlic bromine from the mesytilene derivative (118-1) by treatment with potassium cyanide under phase transfer conditions affords the dinitrile (118-2). Exhaustive... 

The dinitrile complexes [ZrCl4(NCCH2CN)2] and ZrCl4 NC(CH2) CN in = 4 or 8) were obtained as white solids from the reaction of excess nitrile with a suspension of ZrCU in dichloromethane. These complexes exhibit high-frequency shifts of v(C N) upon complexation, characteristic of coordination through the nitrile nitrogen atoms. The... 

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. 

A crude mixture of enzymes isolated from Rhodococcus sp. is used for selective hydrolysis of aromatic and aliphatic nitriles and dinitriles (117). Nitrilase accepts a wide range of substrates (Table 8). Even though many of them have low solubility in water, such as (88), the yields are in the range of 90%. Carboxylic esters are not susceptible to the hydrolysis by the enzyme so that only the cyano group of (89) is hydrolyzed. This mode of selectivity is opposite to that observed upon the chemical hydrolysis at alkaline pH, esters are more labile than nitriles. Dinitriles (90,91) can be hydrolyzed regioselectively resulting in cyanoacids in 71—91% yield. Hydrolysis of (92) proceeds via the formation of racemic amide which is then hydrolyzed to the acid in 95% ee (118). Prochiral 3-substituted glutaronitriles (93) are hydrolyzed by Phodococcus butanica in up to 71% yield with excellent selectivity (119). 

Chain-extension thanks to nitrile bonds From dinitriles [59] ... 

The application of nitrilases is broad. A purified nitrilase from Bacillus pallidus was employed to hydrolyse a wide variety of aliphatic, aromatic and heteroaromatic nitriles and dinitriles (Scheme 6.33) [102]. Nitrilases have also been patented for the hydrolysis of a-substituted 4-methylthio-butyronitriles, however, no stereoselectivity was reported [103]. 

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)). 

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