Nitriles heterogeneous reactions

Reactions of or Hj sources (e.g., Zn-HCl) with alkenes, alkynes, arenes, ketones, nitriles, carboxylic acids and esters are used industrially for C—H bond formation . Heterogeneous reaction catalysts (e.g., Ni, Pt, Pd, Fe, Ni-Cu) are used, e.g. ... 

It can be summarized from the available data in Table 3 that supported palladium catalysts selectively hydrogenated carbon-carbon double bonds in the presence of the nitrile group in NBR. However, there is no detailed fundamental study on heterogeneous catalytic hydrogenation of nitrile rubber in the literature that can provide an insight into the reaction. The available information is limited since most of the literature is patented. 

Imanaka—heterogenization of Rh complexes. In 1991, Imanaka and coworkers124 reported the heterogenization of Rh complexes by binding them to aminated polymers. As discussed previously, these findings led to fruitful research by Ford, Pardey, and others. The isolated polymer-bound Rh carbonyl anion complex was found to be reusable for reactions such as water-gas shift and reduction of nitro compounds. The polymer-bound Rh complexes were characterized by infrared spectroscopy. Water-gas shift activity (80 mol H2 per mol Rh6(CO)i6 in 24 hours) was recorded using the Rh complexes at 100 °C with 0.92 atm of CO, 2.16 ml H20, 0.05 mmol Rh6(CO)16, aminated polystyrene, 5.0 mmol of N, 5.56 ml ethoxyethanol and reduction of nitro-compounds (e.g., aliphatic nitro compounds to nitriles, oximes to nitriles, hydroxylamines to nitriles, and N-oxides to amines) occurred at 40 °C. 

Efficient stirring is of prime importance for satisfactory reaction, because intimate mixing of the heterogeneous mixture is necessary. The rate of dissolution of the nitrile depends on the efficiency of the stirring. 

In general, dehydration means loss of water molecules from chemical substances, irrespective of their structure. Even if all cases where water is bonded in hydrate form are excluded, a number of reactions remain which also include formation of nitriles from amides, lactones from hydroxy acids etc. However, the present treatment will concentrate on the heterogeneous catalytic decomposition of alcohols in the vapour phase, which can be either olefin-forming or ether-forming reactions, and on the related dehydration of ethers to olefins. 

As discussed earlier, the two most important experimental factors in determining heterogeneous rate constants by CV are the precision in the measurement of AFp and the effectiveness with which the l u problem is dealt with. A detailed study of the kinetics of the reduction of benzo-nitrile in DMF—Bu4NBF4 (0.1 M) was carried out using derivative techniques and extensions of the correlations described by Tables 4—6 [42]. The study resulted in k° equal to 0.37 0.02 at 23.5°C for the reaction... 

The heterogeneous catalytic hydrogenation of nitriles has been used in amine preparation for a long time. Generally the products are a mixture of primary, secondary and tertiary amines, the nature of which depends on the catalyst used as well as on reaction conditions (refs. 1,2). The selectivity of nitrile hydrogenation is of importance, particularly in the production of primary amines. In such reactions the catalysts most often proposed are Raney nickel catalysts (refs. 1-3). 

The palladium-catalyzed, microwave-assisted conversion of 3-bromopyridine to 3-cyanopyridine using zinc cyanide in dimethylformamide (DMF) has been reported <2000JOC7984>. Substoichiometric quantities of copper or zinc species improve both conversion rate and efficiency of Pd-catalyzed cyanation reactions <1998JOC8224>. A modification of this procedure uses a heterogeneous catalyst prepared from a polymer-supported triphenylphosphine resin and Pd(OAc)2 the nitriles were obtained from halopyridines in high yields <2004TL8895>. The successful cyanation of 3-chloropyridine is observed with potassium cyanide in the presence of palladium catalysts and tetramethylethylenediamine (TMEDA) as a co-catalyst <2001TL6707>. 

In a recent pubhcation the nitrile (EWG = CN) variant [ 126] of this chemistry was performed in water by applying N,N-diethylaminopropylated sihca gel as heterogeneous catalyst [ 128]. Another variant of this reaction sequence, leading to chiral sulfinylated enones, has been developed by Llera [ 129] employing the enantiomerically pure geminal bis(sulfoxide) 208 (Scheme 54). This bis(sulfoxide) was prepared from (-)-p-toluenesulfinic acid menthyl ester [100], as described by Kunieda [130]. Later this procedure was improved to increase the yield from 35 to 91% [13,131]. Treatment of 208 with enolizable aldehydes or ketones, in the presence of piperidine as a base and thiophile, initiated a reaction cascade involving a condensation step (to 210), a proton shift to allylic sulfoxide 211, and a [2,3]-0-shift followed by a piperidine-mediated desulfuration delivering the alcohols 212 as isomeric mixtures. Oxidation of the latter compounds (one of the R = H) led to enantiomerically pure E-y-oxo vinyl sulfoxides 213. 

---