Amide ammoxidation

Some companies are successfully integrating chemo- and biocatalytic transformations in multi-step syntheses. An elegant example is the Lonza nicotinamide process mentioned earlier (.see Fig. 2.34). The raw material, 2-methylpentane-1,5-diamine, is produced by hydrogenation of 2-methylglutaronitrile, a byproduct of the manufacture of nylon-6,6 intermediates by hydrocyanation of butadiene. The process involves a zeolite-catalysed cyciization in the vapour phase, followed by palladium-catalysed dehydrogenation, vapour-pha.se ammoxidation with NH3/O2 over an oxide catalyst, and, finally, enzymatic hydrolysis of a nitrile to an amide. 

Interestingly, the by-product in the above-described hydrocyanation of butadiene, 2-methylglutaronitrile, forms the raw material for the Lonza process for nicotinamide (see earlier) [123]. Four heterogeneous catalytic steps (hydrogenation, cyclisation, dehydrogenation and ammoxidation) are followed by an enzymatic hydration of a nitrile to an amide (Fig. 1.50). 

The ammoxidation of methyl aromatic and heteroaromatic compounds is a convenient route to many nitriles required for further synthesis of fine chemicals. For example, for the production of amines by hydrogenation or of carboxylic acids and amides by hydrolysis. 

The type of nitrogen functionalities created on the carbon surface largely depends on the method applied. Some of the nitrogen functionalities are not thermally stable and differences in the properties will be found when methods are applied at low and high temperatures. Fig. 2 compiles a scheme of the different nitrogen-containing ftmctionalities that can be fonned on the carbon surfaces, by optimising the experimental conditions. It has been reported that lactams and imides structures are mainly formed by ammination, and amide upon ammoxidation the former are transformed to pyrrole and pyridine by heat treatments [80-83]. 

Due to their synthetic utility and pharmaceutical applications, a number of synthetic routes to a,P-unsatuiated nitriles have been developed. Classical methods include dehydration of amides [15] or aldoximes [16], Wittig- [17] and Peterson-type [18, 19] olefination processes, ammoxidation of alkenes [20], and carbocyanation of alkynes [21], These approaches suffer variously from high waste generation, low yields and poor stereoselectivity. As such the transition metal-catalysed cyanation of vinyl halides is an attractive route for the synthesis of alkaiyl nitriles. Whilst several instances of such transformations have been reported in the literature, the area remains underdeveloped, particularly in comparison to analagous cyanations of aryl halides. 

The reaction of the ammoxidation of toluene has also been investigated. Ammonia adsorbs over the V205/Ti02 monolayer catalysts in two forms, as ammonium ions over Brpnsted acidic sites as well as in coordinated molecular form over Lewis acid sites. Benzylamine appears as an intermediate, likely formed through the reaction of amide species, which is a common intermediate in ammonia oxidation over oxide catalysts and benzyl species. Benzylamine is further oxidatively dehydrogenated to benzonitrile, well evident in the IR spectra. A later IR study of the same reaction performed over V-P oxides showed similar intermediates but suggested that, over these catalysts, the main reaction path consists of the formation of benzaldehyde and benzimine. ... 

Song Q, Feng Q, Yang K (2014) Synthesis of primary amides via copper-catalyzed aerobic decarboxylative ammoxidation of phenylacetic acids and a-hydroxyphenylacetic acids with ammonia in water. Org Lett 16(2) 624-627... 

Ishida T, Watanabe H, Take T, Hamasaki A, Tokunaga M, Haruta M (2012) Metal oxide-catalyzed ammoxidation of alcohols to nitriles and promotion effect of gold nanoparticles for one-pot amide synthesis. Appl Catal A Gen 425 26 85-90... 

The heterogeneously catalyzed ammoxidation is a reaction used by the industry for the last 60 years. A recent review provides a short historic survey [1]. Leonid Andrussow was the first to prepare nitriles and amides by gas phase oxidations in the presence of ammonia. He is also known for his contribution to Andrussow reaction, that is, the formation of hydrogen cyanide fiem methane, ammonia and oxygen [16,17]. Another milestone was the... 

In this chapter, the application of a variety of catalysts for different am-moxidation reaetions was discussed in detail. Special focus was given to two industrially important reactions such as i) ammoxidation of picolines (all the three isomers) and ii) ammoxidation of 2MP. The nitrile products of these two specified ammoxidation reactions are not only important from commercial point of view but also present opportunities for academic research. This report also deals with pharmaceutical chemicals (e.g., TB treatment using pyrazin-amide). 

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