Nitrile, conversion

Reaction time determined by hydrogen nptake measnrements TAV = total amine value made by the titration of amines to give nitrile conversion ° 2/3 A = the percentage of 2° and 3° amines This catalyst was modified with 1.33 mmol H2CO at rt for 1 h... 

Supported Co, Ni, Ru, Rh, Pd and Pt as well as Raney Ni and Co catalysts were used for the hydrogenation of dodecanenitrile to amines in stirred SS autoclaves both in cyclohexane and without a solvent. The reaction temperature and the hydrogen pressure were varied between 90-140 °C and 10-80 bar, respectively. Over Ni catalysts NH3 and/or a base modifier suppressed the formation of secondary amine. High selectivity (93-98 %) to primary amine was obtained on Raney nickel, Ni/Al203 and Ru/A1203 catalysts at complete nitrile conversion. With respect to the effect of metal supported on alumina the selectivity of dodecylamine decreased in the order Co Ni Ru>Rh>Pd>Pt. The difference between Group VIII metals in selectivity can be explained by the electronic properties of d-band of metals. High selectivity to primary amine was achieved on base modified Raney Ni even in the absence of NH3. 

Yamada, H., Shimizu, S. and Kobayashi, M. (2001) Hydratases involved in nitrile conversion screening, characterization and application. Chemical Record, 1, 152-161. 

In order to obtain maximum catalytic TON, pyridine yields, nitrile conversions, as well as high pyridine/benzene ratios in the product, more than 60 [YCoL] complexes were systematically investigated for the catalytic cotrimerization of propionitrile and acetylene [Eq.(9)J [85AG264, 85AG(E)248]. 

The influence of the zeolite catalyst is clearly shown by the change in ester selectivity with the nitrile conversion (Fig. 4) at a 25% conversion, the percentage ester selectivity varies from 80% for the HY to 50% for the He... 

Fig. 4. Ester selectivity as a function of nitrile conversion over o HY2 x H014, + HMg.

Reaction of Jt-excessive heterocycles (e.g. thiophene, indole), enol ethers (e.g. dihydropyran) and enol acetates, and carboxylic acids with chlorosulfonyl isocyanate leads in generally excellent yields to A-chlorosulfonylamides. These intermediates are converted into the corresponding nitriles by heating in DMF, although the yields can be somewhat variable. A recent reinvestigation of the N-chlorosulfonylamide to nitrile conversion revealed that treatment of the amides with one equivalent of triethylamine led to formation of the nitriles in excellent yield. Clearly, the mechanisms of the DMF and the EtsN induced transformations are different. 

Figure 17.1 Nitrile conversion catalyzed by nitrile hydratase (NHase)-amidase (AMase) system from Microbacterium imperiale CBS 498-74 here illustrated.

Example 7.1. High-temperature hydrolysis of butyronitrile [5], Nitriles in toxic aqueous wastes, e.g., from manufacture of explosives, can be hydrolyzed at high temperature and pressure. Amide, acid, and ammonia are formed, and nitrile conversion can be carried to extinction. For butyronitrile as a model compound ... 

Nitrile conversion in presence of barium promoted Cu-Cr/graphite catalysts. Reaction conditions see table 3. (Catalysts are used without reduction treatment). 

Although a few methods for the direct conversion of acids into nitriles are kno vn, the most popular still proceed via dehydration of the corresponding amides. A new, mild, one-pot method to effect the acid-to-nitrile conversion in high yield involves the use of mixed sulphonic-carboxylic anhydrides (Scheme 23) the method, however, is not applicable to acids containing —NHa, — NHR, —OH, or —SH groups. In a similar vein, a new and efficient one-pot synthesis of nitriles from acid chlorides is mediated by sulphonamide at 120 °C. ... 

The new synthesis of aldehydes RCHO from alkyl halides RCHaX outlined in Scheme 16 is reminiscent of the aldehyde- nitrile conversion reported last... 

II. STEREOSELECTIVE NITRILE CONVERSIONS WITHOUT ENZYME SPECIFICATION... 

Another example of a nitrile conversion without enzyme specification is the biotransformation of (i ,5)-3-phenyllactonitrile (phenylacetaldehyde cyanohydrin) to (5)-3-phen-yUactic acid, a precursor for the synthesis of pharmacophores including renin inhibitors, protease inhibitors, and anti-HIV reagents, by Pseudomonas sp. BC-18 [19]. The enantiomeric excess of 75% after biotransformation was increased to 99.8% by repeated crystallization, and the production was enhanced by the addition of 2% (w/v) CaCl2 to the reaction mixture for the precipitation of the (5)-acid. In a mutant strain, the specific activity and the final accumulation were enhanced 16- and 1.2-fold, respectively, compared to the parent strain. A product yield of 70% after biotransformation was obtained due to the... 

Among stereoselective nitrile-converting enzymes, the combined action of a stereoselective nitrile hydratase and a stereoselective amidase has been often described, and stereospecific nitrile conversions by whole cells are frequently found in the patent literature [59,60] however, careful analysis has usually revealed stereoselectivity in the amidase and not or only to a low extent in the hydratase [61,62]. If both enzymes were stereosj ific, nitrile hydratase and amidase have been described to act either synergistically or antagonistically regarding their enantioselectivity. 

Immobilized Rhodococcus sp. SP 361 is an example that shows how complex stereoselective nitrile conversions might sometimes appear [57]. In the bioconversion of R,S)-2-alkylarylacetonitriles an unusual enantioselective diversity was observed. Whereas most racemic 2-alkylarylacetonitriles were converted to (S)-acids and (/ )-amides (Fig. 17), indicating the presence of an (>S)-selective amidase, ibuprofen nitrile was only converted to the ( )-acid (e.e. 32%) without any intermediate amide formation. A slow and strictly R) specific nitrile hydratase and a fast and less strict (5)-amidase were accounted for the (/ )-specific ibuprofen synthesis. The aryl-bound isobutyl moiety of ibuprofen nitrile seemed to invert the molecule orientation at the catalytic center of the nitrile hydratase. Furthermore, in the conversion of (.R,5)-2-(4-methylphenyl)propionitrile, not only the chiral S) acid (e.e. more than 95%, yield 41%) and (/ )-amide (e.e. more than 95%, yield 18%), but also enantiomerically almost pure (fi )-nitrile (e.e. more than 95%, yield 25%) was obtained. In this instance, the nitrile was hydrated with a partial (5)-selectivity. Overall, the absolute configuration of the products was rationalized according to a model assuming the presence of an (5)-selective amidase and a nitrile hydratase with (5)-, (JR)-, or nonspecificity depending on the type of substrate. 

First enantioselective nitrile conversions were recently industrialized such as the preparation of (jR)-mandelic acid (Fig. 6) or are intended to be industrialized such as the synthesis of (5)-piperazine-2-carboxylic acid (Fig. 31). There are various other commercial processes in which the stereospecific conversion of nitriles is desirable. The increasing number of reports on stereoselective nitrile-converting enzymes in recent years shows that biological mechanisms hold much potential for such processes and indicates that nitrileconverting enzymes might be as useful as esterases and lipases for the synthesis of chiral building blocks. 

---