Hydrocyanation examples

Equation 8.65 is an alternative to lumping of the saturated and ligand-deficient species, as was done in the hydrocyanation Example 8.7 in the preceding section, and gives identical results with slightly less algebraic handling. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Another example is the du Pont process for the production of adiponitrile. Tetrakisarylphosphitenickel(0) compounds are used to affect the hydrocyanation of butadiene. A multistage reaction results in the synthesis of dinitrile, which is ultimately used in the commercial manufacture of nylon-6,6 (144-149). 

Additions include the attachment of two univalent atoms or groups (called addends) to an unsaturated system, e. g., to olefins, carbonyl groups, aromatic systems, carbenes, etc. (Rule 2.1). For example, the addition of hydrocyanic acid to the car-... 

Another example of an acid is hydrogen cyanide, HCN, which transfers its proton to water when it dissolves to form the solution known as hydrocyanic acid, HCN(aq). However, only a small fraction of the HCN molecules donate their protons, and so we classify HCN as a weak acid in water. We write the proton transfer reaction with equilibrium half-arrows ... 

The Jacobsen group has also shown that the recycling of the resin-bounded catalyst can be successfully performed [152,154]. Moreover, they have developed an efficient method for the hydrolysis of the aminonitrile into the corresponding amino acid. This method was apphed for the commercial production of optically active K-amino acids at Rhodia ChiRex (e.g. tert-leucine) the catalyst was immobihsed on a resin support (4 mol %, 10 cycles) and the intermediate hydrocyanation adduct was trapped by simply replacing TFAA with HCOOH/AC2O, for example. Highly crystalhne formamide derivatives were thus obtained in excellent yields (97-98% per cycle) with very high enantioselectivities (92-93% per cycle) [158]. 

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. 

The hydrocyanation of conjugated carbonyl compounds is a related reaction.83 Very often such a conjugated addition is carried out in aqueous conditions. For example, in the pioneer work of Lapworth, hydrocyanation of activated olefins was carried out with KCN or NaCN in aqueous ethanol in the presence of acetic acid (Eq. 10.36).84... 

Hydrogen cyanide (Table 15.1) is a colorless, flammable liquid or gas that boils at 25.7°C and freezes at minus 13.2°C. The gas rarely occurs in nature, is lighter than air, and diffuses rapidly. It is usually prepared commercially from ammonia and methane at elevated temperatures with a platinum catalyst. It is miscible with water and alcohol, but is only slightly soluble in ether. In water, HCN is a weak acid with the ratio of HCN to CN about 100 at pH 7.2, 10 at pH 8.2, and 1 at pH 9.2. HCN can dissociate into H+ and CN. Cyanide ion, or free cyanide ion, refers to the anion CN derived from hydrocyanic acid in solution, in equilibrium with simple or complexed cyanide molecules. Cyanide ions resemble halide ions in several ways and are sometimes referred to as pseudohalide ions. For example, silver cyanide is almost insoluble in water, as are silver halides. Cyanide ions also form stable complexes with many metals. 

Poison, Class A A D.O.T. term for extremely dangerous poisons such as poisonous gases or liquids of such a nature that a very small amount of the gas or vapor of the liquid mixed with air is dangerous to life. Examples include phosgene, cyanogen, hydrocyanic acid, and nitrogen peroxide. 

The industrial use of 1,3-dienes and of their electrophilic reactions has strongly stimulated the field in recent years. Because of the low cost of butadiene, abundantly available from the naphtha cracking process, very large scale applications in the synthesis of polymers, solvents and fine chemicals have been developed, leading to many basic raw materials of the modem chemical industry. For example, the primary steps in the syntheses of acrylonitrile and adiponitrile have been the electrophilic addition of hydrocyanic acid to butadiene24. Chlorination of butadiene was the basis of chloroprene synthesis25. 

Many of the early gases used in artillery shell proved unsuitable or were not adapted to field conditions. Thus, out. of more than 50 chem substances loaded into artillery shell, oaly 4 or 5 proved effective in battle. Often the efficiency of a shell could be definitely. ascertained only after a large number of rounds had been fired. For example, the French Vincennite shell was filled with a raixt of hydrocyanic acid arsenic trichloride, which had a marked toxicity in lab tests. Yet, after 4 million shells were filled with this mixt it was not an effective gas under battle conditions... 

For preparative purposes, the use of biphasic solvent systems consisting of an aqueous phase and a water-immiscible organic phase for PaHNL and llhl INI. catalysis has proven to have a broad applicability, also including, for example, pyrrole derivatives [30] (see Table 9.3, Section 9.2.2.3) and to be suitable for industrial scale. DSM established enzymatic hydrocyanation processes, e.g., for the production of (S)-m-phenoxymandelonitrile [31, 32] and large-scale production of (R) -2 - (2 -furyl) - 2 -hydroxyace tonitrile [33]. 

The nature Of the ions.—In 1814, G. F. Parrst12 found that in the electrolysis of aq. soln. of potassium ferrocyanide the alkali accumulated about the negative pole, and ferric oxide and hydrocyanic acid about the positive pole, and the work of J. F. Daniell and W. A. Miller, and of W. Hittorf (1859), showed that double salts are of two kinds, and that in the one kind the metal is bound as a complex negative ion, and in the other it is the positive ion. For example, in the electrolysis of potassium silver cyanide, KCy.AgCy, W. Hittorf (1859) found that silver was deposited on the cathode, whereas with salts of the type AgN03 it is deposited on the anode. Hence, it was inferred that the salt ionizes KAgCy2=K,- -AgCy2 similarly,... 

An impressive example of autoinduction (28) has been observed in the enantioselective hydrocyanation of 3-phenoxybenzaldehyde catalyzed by cyclo[( )-phenylalanyl-(ff)-hystidyl] (Scheme 8) (29). The ee... 

The tests to be made on spirits and liqueurs include a certain number which are common to all these products, such as determinations of the alcoholic strength, extract and ash, and tests for impurities and denaturing agents other investigations are made only with certain products, examples of these being the examination of kirschwasser for hydrocyanic acid, the determination of sugars in liqueurs, etc. The former are treated under General Methods and the latter in the Special Part. 

The most prominent biological feature of silatranes is the remarkable mammalian toxicity exhibited by their 1-aryl derivatives (Table 4). Some of them are several times more toxic than widely known poisons such as hydrocyanic acid and strychnine. At the same time 1-arylsilatranes are almost harmless for cold-blooded animals, plants, and microorganisms. For example, frogs are very resistant to 1-phenylsilatrane (9) doses of 30-40 mg/kg have no effect. 

As discussed above, asymmetric organocatalysis is, in principle, an old branch of organic chemistry, with its beginnings dating back to the early 20th century (for example the first asymmetric hydrocyanation of an aldehyde in 1912). This... 

In addition, acyclic aliphatic N-allyl imines and cycloalkylimines were acceptable starting materials for the asymmetric hydrocyanation and enantioselectivity of up to 95% ee was obtained by use of 10a as catalyst [10]. Representative examples of the range of substrates are summarized in Scheme 5.6. It should be added that as an alternative to the N-allyl imines the analogous N-benzyl imines can be efficiently used as starting material [10]. An optimized procedure for preparation of the catalyst 10a has recently been reported by the Jacobsen group [11]. 

Jacobsen et al. have also demonstrated the usefulness of this method for asymmetric hydrocyanation of cyclic imines [10]. An example is the efficient synthesis of (R)-14 in 88% yield and with 91% ee (Scheme 5.7). Thus, in addition to the hydrocyanation of acyclic imines which are mainly fc-isomcrs, Z-i mines can also be used efficiently. 

Extension of this reaction toward a one-pot asymmetric Mannich-hydrocyanation reaction sequence was also reported by the Barbas group [29]. In this one-pot two-step process proline-catalyzed asymmetric Mannich reaction of unmodified aldehydes with the a-imino glyoxylate was performed first, then diastereoselective in situ cyanation. The resulting /i-cyanohydroxymethyl a-amino acids were obtained with high enantioselectivity (93-99% ee) [29]. Another one-pot two-step reaction developed by Barbas et al. is the Mannich-allylation reaction in which the proline-catalyzed Mannich reaction is combined with an indium-promoted allylation [30], This one-pot synthesis was conducted in aqueous media and is the first example of a direct organocatalytic Mannich reaction in aqueous media [28, 30]. 

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