Quaternary ammonium cyanide

The simplest C-C bond formation reaction is the nucleophilic displacement of a halide ion from a haloalkane by the cyanide ion. This was one of the first reactions for which the kinetics under phase-transfer catalysed conditions was investigated and patented [l-3] and is widely used [e.g. 4-12], The reaction has been the subject of a large number of patents and it is frequently used as a standard reaction for the assessment of the effectiveness of the catalyst. Although the majority of reactions are conducted under liquiddiquid two-phase conditions, it has also been conducted under solidrliquid two-phase conditions [13] but, as with many other reactions carried out under such conditions, a trace of water is necessary for optimum success. Triphase catalysis [14] and use of the preformed quaternary ammonium cyanide [e.g. 15] have also been applied to the conversion of haloalkanes into the corresponding nitriles. Polymer-bound chloroalkanes react with sodium cyanide and cyanoalkanes under phase-transfer catalytic conditions [16],... 

Castells, J., Dunach, E. Polymer-supported quaternary ammonium cyanides and their use as catalysts in the benzoin condensation. Chem. Lett. 1984, 1859-1860. 

It is found that benzoin condensation of aldehydes are strongly catalysed by a PTC (quaternary ammonium cyanide in a two phase system). In a similar way, acyloin condensations are easily effected by stirring aliphatic or aromatic aldehydes with a quaternary catalyst (PTC), N-laurylthiazolium bromide in aqueous phosphate buffer at room temperature. The aromatic aldehydes reacted in a short time (about 5 min). However, aliphatic aldehydes require longer time (5-10 hr) for completion. Mixtures of aliphatic and aryl aromatic aldehydes give mixed a-hydroxy ketones. ... 

The catalytic cycle accounting for the essential features of the cyanide displacement reaction is illustrated in equation 7.2. Note that this is the cycle shown in Sect. 1.4, except that the anions are identified. In essence, the process involves an equilibrium between sodium cyanide and quaternary ammonium cyanide in the aqueous phase, followed by a phase transfer equilibrium occurring across the phase boundary. Once the quaternary ammonium cyanide is present in the organic phase, nucleophilic dis-... 

Sodium cyanide does not dissolve m butyl bromide The two reactants contact each other only at the surface of the solid sodium cyanide and the rate of reaction under these con ditions IS too slow to be of synthetic value Dissolving the sodium cyanide m water is of little help because butyl bromide is not soluble m water and reaction can occur only at the interface between the two phases Adding a small amount of benzyltrimethyl ammonium chlonde however causes pentanemtnle to form rapidly even at room temper ature The quaternary ammonium salt is acting as a catalyst it increases the reaction rate How7... 

Reactions of the Side Chain. Benzyl chloride is hydrolyzed slowly by boiling water and more rapidly at elevated temperature and pressure in the presence of alkaHes (11). Reaction with aqueous sodium cyanide, preferably in the presence of a quaternary ammonium chloride, produces phenylacetonitrile [140-29-4] in high yield (12). The presence of a lower molecular-weight alcohol gives faster rates and higher yields. In the presence of suitable catalysts benzyl chloride reacts with carbon monoxide to produce phenylacetic acid [103-82-2] (13—15). With different catalyst systems in the presence of calcium hydroxide, double carbonylation to phenylpymvic acid [156-06-9] occurs (16). Benzyl esters are formed by heating benzyl chloride with the sodium salts of acids benzyl ethers by reaction with sodium alkoxides. The ease of ether formation is improved by the use of phase-transfer catalysts (17) (see Catalysis, phase-thansfer). 

Nearly all uses and appHcations of benzyl chloride are related to reactions of the active haUde substituent. More than two-thirds of benzyl chloride produced is used in the manufacture of benzyl butyl-phthalate, a plasticizer used extensively in vinyl flooring and other flexible poly(vinyl chloride) uses such as food packaging. Other significant uses are the manufacture of benzyl alcohol [100-51-6] and of benzyl chloride-derived quaternary ammonium compounds, each of which consumes more than 10% of the benzyl chloride produced. Smaller volume uses include the manufacture of benzyl cyanide [140-29-4], benzyl esters such as benzyl acetate [140-11-4], butyrate, cinnamate, and saUcylate, benzylamine [100-46-9], and benzyl dimethyl amine [103-83-8], and -benzylphenol [101-53-1]. In the dye industry benzyl chloride is used as an intermediate in the manufacture of triphenylmethane dyes (qv). First generation derivatives of benzyl chloride are processed further to pharmaceutical, perfume, and flavor products. 

Woodward s strychnine synthesis commences with a Fischer indole synthesis using phenylhydrazine (24) and acetoveratrone (25) as starting materials (see Scheme 2). In the presence of polyphosphor-ic acid, intermediates 24 and 25 combine to afford 2-veratrylindole (23) through the reaction processes illustrated in Scheme 2. With its a position suitably masked, 2-veratrylindole (23) reacts smoothly at the ft position with the Schiff base derived from the action of dimethylamine on formaldehyde to give intermediate 22 in 92% yield. TV-Methylation of the dimethylamino substituent in 22 with methyl iodide, followed by exposure of the resultant quaternary ammonium iodide to sodium cyanide in DMF, provides nitrile 26 in an overall yield of 97%. Condensation of 2-veratryl-tryptamine (20), the product of a lithium aluminum hydride reduction of nitrile 26, with ethyl glyoxylate (21) furnishes Schiff base 19 in a yield of 92%. 

The asymmetric synthesis achieved when the base is an optically active one is proof that the base is present in a transition state with the carbonyl and not just an agent for removal of protons from hydrogen cyanide. It has further been shown that asymmetric synthesis is still achieved even if the only optically active molecules present are quaternary ammonium compounds, i.e., positive ions without any protons to donate. This probably means that the important thing is to have some positive ion near the carbonyl oxygen, an actual covalent... 

Ammonium cyanide, 8 194 Ammonium derivatives, quaternary, 24 45 Ammonium dichromate, 6 538 manufacture, 6 541 Ammonium dichromate(VI), physical properties, 6 528t... 

The hydration number (the number of water molecules intimately associated with the salt) of the quaternary ammonium salt is very dependent upon the anion. The change in the order of reactivity is thus believed to be due to the hydration of the anion the highly hydrated chloride and cyanide ions are less reactive than expected, and the poorly hydrated iodide fares better under phase transfer conditions than in homogeneous reactions. Methanol may specifically solvate the anions via hydrogen bonding, and this effect is responsible for the low reactivity of more polar nucleophiles in that solvent. 

In a sequential continuous process, alcohols are converted initially into the corresponding chloroalkanes, which are flushed without isolation into an aqueous mixture of sodium cyanide and the quaternary ammonium catalyst to produce nitriles [17]. 

Polymer phase-transfer catalysts (also referred to as triphase catalysts) are useful in bringing about reaction between a water-soluble reactant and a water-insoluble reactant [Akelah and Sherrington, 1983 Ford and Tomoi, 1984 Regen, 1979 Tomoi and Ford, 1988], Polymer phase transfer catalysts (usually insoluble) act as the meeting place for two immiscible reactants. For example, the reaction between sodium cyanide (aqueous phase) and 1-bromooctane (organic phase) proceeds at an accelerated rate in the presence of polymeric quaternary ammonium salts such as XXXIX [Regen, 1975, 1976]. Besides the ammonium salts, polymeric phosphonium salts, crown ethers and cryptates, polyethylene oxide), and quaternized polyethylenimine have been studied as phase-transfer catalysts [Hirao et al., 1978 Ishiwatari et al., 1980 Molinari et al., 1977 Tundo, 1978]. 

The resulting catalyst was highly active for cyanide and acetate ion displacements on 1-bromobutane. As expected, soluble low molecular weight quaternary ammonium salts and a soluble quaternized linear poly(ethyleneimine) were even more active, presumably because they had no mass transfer and intraparticle diffusional limitations. These catalysts had a much higher density of charged sites (at least within the micro domains of the poly(ethyleneimine)) than any of the other active quaternary ammonium ion catalysts reported for nucleophilic displacement reactions. 

Later Takahashi et al.19 have reported an alternative synthesis of the cyanooxirane (40a,b) by carrying out the reaction between decyl bromide and potassium cyanide in the presence of quaternary ammonium catalysts. Compounds prepared by this method are similar to those obtained by the Darzens condensation with benzaldehyde in a two-phase system.78... 

Heterocyclic amines have also been used as phase transfer catalysts. However, because these amines quaternize easily, the question is whether the operative catalyst is the tertiary amine or the quaternary ammonium salt formed in situ Furukawa et al.286 have shown that a methyl 2-pyridyl sulfoxide may be used as a phase transfer catalyst and promote substitution reactions between lithium chloride or sodium cyanide and benzyl bromide. According to the authors, the catalyst behaves as a cation complexer and not as a quaternary ammonium salt formed in situ by a Menschutkin reaction. 

Quaternary ammonium salts of triphenylmethane acetonitriles Process of preparing cyanides of triarylrnethane dyes... 

Ooi, T., Uematsu, Y. and Maruoka, K. (2006) Asymmetric Strecker reaction of aldimines using aqueous potassium cyanide by phase-transfer catalysis of chiral quaternary ammonium salts with a tetranaphthyl backbone. J. Am. Chem. Soc., 128, 2548. 

Polymer-supported nucleophilic radiolabelling reactions with [18F]fluoride and [nC]cyanide ions on the surface of quaternary ammonium resins (337, 338) have been found323 valuable in radiopharmaceutical syntheses where fast, simple and easily automated chemical operations are necessary. 3-[18F]-diazepam has been obtained in 30% yield by this method323. 

One of the oldest techniques for overcoming these problems is the use of biphasic water/organic solvent systems using phase-transfer methods. In 1951, Jarrouse found that the reaction of water-soluble sodium cyanide with water-insoluble, but organic solvent-soluble 1-chlorooctane is dramatically enhanced by adding a catalytic amount of tetra-n-butylammonium chloride [878], This technique was further developed by Makosza et al. [879], Starks et al. [880], and others, and has become known as liquid-liquid phase-transfer catalysis (PTC) for reviews, see references [656-658, 879-882], The mechanism of this method is shown in Fig. 5-18 for the nucleophilic displacement reaction of a haloalkane with sodium cyanide in the presence of a quaternary ammonium chloride as FT catalyst. 

Fig. 5-18. Phase-transfer catalyzed nucleophilic displacement reaction of a haloalkane, R-Cl, with sodium cyanide, Na+CN , to yield a nitrile, R-CN, in the presence of sub-stoichiometric amounts of a quaternary ammonium chloride, Q+CP, as PT catalyst.

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