Potassium cyanide-18-Crown

This derivative has been prepared from an indole, the chloromethyl ether, and potassium hydride in 50% yield it is cleaved in 84% yield by potassium cyanide/ 18-crown-6 in refluxing acetonitrile/ ... 

Catalysis by 18-crown-6 of the reaction of solid potassium cyanide with a variety of chlorides and bromides has been demonstrated.38 With primary bromides, yields are high and reaction times are 15-30 h at reflux in acetonitrile (83° C). Interestingly, the... 

A typical phase transfer catalytic reaction of the liquid/liquid type is the cyanation of an alkyl halide in an organic phase using sodium or potassium cyanide in an aqueous phase. When these phases are stirred and heated together very little reaction occurs. However, addition of a small amount of crown ether (or cryptand) results in the reaction occurring to yield the required nitrile. The crown serves to transport the cyanide ion, as its ion pair with the complexed potassium cation, into the organic phase allowing the reaction to proceed. 

The potassium cyanide complex of 18-crown-6 in benzene or acetonitrile undergoes Michael addition to unsaturated carbonyl compounds (Liotta et al., 1977). In the presence of acetone cyanohydrin, the catalytic (i.e. catalytic in potassium cyanide and crown ether) cycle for hydrocyanation shown in (21)... 

The rates of reaction of benzyl bromide and benzyl chloride with potassium cyanide were studied as a function of added water, in the presence and absence of 18-crown-6 (Equation 1). These heterogeneous reactions were carried out in toluene (50 mL) at 85 C and 25 C. 

Table III The Rate of Reaction of Benzyl Broalde with Potassium Cyanide at 25 C In the Presence of 18-Crown 6 as a Function of Added Water...

Catalysts synthesized from crown ether monomers 61 and 62 by copolymerization with styrene and either p-divinylbenzene or p,p -divinylbiphenyl (63) are listed in Table 14 along with their relative activities for solid/solid/liquid reactions of potassium acetate with benzyl chloride (Eq. (13)) and potassium cyanide with 1,4-dichlorobutane (Eq. (14)) in acetonitrile 183). 

CH2OH - —CHiCN.1 This transformation is possible by treatment of a primary alcohol with tri-n-butylphosphine, carbon tetrachloride, potassium cyanide, and 18-crown-6 at room temperature. No reaction occurs in the absence of the crown ether. Yields of nitriles are 70-85%. 

There have been reports of syntheses of cyano complexes in fused potassium cyanide, though the characterization of the products has not always been satisfactory.1 The dry reaction between potassium cyanide and potassium hexaiodoplatinate(IV), however, certainly gives the impure hexacyano-platinate(IV) and substitution of cycloocta-1,5-diene bonded to platinum(II) may be achieved by the use of solid potassium cyanide in the presence of a crown ether catalyst.16... 

Three PTC methods are worthy of note. In the first the alkyl halide is treated with sodium cyanide in decane solution in the presence of catalytic amounts of hexadecyltributylphosphonium bromide.1673 In the second tetraethylammo-nium cyanide in molar quantities is used in dichloromethane solution with the alkyl halide.1676 In the third method, which is reported to be most satisfactory in the case of allylic and benzylic halides, a solid/liquid system of potassium cyanide and 18-crown-6 ether is employed.168... 

Chromium trioxide, 21 Clemmensen reaction, 111 18-Crown-6-potassium cyanide complex, 129... 

The 1 1 complex is conveniently prepared by dissolving 0.652 g (10 mmol) of pulverized potassium cyanide and 2.640 g (10 mmol) of commercial 18-crown-6 (Aldrich Chemical Company, Inc.) in 45 mL of anhydrous methanol by swirling and warming. The methanol is then evaporated at a rotary evaporator and the white complex dried in vacuo over night. 

Chromium trioxide, 60, 21 Clemmensen reaction, 60, 111 Copper chloride (CuCl) [7758-89-6], 61, 122 Crotonic acid, ethyl ester, ( )-, 61, 85 18-Crown-6-potassium cyanide complex, 60,129 Crum Brown-Walker reaction, 60, 4 Cuprous chloride, 60, 42, 121 61, 122 CYANIC ACID, PHENYL ESTER [1122-85-6], 61, 35... 

Addition to ketones. Potassium cyanide in combination with 18-crown-6 is generally superior to Znij as the catalyst for additii n of cyanotrimethylsilane to ketones substituted at the a-position with an electron-withdrawing group. 

In a limited number of cases, arylsilanes react with aldehydes as if they were aryl Grignard or aryllithium reagents. Both trimethyl(perchlorophenyl)silane and trimethyl(perfluoro-phenyl)silane react with benzaldehyde to give the corresponding 7.-(pcrhalophenyl)bcnzyl tri-methylsilyl ethers.163 Benzaldehyde reacts completely with trimethyl(perfluorophenyl)silane in diethyl ether in the presence of either a catalytic amount of the potassium cyanide/18-crown-6 complex in less than 5 hours at room temperature or potassium fluoride in dimethylform-umide.164 In the case of aryltrimcthylsilanes containing electron-withdrawing substituents in the ortho position, the reaction is observed only under the conditions of nucleophilic catalysis by potassium fluoride or cesium fluoride. 

Caution. All the reagents used and the product are toxic. White phosphorus must be kept under water. It ignites on contact with air the fumes generated are irritating and extremely poisonous. Contact of white phosphorus with the skin causes severe burns. Absorption in any form may be lethal. Even small amounts of potassium cyanide are lethal. For [iS]-crown-6 oral) an LD 50 of 705 mg kg is reported. Crown ethers are skin and eye irritants. All used and emptied equipment is immediately rinsed with a dilute solution of bromine in methanol under a well-ventilated hood. 

Generally benzoins are generated by the action of sodium cyanide or potassium cyanide on aromatic aldehydes in aqueous ethanol via cyanohydrin intermediates. Benzoins may also be prepared in good yields by treating aromatic aldehydes with potassium cyanide in the presence of crown ethers in water or aptotic solvents. Other sources for cyanide in this type of condensation are tetrabutylammonium cyanide, polymer-supported cyanide and acetone cyanohydrin with KaCOs. Similarly, addition of aromatic ddehydes to a,3-unsaturated ketones can be accomplished by means of cyanide catalysis in DMF.7... 

Thallium(I) cyanide was introduced by Taylor and McKillop as a reagent. Aromatic and heteroaromatic acyl cyanides are produced in go yield, whereas aliphatic acid halides lead under these conditions mainly to dimerization products. 18-Crown-6 is a good catalyst for the preparation of cyanoformate in methylene chloride with potassium cyanide and chloroformates. Similarly, tetraethylammonium cyanide gives cyanoformates in high yield under very mild conditions. Aroyl cyanides are generated easily by phase transfer catalysis with tetra-n-butylammonium bromide. Tri- -butyltin cyanide proved successful only with aromatic acid halides, leading to dimerization products with aliphatic compounds. ... 

Pictet-Spengler cyclization, 161 Pinacol rearrangements, 51 B-(3>a-Pinanyl-9-borabicyclo[3.3.1 ]-nonane, 320-321 Piperidine, 183 Piperidine enamines, 16 Piperidines, 18 Piperonal, 232 Piperylene, 372 N-Pivaloylaniline, 69 Platinum catalysts, 321 Podophyllotoxin, 165 Polygodial, 167 Polymethoxyarenes, 368 Polymethylpyrimidines, 345 Polynucleotides, 88 Polyphosphate ester, 437 Polyphosphoric acid, 321-322 Potassioacetone, 73 Potassium-Alumina, 322 Potassium bis(trimcthylsilyl)amide, 38 Potassium f-butoxide, 323 Potassium carbonate, 323 Potassium-18-Crown-6, 322 Potassium cyanide, 324 Potassium cyclopentadienide, 111 Potassium 2,6-di-f-butyl-4-methylphen-oxide, 48... 

The solid/liquid phase t reins fear analysis of potassium cyanide in a series of substitution reactions are indicated in Table III. Again, the reactivity of the silacrowns appear comparable to crown ethers. 

The immobilized silacrovm wets added to a two phase mixture containing concentrated aqueous potassium cyanide and substrate dissolved in acetonitrile. The mixture was stirred at 600-1000 rpm. Results are shown in Table IV. The immobilized sila-crown catalyzed cyanide displacement reactions in the three cases. The conversion of benzyl chloride to benzyl cyanide proceeded to 100% conversion, similar to the soluble silacrovm. 

A crown ether can facilitate substitution between an unactivated aryl chloride and potassium methoxide. Thus, heating a solution of the dicyclohexyl-18-crown-6 complex of potassium methoxide in o-dichlorobenzene at 90° gives rise to 40—50% of o-chloroanisole, Eq. (3). No reaction is observed in the absence of the ether.25 This approach is not always successful, however. The same ether failed to induce a reaction between potassium cyanide and o-dichlorobenzene in acetonitrile.24 ... 

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