Cyanide, reaction with supports

Complexation constants of crown ethers and cryptands for alkali metal salts depend on the cavity sizes of the macrocycles 152,153). ln phase transfer nucleophilic reactions catalyzed by polymer-supported crown ethers and cryptands, rates may vary with the alkali cation. When a catalyst 41 with an 18-membered ring was used for Br-I exchange reactions, rates decreased with a change in salt from KI to Nal, whereas catalyst 40 bearing a 15-membered ring gave the opposite effect (Table 10)l49). A similar rate difference was observed for cyanide displacement reactions with polymer-supported cryptands in which the size of the cavity was varied 141). Polymer-supported phosphonium salt 4, as expected, gave no cation dependence of rates (Table 10). 

Few preparations of nitriles have been performed on insoluble supports (Table 13.19). Aromatic and heteroaromatic nitriles have been prepared on solid phase from the corresponding iodoarenes by metallation followed by reaction with tosyl cyanide (Entry 1, Table 13.19). Moreover, the reaction of chloromethyl polystyrene with NaCN has been used to prepare support-bound benzyl cyanide (Entry 2, Table 13.19). Cleavage with simultaneous formation of nitriles can be achieved by treating polystyrene-bound sulfonylhydrazones with KCN (Entry 3, Table 13.19) or by cleaving amides from a Rink or Sieber linker with TFA anhydride (Entry 10, Table 3.38 [262]). Support-bound benzaldehydes have been converted into 3-aryl-2-propenenitriles by means of a Horner-Emmons reaction with (Et0)2P(0)CH2CN [263]. 

Support-bound indoles can be modified in several ways. N-Alkylation of polystyrene-bound indoles has been achieved by treatment with reactive alkylating agents (Mel, BnBr, BrCH2C02R) in conjunction with NaH or KOrBu as a base in DMF at room temperature (Entries 1 and 2, Table 15.7). The aminomethylation of indole at C-3 proceeds smoothly on cross-linked polystyrene. The resulting (aminomethyl)in-doles are thermally unstable and undergo substitution reactions with various carbon nucleophiles (e.g. cyanide or nitroacetates) at higher temperatures (Entry 4, Table... 

Since methionine seems to be bound in both oxidation states, and yet is the more labile axial ligand in the reaction with cyanide ion, the NMR data seem to support that histidine is also an axial ligand in ferri- and ferrocytochrome c. Direct identification of the axial histidine in the... 

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. 

Aryl cyanation. Reaction of iodobenzene with sodium cyanide in the presence of 10 mole % of Pd(0) affords only a 5% yield of benzonitrile. If the sodium cyanide is impregnated on alumina the reaction proceeds in quantitative yield. In the same reaction with aryl bromides higher yields obtain when alumina is present as a co-catalyst rather than as a support. 

Interest in the hydrocyanation of nonactivated olefins with nickel catalysts arose from the discovery that finely divided nickel or nickel cyanide on inert supports gives higher yields of nitrile products at less severe reaction conditions than do cobdt or copper heterogeneous catalysts. ... 

The employment of suitable organic solvents, such as acetonitrile and acetic acid, with oxidation-resistant supporting electrolytes permits the anodic formation of reactive radical cations from many organic materials. Most aromatic compounds and olefins, as well as those alkanes which have particularly weak C—H bonds, are oxidised in acetonitrile containing fluoroborate or hexafluorophosphate electro-lytes. °" 2 Some aromatic radical cations can be further oxidised to dications within the available potential range. Radical cations in general either deprotonate or attack nucleophiles present in the medium reactions with pyridine, methanol, water, cyanide ion, acetate ion or acetonitrile itself produce addition or substitution products. The complete reactions involve a second electron transfer and coupled chemical... 

A pathway for fatty acid activation, involving a reaction with nonphosphorylated high-energy intermediates rather than the formation of acetyl-CoA derivatives has also been postulated. The supporting evidence includes the observations that (1) blocking the electron transport chain with cyanide or uncoupling oxidative phosphorylation with dinitrophenol interferes with the fatty acid oxidation (2) oligomycin, which blocks the biosynthesis of ATP but does not affect the formation... 

Homo- and heteronuclear cyanide complexes are attractive precursors for the preparation of supported catalysts. First of all since the reaction with the support to an inactive compound does not proceed appreciably, and secondly, since the fixed stoichiometry of the complex cyanides results in active particles of a uniform chemical composition. 

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