Epoxides cyanide

The only notable success to date in the use of (salen)metal systems in catalysis of asymmetric cyanide addition to epoxides was achieved by Pietrusiewicz, who reported the aluminium-catalyzed desymmetrization of phospholene meso-epoxide (Scheme 7.23) in moderate ee [47]. Despite these significant efforts, a truly prac-... 

A completely different way of preparing isocyanides involves the reaction of epoxides or oxetanes with trimethylsilyl cyanide and zinc iodide, for example, ... 

By studying the NMR spectra of the products, Jensen and co-workers were able to establish that the alkylation of (the presumed) [Co (DMG)2py] in methanol by cyclohexene oxide and by various substituted cyclohexyl bromides and tosylates occurred primarily with inversion of configuration at carbon i.e., by an 8 2 mechanism. A small amount of a second isomer, which must have been formed by another minor pathway, was observed in one case (95). Both the alkylation of [Co (DMG)2py] by asymmetric epoxides 129, 142) and the reduction of epoxides to alcohols by cobalt cyanide complexes 105, 103) show preferential formation of one isomer. In addition, the ratio of ketone to alcohol obtained in the reaction of epoxides with [Co(CN)5H] increases with pH and this has been ascribed to differing reactions with the hydride (reduction to alcohol) and Co(I) (isomerization to ketone) 103) (see also Section VII,C). 

Isomerization has been observed with many a,j3-unsaturated carboxylic acids such as w-cinnamic 10), angelic, maleic, and itaconic acids (94). The possibility of catalyzing the interconversion of, for example, 2-ethyl-butadiene and 3-methylpenta-l,3-diene has not apparently been explored. The cobalt cyanide hydride will also catalyze the isomerization of epoxides to ketones (even terminal epoxides give ketones, not aldehydes) as well as their reduction to alcohols. Since the yield of ketone increases with pH, it was suggested that reduction involved reaction with the hydride [Co" (CN)jH] and isomerization reaction with [Co (CN)j] 103). A related reaction is the decomposition of 2-bromoethanol to acetaldehyde... 

A variety of reaction conditions have been developed for nucleophilic ring opening by cyanide.123 Heating an epoxide with acetone cyanohydrin (which serves as the cyanide source) and triethylamine leads to ring opening at the less-substituted position. 

A paper concerning the synthesis of miharamycin analogues modified in the sugar moiety demonstrated the hydrolysis of a nitrile upon treatment with silica gel in the presence of water (Scheme 37).174 The cyanide 197 resulting from the opening of epoxide... 

Acrylonitrile is also metabolized to CO which is eliminated through the lungs. Carbon dioxide is produced when acrylonitrile is metabolized to ethylene oxide and degraded to oxidation products and cyanide via the epoxide hydratase pathways (Farooqui and Ahmed 1982 Young et al. 1977). 

Related catalytic enantioselective processes [115] Two catalytic procedures for asymmetric addition of cyanides to meso epoxides have been reported [116]. One is the result of work carried out in these laboratories, shown in Eq. 6.24, promoted by Ti-peptide chiral complexes, while the other, developed by Jacobsen and Schaus, is a Yb-catalyzed enantioselective reaction that is effected in the presence of pybox ligands (Eq. 6.25) [117]. Although the Shibasaki method (Eq. 6.21) is not as enantioselective as these latter methods, it has the advantage that it accomplishes both the epoxidation and subsequent desymmetrization in a single vessel. 

Trichlorobenzene. Trichloroethylene Hydrogen azide, see Alachlor. Aldicarb. Atrazine Hydrogen bromide, see Ethylene dibromide Hydrogen chloride, see Atrazine. Captan. Carbon tetrachloride. Chloroform. Chlorpropham. Chlorpyrifos. 1.2-Dichloroethane. Diuron. Endrin. Formaldehyde. Heptachlor. Heptachlor epoxide. Hexachlorocyclopentadiene. Linuron. Methyl chloride. Methylene chloride. Methyl formate. Monuron. Propanil. Tetrachloroethylene. Trichloroethylene. Vinyl chloride Hydrogen cyanide, see Acetontrile. Alachlor. Aldicarb. 

Snapper and Hoveyda reported a catalytic enantioselective Strecker reaction of aldimines using peptide-based chiral titanium complex [Eq. (13.11)]. Rapid and combinatorial tuning of the catalyst structure is possible in their approach. Based on kinetic studies, bifunctional transition state model 24 was proposed, in which titanium acts as a Lewis acid to activate an imine and an amide carbonyl oxygen acts as a Bronsted base to deprotonate HCN. Related catalyst is also effective in an enantioselective epoxide opening by cyanide "... 

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