Halogenation anodic oxidation

Cyanides. Salts of the complex ion, [Au(CN)2] , can be formed directiy from gold, ie, gold dissolves ia dilute solutions of potassium cyanide ia the presence of air. Additionally, a gold anode dissolves ia a solution of potassium cyanide. The potassium salt can be isolated by evaporation of the solution and purified by recrystallization from water (177). Boiling of the complex cyanide ia hydrochloric acid results ia formation of AuCN [506-65-01]. Halogens add oxidatively to [Au(CN)2] to yield salts of [Au(CN)2X2] which are converted to the tetracyanoaurates usiag excess cyanide (178). These last can also be prepared directiy from the tetrahaloaurates. 

N 24.12% brick red solid mp, decomps when heated over 300°. Insol in w and the usual organic solvents as well as weak acids and alkalies. Comm prepn (Ref 3) is from thiocyanic acid and/or thiocyanates either by anodic oxidation or by interaction with hydrogen peroxide or halogens. The yield is impure because it contains both H and O. The S content varies between 45 and 55%. Lab prepn of the pure polymer is by reacting the Na salt of 5-chlor-3-mercapto 1,2,4-thiodiazols with either acet, ethanol or w (Refs 1 2)... 

Oxidation of thiophene with Fenton-like reagents produces 2-hydroxythiophene of which the 2(570 One isomer is the most stable (Eq. 1) <96JCR(S)242>. In contrast, methyltrioxorhenium (Vn) catalyzed hydrogen peroxide oxidation of thiophene and its derivatives forms first the sulfoxide and ultimately the sulfone derivatives <96107211>. Anodic oxidation of aminated dibenzothiophene produces stable radical cation salts <96BSF597>. Reduction of dihalothiophene at carbon cathodes produces the first example of an electrochemical halogen dance reaction (Eq. 2) <96JOC8074>. 

Anodic oxidation of halogenated tyrosines was studied in connection with some sponge metabolites (cavemicolin model compounds). The methyl exter of 3,5-dibromotyrosine afforded four different products in a 41 10 26 23 ratio with 23% overall yield as a result of equilibration. (Scheme 44) [93JCS(P2)3117], A related compound was obtained as a mixture of stereoisomers 56 from a Diels-Alder reaction between N-acetyldehydroalanine methyl ester and l-methoxy-l,3-cyclohexadiene (87TL2371). 

One of the few anodic transformations of ketones in the presence of halogen derivatives which appears to involve anodic oxidation of the carbonyl compound itself is shown in... 

Halogenated organics are usually toxic, and their electroreduction can make them easily biodegradable. This is also a common goal in the electrochemical decontamination of organic pollutants in wastewaters by anodic oxidation. Although modern processes have seriously reduced the operation... 

It has been proposed that mediated electrochemical oxidation may be used for the ambient temperature destruction of hazardous waste. Using Co(III)- -mediated electrochemical oxidation in sulfuric acid, l,3-dichloro-2-propanol and 2-chloro-l-propanol were oxidized to carbon dioxide259. A series of studies is being conducted on the use of the anodic oxidation of barium peroxide to produce an intermediate that leads to destruction of halogenated organic compounds. 

Haiogenation of aromatic nuclei may also be achieved by halogen or positively charged species of halogen formed in solution by anodic oxidation of halide anions (equation 70). ... 

Anodic oxidation couples the pendant arm and the silyl enolate fragments of 54 to give the annulated product 55 (equation 40) , a key intermediate in the synthesis of hamigerans, an unusual halogenated marine natural product . 

Opening of the vicinal carbon-carbon bond in aminocyclopropane derivatives was achieved by oxidation with various reagents, e.g. Pb(OAc)4 , NaOCP r-BuOCpi Cu2 /0 Cu/0 0s04/0 K3Fe(CN) Cu or fiv/Oa/sens., anodic oxidation Oxidation with halogenating reagents such as NaOCl or t-BuOCl proceeds via N-chloro compounds (see equation 105), which opened the C(l)-C(2) cyclopropane bond when the cyclopropylamine had one substituent at the iV-atom (e.g. 489- 490 equation 125) or a phenyl moiety in the C(2) position. 

In addition, deactivating nitro and halogen substituents have been introduced by anodic oxidation (see Chapter 24.)... 

A somewhat similar ring closure in which a nitrogen anion attacks a halogenated carbon center is obtained in the anodic oxidation of dimethyl Q -(it -tosylaminoalkyl) malonates in methanol containing KI in an undivided cell. Aziridines, azetidines, and pyrrolidines may be formed in good yield [63]. 

Anodic oxidation of disulfides usually gives the equivalent of RS, which may add to double bonds [99] oxidation of (XXXII) in the presence of HX (X = halogen) gives (XXXIII) [100] it is interesting that a five-membered, rather than a six-membered ring is formed, as in Eq. (17) the reaction is proposed to pass through an episulfonium ion [100]. 

Usually only one electrode product is recovered as a product of commercial value the product of the counterelectrode must be removed as waste or as a low-value byproduct. During anodic oxidations, hydrogen gas is evolved and has to be freed of solvent and low-boiling by-products. In the case of cathodic reductions, the gas given off is oxygen, sometimes containing halogens and acids as impurities. 

Shono and coworkers have examined the electrochemical oxidation of sulfonamides [25], presumably with the intent of generating a-alkoxy sulfonamides. However, anodic oxidation of short chain acyclic sulfonamides, like 12, in the presence of halide ion surprisingly afforded the a-sulfonamido acetals 13 (Scheme 6) [25a]. It is believed that oxidation of 12 occurs to initially produce a-methoxy sulfonamide 14. Under the reaction conditions, however, 14 eliminates methanol to produce N-sulfonyl aldimine 15, which can tautomerize to ene sulfonamide 16. Reaction of 16 with a positive halogen species, generated elec-trochemically, probably leads to 17, which can rearrange via an intermediate aziridine to the observed acetal product 13. 

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