Iodine reduction

Ana.lytica.1 Methods. Various analytical methods involve titration with oxidants, eg, hexacyanoferrate (ferricyanide), which oxidize dithionites to sulfite. lodimetric titration to sulfate in the presence of formaldehyde enables dithionite to be distinguished from sulfite because aldehyde adducts of sulfite are not oxidized by iodine. Reductive bleaching of dyes can be used to determine dithionite, the extent of reduction being deterrnined photometrically. Methods for determining mixtures of dithionite, sulfite, and thiosulfates have been reviewed (365). Analysis of dithionite particularly for thiosulfate, a frequent and undesirable impurity, can be done easily by Hquid chromatography (366). 

RuF3 can be made by iodine reduction of RuF5. It is obtained as a dark brown powder that contains corner-shared RuF6 octahedra [15], RuC13 exists in a- and /3-phases ... 

In this connection it should be noted that the most careful studies (N9a, D2) undertaken to confirm the rotating-disk correlation, Eq. (la) in Table VII, used the iodine reduction reaction with very small reactant concentrations, and employed diaphragm cell diffusivities of KI j in KI. 

In 1998, Evans published an improved synthesis of bu-box 3 starting from the same amino acid. The updated synthesis began with sodium borohydride-iodine reduction to afford amino alcohol 23 followed again by treatment with dimethyl-malonyl dichloride 24 to afford 25 in 88% yield (from 23). Cyclization was achieved by treatment of 25 with toluenesulfonyl chloride and triethylamine in the presence of a catalytic amount of dimethylaminopyridine to afford bu-box 3 in 82% yield (Fig. 9.6). 

In an extension of atom-transfer radical reactions to heterocyclic systems, Byers has introduced a novel methodology for the addition of electron-deficient radicals to unprotected pyrroles and indoles in a stannane-fi ee, non-oxidative process <99TL2677>. For exanqrle, photochemical reaction of pyrrole (33) with etl l iodoacetate (34) in presence of thiosulfiite as an iodine reductant, phase transfer catalyst and propylene oxide led to high yields of the 2-alkylated pyrrole 35 <99TL2677>. 

C") Chlorite-iodine-reductant. These systems, which include systems 8 b, 9 b and 10b of Table 8 appear to be only minor variants of type C ) in which (M 9) replaces (M 8). C ") Chlorite-iodide-reductant. The only known example of this type is the chlorite-iodide-malonic acid system, which is of special interest because it supports both batch oscillations and spatial wave patterns. The slow decomposition of iodinated malonic acid species apparently provides a long lasting, indirect flux of iodide (via (M2) + (M9)) in this system. 

Alcohols are converted to alkyl iodides by reaction with A A-diethyl-aniline/borane/iodine. Reductive iodination is observed when this system reacts with ketones or with carboxylic acids934,935. Direct reduction of aromatic aldehydes to benzyl bromide is reported by Le Corre and coworkers, who have brominated benzaldehydes and acetophenones in presence of a trimethylamine/borane complex and have obtained benzyl bromides and a-bromoethylbenzenes, respectively936. See also Reference937. 

A molecule of BuLi is now guided to C-4 of 140 by the chelating diamine to give 141. Reaction with iodine, reduction, demethylation and acetal formation give 143 in reasonable overall yield after a short sequence from 137. 

Among these methods, the Karl Fischer method is the most used. It is a chemical method based on iodine reduction by sulfur dioxide in the presence of water. 

Both epoxides and aromatic ketones have been shown to be iodinated reductively with tetramethyldisiloxane-iodine to the corresponding benzyl iodides in good yields.Allylic acetals will undergo reaction with trimethylsilyl chloride-sodium halide to produce B-iodoacetals on work-up in a sequence equivalent to overall conjugate addition of hydrogen iodide. 

The chlorite-iodide reaction is clearly the minimal oscillator of the subfamily of chlorite-iodide xidant oscillating reactions, and, since iodate and iodine appear to be produced in all of them, it can be considered to be the progenitor of a still larger family that includes the chlorite-iodate-reductant and cWorite-iodine-reductant groups listed in Table 4.1. Clearly, the chlorite-iodide reaction cannot be minimal for the entire family of chlorite-based oscillators since many of them contain no iodine species. It is not at all obvious that a minimal oscillator for the entire chlorite family exists. 

Tyagai, V.A. and Lukyanchikova, N.B. (1968) Electrochemical noise of iodine reduction on a cadmium sulfide surface. Surface Science, 12, 331-340. 

Richards CE, Anderson AY, Martiniani S, Law C, O Regan BC (2012) The mechanism of iodine reduction by Ti02 electrons and the kinetics of recmnbination in dye-sensitized solar cells. J Phys Chem Lett 3 1980-1984... 

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