Chloramine-T, as oxidant

Radfoiodination with iodine-125 using Chloramine-T as oxidant... 

Radioiodination with iodine-125 using Chloramine-T as oxidant 210 Radioiodination with iodine-125 using lodogen as oxidant 210... 

F. L. Hahn, Mikrochemief 17 (1935) 228, recommended chloramine-T as oxidant. This has the advantage that the reaction takes place in a homogeneous medium. The use of an excess... 

An alternative procedure to afford the chiral nitridomanganese complex 15 was developed by our group. This procedure consists of a reaction of the chiral Mnra complex 14 [21] with gaseous NH3 and chloramine-T as the oxidant in MeOH [22] (Scheme 15). Other derivatives 16-21 which have (1 / ,2/ )-diaminocyclohex-ane as a backbone were synthesized by the usual method using aqueous NH3 and NaOCl. Complex 22 was also synthesized from diphenylethylenediamine as a chiral source (Scheme 16). 

Radiolabelling of DOTATATE with I and I was achieved using chloramine T as an oxidizing agent at a molar ratio of chloramine T to tyrosine residue of 2.5-3.5. To this end, 50 gg of (scFv), or 10 gg of peptide in phosphate buffer solution (PBS) at pH7 was mixed with 1.48 MBq (40 gCi) of Na - l or Na l. The pH was adjusted to 7.0 or 10, after which 4 gL of (1 mg/mL) chloramine T was added. The reaction mixture was then gently stirred for 2 min, and the reaction was finally quenched using 4 gL of sodium metabisulphite in a fourfold molar excess of chloramine T. 

A nitrene unit generated in situ from Chloramine-T adds oxidatively to triarylbismuthines to give the corresponding triarylbismuthine A-tosylimides [64CB789, 91CL105]. A-Tosyliminoiodobenzene can also be used as a nitrene precursor [96JCR(S)24]. 

The oxidation can be carried out in acidic, neutral, or basic media. Iodide will be oxidized to iodine in basic and neutral media and to iodine monochloride in acidic medium (HCl). In aqueous solution, chloramine T forms hypochlorous acid (HOCl), which is thought to be the actual oxidizing species. The oxidation can be controlled by the depletion of chloramine T, as the fimiting reagent or by the addition of a reducing agent (sodium bisulfite) to stop it (Robles et al, 2001). 

The iodized protein does not exhibit specific binding Often, the incorporated iodine is to blame, but the reagents used for the iodination can also inactivate the protein. For example, chloramine T oxidizes not only 1 but the a-amino group of peptides and amino acids to nitrile. Sensitive phenol derivatives are also destroyed. By the way, these reactions were the basis for the application of chloramine T as a disinfectant during World War I (Dakin et al. 1996). 

In the iodination of molecules with low MW, Na I usually serves as the source of and chloramine T as the oxidizer (molar ration of the three reactants about 1 1 1). A slightly basic pH of the reaction mixture favors the monoiodination. With compounds that are sensitive to water (e.g., N-succinimidyl derivatives), the iodination reaction is carried out in organic solvents (e.g., acetone, acetonitrile). The iodination efficiency depends on the solvent being used. HPLC or thin-layer chromatography separates free iodine, iodized molecule, and noniodized molecule. 

Orlova et al. optimized the reaction conditions for the synthesis of 83 starting from 82 using Chloramine-T as the oxidizing agent and Na I as the radiohalogen source (Figure 6.4). Variables included the pH, reaction times, and reagent concentrations (Orlova et al., 2004). Already after... 

The commercially available chloramine-T trihydrate (TsNNaCl 3H20) could also be used directly as the oxidant, although slightly more dilute concentrations (0.2 m vs. 0.5 m) had to be employed to ensure comparable yields. The applicability of this trihydrate version to large-scale syntheses was demonstrated by the aziridination of cyclopentene on a 0,5 mol scale reaction, providing 6-tosylazabicyclo-[3.1.0]hexane in 80% isolated yield (Scheme 12.14). 

Chloramine-B (CAB, PhS02NClNa) and chloramine-T (CAT, p-Me-C6H4S02NClNa) have also been used for the oxidation of sulphoxides107-115. The required sulphone is produced after initial attack by the sulphoxide sulphur atom on the electrophilic chlorine-containing species, forming a chlorosulphonium intermediate as shown in equation (34). These reactions take place at room temperature, in water and aqueous polar solvents such as alcohols and dioxane, in both acidic and basic media. In alkaline solution the reaction is slow and the rate is considerably enhanced by the use of osmium tetroxide as a catalyst115. 

Aldoximes can be oxidatively dehydrogenated to nitrile oxides using a variety of oxidants such as lead tetraacetate [16a], alkali hypohalites [lla],NBS in DMF followed by base treatment [16b], chloramine-T [11b], 1-chlorobenzotriazole [16c], mercuric acetate [ 16 d], etc. However, we employed either NaOCl or chloramine-T for most of our INOC reactions. For instance, a piperidine ring fused to an isoxazoline as in 14 was constructed using the INOC methodology (Scheme 3) [17]. Monoalkylation of N-tosylallylamine 10 with the bromoacetal... 

Hexa(hydroxyethyl)pararosaniline nitrile has been used in a chemical radiochromic dosimeter.130 Ferricyanide oxidation of leuco Crystal Violet to Crystal Violet dye finds use in detection of various heavy metals131 at trace quantities. Oxidation of leuco triphenylmethanes by chloramine-T is catalyzed by iodide and therefore is used for detection of iodide.132 On the other hand, the inhibition of the catalytic effect of iodide by some ions can be used for determining traces of Ag(I), Hg(II), Pd(II). In addition, the triphenylmethane leuco dyes, phenolphthalein or phenol red are used extensively as indicators in calorimetric and titrimetric determinations. 

---