Oxidants examples: chloramine

Iodine becomes incorporated into proteins either oxidatively, or enzymatically, or electrochemically. Oxidative incorporation uses organochemical oxidants, such as, for example, chloramine T or lodo-gen (l,3,4,6-tetrachloro-3a,6a-diphenyl glycouril). Enzymatic incorporation is done by means of lactoperoxidase. By these methods iodine is introduced into phenyl (tyrosyl) residues of the protein. 

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). 

Peptides, for example, yield chloramine derivatives on exposure to chlorine gas these derivatives oxidize o-toluidine to a blue semiquinonoid dyestuff in the presence of acetic acid. 

Interesting examples of the addition of N-nucleophiles to nitrile oxides are syntheses of chelated Z-amidoxime, N-[2-(dimethylaminomethyl)phenyl]mesitylene-carboamidoxime (118), and pyranosyl amidoximes (119) from the respective nitrile oxides and amines. Aromatic aldoximes undergo unusual reactions with chloramine-T (4 equiv, in refluxing MeOH). N-(p-toly 1 )-N-(p-tosy 1 )benzamides are formed via addition of 2 equiv of chloramine-T to the intermediate nitrile oxide followed by elimination of sulfur dioxide (120). 

With sulfonamide-derived chloramine salts bearing smaller organic substituents on the sulfur, for example, methanesulfonamide-derived chloramine salt 111 (chloramine-M) as the oxidant, better results are obtained. This reagent can be prepared separately and added to the reaction mixture as the stable anhydrous... 

This approach is used exclusively for the synthesis of the isomeric annelated isothiazoles and isoselenazoles to form the nitrogen-sulfur(selenium) bond and has been discussed in CHEC-II(1996) <1996CHEC-II(7)49>. A wide variety of oxidative cyclizations have been reported, some of which incorpotate an amination. Eor example, reaction of 47 with chloramine gives the corresponding isothiazolo[5,4-7]thiophene 40 (Equation 9) <2000P65>. 

Various types of dyes are prepared from dehydrothiotoluidine. The free base or its sulfonic acid is diazotized and coupled with various naph-tholsulfonic acids such as, for example, e acid (l-naphthol-3,8-disul-fonic acid). The resulting dye is characterized by its high purity of color and can be discharged to a pure white. Such red direct dyes are sold under various names, and are usually referred to as dyes of the erika red type. (Erika Z is the combination from dehydxothioxylidine and e acid. l-Naphthol-3,6-disulfonic acid gives a very similar dye.) In addition to the true azo dyes from dehydrothiotoluidine, two other products are made which are important yellow dyes. One of these dyes is the naphthamine yellow NN (also called chloramine yellow) (Kalle), formed from dehydrothiotoluidinesulfonic acid by oxidation with sodium hypochlorite. The other is thiazole yellow or Clayton yellow, which is made by combining the diazo compound of dehydrothiotoluidinesulfonic acid with a second molecule of the same compound to form a diazoamino compound. 

Chloramine T (Af-chloro-/ -toluenesulfonamide. sodium salt) is a cheap oxidant that has been used occasionally for the deprotection of dithianes.157 In the example depicted in Scheme 2.72. a dithiane is cleaved in the presence of an a, p-unsaturated 0,0-acetaL158 A likely mechanism for the reaction involves the formation of an intermediate sulfilimine. Several heavy metal oxidants have also been exploited for cleaving 5,5-acetals including lead(IV), thallium(lll) [Scheme... 

Sharpless and co-workers first reported the aminohydroxyIation of alkenes in 1975 and have subsequently extended the reaction into an efficient one-step catalytic asymmetric aminohydroxylation. This reaction uses an osmium catalyst [K20s02(OH)4], chloramine salt (such as chloramine T see Chapter 7, section 7.6) as the oxidant and cinchona alkaloid 1.71 or 1.72 as the chiral ligand. For example, asymmetric aminohydroxylation of styrene (1.73) could produce two regioisomeric amino alcohols 1.74 and 1.75. Using Sharpless asymmetric aminohydroxylation, (IR)-N-ethoxycarbonyl-l-phenyl-2-hydroxyethylamine (1.74) was obtained by O Brien et al as the major product and with high enantiomeric excess than its regioisomeric counterpart (R)-N-ethoxycarbonyl-2-phenyl-2-hydroxyethylamine (1.75). The corresponding free amino alcohols were obtained by deprotection of ethyl carbamate (urethane) derivatives. 

Reactions of chloramine include radical, nucleophilic, and electrophilic substitution of chlorine, electrophilic substitution of hydrogen, and oxidative additions, for example ... 

Treatment of thietanes with chloramine T gives N-tosylsulfilimines, for example, 126. Acyclic and five-, six-, and seven-membered cyclic sulfides all react more rapidly than thietane. The mechanism has been investigated. The IR stretching vibrations of the S-N-SO2 system are at 948 and 759 cm", and the nmr spectrum of 3,3-dimethylthietane 1-tosylsulfilimine in benzene and chloroform suggests an equatorial conformation for the sulfilimine. Oxidation of this sulfilimine gives the sulfoximine derivative, 127. The two diastereomeric tosyl-sulfilimines of 3-methyl-3-phenylthietane complex at nitrogen with silver ion. ... 

The first reported example of the preparation of an arsinimine, in 1937, utilized the reaction of the sodium salt of chloramine T with triphenylarsine (equation 41). This reaction, which has been repeated by later workers is not straightforward. Earlier work had shown that chloramine T reacts with the arsine to convert it into an arsine oxide S which then condenses with the tosylamide to provide the final product. Other arsinimines have been made by the same method, but in the majority of cases were isolated as their water adducts In a modification of this reaction, chloramine T itself, rather than a salt, underwent an exothermic reaction with triphenylarsine in dry benzene, and the resultant intermediate, which was not isolated, gave, on treatment with copper powder, an arsinimine (equation 42) . Other arsinimes have also been made by reactions of chloramines with arsines... 

The subsequent fluorescence detection is carried out at an excitation wavelength of 340 nm, the emission is measured at 455 nm. The addition of thiols such as 2-mercaptoetha-nol increases the fluorescence yield. However, OPA only reacts with primary amino acids. Secondary amino acids can only be detected after their oxidation (for example with hypochlorite or chloramine T) [34]. In practical applications, this results in significant difficulties. 

---